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  • Springer  (116)
  • Institute of Physics  (30)
  • 2000-2004  (94)
  • 1990-1994  (52)
  • 1
    Electronic Resource
    Electronic Resource
    Thermally stimulated depolarization current and Mössbauer spectroscopy of iron-doped niobophosphate glasses (1993)
    Springer
    Journal of materials science 28 (1993), S. 4305-4310 
    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 Niobophosphate glasses (P2O5-PbO-Nb2O5-K2O-XFe2O3), were studied using thermally stimulated depolarization currents and Mössbauer spectroscopy in samples of different iron concentrations, and were subjected to oxidation and reduction processes. The use of both techniques provided new information about the distribution of iron and niobium between tetrahedral and octahedral sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01154936
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  • 2
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    Thermally stimulated depolarization current and Mössbauer spectroscopy of iron-doped niobophosphate glasses (1993)
    Springer
    Details
    Publication Date: 1993-08-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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    PAPER CURRENT
  • 3
    Electronic Resource
    Electronic Resource
    Effects of dietary nicotine (0.1%) and parasitism by Cotesia congregata on the growth and food consumption and utilization of the tobacco hornworm, Manduca sexta (1990)
    Springer
    Entomologia experimentalis et applicata 57 (1990), S. 1-8 
    Details
    ISSN: 1570-7458
    Keywords: Tobacco hornworm ; Manduca sexta ; parasitoids ; Cotesia congregata ; allelochemicals ; nicotine ; nutritional indices ; tri-trophic interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Bien que les influences des substances allélochimiques des plantes et du parasitisme aient été étudiées séparément, leurs effets combinés sur l'utilisation des aliments après ingestion par un herbivore n'avaient pas été examinés. Il est probable que les substances allélochimiques peuvent agir sur l'adéquation des herbivores pour leurs parasitoïdes, ou que la présence de parasitoïdes peut influer sur l'action des substances allélochimiques sur les indices nutritionnels des herbivores. Manduca sexta L. et son parasitoïde, Cotesia congregata Say fournissent un bon modèle pour étudier les interactions entre parasitisme et substances allélochimiques sur la croissance, la consommation et l'utilisation de la nourriture ingérée chez les larves de M. sexta. Les taux de croissance, la consommation et l'efficacité de la conversion des chenilles de 33 et 43 stades ne sont pas influencés significativement par les intéractions entre nicotine alimentaire et parasitisme. Cependant, le parasitisme réduit le taux de croissance des chenilles du 5e stade, ce qui se traduit par une réduction de leur consommation. La digestibilité des aliments ingérés a été augmentée chez les chenilles parasitées, mais non lorsque l'aliment consommé contenait de la nicotine. L'examen des valeurs de ECD et de ECI montre que l'ingestion de nicotine alimentaire réduit l'efficacité de la conversion des aliments digérés et ingérés par des chenilles non-parasitées, mais ces indices étaient supérieurs à ceux des chenilles parasitées. Ces résultats suggèrent que lorsque les chenilles sont parasitées après la mue du 33 stade, C. congregata n'influence pas l'alimentation de son hôte jusqu'à ce qu'il atteigne le dernier stade. La nicotine, dans les tissus de l'hôte, dépasse les effets du parasitisme. Il est probable qu'aucun des changements observés ne provient d'un effet direct sur les processus d'assimilation et de conversion mais plutôt de l'exposition des parasitoïdes à la nicotine dans l'hémolymphe de la chenille.
