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  • Polymer and Materials Science  (8)
  • denitrification  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Control of gaseous nitrogen losses from urea applied to flooded rice soils (1988)
    Springer
    Nutrient cycling in agroecosystems 18 (1988), S. 31-47 
    Details
    ISSN: 1573-0867
    Keywords: ammonia loss ; denitrification ; Oryza sativa L. ; algicides ; flooded soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This paper reports field experiments designed to determine whether the two main processes responsible for nitrogen (N) loss from flooded rice (ammonia volatilization and denitrification) are independent or interdependent, and glasshouse studies which investigated the effect of soil characteristics on gaseous nitrogen loss. In the first field experiment ammonia (NH3) loss from the floodwater was controlled using algicides, biocides, frequent pH adjustment, shade or cetyl alcohol, and the effect of these treatments on total N loss and denitrification was determined. Most treatments reduced NH3 loss through their effects on algal growth and floodwater pH. Total gaseous N loss (54% to 35%) and NH3 loss (20% to 1.2%) were affected similarly by individual treatments, indicating that the amount lost by denitrification was not substantially changed by any of the treatments. In a subsequent field experiment NH3 and total N loss were again affected similarly by the treatments, but denitrification losses were very low. In control treatments with different rates of urea application, NH3 and total N loss were each a constant proportion of the urea applied (NH3 loss was 17% and total N loss was 24%). These results indicate that techniques which reduce NH3 loss can be expected to reduce total gaseous N loss. The glasshouse experiment showed that gaseous N losses could be reduced by draining off the floodwater, and incorporating the urea into the 0–0.05 m soil layer before reflooding. Even with this method, losses varied widely (6–27%); losses were least from a cracking clay and greatest from a coarse sand which allowed the greatest mobility of the applied N. Incorporation of applied urea can therefore be expected to prevent losses more successfully from clay soils with high ammonium retention capacity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01064176
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  • 2
    Electronic Resource
    Electronic Resource
    Emission of nitrogen oxides (NO x ) from a flooded soil fertilized with urea: Relation to other nitrogen loss processes (1987)
    Springer
    Journal of atmospheric chemistry 5 (1987), S. 343-365 
    Details
    ISSN: 1573-0662
    Keywords: Nitrogen oxides ; nitric oxide ; biological production ; surface fluxes ; emission ; uptake ; rice paddy ; nitrogen fertilizer ; urea ; ammonia ; nitrification ; denitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00114111
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  • 3
    Electronic Resource
    Electronic Resource
    Loss of ammonia after application of urea at different times to dry-seeded, irrigated rice (1988)
    Springer
    Nutrient cycling in agroecosystems 16 (1988), S. 47-57 
    Details
    ISSN: 1573-0867
    Keywords: direct-seeding ; nitrogen fertilizer ; micrometeorology ; gas exchange ; irrigation ; volatilization ; denitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ammonia loss from urea applied to dry-seeded rice, determined using a micrometeorological technique, varied considerably depending on the time of application. Ammonia volatilization was negligible, before and after flooding, when urea was applied to the dry soil surface two days before permanent flood. Before flooding, the urea prills remained undissolved and urea hydrolysis could not proceed. Thus there was no source of fertilizerderived ammonia for volatilization to occur. Upon flooding, the urea prills were washed into cracks in the soil which subsequently closed. Therefore the movement of soluble nitrogen into the floodwater was prevented, and again there was no ammonia source for the volatilization process. When urea was broadcast into the floodwater a few days after permanent flood, ammonia losses were high and varied from 11–21% of the nitrogen applied. These losses were associated with high floodwater pHs and high wind speeds near the water surface. However, when urea was applied into the floodwater at panicle initiation, ammonia losses were low (3–8% of the applied nitrogen). At this stage of growth the plant canopy shaded the floodwater, inhibiting algal photosynthesis and consequent pH elevation, thus resulting in low ammonia gas concentrations at the floodwater surface. In addition, the plant canopy restricted air movement at the water surface, thereby reducing ammonia transport away from the air-water interface. These findings provide basic information required for improving current fertilizer management practices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01053314
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of water depth on ammonia loss from lowland rice (1988)
    Springer
    Nutrient cycling in agroecosystems 16 (1988), S. 97-107 
