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  • Springer  (48)
  • American Geophysical Union  (6)
  • Oxford University Press  (3)
  • 1995-1999  (17)
  • 1990-1994  (31)
  • 1980-1984  (9)
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  • 1
    Electronic Resource
    Electronic Resource
    A neural network for processing olfactory-like stimuli (1991)
    Springer
    Bulletin of mathematical biology 53 (1991), S. 805-823 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Several critical issues associated with the processing of olfactory stimuli in animals (but focusing on insects) are discussed with a view to designing a neural network which can process olfactory stimuli. This leads to the construction of a neural network that can learn and identify the quality (direction cosines) of an input vector or extract information from a sequence of correlated input vectors, where the latter corresponds to sampling a time varying olfactory stimulus (or other generically similar pattern recognition problems). The network is constructed around a discrete time content-addressable memory (CAM) module which basically satisfies the Hopfield equations with the addition of a unit time delay feedback. This modification improves the convergence properties of the network and is used to control a switch which activates the learning or template formation process when the input is “unknown”. The network dynamics are embedded within a sniff cycle which includes a larger time delay (i.e. an integert s 〈1) that is also used to control the template formation switch. In addition, this time delay is used to modify the input into the CAM module so that the more dominant of two mingling odors or an odor increasing against a background of odors is more readily identified. The performance of the network is evaluated using Monte Carlo simulations and numerical results are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02461485
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  • 2
    Electronic Resource
    Electronic Resource
    Sex ratio genetics and the competitiveness of parasitic wasps (1992)
    Springer
    Bulletin of mathematical biology 54 (1992), S. 295-311 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract In the first part of the paper we analyse dynamics of the genetic mechanisms responsible for maintaining biased sex ratios in host-parasitoid interactions. We begin by reviewing recent results relating to the maintenance of sibmating in haplo-diploid populations. We then investigate the evolutionary stable sex ratio in populations in which all or some of the females mate with their brothers. In particular, we derive a diallelic one-locus model for studying evolutionary stable sex ratios in partially sibmating haplo-diploid populations. In the second part of the paper we review the impact of sex ratio on host-parasitoid populations. We then analyse how the sex ratio strategy of one parasitoid species may affect its interaction with another parasitoid species competing for the same host. In particular we show that, although a female biased sex ratio may enhance the inherent competitiveness of one species, it may also destabilize the ecological interaction of the three species so that all become extinct.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02464835
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  • 3
    Electronic Resource
    Electronic Resource
    Host-parasite dynamics and the evolution of host immunity and parasite fecundity strategies (1997)
    Springer
    Bulletin of mathematical biology 59 (1997), S. 427-450 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We explore evolutionarily stable co-evolution of host-macroparasite interactions in a discrete-time two-species population dynamics model, in which the dynamics may be stable, cyclic or chaotic. The macroparasites are assumed to harm host individuals through decreased reproductive output. Hosts may develop costly immune responses to defend themselves against parasites. Parasites compete with conspecifics by adjusting their fecundities. Overall, the presence of both parasites and the immune response in hosts produces more stable dynamics and lower host population sizes than that observed in the absence of the parasites. In our evolutionary analyses, we show that maximum parasite fecundity is always an evolutionarily stable strategy (ESS), irrespective of the type of population interaction, and that maximum parasite fecundity generally induces a minimum parasite population size through over-exploitation of the host. Phenotypic polymorphisms with respect to immunity in the host species are common and expected in ESS host strategies: the benefits of immunication depend on the frequency of the immune hosts in the population. In particular, the steady-state proportions of immune hosts depend, in addition to all the parameters of the parasite dynamics only on the cost of immunity and on the virulence of parasites in susceptible hosts. The implicit ecological dynamics of the host-parasite interaction affect the proportion of immune host individuals in the population. Furthermore, when changes in certain population parameters cause the dynamics of the host-parasite interaction to move from stability to cyclicity and then to chaos, the proportion of immune hosts tends to decrease; however, we also detected counter-examples to this result. As a whole, incorporating immunological and genetic aspects, as well as life-history trade-offs, into host-macroparasite dynamics produces a rich extension to the patterns observed in the models of ecological interactions and epidemics, and deserves more attention than is currently the case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02459459
