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  • 1
    Electronic Resource
    Electronic Resource
    Soldier production inCamponotus novaeboracensis during colony growth (1989)
    Springer
    Insectes sociaux 36 (1989), S. 28-41 
    Details
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Resume Dans des colonies d'importance différente chez la fourmi charpentièreCamponotus novaeboracensis, on a observé des changements dans les équations allométriques, les courbes de fréquence de taille et la distribution des castes. Les colonies naturelles ont été groupées en trois catégories selon le nombre d'ouvrières dans une colonie: colonie «juvénile» pour moins de 150 ouvrières, colonie «prémature» pour 200 à 2000 ouvrières et colonie «mature» pour plus de 2000 ouvrières et ayant produit des sexués. Il n'y avait pas de différence dans les équations allométriques entre les trois catégories, néanmoins les colonies «matures» contenaient un plus grand nombre de soldats. On a noté des différences notables dans les courbes de fréquence de taille des trois catégories.
    Notes: Summary Changes in allometry equations, size-frequency curves, and caste ratios were examined in different-sized colonies of the polymorphic carpenter antCamponotus novaeboracensis. Field collected colonies broadly grouped into three categories based on the number of workers in a colony: “incipient” if they had fewer than 150 workers, “juvenile” if they had 200 to 2,000 workers, and “mature” if they had more than 2,000 workers and had produced reproductives. There was no difference in the allometry equations between the three groups, but the mature colonies did contain a higher proportion of soldiers. The size-frequency histograms and caste ratios were significantly different between the three groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02225878
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  • 2
    Electronic Resource
    Electronic Resource
    Herbivory and detritivory among gammaridean amphipods from a Florida seagrass community (1979)
    Springer
    Marine biology 54 (1979), S. 41-47 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The gammaridean amphipods Cymadusa compta (Smith), Gammarus mucronatus Say, Melita nitida Smith and Grandidierella bonnieroides Stephensen from a seagrass community in the Indian River estuary of Florida (USA) fed variously upon large drift algae, small algae epiphytic on seagrasses and seagrass leaf debris and detritus. Consumption was measured in the laboratory using an index (CI) equivalent to mg ingested mg-1 amphipod day-1. Observations revealed that the amphipods fed by macrophagy, an attack upon large algae and seagrass debris, and by microphagy, small particle detritus feeding and scraping of plant surfaces for diatoms and other epiphytic algae. C. compta was a macrophagous feeder with a generalized diet of algae and seagrass debris, preferring epiphytic algae and drift algae at mean rates of 1.10 and 0.87 CI, respectively. Gammarus mucronatus fed upon epiphytes and seagrass debris equally at mean rates of 0.90 and 0.97 CI, respectively. The diet of M. nitida condisted primarily of epiphytes, consumed at an average rate of 1.05 CI. Grandidierella bonnieroides fed in a specialized microphagous manner, “grooming” plant surfaces for small particle detritus and diatoms at an approximate CI rate of 1.45. Assimilation of plants ingested, as reflected by carbon-14 uptake, varied similarly among the 4 amphipods. Epiphytic algae appeared to be most useful as food, providing means of 41 to 75% carbon-14 uptake as ingesta. Drift algae and seagrass debris were of less value, with means varying between 11 and 24 % of carbon-14 uptake by the amphipods. The data show a pattern of feeding which resembles resource partitioning of food both by size and kind. Other evidence, however, including population limitation by predators and an apparent overabundance of food, indicate that resource partitioning as seen may be an artifact, and one which has no co-evolutionary basis among the present species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00387050
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  • 3
    Electronic Resource
    Electronic Resource
    Genetic evidence for the occurrence of a cryptic species with the littoral nemerteans Lineus ruber and L. viridis (Nemertea: Anopla) (1995)
    Springer
