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  • 1
    Electronic Resource
    Electronic Resource
    Relative growth rates and the grazing optimization hypothesis (1981)
    Springer
    Oecologia 51 (1981), S. 14-18 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A mathematical analysis of the changes in plant relative growth rates necessary to increase aboveground production following grazing was conducted. The equation derived gives an isoline where production of a grazed and ungrazed plant will be the same. The equation has four variables (mean shoot relative growth rate, change in relative growth rate after grazing, grazing intensity, and recovery time) and may be analyzed graphically in a number of ways. Under certain conditions, small increases in shoot relative growth rate following grazing will lead to increased aboveground production. Under other conditions, very large increases in relative growth rate after grazing can occur without production being increased over that of ungrazed plants. Plants growing at nearly their maximum potential relative growth rate have little opportunity to respond positively to grazing and potentially can sustain less grazing than plants with growth rates far below maximum. Plants with high relative growth rates at the time of grazing require large increases in growth rate while slow growing plants require only small increases. High grazing intensities are least likely to increase production and high grazing frequencies require greater responses than infrequent grazing events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00344645
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  • 2
    Electronic Resource
    Electronic Resource
    Galaxies as gravitational lenses: Realistic models (1981)
    Springer
    General relativity and gravitation 13 (1981), S. 591-597 
    Details
    ISSN: 1572-9532
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The gravitational lens effects associated with a transparent mass distribution are quite different from those of the well-known opaque sphere. We have shown that any spherical galaxy whose mass distribution, when projected onto the plane of the sky, decreases outward from the center of the galaxy and diverges less rapidly than 1/h ash→0, must always produce an odd number of images, usually one or three, of a source located behind the galaxy. Using optical scalar techniques, the amplification of each image can readily be obtained. For a given source and galaxy, we can define a dimensionless focal length, a function of impact parameter, and a dimensionless distance factor, depending on lens parameters and source distance. The central value of the ratio of these quantities determines the multiplicity of the images. The mass distribution of the galaxy is a crucial function, and we show in some detail how this affects the various focal lengths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00757245
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrasonic induction of sister chromatid exchanges in human lymphocytes (1981)
    Springer
    Human genetics 〈Berlin〉 59 (1981), S. 221-226 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary We analyzed sister chromatid exchange (SCE) frequencies as an indicator of DNA damage induced in human lymphocytes by ‘real-time’ ultrasound. A range of exposure times and intensities was tested in a series of blind, randomized, in vitro experiments under spatial and sonographic conditions simulating exposure of a gravid abdomen and uterus. Our studies showed small but consistent effects of ultrasound on SCE frequencies, for each experiment. Differences between matched control and exposed means were significantly different from zero. X 2 tests for homogeneity indicated no significant differences among either the means or the total distributions of the controls, nor among each of the separate dose levels. Consequently, experiments were pooled, and X 2 analysis indicated significant differences both among distributions and among means of SCE frequencies for controls versus exposed cells (P(0.001). The pooled control mean was also significantly different from each of the pooled dose means. Correcting for multiple comparisons gave identical results for the paired comparisons of means except for the 20-min level which was borderline (0.025P(0.01). We conclude that the well-established value of clinical ultrasonography warrants its continued use; however, minimizing the numbers and lengths of exposure per patient would seem prudent, pending further information on clinical implications of our results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00283668
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  • 4
    Electronic Resource
    Electronic Resource
    On the transition from Weyl to Ricci focusing (1981)
    Springer
    General relativity and gravitation 13 (1981), S. 1157-1160 
    Details
    ISSN: 1572-9532
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using the weak-field approximation, we show that the Weyl focusing of rays in a beam of light which passes around a number of spherical deflectors may be approximated by the Ricci focusing of the beam due to the enclosed mass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00759864
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  • 5
    Electronic Resource
    Electronic Resource
    A repetitively pulsed sealed-TE CO2 laser using an oxygen tolerant discharge scheme (1981)
    Springer
    Applied physics 26 (1981), S. 169-172 
    Details
    ISSN: 1432-0649
