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  • Elsevier  (130)
  • Springer  (104)
  • 1995-1999  (133)
  • 1990-1994  (92)
  • 1970-1974  (7)
  • 1935-1939  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Influence of 2,3,5-Triiodobenzoic Acid and 1-N-Naphthylphthalamic Acid on Indoleacetic Acid Transport in Carnation Cuttings: Relationship with Rooting (1999)
    Springer
    Journal of plant growth regulation 18 (1999), S. 183-190 
    Details
    ISSN: 1435-8107
    Keywords: Key Words.Dianthus caryophyllus—Indoleacetic acid—Naphthylphthalamic acid—Polar auxin transport—rooting of cuttings—Triiodobenzoic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. 3H-IAA transport in excised sections of carnation cuttings was studied by using two receiver systems for recovery of transported radioactivity: agar blocks (A) and wells containing a buffer solution (B). When receivers were periodically renewed, transport continued for up to 8 h and ceased before 24 h. If receivers were not renewed, IAA transport decreased drastically due to immobilization in the base of the sections. TIBA was as effective as NPA in inhibiting the basipetal transport irrespective of the application site (the basal or the apical side of sections). The polarity of IAA transport was determined by measuring the polar ratio (basipetal/acropetal) and the inhibition caused by TIBA or NPA. The polar ratio varied with receiver, whereas the inhibition by TIBA or NPA was similar. Distribution of immobilized radioactivity along the sections after a transport period of 24 h showed that the application of TIBA to the apical side or NPA to the basal side of sections, increased the radioactivity in zones further from the application site, which agrees with a basipetal and acropetal movement of TIBA and NPA, respectively. The existence of a slow acropetal movement of the inhibitor was confirmed by using 3H-NPA. From the results obtained, a methodological approach is proposed to measure the variations in polar auxin transport. This method was used to investigate whether the variations in rooting observed during the cold storage of cuttings might be related to changes in polar auxin transport. As the storage period increased, a decrease in intensity and polarity of auxin transport occurred, which was accompanied by a delay in the formation and growth of adventitious roots, confirming the involvement of polar auxin transport in supplying the auxin for rooting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00007068
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  • 2
    Electronic Resource
    Electronic Resource
    Performance and feeding behavior of Ceratitis capitata: comparison of a wild population and a laboratory population (1998)
    Springer
    Entomologia experimentalis et applicata 87 (1998), S. 67-72 
    Details
    ISSN: 1570-7458
    Keywords: fruit flies ; feeding behavior ; diet nutritional values ; insects ; Diptera ; Tephritidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Experiments were carried out to test the performance and some aspects of feeding behavior in two populations of Ceratitis capitata (a population reared in the laboratory for 16 years, i.e., approximately 160 generations, and a wild one obtained from infested coffee, Coffea arabica grains). Two types of food were used in the experiment: an artificial yeast diet used for laboratory rearing and papaya (Carica papaya), a natural host of the fly. The performance parameters tested were percent emergence, time to emergence, adult female size, and egg production during the pre-oviposition phase (first five days of adult life). The behavioral aspects tested were food preference by newly hatched larvae, induction, estimated ingestion of the two diets, whether the larvae placed on one diet stayed there or moved to the other diet, and acceptance of food for oviposition. The results indicated that the performance of the wild population was superior when the flies fed on papaya, whereas the performance of the laboratory population was similar with the two diets; the wild population showed a strong preference for papaya in all choice experiments, whereas the laboratory population showed no diet preference; the females of the wild population only oviposited on pieces of papaya that had not been peeled, and did not oviposit in the artificial diet; the females of the laboratory population oviposited indiscriminately on unpeeled and peeled papaya and on the artificial diet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003211931514
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  • 3
    Electronic Resource
    Electronic Resource
    Variables Aggregation in Time Varying Discrete Systems (1998)
    Springer
    Acta biotheoretica 46 (1998), S. 273-297 
    Details
    ISSN: 1572-8358
    Keywords: Approximate aggregation ; population dynamics ; time scales ; strong ergodicity ; cyclic environment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this work we extend approximate aggregation methods in time discrete linear models to the case of time varying environments. Approximate aggregation consists in describing some features of the dynamics of a general system involving many coupled variables in terms of the dynamics of a reduced system with a few number of variables. We present a time discrete time varying model in which we distinguish two time scales. By using perturbation methods we transform the system to make the global variables appear and build up the aggregated system. The asymptotic relationships between the general and aggregated systems are explored in the cases of a cyclically varying environment and a changing environment in process of stabilization. We show that under quite general conditions the knowledge of the behavior of the aggregated system characterizes that of the general system. The general method is also applied to aggregate a multiregional time dependent Leslie model showing that the aggregated model has demographic rates depending on the equilibrium proportions of individuals in the different patches.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001741327984
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of Individual Aggressiveness on the Dynamics of Competitive Populations (1997)
    Springer
    Acta biotheoretica 45 (1997), S. 321-333 
    Details
    ISSN: 1572-8358