    Marine biology 122 (1995), S. 305-316 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lineus ruber and L. viridis are common intertidal heteronemerteans found on the coasts of northern Europe and the east coast of North America. The two species resemble each other morphologically and were synonymised for many years prior to being separated on the basis of larval development. In this study, specimens of L. ruber and L. viridis were collected from sites along the west and southwest coast of Britain, northern France and the east coast of North America. The external morphology and allele frequencies of isozymes of the two species were compared from all sites. The external morphology of L. ruber and L. viridis was similar but they could generally be separated by colour. Allele frequencies for up to 13 enzyme loci between sympatric populations of L. ruber and L. viridis indicated that these two species are genetically very different (Nei's genetic identity=0.090 to 0.083). Allele-frequency data also indicated the presence of a third genetic type occurring sympatrically with populations of both L. ruber and L. viridis on the coasts of Britain and France but not on the coast of North America. Fixed differences in allele frequencies between populations of the third genetic type and sympatric populations of L. ruber and L. viridis were observed across multiple loci. Genetic identity between the third genetic type and sympatric populations of L. ruber and L. viridis were extremely low (Nei's genetic identity =〈0.078). Such large genetic differences between populations indicate a barrier to gene flow and reproductive isolation. The aberrant type, which exhibits sufficient morphological variation to prevent individuals being distinguished from those of both L. ruber and L. viridis, therefore represents a separate species. The low genetic identities found in intrageneric comparisons of species found in this study have been found in other studies on nemerteans. They may indicate systematic problems within these groups or other phenomena such as morphological stasis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00348944
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  • 4
    Electronic Resource
    Electronic Resource
    Tidal and circadian activity rhythms in juvenile plaice, Pleuronectes platessa (1973)
    Springer
    Marine biology 22 (1973), S. 379-386 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Young plaice (Pleuronectes platessa L.), caught in the intertidal zone, exhibit a short-lived tidal rhythm when their activity is recorded in darkness in the laboratory. This tidal rhythm rapidly changes to one of circadian frequency both in darkness and in light-dark cycles. It is considered that the basic rhythm is circadian in nature, but that it can be entrained to keep in phase with the tides by some, as yet unknown, Zeitgeber present under tidal conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391398
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of particle concentration on filter- and particulate-feeding in the herring Clupea harengus (1985)
    Springer
    Marine biology 88 (1985), S. 109-116 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Observations were made in the laboratory on the feeding behaviour of small shoals of captive juvenile herring (Clupea harengus) using Artemia sp. nauplii as food. The fish used two methods of feeding. The first, filter-feeding, was only used at concentrations exceeding approximately 50 nauplii l-1. Filter-feeding rapidly gave way to particulate-feeding (biting and gulping) as concentrations declined, and biting was the only method used when concentrations were 〈 50 nauplii l-1. There was a positive correlation between particle concentration and feeding acts of both types. Particle concentrations declined exponentially throughout experiments, indicating that a constant proportion was being removed during an experiment. This proportion was inversely related to the initial concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397157
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  • 6
    Electronic Resource
    Electronic Resource
    Relative importance of prey size and concentration in determining the feeding behaviour of the herringClupea harengus (1990)
    Springer
    Marine biology 107 (1990), S. 357-362 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The feeding behaviour ofClupea harengus L. in the light is dependent primarily on prey concentration. In the laboratory the fish feed by biting at low prey concentrations and by filtering at high concentrations. With the brine shrimpArtemia sp. as prey, the concentration required for the onset of filter-feeding was directly dependent on prey size, but the concentration at which 50% of feeding fish were filtering differed little between three sizes of brine shrimp (nauplii, and 2 and 4 mm larvae). When fed onCalanus finmarchicus, however, 50% of fish fed by filtering at concentrations at least six times lower than on any size of brine shrimp. Filter-feeding thresholds forC. finmarchicus were six to ten times lower than for any size ofArtemia sp. and, on the basis of biomass, approximately eight times lower than for equivalent sizedArtemia sp.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01319837
