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  • Ozone  (3)
  • Polymer and Materials Science  (2)
  • 1
    Digitale Medien
    Digitale Medien
    Ozone-induced microscopical changes and quantitative carbohydrate contents of hybrid poplar (Populus × euramericana) (1994)
    Springer
    Trees 8 (1994), S. 183-190 
    Details
    ISSN: 1432-2285
    Schlagwort(e): Ozone ; Carbohydrates ; Microscopy ; Leaf ; Populus × euramericana
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Cuttings of hybrid poplar (Populus × euramericana var. “Dorskamp”) were exposed to ozone (80 μg/m3 from 2100 hours to 0700 hours, 180 μg/m3 from 0700 hours to 2100 hours) for 3 months. Ozone reduced the starch content in leaves and stem bark, whereas starch granules accumulated in bundle sheath cells along small leaf veins. At the same time, sucrose and inositol content increased in the leaves. Mesophyll cells in the vicinity of the stomata were injured first, and droplet-like material appeared on their walls. In the sieve plates of fumigated trees, the pores showed a higher degree of narrowing than those of the control treatment. Cell collapse in the leaves was accompanied by water loss and an increase in air space. In the stems, the ozone treatment led to a reduced radial width, particularly in the xylem tissue. These results are discussed in relation to reduced or inhibited phloem loading and ozone-induced drought stress. The plants injured by ozone showed quite distinct patterns of metabolite responses as well as enzyme activities (PEP- and RubP-carboxylase) in the leaves from the top to the bottom. There were also remarkable differences in the reaction of sucrose and inositol between leaves and stem bark. Future research should therefore increasingly follow a whole-plant approach for a better understanding of complex plant reactions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00196845
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  • 2
    Digitale Medien
    Digitale Medien
    Impairment of gas exchange and structure in birch leaves (Betula pendula) caused by low ozone concentrations (1991)
    Springer
    Trees 5 (1991), S. 5-13 
    Details
    ISSN: 1432-2285
    Schlagwort(e): Ozone ; Betula pendula ; Leaf gas exchange ; Leaf structure ; Senescence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Injury caused by low O3 concentrations (0, 0.05, 0.075, 0.1 μl 1-1) was analyzed in the epidermis and mesophyll of fully developed birch leaves by gas exchange experiments and low-temperature SEM: (I) after leaf formation in O3-free and ozonated air, and (II) after transferring control plants into ozonated air. In control leaves, autumnal senescence also was studied in O3-free air (III). As O3 concentration increased, leaves of (I) stayed reduced in size, but showed increased specific weight and stomatal density. The declining photosynthetic capacity, quantum yield and carboxylation efficiency lowered the light saturation of CO2 uptake and the water-use efficiency (WUE). Carbon gain was less limited by the reduced stomatal conductance than by the declining ability of CO2 fixation in the mesophyll. The changes in gas exchange were related to the O3 dose and were mediated by narrowed stomatal pores (overriding the increase in stomatal density) and by progressive collapse of mesophyll cells. The air space in the mesophyll increased, preceded by exudate formation on cell walls. Ozonated leaves, which had developed in O3-free air (II), displayed a similar but more rapid decline than the leaves from (I). In senescent leaves (III), CO2 uptake showed a similar decrease as in leaves with O3 injury but no changes in mesophyll structure and WUE. The nitrogen concentration declined only in senescent leaves in parallel with the rate of CO2 uptake. A thorough understanding of O3 injury and natural senescence requires combined structural and functional analyses of leaves.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00225329
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  • 3
    Digitale Medien
    Digitale Medien
    Differentiation and structural decline in the leaves and bark of birch (Betula pendula) under low ozone concentrations (1993)
    Springer
    Trees 7 (1993), S. 104-114 
    Details
    ISSN: 1432-2285
    Schlagwort(e): Ozone ; Betula pendula ; Leaf differentiation ; Leaf and bark decline ; Senescence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Leaf and bark structure of a birch clone (Betula pendula Roth) continuously exposed to charcoal-filtered air or charcoal-filtered air plus ozone (0.05, 0.075, 0.1 μl 1-1) was investigated throughout one growing season. Increasing ozone dose influenced leaf differentiation by reducing leaf area and increasing inner leaf air space, density of cells developing into stomata, scales and hairs. When approximately the same ozone dose had been reached, macroscopical and microscopical symptoms appeared irrespective of the ozone concentration used during treatment. Structural decline began in mesophyll cells around stomatal cavities (droplet-like exudates on the cell walls), continued with disintegration of the cytoplasma and ended in cell collapse. Epidermal cells showed shrinkage of the mucilaginous layer (related to water loss). Their collapse marked the final stage of leaf decline. When subsidiary cells collapsed, guard cells passively opened for a transitory period before collapsing and closing. With increasing ozone dose starch remained accumulated along the small leaf veins and in guard cells. IIK-positive grains were formed in the epidermal cells. This contrasted with the senescent leaves, where starch was entirely retranslocated. Injury symptoms in stem and petiole proceeded from the epidermis to the cambium. Reduced tissue area indicated reduced cambial activity. In plants grown in filtered air and transferred into ozone on 20 August, injury symptoms developed faster than in leaves formed in the presence of ozone. Results are discussed with regard to O3-caused acclimation and injury mechanisms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00225477
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  • 4
    Digitale Medien
    Digitale Medien
    Über Eigenschaften und Reaktionen von Chromsulfiden als Produkte der Hochtemperaturkorrosion von NiCr20TiAl (Nimonic 80A) (1971)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 22 (1971), S. 148-157 
    Details
    ISSN: 0947-5117
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Properties and reactions of chromium sulphides as products of the high-temperature corrosion of NiCr2OTiAl (Nimonic 80 A)The sulphide phase on corroded blades of gas turbines (for natural gas and blast furnace gas) has been identified, by means of electron micro-analysis and X-ray diffraction, as CrNi sulphide with variable Ni and Ti content. This sulphide is of the same type as Cr3So4, and the Structure is not affected by the Ti content. At high temperatures, the CrNi(Ti) sulphides undergo transformations in the solide state, giving rise to Cr and Ni sulphides with higher sulphur contents. It has been possible to prove experimentally that the presence of small discs or bars of crNi sulphide amid the NiS was due to the crystallisation of Ni Cr2So4 from a eutectic Ni3S2Ni melt. At temperatures in excess of 750°C, monoclinic Ni0.5Cr2.5S4 is transformed into a hexagonal modification, just as Ni0.5Ti0.3Cr2.2S4.