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two populations are subdivided into two categories of individuals (hawks and doves). Individuals fight to have access to a resource which is necessary for their survival. Conflicts occur between individuals belonging to the same population and to different populations. We investigate the long term effects of the conflicts on the stability of the community. The modelis a set of ODE's with four variables corresponding to hawk and dove individuals of the two populations. Two time scales are considered. A fast time scale is used to describe frequent encounters and fightings between individuals trying to monopolize the resource. A slow time scale is used for the demography and the long term effects of encounters. We use aggregation methods in order to reduce this model into a system of two ODE's only for the total densities of the two populations which is found to be a classical Lotka-Volterra competition model. We study different cases of proportions of hawks and doves in both populations on the global coexistence and the mutal exclusion of the two populations. Pure dove tactics in both populations are unstable. In cases of mixed hawk and dove in both populations, there is coexistence. Pure dove or mixed hawk-dove tactics in one population can coexist with pure hawks in the other one when the costs of fightings between hawks are large enough.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1000688111421
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  • 5
    Electronic Resource
    Electronic Resource
    Linear discrete models with different time scales (1995)
    Springer
    Acta biotheoretica 43 (1995), S. 465-476 
    Details
    ISSN: 1572-8358
    Keywords: Approximate aggregation of variables ; population dynamics ; perturbations ; time scales ; eigenvalues and eigenvectors analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Aggregation of variables allows to approximate a large scale dynamical system (the micro-system) involving many variables into a reduced system (the macro-system) described by a few number of global variables. Approximate aggregation can be performed when different time scales are involved in the dynamics of the micro-system. Perturbation methods enable to approximate the large micro-system by a macro-system going on at a slow time scale. Aggregation has been performed for systems of ordinary differential equations in which time is a continuous variable. In this contribution, we extend aggregation methods to time-discrete models of population dynamics. Time discrete micro-models with two time scales are presented. We use perturbation methods to obtain a slow macro-model. The asymptotic behaviours of the micro and macro-systems are characterized by the main eigenvalues and the associated eigenvectors. We compare the asymptotic behaviours of both systems which are shown to be similar to a certain order.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00713565
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  • 6
    Electronic Resource
    Electronic Resource
    Population Dynamics Modelling in an Hierarchical Arborescent River Network: An Attempt with Salmo trutta (1998)
    Springer
    Acta biotheoretica 46 (1998), S. 223-234 
    Details
    ISSN: 1572-8358
    Keywords: arborescent river network ; Leslie matrix ; aggregation methods ; discrete time models ; Salmo trutta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The balance between births and deaths in an age-structured population is strongly influenced by the spatial distribution of sub-populations. Our aim was to describe the demographic process of a fish population in an hierarchical dendritic river network, by taking into account the possible movements of individuals. We tried also to quantify the effect of river network changes (damming or channelling) on the global fish population dynamics. The Salmo trutta life pattern was taken as an example for. We proposed a model which includes the demographic and the migration processes, considering migration fast compared to demography. The population was divided into three age-classes and subdivided into fifteen spatial patches, thus having 45 state variables. Both processes were described by means of constant transfer coefficients, so we were dealing with a linear system of difference equations. The discrete case of the variable aggregation method allowed the study of the system through the dominant elements of a much simpler linear system with only three global variables: the total number of individuals in each age-class. From biological hypothesis on demographic and migratory parameters, we showed that the global population dynamics of fishes is well characterized in the reference river network, and that dams could have stronger effects on the global dynamics than channelling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001785110237
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  • 7
    Electronic Resource
    Electronic Resource
    Profile of the “Departamento de Ciencia de Materiales e Ingeniería Metalúrgica, Escuela Politécnica Superior, Universidad Carlos III de Madrid” (1999)
    Springer
    Advanced performance materials 6 (1999), S. 85-98 
    Details
    ISSN: 1572-8765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008730130021
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  • 8
    Electronic Resource
    Electronic Resource
    Coronal hole flux tubes and the problem of relating interplanetary and solar features (1996)
    Springer
    Astrophysics and space science 243 (1996), S. 113-121 
    Details
    ISSN: 1572-946X
    Keywords: Coronal holes ; Solar wind sources
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Coronal flux tubes have in general very large divergence, and the properties of their flow vary greatly inside the flux tube. We present here a general description of the evolution and the characteristics of coronal holes and discuss how these characteristics may lead to erroneous associations, between interplanetary and solar structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00644040
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  • 9
    Electronic Resource
    Electronic Resource
    Disconnection of coronal field lines due to the emergence of new photospheric flux as the cause of CMEs and interplanetary shocks (1996)
    Springer
    Astrophysics and space science 243 (1996), S. 123-127 
    Details
    ISSN: 1572-946X
    Keywords: Solar activity ; CMEs ; Interplanetary shocks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A scenario is presented whereby CMEs and interplanetary shocks are consequences of a large scale rearrangement of the coronal magnetic field induced by the disconnection of field lines from the solar surface due to the emergence of flux with opposite polarity. In this scenario the CME is the mass released from the previously closed structure and the interplanetary shock is formed by the injection of faster solar wind from an extended or newly created coronal hole which results from the opening of the field lines. Here CMEs and interplanetary shocks are associated events, but not cause-effect related. Observational and computational evidence supporting this view is provided.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00644041
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  • 10
    Electronic Resource
    Electronic Resource
    Consequences of the Collision Between the Gas Ejected in the Collapse of a White Dwarf and a Low-Mass Star (1998)
    Springer
    Astrophysics and space science 263 (1998), S. 287-290 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1002159607585
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