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  • 7
    Electronic Resource
    Electronic Resource
    Internal material damping of polymer matrix composites under off-axis loading (1985)
    Springer
    Journal of materials science 20 (1985), S. 2575-2585 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The objective of this paper is to determine theoretically the material damping of short fibre-reinforced polymer matrix composites. The major damping mechanism in such composites is the viscoelastic behaviour of the polymer matrix. The analysis was carried out by developing a finite-element program which is capable of evaluating the stress and strain distribution of short fibre composites under axial loading (see Fig. 1a). Using the concept of balance of force we can express the modulusE x along the loading direction as a function of the mechanical properties of the fibre and matrix materials, fibre aspect ratio,l/d, loading angle,θ, and fibre volume fraction,V f. Then we apply the elastic-viscoelastic correspondence principle to replace all the mechanical properties of the composite, fibre and matrix materials such asE x,E f,E m,G m, by the corresponding complex moduli such asE x ′ +iE x ″ , andE f ′ +iE f ″ . After separation of the real and imaginary parts, we can expressE ' x/t' andE x t" as functions of the fibre aspect ratio,l/d, loading angle,θ, stiffness ratio,E f/E m, fibre volume fraction,V f, and damping properties of the fibre and matrix materials such asη f andη m. Numerical results of the composite storage modulus,E x ′ , loss modulus,E x ″ , and loss factor (damping),η C, are plotted as functions of parameters such asl/d,θ,V f, and are discussed in terms of variations ofl/d,θ, andE f/E m, in detail. It is observed that for a given composite, there exist optimum values ofl/d andθ at whichE x ″ andη c are maximized. The results of this paper can be used to optimize the performance of composite structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00556089
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  • 8
    Electronic Resource
    Electronic Resource
    The significance of the Vredefort Dome for the thermal and structural evolution of the Witwatersrand Basin, South Africa (1999)
    Springer
    Mineralogy and petrology 66 (1999), S. 5-23 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Der Vredefort Dom ist ein Gebiet von signifikantem (ca. 10 km), strukturellem Uplift im Zentralbereich des wirtschaftlich bedeutungsvollen Witwatersrand-Beckens. Die Ges-teine des Doms haben höhere Metamorphosebedingungen erfahren als die stratigraphisch äquivalenten Lagen, die im Randbereich des Beckens aufgeschlossen sind. Kürzlich durchgeführte Untersuchungen dieser mittel-bis hochgradigen Metamorphose und neueste Ergebnisse zur Entstehung des Domes haben einen Beitrag zu einem Metamorphose-Modell für das gesamte Witwatersrand-Becken geleistet. Diese neuen Befunde zeigen, daß die Gold-hältigen Gesteinsschichten zumindest zwei metamorphe Ereignisse vor ca. 2 Ga erfahren haben. Die ungewöhnlich hohen Beanspruchungsraten und die Stoßwellendeformationsstrukturen, die in den Gesteinen des Doms belegt sind, sprechen gegen einen endogenen Ursprung durch tektonische oder diapirische Prozesse. Neuere Arbeiten an diesen Phänomenen haben gezeigt, daß der Dom am besten als die zentrale Struktureinheit (‘Zentralberg’) einer sehr grossen, 250–300 km weiten und 2023±4 Ma alten Meteoriteneinschlagsstruktur verstanden werden kann, deren Ausmaß eng mit den jetzigen Grenzen des Witwatersrand-Beckens übereinstimmt. Die Gegenwart von Impakt-bezogenen Deformationsstrukturen in Vredefort-Gesteinen erlaubt es, die metamorphen Texturen, die während eines hochgradigen, mit dem 2.05–2.06 Ga Bushveld Magmatismus korrelierten, metamorphen Stadiums vor dem Impaktereignis entstanden sind, von den Texturen zu trennen, die ein statisch metamorphes Ereignis von etwas geringerer Stärke, das nach dem Impakt stattfand, produzierte. Die Spuren des post-Impakt Ereignisses nehmen in ihrer Stärke zum Rand des Domes ab. Dieser Effekt wird durch eine massive Störung der thermischen Krusten-Struktur erklärt, die als Resultat einer Kombination von Impakt-induzierter Exhumierung, von Schock-Aufheizung der Krustengesteine, und von Erwärmung durch einen gewaltigen, jetzt erodierten Impaktschmelzgesteinskörper gesehen wird.
