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  • 1
    Electronic Resource
    Electronic Resource
    Phase resetting and dynamics in isolated atrioventricular nodal cell clusters (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 5 (1995), S. 184-192 
    Details
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the heart, the AV node is the primary conduction pathway between the atria and ventricles and subserves an important function by virtue of its rate-dependent properties. Cell clusters isolated from the rabbit atrioventricular (AV) node beat with a stable rhythm (cycle length: 300–520 ms) and are characterized by slow action potential upstroke velocities (7 to 30 V/s). The goal of this study is to better characterize the phase resetting and the rhythms during periodic stimulation of this slow inward current system. Single or periodic depolarizing pulses (20 ms in duration) were injected into AV nodal cell clusters using glass microelectrodes. Phase resetting curves of both strong, weak as well as discontinuous types were obtained by applying single current pulses of different intensities and latencies following every ten action potentials. Graded responses were elicited in a wide range of stimulus phases and amplitudes. A single premature stimulus caused a transient prolongation of the cycle length. Sustained periodic stimulation, at rates faster than the intrinsic beat rate, resulted in various N:M (stimulus frequency: action potential frequency) entrainment rhythms as well as periodic or irregular changes in action potential morphology. The changes in action potential characteristics were evaluated by computing the area under the action potential trace and above a fixed threshold (−45 mV). We show that the variations in action potential morphology play a major role in the onset of complicated dynamics observed in this experimental preparation. In this context, the prediction of entrainment rhythms using techniques based on the iteration of phase resetting curves (PRCs) is inadequate since the PRC does not carry information directly related to the changes in action potential morphology. This study demonstrates the need to consider graded events which, though not propagated, have important implications in the understanding of dynamical diseases of the heart. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.166066
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization and inheritance of partial resistance to downy mildew, Peronospora parasitica, in breeding material of broccoli, Brassica oleracea convar. botrytis var. italica (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 118 (1999), S. 0 
    Details
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Twenty doubled haploid broccoli lines from breeding material were evaluated for resistance to Peronospora parasitica at the seedling stage. All lines supported sporulation of the pathogen but to varying extents and intensities. Partial resistance of the more resistant lines,‘br8’and ‘br9′, reduced conidia production on cotyledons by 50-70% compared with the most susceptible lines. Inoculation of the two most resistant lines with 13 isolates of different geographical origins revealed that ‘br9′, showed a rather uniform level of resistance to all isolates while ‘br8’showed some isolate specificity Partial resistance was evaluated in six of the broccoli lines in a half diallel set of crosses. Disease assessment of seedlings showed that additive genetic effects explained 45.8% and 31.8% of the total variation of sporulation score and conidia production, respectively This suggests that recurrent selection for partial resistance to P. parasitica in early generation in breds or in populations of broccoli will be efficient to obtain cotyledon resistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1439-0523.1999.00409.x
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  • 3
    Electronic Resource
    Electronic Resource
    Comparison of mobile and stationary spore-sampling techniques for estimating virulence frequencies in aerial barley powdery mildew populations (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 44 (1995), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Gene frequencies in samples of aerial populations of barley powdery mildew (Erysiphe graminis f.sp. hordei), which were collected in adjacent barley areas and in successive periods of time, were compared using mobile and stationary sampling techniques. Stationary samples were collected from trap plants in three periods within 1 week at a distance of more than 1000 m from the nearest barley field. At four dates within the same 8-day period, other samples were collected by a mobile spore trap along four sampling routes of a total distance of 130 km around the stationary stand of exposure. The samples were characterized by virulence genotypes defined according to infection types on 12 near-isogenic barley lines, and frequencies of single virulence genes were subsequently calculated. The three samples collected at the stationary site differed significantly with respect to allele frequencies at three loci. The main wind direction was different in the three sampling periods, implying different powdery mildew sources. For the mobile exposure, the differences between routes were not significant for any locus. However, the routes differed most for the loci under direct selection by host resistances genes, indicating a different distribution of source varieties along routes. There was no difference between allele frequencies at different dates, indicating that the proportions of spores from different source varieties were similar at these dates. In conclusion, samples collected by the stationary technique will mainly reflect the source varieties present in the local area, whereas samples collected by the mobile spore trap will mainly reflect sources close to the sampling route. Therefore, sampling sites as well as sampling routes should be defined such that source varieties are representative for the overall varietal distribution in the survey region considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3059.1995.tb02742.x
