Showing papers on "Ammonia published in 1987"
TL;DR: Two classes of procaryotic organisms were cultured on specific inorganic and organic nitrogenous substrates and the application of the coupled separation-isotopic analysis of amino acids yield a better understanding of comparative biochemistry for these organisms.
535 citations
TL;DR: In this article, it was shown that the relative order of activity for ammonia formation was Fe(111) > Fe(100), Fe(110), and Fe(212), and the presence of highly coordinated sites is more important than surface roughness.
210 citations
TL;DR: The kinetics of ammonia oxidation and the ability of a marine ammonia-oxidizing bacterium, Nitrosococcus oceanus, to metabolize methane were investigated in semicontinuous batch culture and inhibitors and coreactants were determined in order to elucidate the behavior of the ammonia oxygenase enzyme in N. oceanus.
Abstract: The kinetics of ammonia oxidation and the ability of a marine ammonia-oxidizing bacterium, Nitrosococcus oceanus, to metabolize methane were investigated in semicontinuous batch culture. The effects of inhibitors (acetylene and nitrapyrin) and coreactants were determined in order to elucidate the behavior of the ammonia oxygenase enzyme in N. oceanus. Acetylene and nitrapyrin were potent inhibitors and their effects were not mitigated by increased ammonia concentrations. Oxygen concentration had the effect of a mixed-type inhibitor; reduced oxygen inhibited the rate or ammonia oxidation at high substrate concentration but may enhance the rate at low substrate concentrations. Substrate affinity in terms of NH
4
+
increased (K
m decreased) with increasing pH. Optimal pH was about 8. Methane inhibited ammonia oxidation; the interaction was not simple competitive inhibition and the presence of multiple active sites on the enzyme was indicated by the behaviour of the inhibited treatments. Half-saturation constants for methane (K
i=6.6 μM) and ammonia (K
m=8.1 μM) were similar. N. oceanus oxidized methanol and methane linearly over time, with CO2 and cell material being produced at approximately equal rates.
155 citations
TL;DR: In this paper, the Lagrangian model of turbulent mixing was modified by the introduction of several correction factors derived from detailed diffusion calculations, and the results of a sensitivity analysis were shown and the computed ammonium concentrations in air and precipitation are in agreement with the available measured data.
155 citations
TL;DR: The acid-base and oxidizing properties and the structures of ZrOn prepared with ammonia or urea and ZrO 2 treated with sulfuric acid or ammonium sulfate have been investigated as mentioned in this paper.
127 citations
Patent•
03 Aug 1987TL;DR: Polyaspartic acid and its salts, which can be obtained by reacting maleic acid with ammonia in a molar ratio of 1:1-1.5 at 120°-150° C. and, if appropriate, converting the acid into salts, are used for removing and preventing incrustations formed by the hardness constituents of water, or as a fertilizer as discussed by the authors.
Abstract: Polyaspartic acid and its salts, which can be obtained by reacting maleic acid and ammonia in a molar ratio of 1:1-1.5 at 120°-150° C. and , if appropriate, converting the acid into salts, are used for removing and preventing incrustations formed by the hardness constituents of water, or as a fertilizer.
125 citations
TL;DR: In this paper, the mechanism of nitric oxide reduction with ammonia to form N/sub 2/O/sub 5, H/sub 3/O and N/ sub 2/N/O was investigated both in the presence and in the absence of O/sub O 2.
Abstract: The mechanism of nitric oxide reduction with ammonia to form N/sub 2/, H/sub 2/O and N/sub 2/O both in the presence and in the absence of O/sub 2/ over the following series of catalysts, unsupported V/sub 2/O/sub 5/, V/sub 2/O/sub 5/ on TiO/sub 2/, V/sub 2/O/sub 5/ on SiO/sub 2//Al/sub 2/O/sub 3/, and V/sub 2/O/sub 5/ on Al/sub 2/O/sub 3/, has been investigated with the aid of labeled O/sub 2/ and labeled NH/sub 3/ at 400/sup 0/C. The behavior of ammonia was studied both in the presence and in the absence of O/sub 2/. The presence of labeled O/sub 2/ gives extra information about the product distribution and the reaction mechanism. Evidence is given that ammonia does not react with O/sub 2/ or O from any source during the reaction, but that nitrogen and nitrous oxide were produced by a reaction involving all three species, NO, NH/sub 3/, and/or O/sub 2/. Nitrous oxide and water are both formed at two different sites of the catalyst. A series of transient tracing studies were performed in a plug-flow reactor using /sup 15/NH/sub 3/ and /sup 18/O/sub 2/. Both /sup 15/NN and /sup 15/NNO were produced on the unsupported V/sub 2/O/sub 5/, V/submore » 2/O/sub 5/ on TiO/sub 2/, V/sub 2/O/sub 5/ on SiO/sub 2//Al/sub 2/O/sub 3/, and V/sub 2/O/sub 5/ on Al/sub 2/O/sub 3/ with very high selectivities. The mechanism of the reaction of NO, NH/sub 3/, and O/sub 2/, proposed in a previous paper, is further evaluated on the basis of this new experimental evidence.« less
104 citations
TL;DR: The effect of aluminum oxide and potassium on the ammonia synthesis over the (111), (100), and (110) faces of iron has been investigated in this article, where a restructuring of the Fe(110) and Fe(100) surfaces, induced by the presence of aluminium oxide and 20 Torr of water vapor, takes place making the restructured surfaces almost as active as the clean Fe(111) plane in the ammonia reaction (20 atm reactant pressure of hydrogen and nitrogen).
