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  • Springer  (79)
  • 1990-1994  (56)
  • 1965-1969  (7)
  • 1905-1909  (16)
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  • 1
    Electronic Resource
    Electronic Resource
    Al3+-Ca2+ interactions in aluminum rhizotoxicity (1993)
    Springer
    Planta 192 (1993), S. 104-109 
    Details
    ISSN: 1432-2048
    Keywords: Aluminum toxicity ; Calcium displacement ; Electrical potential ; Root ; Triticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several mineral rhizotoxicities, including those induced by Al3+, H+, and Na+, can be relieved by elevated Ca2+ in the rooting medium. This leads to the hypothesis that the toxic cations displace Ca2+ from transport channels or surface ligands that must be occupied by Ca2+ in order for root elongation to occur. In this study with wheat (Triticum aestivum L.) seedlings, we have determined, in the case of Al3+, that (i) Ca2+, Mg2+, and Sr2+ are equally ameliorative, (ii) that root elongation does not increase as Ca2+ replaces Mg2+ or Sr2+ in the rooting media, and (iii) that rhizotoxicity is a function solely of Al3+ activity at the root-cell membrane surface as computed by a Gouy-Chapman-Stern model. The rhizotoxicity was indifferent to the computed membrane-surface Ca2+ activity. The rhizotoxicity induced by high levels of tris(ethylenediamine)cobaltic ion (TEC3+), in contrast to Al3+, was specifically relieved by Ca2+ at the membrane surface. The rhizotoxicity induced by H+ exhibited a weak specific response to Ca2+ at the membrane surface. We conclude that the Ca2+-displacement hypothesis fails in the case of Al3+ rhizotoxicity and that amelioration by cations (including monovalent cations) occurs because of decreased membrane-surface negativity and the consequent decrease in the membrane-surface activity of Al3+. However, TEC3+, but not Al3+, may be toxic because it inhibits Ca2+ uptake. The nature of the specific H+-Ca2+ interaction is uncertain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198699
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  • 2
    Electronic Resource
    Electronic Resource
    The kinetics of type 1 phytochrome in green, light-grown wheat (Triticum aestivum L.) (1994)
    Springer
    Planta 194 (1994), S. 136-142 
    Details
    ISSN: 1432-2048
    Keywords: Light and plant growth ; Photoperiodism ; Phytochrome (type 1) ; Triticum (phytochrome)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The kinetics of type 1 phytochrome were investigated in green, light-grown wheat. Phytochrome was measured by a quantitative sandwich enzyme-linked immunosorbent assay using monoclonal antibodies. The assay was capable of detecting down to 150 pg of phytochrome. In red light, rapid first-order destruction of the far-red-light-absorbing form of phytochrome (Pfr) with a half-life of 15 min was observed. Following white light terminated by red, phytochrome synthesis was delayed in darkness by about 15 h compared to plants given a terminal far-red treatment. Synthesis of the red-light-absorbing form of phytochrome (Pr) was zero-order in these experiments. Phytochrome synthesis in far-red light was approximately equal to synthesis in darkness in wheat although net destruction occurred in light-grown Avena sativa tissues in continuous far-red light, as has been reported for other monocotyledons. In wheat, destruction of Pfr apparently did not occur below a certain threshold level of Pfr or Pfr/total phytochrome. These results are consistent with an involvement of type 1 phytochrome in the photoperiodic control of flowering in wheat and other long-day plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201044
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  • 3
    Electronic Resource
    Electronic Resource
    Preface (1993)
    Springer
    Theoretical and computational fluid dynamics 5 (1993), S. 139-139 
    Details
    ISSN: 1432-2250
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00271654
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  • 4
    Electronic Resource
    Electronic Resource
    The urate oxidase gene of Drosophila pseudoobscura and Drosophila melanogaster: Evolutionary changes of sequence and regulation (1992)
    Springer
    Journal of molecular evolution 34 (1992), S. 62-77 
    Details
    ISSN: 1432-1432
    Keywords: Urate oxidase ; Drosophila pseudoobscura ; Drosophila melanogaster ; Nucleotide sequence ; Evolutionary comparison ; Gene regulation ; Malpighian tubules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The urate oxidase (UO) transcription unit of Drosophila pseudoobscura was cloned, sequenced, and compared to the UO transcription unit from Drosophila melanogaster. In both species the UO coding region is divided into two exons of approximately equal size. The deduced D. pseudoobscura and D. melanogaster UO peptides have 346 and 352 amino acid residues, respectively. The nucleotide sequences of the D. pseudoobscura and D. melanogaster UO protein-coding regions are 82.2% identical whereas the deduced amino acid sequences are 87.6% identical with 42 amino acid changes, 33 of which occur in the first exon. Although the UO gene is expressed exclusively within the cells of the Malpighian tubules in both of these species, the temporal patterns of UO gene activity during development are markedly different. UO enzyme activity, UO protein, and UO mRNA are found in the third instar larva and adult of D. melanogaster but only in the adult stage of D. pseudoobscura. The intronic sequences and the extragenic 5′ and 3′ flanking regions of the D. pseudoobscura and D. melanogaster UO genes are highly divergent with the exception of eight small islands of conserved sequence along 772 by 5′ of the UO protein-coding region. These islands of conserved sequence are possible UO cis-acting regulatory elements as they reside along the 5′ flanking DNA of the D. melanogaster UO gene that is capable of conferring a wild-type D. melanogaster pattern of UO regulation on a UO-lacZ fusion gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00163853
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of in situ post-deposition annealing on the formation of α-In2Se3 thin films grown by elemental evaporation (1992)
    Springer
    Applied physics 54 (1992), S. 293-299 
    Details
    ISSN: 1432-0630
    Keywords: 68.55 ; 73.60F ; 78.65J ; 81.15E
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Stoichiometric polycrystalline In2Se3 thin films have been grown by elemental evaporation on both glass and quartz substrates. The compositions are examined by DAN fluorimetry and X-ray photoelectron spectroscopy (XPS). Structure of the films are characterized by X-ray diffraction. The structure of this α-form of thin films have been determined to be hexagonal. Optimization of the preparative conditions employed for elemental evaporation, helped in preparing monophasic films by the suppression of other phases to a very minor extent. Influence of annealing conditions on the stoichiometry of the films are investigated in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323853