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  • 4
    Electronic Resource
    Electronic Resource
    Prey size spectra and prey availability of larval and small juvenile cod (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 51 (1997), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The aim of the present study is to describe the prey preference characteristics of cod larvae and assess preference variability in relation to species and size composition of copepod prey. A further aim is to examine the hypothesis that dietary prey size spectra remain the same during the larval stage when viewed on a relative predator/prey size scale. The study is based on stomach analysis of larval/juvenile cod in the size range 10–35 mm from nursery grounds in the North Sea. Stomach contents (species, size) were compared to environmental composition and preference indices were calculated. Prey size spectra had the expected relationship to larval cod size, and preference for given copepod species could be ascribed to their relative size. Additional species-specific preferences were evident, for example the larger Pseudocalanus and the larger Calanus spp. were highly preferred. Available prey biomass was highest in the areas of a hydrographic front, where larvae have been shown to concentrate. Changes in prey availability with larval growth depend strongly on specific prey biomass spectra at a given location. Both increasing and decreasing prey availability at increasing larval size were indicated, dependent on location. The findings illustrate the usefulness of coupling dietary prey size spectra and biomass spectra of available prey sizes during studies of ichthyoplankton feeding ecology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1997.tb06107.x
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  • 5
    Electronic Resource
    Electronic Resource
    Seedling and adult plant resistance to downy mildew (Peronospora parasitica) in cauliflower (Brassica oleracea convar. botrytis var. botrytis) (1999)
    Oxford, U.K. and Cambridge, USA : Blackwell Science Ltd
    Plant pathology 48 (1999), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Seedlings of six cauliflower cultivars (Brassica oleracea convar. botrytis var. botrytis) were assessed for resistance to a Danish isolate of Peronospora parasitica, under controlled conditions. Resistance, characterized by restricted sporulation and necrotic dark flecks at the inoculation site on the cotyledons, was expressed in the hybrids 9306 F1, 9311 F1, and the open pollinated cultivar Perfection. Testing of the parent lines and F2 generations of the two resistant hybrids suggested that resistance was a dominantly inherited trait controlled by a single gene. Inoculation of the cultivars with seven isolates, from different geographical origins, showed that the resistance was isolate specific. The two hybrid cultivars expressing cotyledon resistance and two hybrids expressing susceptibility were assessed for adult plant resistance under field conditions. The AUDPC (Area Under the Disease Progress Curve), based on disease incidence and severity, revealed significant differences between the cultivars. At harvest, the cultivars exhibited significantly different levels of defoliation and curd attack. The cultivars 9306 F1 and 9311 F1 showed high levels of resistance in all assessments, whereas the two cultivars exhibiting susceptibility at the seedling stage, 9304 F1 and 9305 F1, also exhibited susceptibility through the adult plant stage. Thus, the resistance exhibited under field conditions resembled that identified at the seedling stage under controlled conditions. The results suggest that cotyledon resistance similar to that described could provide resistance throughout the adult plant stage, including curds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1999.00388.x
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  • 6
    Electronic Resource
    Electronic Resource
    Nitrogen-induced changes in colony density and spore production of Erysiphe graminis f.sp. hordei on seedlings of six spring barley cultivars (1997)
    Oxford, U.K. and Cambridge, USA : Blackwell Science Ltd
    Plant pathology 46 (1997), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The influence of increasing nitrogen supply (30, 60, 120 and 240 mg N per pot) on susceptibility was studied on seedlings of six cultivars of spring barley inoculated with virulent isolates of powdery mildew. The colony density (CD) measured as colonies per cm2 was significantly increased with increasing application of nitrogen on all cultivars, and a significant interaction was found between N and cultivar. The different reactions of the cultivars could not be ascribed to lack of N uptake. In general, increasing N application enhanced the sporulation capacity of colonies (CSC) irrespective of increased CD and the cumulative production of spores per cm2 leaf (CSCM) increased strongly with N application in all cultivars. No interaction between N and cultivar was found for the latter component. The increase in CSCM closely corresponded with the increase in N content and fresh weight of uninoculated leaves. No interaction between N treatment and powdery mildew isolates was found for infection efficiency and spore production per colony, when tested on one cultivar. The N-induced changes in infection and sporulation can explain the main part of the increasing effect of N fertilization on powdery mildew development in the field. The results indicate that it may be possible to breed for or select barley cultivars with low N impact on powdery mildew development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1997.d01-224.x
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  • 7
    Electronic Resource
    Electronic Resource
    A Prescription Rejected: Market Solutions to Problems of Public Sector Governance (1998)
    Boston, USA and Oxford, UK : Blackwell Publishers Inc.
