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  • Polymer and Materials Science  (8)
  • micrometeorology  (3)
  • 23.20.Ck  (2)
  • Ammonia loss  (2)
Materialart
Erscheinungszeitraum
Schlagwörter
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of atmospheric chemistry 6 (1988), S. 133-147 
    ISSN: 1573-0662
    Schlagwort(e): Ammonia loss ; energy balance ; micrometeorology ; water-air transfer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: 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.
    Materialart: Digitale Medien
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  • 2
    ISSN: 1434-601X
    Schlagwort(e): 21.10 R ; 23.20.Ck ; 23.20.−g ; 27.50.+e
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The band structure of83Zr has been investigated using the Daresbury recoil separator and TESSA array with 20 Compton suppressed Ge detectors and the reaction28Si (58Ni, 2pn) at 195 MeV. DCO ratios have been used to make many new spin assignments. The three known rotational bands have been extended up to the onset of the five quasiparticle bands. On the basis of the 21/2+, 23/2+ and 25/2+ yrast and yrare states, a (3qp) structure similar to those found in the isotones79Kr and81Sr has been identified. Additional bands have been observed for the first time, one of which appears to be non-collective. Strong mixing between the various negative parity bands is evident. A multiplet of states feeding the three quasiparticle region of the negative parity yrast band has been found. The data is interpreted in the framework of the cranked shell model.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1434-601X
    Schlagwort(e): 21.10.Hw ; 23.20.Lv ; 23.20.Ck
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract High-spin states up to I=22ħ have been observed for the first time in the odd-odd nucleus142Eu above the 8− β+ -decaying isomer. A new isomer of mean life τm=9.0± 0.6 ns and Jπ=8+ has been identified. The low energy part of the level scheme is interpreted in terms of single-particle excitations in the 2d5/2 and h11/2 orbitals and of the N=80 core excitations.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1573-0867
    Schlagwort(e): direct-seeding ; nitrogen fertilizer ; micrometeorology ; gas exchange ; irrigation ; volatilization ; denitrification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: 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.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 16 (1988), S. 97-107 
    ISSN: 1573-0867
    Schlagwort(e): nitrogen loss ; volatilization ; micrometeorology ; denitrification ; gas exchange ; lowland rice
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: 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.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1573-0867
    Schlagwort(e): Ammonia loss ; denitrification ; nitrogen balance ; algal growth ; transfer processes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: 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.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 13 (1979), S. 337-338 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 32 (1996), S. 55-63 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: 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.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 9
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: 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.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 867-878 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: 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.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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