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  • Springer  (1,016)
  • American Geophysical Union (AGU)
  • 2000-2004  (374)
  • 1975-1979  (642)
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  • 1
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    Abstracts (1977)
    Springer
    Details
    Publication Date: 1977-01-01
    Print ISSN: 0364-152X
    Electronic ISSN: 1432-1009
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering
    Published by Springer
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    PAPER CURRENT
  • 2
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    Benign prostate hyperplasia: evaluation of treatment response with DCE MRI (2004)
    Springer
    Details
    Publication Date: 2004-06-23
    Print ISSN: 0968-5243
    Electronic ISSN: 1352-8661
    Topics: Medicine , Physics
    Published by Springer
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  • 3
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    Membrane Fluidity of the Pentachlorophenol-MineralizingSphingomonassp. UG30 (2003)
    Springer
    Details
    Publication Date: 2003-09-01
    Print ISSN: 1053-0509
    Electronic ISSN: 1573-4994
    Topics: Physics
    Published by Springer
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  • 4
    Electronic Resource
    Electronic Resource
    Changes in barnacle population structure along an intertidal community gradient in the Florida Keys (1979)
    Springer
    Marine biology 53 (1979), S. 345-351 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Population distributions, densities and percentage deaths and individual size variations of the barnacles Chthamalus stellatus and Tetraclita squamosa, and the distribution of the vermetid snail Spirogluphus annulatus are measured to clarify determinants the Florida Keys (USA). The species composition of the pilings community and barnacle population densities correspond to physical gradients dependent on piling distance from shore. Interspecific competition for space is insignificant in determining C. stellatus presence or absence on pilings. Intraspecific crowding in highdensity zones of adult T. squamosa is evidenced by a significant decrease in basal diameter as density increases. The peak percentage of dead C. stellatus coincides with peak densities. The percentage of dead T. squamosa is at a low point at peak densities due to the ability of T. squamosa cyprids to settle and survive on adult shells in high-density regions. Feasible perturbation experiments for testing the importance of interspecific competition in determining the densities and vertical distributions of the species are discussed. The results of such experiments can be used to test the assumptions and predictions of the widely applied competition coefficient measure proposed by Levins (1968). Several theoretical deficiencies of Levins' measure are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391617
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Community interactions and zoogeography of the Indian Ocean Candaciidae (Copepoda: Calanoida) (1977)
    Springer
    Marine biology 43 (1977), S. 71-92 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eighteen species of Candaciidae have been identified from collections made at 339 stations in the Indian Ocean. Most species are zonally distributed; however, on the eastern and western sides of the Indian Ocean, species ranges are extended north or south by boundary currents. Factor analysis was used to cluster phenotypically similar species based on 130 characters taken from the maxilla (a feeding appendage), the first swimming foot, and the fifth foot (a secondary sexual structure). Four morphological clusters were extracted. Clusterings based on separate factor analyses limited to characters from feeding or from sexually adapted appendages are in substantial agreement with the clusters based on composite morphology. Two geographically recurrent groups of species were also identified, one from equatorial waters, one from the central gyre. Each recurrent group is composed of species exceptionally different in body size and belonging to different morphological clusters. Niches of the species are compared using Hutchinson's multidimensional hypervolume as a model. An attempt is made to describe the niche of each species in terms of environmental variables measured at stations where the species was abundant. Environmental variables (dimensions) included in this study are space, time, temperature, food, oxygen and salinity. Mean niche adaptations of most of the species are separable from congeners along at least one niche dimension. It is proposed that community relationships among the Candaciidae developed to prevent both gamete loss and to avoid trophic competition. It is postulated that newly evolving species underwent contemporaneous displacement of both secondary sexual and trophic characters as a condition for sympatry, or diverged in their physiological adaptations to escape sympatric interference.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392573
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of nitrogen deficiency on the growth and metabolism of Lemna minor L. (1977)
    Springer
    Planta 137 (1977), S. 259-264 
    Details
    ISSN: 1432-2048
    Keywords: Glycolysis ; Lemna ; Nitrogen deficiency ; Protein degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When Lemna is deprived of nitrogen, growth and respiration decrease and the pattern of 14CO2 release from [1-14C]glucose and [6-14C]glucose is consistent with a relatively strong inhibition of glycolysis. Protein degradation is enhanced but the concentration of free amino acid decreases. It is argued that the biological significance of the increased protein degradation does not lie in its contribution to respiration but as a mechanism to replace one set of enzymes adapted to a particular environmental condition (high nitrogen) with another set of enzymes adapted for low nitrogen in the environment. The change in enzyme pattern associated with the change from high to zero nitrogen in the growth medium has been examined for nine enzymes. The changes in activity observed are consistent with the observed apparent inhibition of glycolysis during nitrogen starvation, but do not explain the inhibition of the pentose phosphate pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388160
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  • 7
    Electronic Resource
    Electronic Resource
    Circadian rhythms of melatonin in European starlings exposed to different lighting conditions: relationship with locomotor and feeding rhythms (2000)
    Springer
    Journal of comparative physiology 186 (2000), S. 205-215 
    Details
    ISSN: 1432-1351