97 citations
TL;DR: The effect of relative humidity on the constant for dissociation of ammonium chloride into gaseous HCl and NH 3 has been estimated for different temperatures, using thermodynamic data.
92 citations
TL;DR: In this paper, the equilibrium constant for dissociation of solid ammonium chloride aerosol into gaseous hydrogen chloride and ammonia has been calculated using thermodynamic data, and it is shown that it is thermodynamically possible at temperatures and concentrations observed in the troposphere, but significant gas phase concentrations of hydrogen and ammonia will also be present.
88 citations
Patent•
11 Feb 1987
TL;DR: Chlorine can be efficiently produced at a low temperature and with a high hourly space velocity by oxidizing hydrogen chloride with an oxygen-containing gas in the presence of a catalyst obtained by calcining a compound, which has in turn been obtained by reacting chromium nitrate, chromium chloride, the chromium salt of an organic acid or the like with ammonia.
Abstract: Chlorine can be efficiently produced at a low temperature and with a high hourly space velocity by oxidizing hydrogen chloride with an oxygen-containing gas in the presence of a catalyst obtained by calcining a compound, which has in turn been obtained by reacting chromium nitrate, chromium chloride, the chromium salt of an organic acid or the like with ammonia, or by calcining a mixture of the compound and a silicon compound, preferably, at a temperature lower than 800° C.
TL;DR: In this article, the adsorption of CO and hydrogen was studied over Ru/Al 2 O 3 catalysts derived from RuCl 3 ·3H 2 O reduced at temperatures of up to 1000 K. When the reduction was carried out at 600 K, large amounts of chloride remained on the catalyst surface.
TL;DR: Ion chromatography is used to determine the concentrations of organic (formate, acetate and methanesulphonate) and inorganic (fluoride and ammonium) ions present in Antarctic ice at less than 10−9 g g−1 levels as mentioned in this paper.
TL;DR: In this article, microscopic anhydrous ammonium nitrate particles are levitated in a vacuum in an electric quadrupole trap at 25°C and the measured vapor pressure of the liquid is p = (3.18 ± 0.45) × 10−6 torr.
TL;DR: In this paper, the deactivation effect of ammonia on propane conversion, interpreted as a competitive adsorption on the sites for activation of propane by oxidative dehydrogenation to propylene, was studied on (VO)2P2O7, on vanadium, titanium mixed oxide, vanadium-antimonate with different Sb:V atomic ratios, and on iron, sb:Fe=2.0) catalysts.
TL;DR: Deuterium isotope effects on 15N chemical shifts have been investigated for the ammonium ion, ammonia, and aniline; 1Δ15N(2/1H) equals −293.3, −622.9, and −714.6
Abstract: Deuterium isotope effects on 15N chemical shifts have been investigated for the ammonium ion, ammonia, and aniline; 1Δ15N(2/1H) equals −293.3, −622.9, and −714.6 ppb respectively. Deviations from a...
TL;DR: In this paper, the authors studied the emissions of nitrogen oxides from a flooded rice field after urea had been broadcast into the floodwater and found that the NO fixme x¯¯ flux from the fertilized area was very low (0.2×10-9 g N m-2 s-1) for the first few days after application of urea and was high in the subsequent period when significant nitrite and nitrate were present in the flood water.