    Details
    ISSN: 1573-0867
    Keywords: nitrogen loss ; volatilization ; micrometeorology ; denitrification ; gas exchange ; lowland rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This paper reports a study on the effects of water depth in modifying rates of ammonia emission and total nitrogen loss from flooded rice fields after fertilization with urea. Ammonia loss was determined by the mass balance micrometeorological method and total nitrogen loss by15N balance. Initially ammonia was lost at a faster rate from the shallow (0.05 m) than from the deep (0.14 m) floodwater; this was due to higher ammoniacal nitrogen concentrations and higher temperatures in the shallow water. Emission rates were more nearly comparable later in the experiment, but overall, 26% of the applied nitrogen was lost as ammonia from the shallow pond and only 18% from the deep pond. Even though changes in water depth markedly affected ammonia emission rates and the amounts of ammonia lost, they did not significantly affect total nitrogen loss. The results suggest that management practices based only on changes in water depth may not result in increased efficiency of fertilizer nitrogen for flooded rice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01049767
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  • 5
    Electronic Resource
    Electronic Resource
    Processes of nitrogen loss from fertilizers applied to flooded rice fields on a calcareous soil in north-central China (1988)
    Springer
    Nutrient cycling in agroecosystems 18 (1988), S. 101-115 
    Details
    ISSN: 1573-0867
    Keywords: Ammonia loss ; denitrification ; nitrogen balance ; algal growth ; transfer processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Losses of nitrogen were investigated after applications of ammonium bicarbonate and urea to flooded rice at transplanting. Ammonia (NH3) volatilization was determined by direct micrometeorological methods, and total loss of fertilizer nitrogen (N) was measured by15N balance. All the loss appeared to be in gaseous forms, since there was no evidence of leaching and runoff was prevented. The difference between N loss and NH3 loss was thus assumed to be denitrification loss. Both NH3 volatilization and denitrification losses were large, being 39% and 33%, respectively, of the ammonium bicarbonate N, and 30% and 33%, respectively, of the urea N applied by farmers' methods. Ammonia fluxes from the field fertilized with ammonium bicarbonate were very high for two days, and then declined rapidly as the NH3 source in the floodwater diminished. Moderate fluxes from the field fertilized with urea continued over 6 days, but calculations showed that NH3 transfer from floodwater to atmosphere was retarded during the middle period of the experiment, particularly on day 2 when a thick algal scum appeared on the water surface. The results indicate that this algal mass obstructed the transport of NH3 across the water-air interface until the scum was dispersed by wind action. Nevertheless, the prolonged NH3 losses on the urea treatment were due primarily to high floodwater pH values promoted by the strong algal growth during the daylight hours. Nitrogen-15 balance studies showed that incorporation of fertilizer into drained soil substantially increased recoveries of fertilizer N in rice plants and soil compared with incorporation of fertilizer in the presence of standing floodwater. Ammonia loss measurements on these treatments when urea was applied suggested that the improvement in fertilizer N efficiency was due mainly to reductions in NH3 loss.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01049507
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  • 6
    Electronic Resource
    Electronic Resource
    Die Langzeit-Korrosionsgeschwindigkeit des passiven Eisens in anaeroben alkalischen LösungenHerrn Prof. Dr. rer. nat. Wilhelm Schwenk zum 60. Geburtstag gewidmet (1991)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 42 (1991), S. 637-642 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: The long-term corrosion rate of passive iron in anaerobic alcaline solutionsGas generation is an important issue in safety assessments of low and intermediate level radioactive repositories. In this connection the hydrogen production from corrosion of passive iron in saturated calcium hydroxide, in dilute alkali hydroxide and cement porewater solutions has been determined. The measurements were performed manometrically using fusion sealed glass cells, the measurement periods being between 275 and 560 days.In 0.1 M and 0.04 M alkali hydroxide solutions the initial hydrogen generation rate was 12 mmol/m2yr corresponding to a linear corrosion rate of 64 nm/yr. The reaction rate decreases with time. The smallest value obtained after 330 days is 0.3 mmol/m2yr corresponding to 1.5 nm/yr.The influence on iron of the saturated calcium hydroxide solution and the calcic porewater solutions differs from that of the alkali hydroxide solutions. At pH 12.5 the hydrogen generation rate remains practically constant up to breaking off the experiment, the value being about 1 mmol/m2yr corresponding to 5 nm/yr.
