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  • 1
    Electronic Resource
    Electronic Resource
    Spontaneous intracranial hypotension: use of unenhanced MRI (2000)
    Springer
    Neuroradiology 42 (2000), S. 529-531 
    Details
    ISSN: 1432-1920
    Keywords: Key words Meninges ; Hypotension ; spontaneous intracranial ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report a case of spontaneous intracranial hypotension diagnosed with unenhanced cranial MRI, showing laminar subdural fluid and engorgement of the hypophysis and perisellar sinuses. Cerebrospinal fluid pressure was low. MRI was normal after resolution of symptoms. Prior reports emphasise the enhancing pachymeninges seen in this syndrome. We maintain that, when subdural collections and perisellar engorgement are detected on unenhanced MRI in the proper clinical setting, contrast enhancement may not be necessary for the diagnosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340000327
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  • 2
    Electronic Resource
    Electronic Resource
    Responses of the trunk routes of a harvester ant to plant density (1993)
    Springer
    Oecologia 93 (1993), S. 109-113 
    Details
    ISSN: 1432-1939
    Keywords: Trunk routes ; Harvester ants ; Phalanx ; Guerilla ; Messor barbarus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Messor barbarus is a Mediterranean harvester ant that constructs physically defined trunk routes on the ground to connect nest entrances with foraging areas. Some responses of these trunk routes to plant density (and therefore resource abundance) were analyzed by testing the preferential allocation of different parts (trunk route ends, segments and branching points) in a patchy environment. Maps of grass density in four categories and Messor barbarus trunk routes were compiled for a Mediterranean pasture in Central Spain over four consecutive years. The proportions of the density categories in each year were used to calculate random expected frequencies of the trunk route points and the predominance of higher or lower grass densities. Trunk route ends discriminate and selectively reach patches with a greater abundance of resources in all study years. Branching points are also allocated preferentially in areas with higher vegetation density, but only in years with a predominance of the higher categories of grass density. In these years, the colonies of Messor barbarus have a “phalanx” strategy at a colonial level, and branching is more profuse. Finally, trunk route segments do not indicate any preference for crossing determined vegetation densities, but rather connect successive branching points or trunk route ends by the shortest route. These results concur with a model of structural strategy change (“guerilla” — “phalanx”) (Hutchings 1988) at the level of trunk routes. They are probably constituted by “transitory” sections with few branches, that expand other more profusely branched sections which are more dedicated to foraging.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00321199
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  • 3
    Electronic Resource
    Electronic Resource
    High Prevalences of Lead Poisoning in Wintering Waterfowl in Spain (1998)
    Springer
    Archives of environmental contamination and toxicology 35 (1998), S. 342-347 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. Some Mediterranean wetlands are found between the areas with the highest prevalence of lead pellet exposure for waterfowl in the world. To assess the situation in Spain, availability of pellets in sediments and rates of ingestion by waterfowl were determined in four important wetlands: Albufera de València, El Fondo, Tablas de Daimiel, and Doñana (Guadalquivir Marshes). Lead pellet density in sediment was maximum in the Albufera, with 2.8 million pellets/ha. In Tablas de Daimiel, where hunting was banned in 1965, about 1.0 million pellets/ha were found. Percentages of shot waterfowl with ingested pellets were maximum in the wetlands on the Mediterranean coast (El Fondo and Albufera de València): 87.5% of common pochard (Aythya ferina) and approximately 33% of mallard (Anas platyrhynchos) and shoveler (Anas clypeata) contained ingested pellets. It was found that mallards with 〉 5 μg/g dry weight of lead in the liver had 8.5% lower body condition and 7.7% less body weight than birds with lower lead concentrations. Moreover, lead poisoning was diagnosed as the cause of death in 16 out of 75 birds, mainly greylag geese (Anser anser), found dead in some of these zones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002449900385
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  • 4
    Electronic Resource
    Electronic Resource
    Asymmetric interactions between plants and seed-harvesting ants in a Mediterranean pasture (2000)
    Springer
    Ecological research 15 (2000), S. 449-452 
    Details
    ISSN: 1440-1703