    Keywords: 42.55 DK
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A repetitively pulsed (≦40 Hz) TE CO2 laser using an oxygen tolerant discharge scheme is described. Long lived (〉105 shots) stable discharges at high pump energy density (∼200 J.l−1 atm−1) have been achieved both with and without the use of additive gases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00692442
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  • 6
    Electronic Resource
    Electronic Resource
    Examination of North American bison saliva for potential plant growth regulators (1981)
    Springer
    Journal of chemical ecology 7 (1981), S. 239-246 
    Details
    ISSN: 1573-1561
    Keywords: Saliva ; bison ; Bison bison ; Avena sativa ; oats ; Cucumus sativus ; cucumber ; Avena coleoptile ; indoleacetic acid ; plant growth regulator ; herbivore
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A series of laboratory bioassays were utilized to test for the presence of potential plant growth factors in saliva from a large native ungulate, the North American bison (Bison bison L.). Whole saliva enhancedAvena coleoptile growth at high pH, whether alone or in combination with indoleacetic acid (IAA). However, this enhancement was a result of salts in the saliva (primarily NaHCO3) rather than of other compounds acting hormonally, enhancing IAA activity, or inhibiting IAA oxidase activity as possibly occurs with some insect salivas. Additionally, the absence of detectable cytokinins in the saliva was indicated by its failure to enhance cucumber cotyledon expansion. This suggests that biochemical control of plant growth by salivary compounds following grazing is probably not an important component of this ruminant's interactions with its food plants, as has been suggested for some herbivores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00995746
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  • 7
    Electronic Resource
    Electronic Resource
    Flow distortion by supporting structures (1981)
    Springer
    Boundary layer meteorology 20 (1981), S. 243-251 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract During the 1976 International Turbulence Comparison Experiment, a number of participants found significant values of upflow over the horizontal support arm of the sensor used. For example, the Japanese sonic anemometer reported an average upflow of 2.4 °. By means of model experiments and fitting to a potential flow solution, it is predicted that the horizontal support would introduce an upflow of 0.5 °. Further model experiments with a full sonic anemometer model plus associated structures predicted an upflow of 2.2 °, in reasonable agreement with the observed result. The need for extreme care in the exposure of turbulence sensors is emphasized. The theory is capable of predicting the error incurred in the various turbulence parameters, such as u′w′, and these error equations bear a close similarity to those normally used in applying a tilt correction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00119905
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  • 8
    Electronic Resource
    Electronic Resource
    A physical map of wheat chloroplast DNA showing the location of the structural genes for the ribosomal RNAs and the large subunit of ribulose 1,5-bisphosphate carboxylase (1981)
    Springer
    Molecular genetics and genomics 183 (1981), S. 93-101 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The restriction endonucleases SalGI and PstI have been used to construct a physical map of wheat ctDNA. The molecule was found to contain approximately 135 kbq, and in common with many other higher plant ctDNAs about 15% of the sequences are repeated in an inverted orientation. It was established by electron microscopy that, in wheat, each segment of the inverted repeat contains 21.0 kbp, and that the single copy regions separating the two repeated segments contain 12.8 kbp and 80.2 kbp. Blot hybridisation showed that one set of ribosomal genes is located in each segment of the inverted repeat region and the sizes of these genes were accurately determined by measuring the dimensions of hybrids between the chloroplast rRNAs and the identified Sal and Eco fragments on electron micrographs: the genes for the 16S and 23S rRNAs contain 1530 bp and 2850 bp respectively and are separated by a spacer region of 2350 bp. The Bgl fragment of maize ctDNA known to contain the structural gene for the large-subunit (LS) of ribulose 1,5-bisphosphate carboxylase was used as a probe to locate the LS gene in wheat ctDNA. A small (2.8 kbp) Eco fragment was found to contain most of the wheat LS gene and is derived from the larger single-copy region, 23.5 kbp away from one segment of the inverted repeat and 54.8 kbp from the other.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00270145
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  • 9
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    A repetitively pulsed sealed-TE CO2 laser using an oxygen tolerant discharge scheme (1981)
    Springer
    Details
    Publication Date: 1981-11-01
    Print ISSN: 0947-8396
    Electronic ISSN: 1432-0630
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 10
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    Flow distortion by supporting structures (1981)
    Springer
    Details
    Publication Date: 1981-03-01
    Print ISSN: 0006-8314
    Electronic ISSN: 1573-1472
    Topics: Geosciences , Physics
    Published by Springer
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