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  • Springer  (229)
  • American Association for the Advancement of Science (AAAS)
  • 1985-1989  (235)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 44 (1987), S. 177-185 
    ISSN: 1570-7458
    Keywords: spotted alfalfa aphid ; Therioaphis trifolii ; aphid-resistant plants ; lucerne = alfalfa ; Medicago sativa ; variation ; bioassay ; antibiosis non-preference ; inter-plant movement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé L'étude de la multiplication initiale des effectifs de T. trifolii, élevés au laboratoire sur pousses de différents pieds de luzerne, a servi de test d'antibiose pour les cultures en plein champ. La distribution de l'antibiose, dans des échantillons importants de plantes appartenant à des cultivars sélectionnés pour leur résistance aux pucerons, a présenté une forme en J, c'est-à-dire que la majorité des plantes était très résistante, quelques unes apparemment sensibles, et un certain nombre intermédiaires entre ces deux extrêmes. Pour un niveau donné d'antibiose, la reproduction, la mortalité et ainsi la distribution initiale en âges dans les populations de pucerons ont été généralement identiques. La multiplication végétative de plantes présentant un gradient de résistance à l'intérieur d'un cultivar et l'utilisation d'un plan de distribution des boutures ont permis l'étude de ce qui semble être l'effet de l'hétérogénéité spatiale sur la résistance des cultures aux attaques de pucerons. La simulation d'une invasion de la culture par les pucerons en plaçant des adulte sur toutes les boutures d'un rang ne pouvait donner une explication de la croissance de la population que si les pucerons se déplacaient le long du rang pour découvrir et exploiter les pieds les plus sensibles. Une distribution par taches, comme on peut l'envisager dans un champ, ne devrait pas gêner les pucerons, car bien que les mouvements d'évasion soient stimulés par les niveaux de résistance élevés (de non-préférence), on peut en déduire que les pucerons se déplaceront sur des plantes très résistantes, eventuellement pour atteindre des plantes moins résistantes placées derriere.
    Notes: Abstract Initial population growth of spotted alfalfa aphid reared on shoots cut from individual lucerne plants, was tested and used as a realistic bioassay of antibiosis. Within cultivars selected for aphid-resistance there was a J-shaped distribution of antibiosis between plants of the crop, the majority being highly resistant, a few apparently susceptible and a proportion partly-resistant. For a given level of antibiosis, reproduction, mortality and thus initial age distribution of aphid populations were generally similar. Vegetative cloning of plants from the range of resistance available in a cultivar has allowed studies of the likely effect of spatial variation of resistance in crops on aphid infestations, using experimental arrays of cut shoots. Simulation of aphid invasion of crops by the placement of adults on all shoots of an array gave results explicable only if the aphids moved through the array to find and breed on the more susceptible plants. A patchy arrangement of these, as might be expected in a field crop, would not hinder the aphids, for although movement off a plant is stimulated by higher resistance (non-preference) levels, it was inferred that aphids will move onto higher resistance plants, eventually to reach lower resistance plants beyond.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 49 (1988), S. 75-82 
    ISSN: 1570-7458
    Keywords: aphid-resistance ; lucerne ; alfalfa ; Medicago sativa ; spotted alfalfa aphid ; Therioaphis trifolii f. maculata ; antibiosis ; bioassay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In autumn 1981 there were widespread reports of a reduced level of antibiosis in lucerne crops and field trials where cultivars selected for resistance to the aphid, Therioaphis trifolii f. maculata, had been used. On our field trial, the plot of ‘CUF 101’ lucerne was infested to a level about 40% of that on the aphid-susceptible ‘Hunter River’, compared with an average of about 3% over the two years before and the two years after. An experimental study of possible causes using a bioassay technique on cloned plants representing the spectrum of resistance in CUF 101 indicated that loss of resistance was temporary and occurred apparently randomly among the tests, but that certain treatments increase the frequency of its occurrence. Lowered temperatures and the use of either young regrowth or senescent lucerne, each increased the frequency of loss of resistance. Inundation of lucerne by large numbers of aphids did not affect the expression of resistance directly, but the few progeny that survived to adulthood on partly-resistance lucerne were habituated and were then able to interact with the plants to increase the apparent frequency of breakdown of resistance. Plants which showed the loss of resistance developed aphid populations between 4x ad 25x those when they expressed their normal resistance level. Investigations suggest that the situation in autumn 1981 may have been the result of a prolonged and massive immigration of aphids into lucerne crops, which, on the aphid resistant cultivars allowed surviving aphids to exploit maximally the combined effects of factors causing some loss of resistance.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Behavioral ecology and sociobiology 17 (1985), S. 385-387 
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Adult female whitespotted sawyers Monochamus scutellatus (Coleoptera: Cerambycidae) were placed on succeeding days with two males differing visibly in size. Females showed a significant preference for the larger of two males. The rate of oviposition was significantly higher when the female was paired with the larger male. Both the rate of movement by the paired female and her rate of indicating non-receptivity were significantly lower when the female was paired with the larger male. This species exhibits resource defense polygyny, and females appear to choose mates mainly on the basis of the quality of resources defended. This study suggests, however, that when resource quality is constant, females choose mates on the basis of their size.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Environmental geology 13 (1989), S. 73-127 
    ISSN: 1432-0495
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Hydrogeological studies at Figeh Springs were directed to determine groundwater flow paths, research, storage and discharge units, and the maximum reliable yield. The project was designed to provide information upon which to base pumpage to augment low-season flows from the spring which is the major water supply for the city of Damascus, Syria. As a basis for conclusions and recommendations, work included extensive surface geologic mapping, air photographic interpretation, a detailed well and spring inventory, and a quality of water sampling program. Geologic structural work included mapping and jointing, faulting, and folding, and an analysis of their impact on groundwater movement.