    Keywords: asymmetric interactions ; foraging strategies ; Messor barbarus ; seed-harvesting ants ; vegetation dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: A four-year study on the interactions between plants and seed-harvesting ants in a Mediterranean pasture is reviewed in this paper. As previously reported in many studies on plant–herbivore interactions, ant–plant relationships are also asymmetric; plants had a larger impact on herbivore dynamics than vice versa. However, the asymmetry did not refer to population dynamics but rather to animal foraging strategies. Ants did not exert a significant influence on vegetation dynamics in terms of plant abundance. The main constraints underlying vegetation change were self-regulation and rainfall. In contrast, the structural characteristics and abundance of vegetation had a significant impact on several important features of food harvesting by ants. This influence was not only associated with their feeding requirements but also with their foraging activities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1440-1703.2000.00364.x
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  • 5
    Electronic Resource
    Electronic Resource
    The dynamics of a therophytic community in relation to self-regulation, herbivores and environmental variation (1992)
    Springer
    Plant ecology 98 (1992), S. 59-71 
    Details
    ISSN: 1573-5052
    Keywords: Vegetation dynamics ; Grasses ; Markovian models ; Granivory ; Ants ; Environmental influence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The dynamics of a therophytic plant community in Central Spain has been studied, taking into account endogenous and exogenous factors. Using a simplified descriptive resolution a multi-species grass community and four canopy density types have been described in permanent quadrats. Transition matrices expressing the changes of vegetation state have been constructed. The importance of self-regulation was shown by the dependence of successive transitions on each other (highly significative log-linear models). The functioning cannot however be explained through a strict Markovian model because the transition probabilities are not stationary. The external local factors tested (microtopography, compactness and granivory) do not have a consistent effect on the vegetation dynamics, being variable over years, implying the importance of other more general factors on vegetation dynamics. Making transition probabilities dependent on external environmental factors represents a way of further developing projective models of the dynamics of these therophytic systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00031637
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Functional features and ontogenetic changes in reproductive allocation and partitioning strategies of plant modules (1997)
    Springer
    Plant ecology 132 (1997), S. 71-76 
    Details
    ISSN: 1573-5052
    Keywords: Cistus ladanifer ; Module iterativity ; Plant modularity ; Pre-dispersal fitness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the concept of modularity, plant modules are considered as iterative units and their changes are analyzed in terms of number or size. This paper, however, analyses changes with respect to the reproductive functional performance of modules and individual plant age. Patterns of resource allocation and partitioning in reproductive modules (fruits) are compared between two different age groups of a bushy perennial plant, Cistus ladanifer. Although modules do not differ in their allocation strategies (young plant modules produce the same seed and packing/protective structure biomass as old plant modules), their partitioning strategies change with plant age: young plant modules produce a larger number of lighter seeds than old plants. These differences have a direct consequence on the plant pre-dispersal fitness, which is not counteracted by insect predation on reproductive modules. These results are empirical evidence of a differentiation in the performance of reproductive modules with the ontogenetic development of this plant species. We think that the consideration of such kind of changes in module features is essential in the analysis of the iterative construction of plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009799102985
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  • 7
    Electronic Resource
    Electronic Resource
    Temperature-vegetation structure interaction: the effect on the activity of the ant Messor barbarus (L.) (1992)
    Springer
    Plant ecology 99-100 (1992), S. 119-128 
    Details
    ISSN: 1573-5052
    Keywords: Microclimate ; Canopy type ; Evergreen oak ecosystem ; Colony activity ; Ants ; Messor barbarus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several canopy types in an evergreen oak forest with open pastures have been used to examine climatic features of this system related to temperature. Circadian variation in temperature seems to be related to structural characteristics of the vegetation, with an apparent influence of the plant micro- and meso-environments analyzed. The activity of a population of granivorous ants (Messor barbarus (L.)), studied in the same area, showed a clear dependence on ambient temperature, but, although the colonies were always inside one of the vegetation types, there was no significant relationship between the activity of ants and grasscover. This, together with other observations, indicates that the possible controlling effect of the vegetation is limited by the tolerance of ants (when faced with adverse conditions) during each daily foraging period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00118217
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