    Governance 11 (1998), S. 0 
    Details
    ISSN: 1468-0491
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Political Science
    Notes: The New Public Management includes the idea of incorporating market mechanisms in public sector governance. In the Danish case, market reforms have scarcely been used; private sector supplies of public services have not increased during the last decade. The lack of success of market reform in Denmark is explained by the strong institutions of traditional public sector governance operating at the micro-level. Formal and informal hierarchy and formal and informal corporatism hold a strong grip on public sector governance. The very decentralized structure of the Danish public sector decreases the importance of central government in terms of reform strategies. Strong interests and institutional constraints keep reforms in the Danish public sector within a hierarchical mode of governance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/0952-1895.00072
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  • 8
    Electronic Resource
    Electronic Resource
    Collective action in watershed management -- experiences from the Andean hillsides (1999)
    Springer
    Agriculture and human values 16 (1999), S. 257-266 
    Details
    ISSN: 1572-8366
    Keywords: Collective action ; Colombia ; Negotiation ; Platforms ; Representation ; Social constructivism ; Stakeholder analysis ; Third party facilitation ; Watershed management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Watersheds constitute a special case of multiple-use common pool resources (CPRs). In a textual sense, watersheds tend to be mosaics of privately owned and managed patches of land. At the same time, however, watersheds are also ecosystems in which multiple resources and people interact through an infinity of bio-physical processes. Through such interaction, new watershed-level qualities emerge that, together with other factors, condition watershed users' continued resource use and access. In this perspective, watersheds become common-pool resources. Hence, watershed users do not only manage their individual plots, crops, forests, etc., knowingly or not, they manage landscape patterns and bio-physical processes that transcend their private property. In this context, drawing on experiences gained through participatory action research in a micro-watershed in the Andean hillsides of southern Colombia, this paper describes a process aimed at fostering collective watershed management. The paper illustrates the importance of platforms as a mechanism for negotiating and coordinating collective action by multiple users and discusses the issues of representation on such platforms as well as the importance of third party facilitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007522912099
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  • 9
    Electronic Resource
    Electronic Resource
    Intermolecular contact interactions and their temperature dependence (1995)
    Springer
    Journal of solution chemistry 24 (1995), S. 267-284 
    Details
    ISSN: 1572-8927
    Keywords: Contact interactions ; solubility parameters ; cohesive energy ; thermodynamics of mixing ; inverse gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A model, based on inverse gas chromatography experiments, has been developed for intermolecular interaction and its temperature dependence. The model ascribes to each substance a four-component solubility parameter; the four components reflect the van der Waals, polar, electron donor, and electron acceptor interactive properties. Their values depend on temperature in the same manner as does the cohesive energy. The latter was found to depend only on the critical temperature, the acentric factor, and the reduced temperature. The model was used for evaluation of the solubility parameters from polymer-solvent interaction coefficients and their temperature dependence with high accuracy. For binary solventsolvent mixtures, the free energy of mixing and its temperature dependence, as well as enthalpy of mixing can be derived from this model with a good accuracy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00979194
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  • 10
    Electronic Resource
    Electronic Resource
    A Simple Goodness-of-fit Test for Linear Models Under a Random Design Assumption (1998)
    Springer
    Annals of the Institute of Statistical Mathematics 50 (1998), S. 253-275 
    Details
    ISSN: 1572-9052
    Keywords: Nonparametric regression check ; validation of goodness of fit ; L2-distance ; equivalence of regression functions ; random design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Let (X,Y) denote a random vector with decomposition Y = f(X) + ε where f(x) = E[Y ¦ X = x] is the regression of Y on X. In this paper we propose a test for the hypothesis that f is a linear combination of given linearly independent regression functions g1,..,gd. The test is based on an estimator of the minimal L2-distance between f and the subspace spanned by the regression functions. More precisely, the method is based on the estimation of certain integrals of the regression function and therefore does not require an explicit estimation of the regression. For this reason the test proposed in this paper does not depend on the subjective choice of a smoothing parameter. Differences between the problem of regression diagnostics in the nonrandom and random design case are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003439114929
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