    Keywords: Key words Circadian rhythms ; Melatonin ; Light intensity ; Locomotor activity ; Starling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In passerine birds, the periodic secretion of melatonin by the pineal organ represents an important component of the pacemaker that controls overt circadian functions. The daily phase of low melatonin secretion generally coincides with the phase of intense activity, but the precise relationship between the melatonin and the behavioral rhythms has not been studied. Therefore, we investigated in European starlings (Sturnus vulgaris) (1) the temporal relationship between the circadian plasma melatonin rhythm and the rhythms in locomotor activity and feeding; (2) the persistence of the melatonin rhythm in constant conditions; and (3) the effects of light intensity on synchronized and free-running melatonin and behavioral rhythms. There was a marked rhythm in plasma melatonin with high levels at night and/or the inactive phase of the behavioral cycles in almost all birds. Like the behavioral rhythms, the melatonin rhythm persisted for at least 50 days in constant dim light. In the synchronized state, higher daytime light intensity resulted in more tightly synchronized rhythms and a delayed melatonin peak. While all three rhythms usually assumed a rather constant phase relationship to each other, in one bird the two behavioral rhythms dissociated from each other. In this case, the melatonin rhythm retained the appropriate phase relationship with the feeding rhythm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003590050020
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  • 8
    Electronic Resource
    Electronic Resource
    Introduction to the modelling of venereal disease (1979)
    Springer
    Journal of mathematical biology 8 (1979), S. 301-322 
    Details
    ISSN: 1432-1416
    Keywords: Mathematical modelling ; Venereal disease ; Gonorrhoea ; Criss-cross infection ; Nonhomogeneous mixing ; Asymptomatic infections ; Public health control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Summary The continually rising trend in the incidence of venereal diseases, especially gonorrhoea, in a large number of countries, both developed and developing is causing considerable public health concern. There is a disquieting volume of human suffering involved, as well as large economic losses in treatment and hospitalization. The present paper reviews the existing state of development in the mathematical modelling of the relevant disease dynamics. The ‘criss-cross’ nature of the infections, which in heterosexual contacts switch between the male and female populations, together with the nonlinear form of the rate of spread normally occurring in infectious diseases, leads to special types of simultaneous nonlinear differential equations. The simplest deterministic models available entail threshold phenomena connecting the maintenance of endemic states to the contact-rates, the personto-person infection-rates, and the removal-rates. A few stochastic results are also available. Special attention is given to the aspects of nonhomogeneous mixing, analysis of contact-rates, infection without immunity, allowance for asymptomatic infection, the recognition of many different classes of infected individuals, and the problems of public health forecasting and control. In some cases transient solutions of the equations can be used to forecast future trends in disease incidence, depending on appropriate assumptions about alternative public health interventions. It is concluded that further mathematical work should be concentrated on relatively simple models comprising no more than three or four district epidemiological groups for each sex. There should be both (i) more intense mathematical investigations, and (ii) new attempts to assimilate the models directly to public health venereal disease control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00276315
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  • 9
    Electronic Resource
    Electronic Resource
    Dual inhibitory control in crab leg muscles (1975)
    Springer
    Journal of comparative physiology 99 (1975), S. 211-230 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The physiological effects of two inhibitory axons supplying the stretcher muscles of three crabs (Hyas, Gecarcinus andGrapsus) were investigated, with a view to establishing the relative importance of pre- and postsynaptic inhibition. 2. InHyas, the specific inhibitory (SI) axon and the common inhibitory (CI) axon both exerted powerful presynaptic inhibition on the terminals of the excitatory axon. The effect of the SI axon was generally stronger, but some excitatory terminals were found in which CI axon stimulation was more effective. Thus, inhibition of the excitatory postsynaptic potential recorded intracellularly from the muscle fiber is the statistical result of variable inhibition at different excitatory terminals. 3. InHyas, postsynaptic inhibition was insignificant at low frequencies of stimulation, but increased at higher frequencies, for both SI and CI axons. The SI axon had a stronger postsynaptic effect than the CI axon. 4. InGecarcinus, the CI axon had a more powerful postsynaptic effect than the SI axon, whereas the SI axon was more effective at the presynaptic level. The two axons are specialized for different types of inhibition. 5. InGrapsus, the SI axon was more effective than the CI axon at both pre- and postsynaptic levels. Thus, considerable variation in pre- and postsynaptic connections of the two inhibitor axons occurs in different species of crabs. 6. In all species, the CI axon was least effective in muscle fibers with small, facilitating excitatory postsynaptic potentials. Sometimes the CI axon did not produce any effect at all in such fibers. 7. Presynaptic inhibition in crabs probably occurs mainly at narrow “bottlenecks” of the excitatory axon, where impulses are easily blocked by inhibitory synaptic action.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00613836
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  • 10
    Electronic Resource
    Electronic Resource
    Storing covariance with nonlinearly interacting neurons (1977)
    Springer
    Journal of mathematical biology 4 (1977), S. 303-321 
    Details
    ISSN: 1432-1416
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Summary A time-dependent, nonlinear model of neuronal interaction which was probabilistically analyzed in a previous article is shown here to be a natural generalization of the Hartline-Ratliff model of the Limulus retina. Although the primary physical variables in the model are the membrane potentials of neurons, the equations which govern the means and covariances of the membrane potentials are coupled through the average firing rates; as a consequence, the average firing rates control the selective storage and retrieval of covariance information. Motor learning in the cerebellar cortex is treated as a problem of covariance storage, and a prediction is made for the underlying synaptic plasticity: the change in synaptic strength between a parallel fiber and a Purkinje cell should be proportional to the covariance between discharges in the parallel fiber and the climbing fiber. Unlike previous proposals for synaptic plasticity, this prediction requires both facilitation and depression to occur (under different conditions) at the same synapse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00275079
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