    Notizen: An korrodierten Gasturbinenschaufeln (aus Erdgas- und Gichtgasturbinen) wurde die Sulfidphase mittels Elektronenstrahl-Mikroanalyse und Röntgenbeugung als CrNi-Sulfid mit variablem Ni- und Ti-Gehalt identifiziert. Dies Sulfid ist isotop mit Cr3So4; der Ti-Gehalt verändert die Struktur nicht. Die CrNi(Ti)-Sulfide erleiden bei hohen Temperaturen Umwandlungen im festen Zustand, wobei schwefelreichere Cr-Sulfide und Ni-Sulfide entstehen. Plättchen- und stäbchenförmige CrNi-Sulfide inmitten von NiS sind - wie experimentell nachgewiesen werden konnte - auf Kristallisation von NiCr2S4 aus einer eutektischen Ni3S2-Ni-Schmelze zurückzuführen. Bei Temperaturen 〉 750°C wandelt sich monoklines Ni0,5Cr2,5S4 um in ene hexagonale Modifikation, ebenso wie Ni0,5Ti0,3Cr2,2S4.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/maco.19710220207
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  • 5
    Digitale Medien
    Digitale Medien
    Loch- und Spaltkorrosion von Chrom- und Chromnickelstählen in chloridhaltigen Lösungen (1980)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 31 (1980), S. 387-393 
    Details
    ISSN: 0947-5117
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Pitting and crevice corrosion of stainless steels in chloride solutionsIn practice stainless steels in chloride containing waters are found to be susceptible to crevice corrosion and pitting. Corrosion tests were carried out on AISI 304 L stainless using a simulated crevice and the compositions of the electrolyte in the crevice determined. Long term potentiostatic tests were used to determine the critical potentials for crevice corrosion (US), for various steels in sodium chloride solutions at different concentrations and temperatures. The steels studied were 22 CrMo V 121, X 22 CrNi 17 and AISI 304 L.Like the critical pitting potential (UL), US was found to have a strong dependence on the chloride content of the external solution. At higher concentrations the two potentials were similar. At lower concentrations the US was lower than UL. The knowledge of these critical potentials together with well known rest potentials for a steel in an electrolyte of known concentration, allows conclusions to be drawn about its susceptibility to pitting and crevice corrosion.The method is suitable also for other passive metals.
    Notizen: In der Praxis entstehen bei rostfreien Stählen, die in chloridhaltigem Wasser eingesetzt werden, immer wieder Schäden durch Spaltkorrosion. Es wurden Korrosionsversuche in einem Spaltmodell mit dem Stahl AISI 304 L angestellt und die Zusammensetzung des Spaltelektrolyten bestimmt. Anhand potentiostatischer Langzeitversuche in Natriumchloridlösungen verschiedener Konzentration und Temperatur wurden in einer Spaltkorrosionszelle die kritischen Potentiale für Spaltkorrosion (US) folgender Stähle bestimmt: 22 CrMo V 121, X 22 CrNi 17 und AISI 304 L.Analog zu den kritischen Potentialen für Lochkorrosion (UL) zeigte US eine starke Abhängigkeit vom Chloridgehalt der Außenlösung. Bei hohen Konzentrationen lagen beide Potentiale nahe beisammen, bei tiefen Chloridkonzentrationen war US tiefer als UL. Die Kenntnis der kritischen Potentiale erlaubt, bei bekanntem Ruhepotential UR eines Stahles in einem Elektrolyten bekannter Chloridkonzentration Rückschlüsse auf die Gefährdung durch Loch- und Spaltkorrosion zu ziehen.Die Methode eignet sich auch für andere passivierbare Metalle.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/maco.19800310509
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