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  • Polymer and Materials Science  (8)
  • micrometeorology  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of atmospheric chemistry 6 (1988), S. 133-147 
    ISSN: 1573-0662
    Keywords: Ammonia loss ; energy balance ; micrometeorology ; water-air transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Vertical flux densities of ammonia, water vapour and sensible heat were measured over a flooded rice field in China following the application of ammonium bicarbonate fertilizer. Aqueous and gaseous phase transfer resistances for ammonia were deduced from these measurements. The aqueous phase resistance was maximal in the morning and least in the afternoon. Stable stratification of the floodwater immediately adjacent to the air-water interface was observed during the morning when evaporation rates were low, and may be responsible for inhibiting the transfer of ammonia to the atmosphere.
    Type of Medium: Electronic Resource
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  • 2
    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
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 16 (1988), S. 97-107 
    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
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 42 (1991), S. 637-642 
    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
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 718-723 
    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
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  • 6
    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
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 13 (1979), S. 337-338 
    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
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  • 8
    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.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 867-878 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Mechanisms of corrosion at the areas of contact between screw heads and plate holes were investigated using electrochemical potential recording techniques. Static crevice corrosion was studied with plates and screws in isotonic and hypertonic saline solutions (0.9 to 7.2% NaCl). Fretting corrosion was studied in vitro with plates screwed to tubular bone analogs which were subjected to cyclic axial loads, and was studied in vivo with plates screwed on the tibia of sheep. Static tests showed that crevice corrosion does not occur in isotonic saline for periods up to one year, but can occur in hypertonic saline solutions. Dynamic loading tests demonstrated immediate potential changes which were related to the magnitude of the applied load, indicating fretting corrosion due to motion between screw head and plate, both in vitro and in vivo. A mechanism for screw-plate relative motion is proposed. It is hypothesized that corrosion seen in clinically retrieved implants due to fretting corrosion which predisposes the contact area to crevice corrosion attack.
    Additional Material: 9 Ill.
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  • 10
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Titanium (Ti) surface roughness affects proliferation, differentiation, and matrix production of MG-63 osteoblast-like cells. Cytokines and growth factors produced in the milieu surrounding an implant may also be influenced by its surface, thereby modulating the healing process. This study examined the effect of surface roughness on the production of two factors known to have potent effects on bone, prostaglandin E2 (PGE2) and transforming growth factor β1 (TGF-β1). MG-63 cells were cultured on Ti disks of varying roughness. The surfaces were ranked from smoothest to roughest: electropolished (EP), pretreated with hydrofluoric acid-nitric acid (PT), fine sand-blasted, etched with HCl and H2SO4, and washed (EA), coarse sand-blasted, etched with HCl and H2SO4, and washed (CA), and Ti plasma-sprayed (TPS). Cells were cultured in 24-well polystyrene (plastic) dishes as controls and to determine when confluence was achieved. Media were collected and cell number determined 24 h postconfluence. PGE2 and TGF-β1 levels in the conditioned media were determined using commercial radioimmunoassay and enzyme-linked immunosorbent assay kits, respectively. There was an inverse relationship between cell number and Ti surface roughness. Total PGE2 content in the media of cultures grown on the three roughest surfaces (FA, CA, and TPS) was significantly increased 1.5-4.0 times over that found in media of cultures grown on plastic or smooth surfaces. When PGE2 production was expressed per cell number, CA and TPS cultures exhibited six- to eightfold increases compared to cultures on plastic and smooth surfaces. There was a direct relationship between TGF-β1 production and surface roughness, both in terms of total TGF-β1 per culture and when normalized for cell number. TGF-β1 production on rough surfaces (CA and TPS) was three to five times higher than on plastic. These studies indicate that substrate surface roughness affects cytokine and growth factor production by MG-63 cells, suggesting that surface roughness may modulate the activity of cells interacting with an implant, and thereby affect tissue healing and implant success. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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