    Notes: Summary The Vredefort Dome represents an area of significant (∼ 10 km) structural uplift within the central parts of the economically important Witwatersrand Basin. Its rocks experienced higher grades of metamorphism than the equivalent stratigraphic horizons exposed around the periphery of the basin. Recent studies of this medium- to high-grade metamorphism, as well as new evidence concerning the origin of the dome, have contributed to a metamorphic model for the Witwatersrand Basin as a whole. This evidence shows that the gold-bearing strata experienced at least two metamorphic events at ca. 2 Ga. The unusually high strain rate and shock deformation features exposed in the rocks of the dome rule out an endogenous origin by tectonic or diapiric processes. Recent work on these features has shown that the dome is best explained as the central uplift of a large, 250–300 km diameter, 2023±44 Ma old meteorite impact structure, the extent of which closely correlates with the present-day limits of the Witwatersrand Basin. Impact-related deformation features in the Vredefort rocks facilitate the separation of metamorphic textures developed during a pre-impact event associated with the 2.05–2.06 Ga Bushveld magmatism, and textures developed during a slightly lower-grade, post-impact, static overprint. The post-impact overprint decreases in intensity outwards from the dome. It is attributed to the massive disturbance of the thermal structure of the crust by impact-induced exhumation, and to shock heating of the rocks as a consequence of the impact event.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01161720
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  • 9
    Electronic Resource
    Electronic Resource
    Some results concerning displacements in a non-homogeneous elastic layer (1971)
    Springer
    Zeitschrift für angewandte Mathematik und Physik 22 (1971), S. 855-864 
    Details
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Résumé On sait qu'un semi-espace de terrain isotrope, élastique et incompressible — dont le module de cisaillement accroît linéairement avec la profondeur, partant de zéro à la surface — réagit à la charge superficielle exactement selon les hypothèses faites par Winkler dans sa théorie de la réaction du niveau de fondation. On examine ici jusqu'à quel point la validité de ce résultat s'applique à un milieu de profondeur limitée. On y démontre que, si la profondeur de la couche dépasse la largeur de la surface chargée, le tassement d'une charge répartie uniformément est aussi pratiquement uniforme. Cependant, au delà du sol chargé, la surface se souleve d'une manière sensible, même lorsque la couche est d'une épaisseur modérée.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01591813
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  • 10
    Electronic Resource
    Electronic Resource
    Resistance to potato leaf roll virus and potato virus Y in somatic hybrids between dihaploid Solanum tuberosum and S. brevidens (1988)
    Springer
    Theoretical and applied genetics 76 (1988), S. 113-117 
    Details
    ISSN: 1432-2242
    Keywords: Potato ; Solanum brevidens ; somatic hybrid ; PLRV ; PVY
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Many somatic fusion hybrids have been produced between a dihaploid potato Solanum tuberosum and the sexually-incompatible wild species S. brevidens using both chemical and electrical fusion techniques. S. brevidens was resistant to both potato leaf roll virus (PLRV) and potato virus Y (PVY), the viruses being either at low (PLRV) or undetectable (PVY) concentrations as determined by enzyme-linked immunosorbent assay (ELISA). The S. tuberosum parent was susceptible to both viruses. A wide range of resistance, expressed as a decrease in virus concentration to both viruses was found amongst fusion hybrids, four of which were especially resistant. The practicality of introducing virus resistance from S. brevidens into cultivated potatoes by somatic hybridisation is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00288840
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