    Notes: Abstract The interactive effects of dietary nicotine (0.1%) and parasitism by Cotesia congregata (Say) (Braconidae) on post-ingestive utilization of food by the tobacco hornworm, Manduca sexta (L.) (Sphingidae) were studied in the laboratory. The rates of growth and consumption and the food utilization indices of third and fourth instar hornworms were not significantly influenced by the interactive effect of dietary nicotine and parasitism. However, parasitism reduced the growth rate of fifth instar hornworms, resulting from a reduction in their consumption rate. Efficiency of digestion of ingested food was enhanced in parasitized larvae, but not when they ingested diets containing nicotine. Ingestion of dietary nicotine reduced the efficiency of conversion of digested and ingested food of unparasitized hornworms as reflected in ECD and ECI values, but these indices were larger than in parasitized hosts. Results suggest that when hornworm larvae are parasitized after ecdysis to the third instar, C. congregata does not influence feeding by its larval host until the host reaches its terminal instar. Nicotine, within host tissues, ‘over-rides’ any effect caused by parasitism. It is probable that any change observed may not result from a direct effect on the assimilation and conversion processes of the hornworm larva but due to parasitoids' exposure to nicotine in the hornworm's hemolymph.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349589
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  • 4
    Electronic Resource
    Electronic Resource
    Soil conservation in Cuba: A key to the new model for agriculture (1993)
    Springer
    Agriculture and human values 10 (1993), S. 16-23 
    Details
    ISSN: 1572-8366
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Most aspects of agriculture in Cuba prior to 1989 were comparable to California: a high energy input, conventional agriculture (based on what the Cubans now call the “classical model”) in which little was done to protect the nation's soils from erosion, loss of fertility, salinization, and other forms of degradation. In stark contrast the new “Alternative Model,” which has been rapidly replacing the previous model since 1989, emphasizes soil conservation and rehabilitation and the general improvement of the nation's soils as the key to sustaining low-input production and attainment of food security. One of the first steps in implementing the new model was the launching of an ambitious program to reclassify, evaluate, and map the nation's soils in great detail, and to interpret the maps for management of sustainable production. A main feature of this program is coordinated fertility trials to determine, for each combination of crop and soil, the minimum quantity of plant nutrients needed to produce the crop. The build up and maintenance of soil fertility and productivity is being accomplished with various organic and mineral amendments and biofertilizers, produced or mined within the country (locally, where possible) and through rational management utilizing cover crops, green manures, crop successions (intercropping and rotations), and other appropriate technologies. Rehabilitation of degraded soils, tillage reduction, reforestation, vermiculture, vermicomposting, and other forms of waste cycling are other features of the new model that are important to soil conservation and maintenance for sustainable production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02217835
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of dietary nicotine and partial starvation of tobacco hornworm,Manduca sexta, on the survival and development of the parasitoidCotesia congregata (1992)
    Springer
    Entomologia experimentalis et applicata 65 (1992), S. 241-245 
    Details
    ISSN: 1570-7458
    Keywords: Allelochemicals ; partial starvation ; tri trophic interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A factorial experiment tested the effects of dietary nicotine and of partial starvation of fifth instar tobacco hornworm,Manduca sexta (L.) (Lepidoptera: Sphingidae), on the survival and development of the parasitoidCotesia congregata (Say) (Hymenoptera: Braconidae) in the laboratory. More parasitoids failed to emerge from partially starved hosts when reared on 0.1% nicotine diet, than from partially starved hosts fed control diet. Parasitoids reared from hornworms starved by 75% on nicotine diet had the longest development. The number of wasps was reduced when reared from hosts that were fed less than 50% of their daily consumption on nicotine diet. Pupal mortality was increased by dietary nicotine. Nicotine, within the host tissues, may be directly toxic to the parasitoids before their emergence from hornworms. Our data suggest that nicotine may act by mediating the availability of nutrients or reduce assimilation of nutrients by developing parasitoids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02343857
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of postemergence experience on searching and landing responses of the insect parasitoid,Cotesia congregata (Say) (Hymenoptera: Braconidae), to plants (1992)
    Springer
    Journal of insect behavior 5 (1992), S. 301-320 
    Details
    ISSN: 1572-8889
    Keywords: postemergence learning ; cross-induction ; foraging behavior ; Cotesia congregata (Say) ; Braconidae ; Hymenoptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Postemergence experience with one of six plant species, in the presence of the host larva, modified the searching response of reproductively mature females of Cotesia congregata(Say) to these plants in at least one of three ways: (1) an increased response to the plant experienced at emergence, (2) an increased response to other plants, or (3) an inhibited response to other plants. Landing and searching responses were differentially affected by postemergence experience. For example, postemergence experience with tobacco (a common plant) in the presence of the host larva induced a landing preference for this plant over parsley (a novel plant) but did not affect searching responses to either plant, whereas experience with parsley and the host larva induced an increased searching response to parsley but a landing preference for tobacco. Differential effects of postemergence experience may reflect the type of stimuli involved in searching or landing and may have adaptive significance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01049840