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  • 4
    Electronic Resource
    Electronic Resource
    Development of intra-natural killer complex (NKC) recombinant and congenic mouse strains for mapping and functional analysis of NK cell regulatory loci (1999)
    Springer
    Immunogenetics 49 (1999), S. 238-241 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050486
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of seed size on seedling size in Virola surinamensis; a within and between tree analysis (1982)
    Springer
    Oecologia 53 (1982), S. 347-351 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We conducted a greenhouse study of the effects of initial seed mass on seedling characteristics in a Panamanian population of Virola surinamensis, a canopy tree in which mean seed mass of different individuals ranges from 1.34 to 4.04g. The system is of particular interest because birds preferentially eat fruits of small-seeded plants, leaving seedlings of large-seeded individuals under conditions of potentially severe sibling competition (Howe and Vande Kerckhove 1980). Effects of differences of mean seed mass between trees are explored using an analysis of variance, while effects of seed-mass variation within crops are demonstrated with a regression analysis. A two-way analysis of variance decisively shows effects of parental source and light condition on seedling height, leaf length, and dry shoot mass (all P〈0.0001). A posteriori tests show that differences in seedling characteristics reflect differences in initial seed mass, with especially strong differences apparent in shoot mass. Regression of seedling characteristics on initial seed mass shows that variation of seed size within a crop is sufficient to influence shoot mass at 15 weeks (P〈0.0001). Effects of size differences of seeds that land adjacent to each other, either under the parent or in monkey droppings, are documented with growth of pairs of seedlings in pots. Differences in shoot height and mass at 15 weeks are evident when seeds of average size differ by only 0.2 g, and dramatic differences are evident when paired seeds differ by an average of 1.5 g. Seedlings grow more when isolated than when planted with conspecifics. These experimental results offer indirect support for the hypothesis that small-seeded Virola parents secure an advantage in reproduction through differential dispersal, while large-seeded plants produce more competitive seedlings under their own crowns — an advantage most likely to be of importance when frugivores are scarce.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389011
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  • 6
    Electronic Resource
    Electronic Resource
    Response of American cockroach (Periplaneta americana) olfactory receptors to selected alcohol odorants and their binary combinations (1997)
    Springer
    Journal of comparative physiology 180 (1997), S. 701-709 
    Details
    ISSN: 1432-1351
    Keywords: Key words Olfaction  ;  Odor discrimination  ; Mixture perception
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The cockroach is known to possess several morphologically distinct types of sensilla on its antenna, each of which contain a couple or a few receptor cells that respond to an array of compounds. We recorded the response of cells exclusively from one type of sensillum to evaluate the variation in the response of the cells in these sensilla to three closely related alcohols and their binary mixtures. Our results indicate that cells within the class of those responsive to aliphatic alcohols are otherwise variable in their response to particular aliphatic alcohols and not easily classifiable into subclasses. They also indicate that patterns of responses among cells are not robust with respect to concentration. Finally, a considerable level of inhibition is indicated in the response of the receptor cells to binary mixtures compared with the response to pure odorants. The data suggest that discrimination of alcohols (and other odorants of general but not special significance) by the cockroach cannot be understood simply in terms of labeled lines or linear filters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003590050084
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  • 7
    Electronic Resource
    Electronic Resource
    BOOK REVIEW: Classical Electrodynamics, by John David Jackson (1999)
    Springer
    Foundations of physics 29 (1999), S. 133-135 