Abstract: Emissions of nitric oxide and other odd nitrogen oxides (NO
x
) from a flooded rice field were studied after urea had been broadcast into the floodwater. The NO
x
flux from the fertilized area was very low (0.2×10-9 g N m-2 s-1) for the first few days after application of urea and was high (0.95×10-9 g N m-2 s-1) in the subsequent period when significant nitrite and nitrate were present in the floodwater. At night, little if any NO
x
was exhaled but ambient NO2 was absorbed by the floodwater. An uptake velocity for NO2 of 3×10-4 m s-1 was measured during one night. Maximum NO
x
losses were observed near 1300 h when temperature and solar ultraviolet light were maximum. While the amounts of nitrogen oxides emitted are of little agronomic importance (∼2×10-3 per cent of the fertilizer nitrogen was lost as NO
x
during the 10-day study period), they may well be of significance as a source for some gas reactions in the atmosphere and for the global nitrogen cycle. Of the fertilizer nitrogen applied (as urea) approximately 30% was lost to the atmosphere by NH3 volatilization, 15% by denitrification, presumably as N2, and the remainder, less minor losses of NO and N2O, remained in the plant/soil/water system.
TL;DR: A mechanistic study of the aeration reaction used for removing iron from a reduced ilmenite matrix is described in this paper, where it is shown that the rate of aeration in ammonium chloride solution is largely determined by the speed at which oxygen diffuses to the reduced lmenite surface.
TL;DR: In this paper, the influence of soil water potential and air relative humidity on ammonia volatilization from surface-applied urea was evaluated, and a laboratory study was conducted to evaluate it.
Abstract: Environmental conditions are important in determining the potential for ammonia volatilization from surface-applied urea. This study evaluated the influence of soil water potential and air relative humidity on ammonia volatilized from surface-applied urea. A laboratory study was conducted to evaluat
TL;DR: Most of the urea ingested by a normal infant is not bioavailable, and urinary excretion of di-15N-urea is determined, indicating that nitrogen from this source becomes bioavailable only by release of ammonia by bacterial hydrolysis in the intestines.
TL;DR: When mixed ruminal bacteria were provided with growth rate limiting amounts of mixed carbohydrates, more than 50 mg ammonia/L were required for maximal protein synthesis, consistent with the assumption that active ammonium transport was not readily or maximally induced.
TL;DR: In this article, the preparation of Na-P-O-N glasses was investigated in dry ammonia, forming gas and 90% N2+ 10% CO atmospheres, and significant nitrogen dissolution, up to 13 wt% in a NaPO3 melt, occurred only in ammonia.
Abstract: The preparation of sodium phosphate oxynitride (Na-P-O-N) glasses was investigated in dry ammonia, forming gas and 90% N2+ 10% CO atmospheres. Significant nitrogen dissolution, up to 13 wt% in a NaPO3 melt, occurred only in ammonia. The kinetics of nitrogen dissolution was studied as a function of remelting time (1 to 96 h) and temperature (660° to 760°C). Higher temperature accelerates nitrogen dissolution, but the temperature should not exceed 760°C. Great improvement in chemical durability occurs with nitrogen dissolution in a NaPO3 melt. Other property changes reported include softening temperature, thermal expansion coefficient, refractive index, microhardness, etc. A double chain structure model is proposed for the Na-P-O-N glass.
TL;DR: In hyperammonemia, urea production and N-acetylglutamate levels were decreased by sodium benzoate and Pretreatment of mice with L-carnitine suppressed mortality following ammonium acetate plus sodium Benzoate administration.
TL;DR: The purpose of this review is to examine the factors regulating ammonium production in the kidney and to place these factors in the perspective of acid-base balance.
Abstract: The purpose of this review is to examine the factors regulating ammonium production in the kidney and to place these factors in the perspective of acid-base balance. Renal ammonium production and excretion are required to maintain acid-base balance. However, only a portion of renal ammonium production is specifically stimulated by metabolic acidosis. One should examine urinary ammonium excretion at three levels: distribution of ammonium between blood and urine, augmented glutamine metabolism, and an energy constraint due to ATP balance considerations. With respect to the biochemical regulation of acid-base renal ammonium production, an acute stimulation of alpha-ketoglutarate dehydrogenase by a fall in pH seems to be important but this may not be the entire story. In chronic metabolic acidosis augmented glutamine entry into mitochondria (dog) or increased phosphate-dependent glutaminase activity (rat) become critical to support a high flux rate. Metabolic alterations, which diminish the rate of oxidation of alternate fuels, might also be important. The above principles are discussed in the ketoacidosis of fasting, the clinically important situation of high rates of renal ammonium production.
TL;DR: Calculations show that the nitrogenase-catalysed hydrogen production has more influence on the efficiency of nitrogen fixation than the absence or presence of a hydrogen uptake system.