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  • 6
    Electronic Resource
    Electronic Resource
    Spike initiation and propagation on axons with slow inward currents (1993)
    Springer
    Biological cybernetics 68 (1993), S. 209-214 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract We investigate spike initiation and propagation in a model axon that has a slow regenerative conductance as well as the usual Hodgkin-Huxley type sodium and potassium conductances. We study the role of slow conductance in producing repetitive firing, compute the dispersion relation for an axon with an additional slow conductance, and show that under appropriate conditions such an axon can produce a traveling zone of secondary spike initiation. This study illustrates some of the complex dynamics shown by excitable membranes with fast and slow conductances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224853
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  • 7
    Electronic Resource
    Electronic Resource
    Reduction of conductance-based neuron models (1992)
    Springer
    Biological cybernetics 66 (1992), S. 381-387 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract We present a scheme for systematically reducing the number of differential equations required for biophysically realistic neuron models. The techniques are general, are designed to be applicable to a large set of such models and retain in the reduced system as high a degree of fidelity to the original system as possible. As examples, we provide reductions of the Hodgkin-Huxley system and the A-current model of Connor et al. (1977).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197717
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  • 8
    Electronic Resource
    Electronic Resource
    Binding by temporal structure in multiple feature domains of an oscillatory neuronal network (1994)
    Springer
    Biological cybernetics 70 (1994), S. 397-405 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract. An important step in visual processing is the segregation of objects in a visual scene from one another and from the embedding background. According to current theories of visual neuroscience, the different features of a particular object are represented by cells which are spatially distributed across multiple visual areas in the brain. The segregation of an object therefore requires the unique identification and integration of the pertaining cells which have to be “bound” into one assembly coding for the object in question. Several authors have suggested that such a binding of cells could be achieved by the selective synchronization of temporally structured responses of the neurons activated by features of the same stimulus. This concept has recently gained support by the observation of stimulus-dependent oscillatory activity in the visual system of the cat, pigeon and monkey. Furthermore, experimental evidence has been found for the formation and segregation of synchronously active cell assemblies representing different stimuli in the visual field. In this study, we investigate temporally structured activity in networks with single and multiple feature domains. As a first step, we examine the formation and segregation of cell assemblies by synchronizing and desynchronizing connections within a single feature module. We then demonstrate that distributed assemblies can be appropriately bound in a network comprising three modules selective for stimulus disparity, orientation and colour, respectively. In this context, we address the principal problem of segregating assemblies representing spatially overlapping stimuli in a distributed architecture. Using synchronizing as well as desynchronizing mechanisms, our simulations demonstrate that the binding problem can be solved by temporally correlated responses of cells which are distributed across multiple feature modules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004220050043
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  • 9
    Electronic Resource
    Electronic Resource
    Binding by temporal structure in multiple feature domains of an oscillatory neuronal network (1994)
    Springer
    Biological cybernetics 70 (1994), S. 397-405 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract An important step in visual processing is the segregation of objects in a visual scene from one another and from the embedding background. According to current theories of visual neuroscience, the different features of a particular object are represented by cells which are spatially distributed across multiple visual areas in the brain. The segregation of an object therefore requires the unique identification and integration of the pertaining cells which have to be “bound” into one assembly coding for the object in question. Several authors have suggested that such a binding of cells could be achieved by the selective synchronization of temporally structured responses of the neurons activated by features of the same stimulus. This concept has recently gained support by the observation of stimulus-dependent oscillatory activity in the visual system of the cat, pigeon and monkey. Furthermore, experimental evidence has been found for the formation and segregation of synchronously active cell assemblies representing different stimuli in the visual field. In this study, we investigate temporally structured activity in networks with single and multiple feature domains. As a first step, we examine the formation and segregation of cell assemblies by synchronizing and desynchronizing connections within a single feature module. We then demonstrate that distributed assemblies can be appropriately bound in a network comprising three modules selective for stimulus disparity, orientation and colour, respectively. In this context, we address the principal problem of segregating assemblies representing spatially overlapping stimuli in a distributed architecture. Using synchronizing as well as desynchronizing mechanisms, our simulations demonstrate that the binding problem can be solved by temporally correlated responses of cells which are distributed across multiple feature modules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203232
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  • 10
    Electronic Resource
    Electronic Resource
    Preface (1991)
    Springer
    Theoretical and computational fluid dynamics 2 (1991), S. 251-252 
    Details
    ISSN: 1432-2250
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00271464
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