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  • 7
    Electronic Resource
    Electronic Resource
    Postemergence learning in the insect parasitoid,Cotesia congregata (Say) (Hymenoptera: Braconidae) (1991)
    Springer
    Journal of insect behavior 4 (1991), S. 727-742 
    Details
    ISSN: 1572-8889
    Keywords: postemergence learning ; early-adult experience ; Cotesia congregata (Say) ; Braconidae ; Hymenoptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Exposing newly emerged females of Cotesia congregata(Say) to wild cherry, an inherently unattractive plant, and their host larvae at 0–4 h after adult emergence induced a positive searching response to wild cherry and an inhibited response to cabbage, an attractive plant. Inherent responses were not affected when females were exposed to their hosts at 0–12 h and to cherry at 8–12 h after emergence. The induced response to cherry was constant until its disappearance at 6–7 days;inhibition of the response to cabbage was released at 4–5 days after emergence. Postemergence exposure to cherry and parasitoid cocoons induced similar but weaker searching responses. Induced searching responses exhibit features of associative learning and receptor modification. In addition to its presumed role in foraging, postemergence experience with plants may encourage assortative mating of C. congregatawithin suitable host habitats and, thus, facilitate local adaptations to specific plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01052227
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  • 8
    Electronic Resource
    Electronic Resource
    An analytical approach to neuronal connectivity (2004)
    Springer
    The European physical journal 42 (2004), S. 573-580 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. This paper describes how to analytically characterize the connectivity of neuromorphic networks taking into account the morphology of their elements. By assuming that all neurons have the same shape and are regularly distributed along a two-dimensional orthogonal lattice with parameter Δ, we obtain the exact number of connections and cycles of any length by applying convolutions and the respective spectral density derived from the adjacency matrix. It is shown that neuronal shape plays an important role in defining the spatial distribution of synapses in neuronal networks. In addition, we observe that neuromorphic networks typically present an interesting property where the pattern of connections is progressively shifted along the spatial domain for increasing connection lengths. This arises from the fact that the axon reference point usually does not coincide with the cell center of mass of neurons. Morphological measurements for characterization of the spatial distribution of connections, including the adjacency matrix spectral density and the lacunarity of the connections, are suggested and illustrated. We also show that Hopfield networks with connectivity defined by different neuronal morphologies, which are quantified by the analytical approach proposed herein, lead to distinct performances for associative recall, as measured by the overlap index. The potential of our approach is illustrated for digital images of real neuronal cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2005-00017-7
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  • 9
    Electronic Resource
    Electronic Resource
    Characterizing neuromorphologic alterations with additive shape functionals (2003)
    Springer
    The European physical journal 37 (2003), S. 109-115 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The complexity of a neuronal cell shape is known to be related to its function. Specifically, among other indicators, a decreased complexity in the dendritic trees of cortical pyramidal neurons has been associated with mental retardation. In this paper we develop a procedure to address the characterization of morphological changes induced in cultured neurons by over-expressing a gene involved in mental retardation. Measures associated with the multiscale connectivity, an additive image functional, are found to give a reasonable separation criterion between two categories of cells. One category consists of a control group and two transfected groups of neurons, and the other, a class of cat ganglionary cells. The reported framework also identified a trend towards lower complexity in one of the transfected groups. Such results establish the suggested measures as an effective descriptors of cell shape.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2004-00035-y
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  • 10
    Electronic Resource
    Electronic Resource
    Nickel molybdate as precursor of HDS catalysts: Effect of phase composition (1994)
    Springer
    Catalysis letters 26 (1994), S. 329-337 
    Details
    ISSN: 1572-879X
    Keywords: nickel molybdate ; HDS catalysts ; catalyst characterization (TPR)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sulfided αand β-NiMoO4 have been employed as model HDS catalysts, aiming to investigate the effect of phase composition of the precursor mixed oxide on the physicochemical characteristics and activity of the sulfides. Both sulfides are highly amorphous or microcrystalline, and could not be differentiated by means of XRD. The differences in BET area were also found to be minimal. However, it was found by means of TPR that the stable α-isomorph is reduced at lower temperatures than the unstable β-phase in both the oxidic and sulfided states. Sulfided β-NiMoO4 was found to be a better catalyst for the HDS of thiophene than the sulfided α-isomorph. This could be related to the higher stability of the former in H2, as decomposition of the active, amorphous Ni-Mo-S structures results in less active and more crystalline phases, as found by XRD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00810606
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