    Notes: Im Zusammenhang mit der Gasentwicklung in einem Endlager für schwach- und mittelradioaktive Abfälle ist die Wasserstoffentwicklung am passiven Eisen in verdünnten Alkalihydroxidlösungen, in gesättigter Calciumhydroxidlösung und in synthetischen Zementporenwässern bestimmt worden. Die Messung erfolgte manometrisch in zugeschmolzenen Glaszellen; die Meßzeiten lagen zwischen 275 und 560 Tagen.In 0,1 und 0,04 M Alkalihydroxidlösungen beträgt die anfängliche Wasserstoffbildungsrate 12 mmol/m2a (entsprechend einem Materialabtrag von 64 nm/a). Korrosionsgeschwindigkeiten in diesem Bereich wurden von anderen Autoren auch elektrochemisch gemessen. Die Reaktionsgeschwindigkeit nimmt mit der Zeit ab. Der kleinste gemessene Wert liegt nach 330 Tagen bei 0,3 mmol/m2a (1,5 nm/a).Gesättigte Calciumhydroxidlösung und die calciumhaltigen Zementporenwässer unterscheiden sich in ihrer Einwirkung auf das Eisen von den Alkalihydroxidlösungen. Bei pH 12,5 ist die Wasserstoffbildungsrate mit etwa 1 mmol/m2a (5 nm/a) bis zum Versuchsabbruch praktisch konstant.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19910421205
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  • 7
    Electronic Resource
    Electronic Resource
    Microscopic and macroscopic investigation of electrical contacts to n-ZnSe (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 718-723 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The formation of Schottky barriers at the Sb/n-ZnSe interface has been investigated for a selected number of chemically etched n-ZnSe surfaces. Microscopic properties of the surfaces and interfaces have been observed with SEM, XPS, AES and SIMS, while the conventional I-V technique has been used to determine the macroscopic electrical properties. Both polycrystalline ZnSe wafers and molecular beam epitaxy-grown layers of n-ZnSe on n+-GaAs substrates were used for this investigation. Stoichiometric variations resulting from wet chemical etching of n-ZnSe were investigated using XPS, AES and SIMS techniques. The electrical properties of Sb contacts formed by vacuum evaporation on the etched surfaces were also determined. Possible intermixing at the Sb/n-ZnSe interface was studied using the SIMS imaging technique. The correlation between macroscopic electrical properties and microscopic interactions at the interface will be presented in this paper.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740211007
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  • 8
    Electronic Resource
    Electronic Resource
    Combination of ion beam techniques, AES and SIMS for the analysis of samples exposed in the plasma boundary of the JET tokamakPaper presented at the IB-SA88 Meeting, University of Paris VII (Jussieu), 7-8 December 1988. (1989)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 14 (1989), S. 543-551 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A system combining ion beam and surface-specific techniques for the analysis of probes exposed in the edge region of the plasma produced by the Joint European Torus (JET) is described. Among examples of the use of the system are the demonstration that 10-40% of the ionic charge flux in the boundary can be due to impurities, erosion and redeposition phenomena can be observed with small probes placed in the plasma boundary, and most of the oxygen observed on collector probes is an artefact resulting from exposure to air.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740140909
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  • 9
    Electronic Resource
    Electronic Resource
    Electrochemical dissolution of metallic implants prior to histologic sectioning (1979)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 13 (1979), S. 337-338 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820130212
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of titanium surface roughness on chondrocyte proliferation, matrix production, and differentiation depends on the state of cell maturation (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 30 (1996), S. 145-155 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Although it is well accepted that implant success is dependent on various surface properties, little is known about the effect of surface roughness on cell metabolism or differentiation, or whether the effects vary with the maturational state of the cells interacting with the implant. In the current study, we examined the effect of titanium (Ti) surface roughness on chondrocyte proliferation, differentiation, and matrix synthesis using cells derived from known stages of endochondral development. Chondrocytes derived from the resting zone (RCs) and growth zone (GCs) of rat costochondral cartilage were cultured on Ti disks that were prepared as follows: HF-HNO3-treated and washed (PT); PT-treated and electropolished (EP); fine sand-blasted, HCl-H2SO4-etched, and washed (FA); coarse sand-blasted, HCl-H2SO4-etched, and washed (CA); or Ti plasma-sprayed (TPS). Based on surface analysis, the Ti surfaces were ranked from smoothest to roughest: EP, PT, FA, CA, and TPS. Cell proliferation was assessed by cell number and [3H]-thymidine incorporation, and RNA synthesis was assessed by [3H]-uridine incorporation. Differentiation was determined by alkaline phosphatase specific activity (AL-Pase). Matrix production was measured by [3H]-proline incorporation into collagenase-digestible (CDP) and noncollagenase-digestible (NCP) protein and by [35S]-sulfate incorporation into proteoglycan. GCs required two trypsinizations for complete removal from the culture disks; the number of cells released by the first trypsinization was generally decreased with increasing surface roughness while that released by the second trypsinization was increased. In RC cultures, cell number was similarly decreased on the rougher surfaces; only minimal numbers of RCs were released by a second trypsinization. [3H]-thymidine incorporation by RCs decreased with increasing surface roughness while that by GCs was increased. [3H]-Uridine incorporation by both GCs and RCs was greater on rough surfaces. Conversely, ALPase in the cell layer and isolated cells of both cell types was significantly decreased. GC CDP and NCP production was significantly decreased on rough surfaces while CDP production by RC cells was significantly decreased on smooth surfaces. [35S]-sulfate incorporation by RCs and GCs was decreased on all surfaces compared to tissue culture plastic. The results of this study indicate that surface roughness affects chondrocyte proliferation, differentiation, and matrix synthesis, and that this regulation is cell maturation dependent. © 1996 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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