    Details
    ISSN: 1572-9516
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018821305089
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  • 8
    Electronic Resource
    Electronic Resource
    Olfactory perception in honeybees: Concatenated and mixed odorant stimuli, concentration, and exposure effects (1991)
    Springer
    Journal of comparative physiology 169 (1991), S. 215-230 
    Details
    ISSN: 1432-1351
    Keywords: Differential conditioning ; Proboscis extension reflex ; Learning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Here we present results obtained from 7 different series of experiments, all employing odor conditioning of proboscis extension in worker honeybees and each designed to address a particular question involving olfactory perception. The questions relate to: temporal complexity of odor cues; effects of concentration, suppression, and/or potentiation in mixture perception; acquisition and extinction rates, as well as levels of generalization associated with aliphatic compounds that have the same functional groups or same alkyl radical length; and the effects of continuous exposure to odorants in the first several days of adult life on various learning and discrimination tasks involving olfactory perception. From the data obtained in these experiments we were able to conclude the following: First, worker honeybees have a limited ability to perceive complex temporal odor-quality patterns in olfactory stimuli — they learn to associate the quality of only the last part of the stimulus with a sucrose reward. Second, we confirm that citral is qualitatively different in several perceptual contexts involving odor learning and conditioning and our results help elucidate the nature of these differences as they relate to learning, discrimination, mixture perception, and continuous exposure to particular odorants. Third, we appear to have uncovered some important perceptual differences between functional groups attached to the first as opposed to the second carbon atom of alkyl radicals. Finally, we failed to uncover any significant effects relating to continuous exposure to odorants during the first several days of a worker's adult life, despite evidence that considerable sensory development takes place during this period. Thus ontogenetic changes to the peripheral system due to environmental effects appear to leave basic perceptual systems unaltered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215869
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  • 9
    Electronic Resource
    Electronic Resource
    G. R. Carmichael, G. E. Folk and J. L. Schnoor (eds.): 1995, Preparing for Global Change: A Midwestern Perspective (1997)
    Springer
    Climatic change 37 (1997), S. 569-573 
    Details
    ISSN: 1573-1480
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005330330263
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  • 10
    Electronic Resource
    Electronic Resource
    Transgenic analysis of the 5′- and 3′-flanking regions of the NADH-dependent hydroxypyruvate reductase gene from Cucumis sativus L. (1995)
    Springer
    Plant molecular biology 28 (1995), S. 821-836 
    Details
    ISSN: 1573-5028
    Keywords: cucumber ; light-regulated gene expression ; NADH-dependent hydroxypyruvate reductase ; organ-specific gene expression ; peroxisome ; photorespiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 5′- and 3′-flanking regions of HPRA, a cucumber gene that encodes hydroxypyruvate reductase, were evaluated for regulatory activity with respect to light responsiveness and organ specificity. To define the functional regions of the 5′-flanking region of HPRA, a series of deletions was generated and the remaining portions fused to the β-glucuronidase (GUS) reporter gene (uidA) containing a minimal 35S promoter truncated at −90. The region from −66 to +39 was found to be necessary for light-regulated expression of the uidA reporter gene, while the region from −382 to −67 was found to be necessary for its leaf-specific expression. Further deletion of the HPRA 5′ flanking region to −590 resulted in high levels of root expression, suggesting the presence of a negative regulatory element responsible for silencing root expression of the HPRA gene between −590 and −383. The 3′-flanking region of the HPRA gene downstream of the polyadenylation site contains several sequence motifs resembling regulatory elements present in the promoters of several light-responsive genes. An 823 bp portion of the HPRA 3′-flanking region containing these putative regulatory elements enhanced GUS expression in leaves when placed downstream of the uidA reporter gene in the forward orientation, but not in the reverse orientation. When placed 5′ of the −90 35S promoter, the 823 bp fragment enhanced slightly, independently of orientation, the root tip-specific expression pattern intrinsic to the −90 35S promoter, indicating that in some cases this region can act as a transcriptional enhancer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00042068
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