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  • Blackwell Publishing Ltd  (12)
  • Nature Publishing Group  (5)
  • 1990-1994  (17)
  • 1930-1934
  • 1991  (17)
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 46 (1991), S. 0 
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Perennial ryegrass/white clover pastures were grazed at different times in the winter to study the effect of time of grazing on subsequent plant growth. In 1983–84, 1984–85, and 1985–86, pastures were grazed to a residual of 400 kg dry matter ha-1 by sheep once in early December (D), January (J), February (F), March (M), or April (A) and compared with an ungrazed control (C). Rates of herbage accumulation on C in the winter were low, averaging 6, -9, and 2 kg dry matter ha-1 in December, January, and February, respectively. Little forage production occurred during the month immediately following winter grazing. Herbage accumulation rate then increased sufficiently to replace the forage removed from winter-grazed paddocks by early spring. By May, herbage mass on grazed treatments was similar to C except for D and A which averaged 20 and 47% less forage than C, respectively (P〈0·01). Herbage accumulation rates of D were unique among winter grazing treatments in never exceeding those of C. By May 1986, D yielded less perennial ryegrass compared with C (P〈0·05). Grazing reduced the number of leaves per ryegrass tiller for 1 to 2 months following grazing. By May, J, F and M had numerically more tillers m-2 and more leaves per tiller than C. Similar May yields of J, F, M, and C resulted from fewer but larger and slightly less leafy tillers of ungrazed compared with winter grazed plants.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 39 (1991), S. 0 
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: The dynamic inversion of reflection seismic data is investigated with reference to the influence of noise on pseudo-impedance logs. Model traces are calculated with 0, 5, 15 and 50% noise, respectively. In solving the inversion problem, the algorithm of Marquardt and Levenberg is used in connection with singular value decomposition (SVD). The results are within a 1% error range so that there was no visible change in the logs. Further signal analysis show that there is no dependence on the phase content of the wavelet used if all other parameters of the model are known.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 639 (1991), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 633 (1991), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 629 (1991), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 5 (1991), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A macro-restriction map of the Neisseria gonorrhoeae chromosome was constructed using the enzymes Nhel and Spel. Combinations of one-and two-dimensional electrophoresis of completely or partially digested chromosomal DNA were performed to align the restriction fragments. The chromosome is circular, with an estimated size of 2.33Mb±35kb. A genetic map was derived from the physical map; positions of over 60 defined loci were determined by Southern hybridization.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 5 (1991), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Phase- and antigenic variation of pilin expression in Neisseria gonorrhoeae is based on the genetic exchange between silent pilin genes (pilS)and the pilin expression locus (pilE). Similarly, the non-piliated L-variants of strain MS11, which show an increased resistance to certain antibiotics, are the result of recombination with the pilElocus. However, this recombination is atypical in that pilE(L) carries a tandem arrangement of a complete pilin gene and additional partial pilin genes under the control of the same pilE promoter. Since the two pilin gene copies are tandemly arranged and are often in the same translational frame, oversized pilin molecules are produced, which do not assemble into pili. The tandem gene copies introduced in a piiE(L)locus originate from silent loci where they are already joint. Upon reversion to the P+ phenotype the L-variants lose one pilin gene copy from the pilE(L) in a process reminiscent of the deletion events that otherwise lead to the formation of the non-revertible and non-piliated Pn mutants of MS11 gonococci. Thus deletion of pilin genes from pHE can be regarded as a third mechanism of pilin variation in gonococci.
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  • 8
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Variants of Neisseria gonorrhoeae MS11 show distinct colony morphologies because of the expression of a class of surface components called opacity (Opa, PII) proteins. Southern analyses combined with molecular cloning of genomic DNA from a single variant of MS11 has identified 11 opa genes contained in separate loci. These opa genes code for distinct opacity proteins which are distinguishable at their variable domains. The opa gene analyses were also extended to divergent variants of MS11. These studies have shown that, during in vitro and in vivo culture, 10 of the 11 opa genes did not undergo significant change in their primary sequence. However, in these variants, one gene (opaE) underwent non-reciprocat inter-opa recombinations to generate newer Opa variants. Phylogenic analysis of the opa gene sequences suggests that the opa gene family have evolved by a combination of gene duplication, gene replacement and partial inter-opa recombination events.
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  • 9
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Within the DEKORP project (DEKORP: Deutsches Kontinentales Reflexionsseismisches Programm) a joint deep seismic reflection venture with the BELCORP (Belgian Continental Reflection Seismic Programme) group of the Belgian Geological Survey was carried out in 1987 across the Rhenish Massif, a part of the mid-European Variscides. This orogenic belt developed in the Upper Devonian/Carboniferous. Mostly Devonian rocks crop out at the surface. The Rhenish Massif is bordered by two sedimentary troughs: the sub-Variscan Foredeep in the north and the Permo-Carboniferous Saar-Nahe Basin in the south. In the east-west direction it is subdivided by the axial depression of the Eifel Nord-Süd Zone.The aim of the survey which totals almost 220 km of seismic profiling, was to investigate the crustal structure of the western part of the Rhenish Massif and to compare it with the line DEKORP 2-N which crosses the eastern portion of the massif. The results indicate the presence of NW-vergent tectonics of various styles that can often be traced down to deep parts of the crust. Horizontal Variscan compression plays a dominant role in the northern part while post-Variscan extension seems to dominate in the Saar-Nahe Basin, although even there traces of Variscan compression seem to be preserved in the middle crust. Common characteristics of the pre-Palaeozoic basement, differences between the western and eastern parts of the Rhenish Massif, and the deep extension of the Aachen Thrust (Faille du Midi) have been clearly observed. This prominent thrust in the north with its characteristic ramp and flat structure has been followed over 100 km length down
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  • 10
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Organic solutes, in particular glycine betaine and proline, have been detected as osmoprotective compounds in many microorganisms and herbaceous species. However, for woody plants, very little information is available on mechanisms of adaptation to salt stress. In the present study, effects of NaCI treatment on betaine and free amino acid contents in a clone of Populus trichocarpa X deltoides micropropagated vitroplants were analyzed using HPLC and silicate plate chromatography. The application during 12 days of 50 to 200 mM NaCI to viroplants cultured on Murashige and Skoog medium (Murashige and Skoog 1962. Physiol. Plant. 15: 473–497) led to a progressive decrease of growth, leaf senescence, abscission, and apical necrosis. Populus trichocarpa X deltoides was characterized by the absence of glycine betainc and/or proline accumulation. However, trigonelline was found to increase in vitroplants subjected to 100 mM NaCI. Trigonelline was also present in dormant buds harvested in natural conditions and missing in active buds. In vitroplants, the content of some amino acids was strongly modified by salt stress. A progressive accumulation of alanine and γ-amino butyrate was particularly significant in roots, whereas the relative concentration of glutamine was strongly enhanced in leaves. Leaf content of glutamate and ornithine attained maximum in the presence of 100 and 150 mM NaCI concentrations, and then decreased. Arginine and serine pools were not significantly modified by salt treatment. The variations in vitroplants were of small amplitude compared to those observed in mature poplars where winter rest was associated with a very high arginine level and with a disappearance of nearly all other free amino acids. The results are discussed in relation to previous data obtained with herbaceous species and in relation to some metabolic pathways in poplars where trigonelline could be considered as a sensitive stress indicator.
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