Abstract: The high energy costs of biological nitrogen fixation are partly caused by hydrogen production during the reduction of dinitrogen to ammonia. Some nitrogen-fixing organisms can recycle the evolved hydrogen via a membrane-bound uptake hydrogenase. The energetic aspects of hydrogen metabolism and nitrogen fixation are discussed.
Studies on both isolated nitrogenase proteins and nitrogen-fixing chemostat cultures show that energy limitation will result in a high hydrogen production by nitrogenase. In plant-Rhizobium symbiosis, the supply of oxygen or photosynthetate is the limiting factor for nitrogen fixation. In both cases, nitrogen fixation is energy-limited, and it is concluded that a large amount of hydrogen is produced during nitrogen fixation in these symbioses.
Hydrogen reoxidation yields less energy than the oxidation of endogenous substrates, and therefore expression of hydrogenase under oxygen-limited conditions is energetically unfavourable. Moreover, hydrogen reoxidation can never completely regain the energy invested during hydrogen production. The controversial reports of the effect of hydrogen reoxidation on the efficiency of nitrogen fixation are being discussed.
The determination of the energy costs of nitrogen fixation (expressed as the amount of ATP needed to fix 1 mol of N2) using chemostat cultures is described. Calculations show that the nitrogenase-catalysed hydrogen production has more influence on the efficiency of nitrogen fixation than the absence or presence of a hydrogen uptake system.
TL;DR: In this paper, an aqueous suspension of hydrous ferric oxide photocatalyses was used for the reduction of molecular nitrogen to ammonia with oxidation of water; the catalytic activity of this material was attributed to the strongly negative flat band potential and chemisorption of N2.
Abstract: An aqueous suspension of hydrous ferric oxide photocatalyses reduction of molecular nitrogen to ammonia with oxidation of water; the catalytic activity of this material is attributed to the strongly negative flat band potential and chemisorption of N2.
TL;DR: The permeability properties of ammonia and methylamine are very different; this poses problems in the interpretation of experiments where14C-methylamine is used as an ammonia analogue, suggesting that net amine fluxes are rate limited by proton fluxes to an upper limit of about 700 nmol m−2 sec−1.
Abstract: Permeabilities of ammonia (NH3), methylamine (CH3NH2) and ethylamine (CH3CH2NH2) in the cyanobacterium (cyanophyte)Synechococcus R-2 (Anacystis nidulans) have been measured. Based on net uptake rates of DCMU (dichlorophenyldimethylurea) treated cells, the permeability of ammonia was 6.44±1.22 μm sec−1 (n=13). The permeabilities of methylamine and ethylamine, based on steady-state14C labeling were more than ten times that of ammonia (Pmethylamine=84.6±9.47 μm sec−1 (76),Pethylamine=109±11 μm sec−1 (55)). The apparent permeabilities based on net uptake rates of methylamine and ethylamine uptake were significantly lower, but this effect was partially reversible by ammonia, suggesting that net amine fluxes are rate limited by proton fluxes to an upper limit of about 700 nmol m−2 sec−1. Increasing concentrations of amines in alkaline conditions partially dissipated the pH gradient across the cell membrane, and this property could be used to calculate the relative permeabilities of different amines. The ratio of ethylamine to methylamine permeabilities was not significantly different from that calculated from the direct measurements of permeabilities; ammonia was much less effective in dissipating the pH gradient across the cell membrane than methylamine or ethylamine. An apparent permeability of ammonia of 5.7±0.9 μm sec−1 could be calculated from the permeability ratio of ammonia to methylamine and the experimentally measured permeability of methylamine. The permeability properties of ammonia and methylamine are very different; this poses problems in the interpretation of experiments where14C-methylamine is used as an ammonia analogue.
TL;DR: A quantitative model of ammonia volatilization from the calcareous soil uppermost 1 cm layer was developed and tested in this article, which accounts for the following processes: ammonium-ammonia equilibration in the soil solution, cation exchange between calcium and ammonium which results in ammonium distribution between soil liquid and solid phases, nitrification of dissolved ammonium.
Abstract: A quantitative model of ammonia volatilization from the calcareous soil uppermost 1-cm layer was developed and tested. The model accounts for the following processes: ammonium-ammonia equilibration in the soil solution, cation exchange between calcium and ammonium which results in ammonium distribution between soil liquid and solid phases, nitrification of dissolved ammonium, distribution of ammonia between liquid and gaseous phases and diffusion of gaseous ammonia in the soil air.