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  • 5
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cross-infection experiments were performed to determine the influence of temperature on infection rate in the Chondrus crispus Stackhouse-Petersenia pollagaster (Petersen) Sparrow pathosystem. C. crispus thalli were collected at Pubnico Harbor, Nova Scotia, Canada in the fall of 1981 to 1984. Infective zoospores were used to inoculate healthy thalli at five different temperatures. The highest infection rate was obtained at 20°C, while significantly lower rates were obtained at temperature extremes. The parasite's life cycle, consisting of infection of healthy thalli, endobiotic development, and release of zoospores, was completed in 48 to 72 h at 15° to 20°C.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Mathematische Annalen 282 (1988), S. 535-544 
    ISSN: 1432-1807
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Microbial ecology 11 (1985), S. 71-79 
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A total of 450 yeast isolates were obtained from up to 34 sites on 59 human subjects. The yeasts were characterized using morphological features and assimilation tests. Ten species were identified but, of these,Candida albicans andCandida parapsilosis were the most common and accounted for 84% of the isolates. An examination of the biotypes of the various species indicated a much greater diversity in the yeast microflora than that detected by species identifications alone. Fifty-five biotypes were differentiated and it is suggested that these could be regarded as distinct taxonomic or ecological entities.
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  • 8
    ISSN: 1432-072X
    Keywords: Copper-limitation ; Escherichia coli ; Cytochrome oxidases ; Oxygen reduction ; Respiratory chains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role(s) of copper in a bacterial cytochrome oxidase of the aa 3-type was investigated by growth of Paracoccus denitrificans NCIB 8944, in batch and steady state continuous culture, in a medium from which the bulk of the copper had been extracted. In a medium containing approximately 0.02 μM copper, cellular copper content, cytochromes a+a 3 and cytochrome a 3 were reduced to 55%, 58% and 33% respectively of control values and there were also less marked decreases in cytochromes c+c 1 (to 85%) and a CO-binding b-type cytochrome, possibly cytochrome o (to 71%). Copper deficiency elicited in reduced minus oxidized difference spectra a shift to shorter wavelengths and narrowing of the band width of the α-band of the oxidase, and loss of a (negative) band near 830 nm attributable to CuA (the copper functionally associated with haem a in the oxidase complex). The oxidase in copper-deficient cells reacted with oxygen to form the oxy “Compound A” at rates similar to that in control cells but CO recombination to ferrous haem a 3 was slowed 4-fold in the copper deficient case. The results are interpreted as indicating loss of CuA and changes in the proportions of haems a and a 3 with retention of catalytic activity. Titrations of respiration rates with antimycin suggested that copper deficiency did not result in diversion of electron flux through an antimycin A-insensitive, cytochrome o-terminated branch of the respiratory chain.
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  • 9
    ISSN: 1432-072X
    Keywords: Iron-limitation ; Escherichia coli ; Respiratory chains ; Cytochromes ; Gallium ; Metal uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of iron limitation on growth, the composition and function of the respiratory chains, and gallium uptake inEscherichia coli have been studied. Decreasing the iron concentration in a defined medium using Chelex resin gave lower growth yields in both continuous culture and prolonged batch culture. In the former, ironlimited (entering [Fe]≤2.0 μM) cells exhibited diminished respiration rates, respiration-driven proton translocation quotients, and levels of non-haem iron and cytochromes. The cellular concentration of haemoproteinb-590 (a cytochromea 1-like hydroperoxidase) decreased 20-fold on iron limitation, whilst a CO-binding pigment with an absorption maximum in the dithionite-treated form near 500 nm appeared. Gallium(III) (9 μM) added to iron-limited, but not iron-sufficient, cultures diminished growth yields further; cells grown with low entering concentrations of iron took up less gallium than iron-sufficient cells. These results are attributed to the interference by gallium(III) with siderophore-mediated metal uptake. Gallium also stimulated iron uptake and was itself accumulated by iron-sufficient cells, suggesting that gallium(III) also affects the iron transport system(s) of low affinity.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 49 (1989), S. 323-325 
    ISSN: 1432-0649
    Keywords: 42.60 ; 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The modelocking of a Nd:YAG laser using second-harmonic generation in an external cavity as the only pulse shortening process is reported. The output of a long pulse Nd:YAG laser was simultaneously modelocked and Q-switched. The average pulse duration was 30–50 ps and the peak power was in the range 60–160 kW.
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