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  • 1
    Electronic Resource
    Electronic Resource
    Gas exchange and SO2 fumigation studies with irrigated and unirrigated field grown Diplacus aurantiacus and Heteromeles arbutifolia (1988)
    Springer
    Oecologia 75 (1988), S. 386-393 
    Details
    ISSN: 1432-1939
    Keywords: Diplacus aurantiacus (Curtis) Jeps. ; Heteromeles arbutifolia (Ait.) Roem. ; Gas exchange ; Irrigation ; Sulphur dioxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Experiments were performed on an evergreen (Heteromeles arbutifolia) and a drought deciduous shrub (Diplacus aurantiacus) to determine, 1) whether approaches for evaluating SO2 absorption by leaves in laboratory studies could be extended to field studies, 2) the effects of irrigation on metabolism and SO2 responses of the study species during a season when water was limiting, 3) to interpret SO2 responses on the basis of SO2 flux rates. Laboratory-developed approaches for evaluating SO2 absorption by leaves were found to be suitable for use with field plants, despite field plants having lower gas exchange rates. Supplementing water during times of deficit did not override all the biological and environmental factors that limited photosynthesis (A). Irrigation increased leaf longevity of D. aurantiacus, and stomatal conductance to water vapour (g); g was also shown to increase with H. arbutifolia on irrigation. Irrigation profoundly influenced plant response to SO2. Unwatered D. aurantiacus had only a small g and therefore a reduced capacity to absorb SO2 and respond to SO2; which resulted in apparent SO2 avoidance. Water availability and SO2 both affect g and therefore, SO2 flux rates into the mesophyll. Different ambient SO2 concentrations of 8.3 and 26.2 μmol m-3 (0.2 and 0.6 ppm) were both found to result in similar SO2 flux rates into the leaf, due to variations in g in response to water availability. Changes in g did not always result in changes in A, implying that carbon fixation may be little affected by some SO2 exposures, although still potentially affecting such processes as maintenance of leaf water potential, transpirational cooling and nutrient uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00376941
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Interactions of SO2 with other environmental stresses in influencing leaf gas exchange (1990)
    Springer
    Oecologia 84 (1990), S. 500-505 
    Details
    ISSN: 1432-1939
    Keywords: Air pollution ; Diplacus aurantiacus (Curtis) Jeps ; Heteromeles arbutifolia (Ait.) Roem ; Environmental stresses ; Gas exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Leaves of two field growing co-occuring perennial shrubs (drought-deciduous Diplacus aurantiacus and the evergreen Heteromeles arbutifolia) from the Californian chaparral were exposed to small doses of SO2. During this exposure the leaf environment was manipulated to determine how the presence of SO2 alters the response of gas exchange to other environmental stresses. The data show that no direct changes in stomatal conductance (g) or net assimilation rate (A) could be attributed to short-term (7 h) SO2 (4.2 μmol m-3, 0.1 μl l-1) exposure. D. aurantiacus leaves possessed features which demonstrate that they were sensitive to changes in environment e.g. light flux and atmospheric relative humidity. The interspecific differences in stomatal sensitivity to water vapour were extremely important, as relative humidity is a major factor influencing carbon fixation and the rate of pollutant absorption. Conditions of high relative humidity and high xylem water potentials are suggested to pre-dispose leaves of D. aurantiacus to greater pollutant doses than the more stomatally-conservative evergreen, H. arbutifolia. In the presence of SO2 there was some indication of increased g for both D. aurantiacus and H. arbutifolia as ΔW became smaller. This SO2-effect was only obvious as increasing atmospheric humidity induced further stomatal opening. The important consequences of an SO2 enhanced g, were a reduction in WUE, which may cause earlier leaf abscission and a concomitant decline in productivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328166
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  • 3
    Electronic Resource
    Electronic Resource
    Kinked cracks in anisotropic elastic materials (1998)
    Springer
    International journal of fracture 93 (1998), S. 387-407 
    Details
    ISSN: 1573-2673
    Keywords: stress singularities ; general elastic anisotropy ; kinked cracks ; dislocation models ; singular integral equations ; reciprocal theorem ; stress intensity factors ; generalised stress intensity factors.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The problem of a kinked crack is analysed for the most general case of elastic anisotropy. The kinked crack is modelled by means of continuous distributions of dislocations which are assumed to be singular both at the crack tips and at the kink vertex. The resulting system of singular integral equations is solved numerically using Chebyshev polynomials and the reciprocal theorem. The stress intensity factors for modes I, II and III and the generalised stress intensity factor at the vertex are obtained directly from the dislocation densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007475627402
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of sharp angular notches in anisotropic materials (1998)
    Springer
    International journal of fracture 93 (1998), S. 373-386 
    Details
    ISSN: 1573-2673
    Keywords: stress singularities ; general elastic anisotropy ; kinked cracks ; angular notches ; dislocation models ; reciprocal theorem ; generalised stress intensity factors.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The singular stresses at the tip of a sharp angular notch are analysed for the most general case of elastic anisotropy. The problem is stated in relation with the kinked crack and is modelled by means of continuous distributions of dislocations which are assumed to be singular at the notch vertex, the kind of the main singularity λ being unknown and weaker than at the crack tip. The Mellin transform is applied to obtain a system of simultaneous functional equations that enables one to find the parameter λ. The reciprocal theorem is used to compute the generalised stress intensity factor which characterises the singular stresses in a neighbourhood of the notch tip.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007467410563
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    Paper (German National Licenses)
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