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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 5 (1965), S. 0 
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary. Achenes of Chenopodium album are polymorphic; four categories can be recognized visually, brown-smooth, brown-reticulate, black-smooth and black-reticulate. All four types may be borne by one plant. The polymorphic seeds differ in germination requirements, responding differently to chilling and nitrate application.Dormant seeds contain at least one extractable germination inhibitor. The inhibitor fails to act in the presence of added nitrate.Nitrate is replaceable by some other nitrogen compounds and by chlorate. Nitrate application stimulates germination of C. album in soil.The ecological significance of seed polymorphism and the relevance of polymorphism to the interpretation of germination tests are briefly discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 33 (1985), S. 0 
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: The basic formulation for the mutual coupling between grounded circuits in the presence of a vertical conductor is used to examine the full electromagnetic and induced polarization response for a homogeneous half-space model. Both interfacial polarization at the steel/electrolyte boundary and induced eddy currents in the casing are accounted for in the analysis. It is shown that for mild steel casings the eddy currents, hitherto neglected, play an important role because of their strong frequency dependence. Calculated curves of the appar- ent complex resistivity as a function of frequency show that the overall response can be influenced by the state of corrosion at the surface of the casing.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 33 (1985), S. 0 
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Some numerical results for the apparent resistivity of a homogeneous half space containing a vertical steel well casing as measured by a dipole-dipole array are presented. The basic model includes the electromagnetic and induced polarization effects by allowing for frequency dependent eddy currents and an electrochemical boundary of the well casing. It is shown that the well casing produces an apparent complex resistivity response that could be mistaken for an induced polarization anomaly existing above a hydrocarbon deposit. This response of the well casing is strongly dependent on frequency.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 11 (1971), S. 0 
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary. The morphology of Rumex crispus L., R. obtusifolius L. and putative hybrids was examined. There appeared to be evidence of introgressive hybridization, particularly with backcrossing to R. crispus. Seed germination in plants from a mixed population varied widely, but when plotted against the hybrid index for the parent plants the could be partially separated in respect of germination behaviour. Some of the polymorphism previously described may have resulted from inclusion in the tests, together with pure parental types, of plants of hybrid origin which had introgressed to such an extent that they were almost indistinguishable from the parent species. The implications of the discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 22 (1995), S. 0 
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Dopamine D1 and SHT1d receptors are found on the terminals of afferent GABA neurons that synapse on the ventral tegmental area (VTA) dopamine neurons. The role of these receptors in the actions of cocaine was investigated using intracellular recordings in a brain slice preparation. Synaptic potentials were generated in the slice and GABA-mediated inhibitory post-synaptic potentials (IPSP) were identified.2. Stimulation of dopamine D1 receptors selectively enhanced the GABAb IPSP, and this effect was blocked by D1 antagonists. The magnitude of the IPSP was decreased when D1 antagonists were applied in isolation, suggesting tonic D1 receptor stimulation via dendritically released dopamine.3. Cocaine had an opposite effect and selectively decreased the magnitude of the GABAb IPSP. This action was mimicked by 5HT and the SHT1d agonist sumatriptan, and attenuated by the 5HTI1D/2c antagonist, metergoline. The action of cocaine was also mimicked by the 5HT-releasing agent, fenfluramine, and blocked by pre-incubation of the slice with the 5HT-depleting agent, para-chloroamphetamine.4. The results of this study suggest that dopamine and 5HT have opposing roles in modulating GABA input into VTA dopamine neurons. The actions of cocaine on this interplay may have implications for understanding its addictive properties.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 394 (1998), S. 78-82 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Rapid information transfer within the brain depends on chemical signalling between neurons that is mediated primarily by glutamate and GABA (γ-aminobutyric acid), acting at ionotropic receptors to cause excitatory or inhibitory postsynaptic potentials (EPSPs or IPSPs), respectively. In ...
    Type of Medium: Electronic Resource
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  • 7
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    Unknown
    Urbana, etc. : Periodicals Archive Online (PAO)
    American Journal of Psychology. 81:2 (1968:June) 258 
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 15 (1967), S. 169-189 
    ISSN: 1573-5052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé On a examiné les divers types de paturâges dans une région de montagnes en Angleterre. Voici un resumé des commenautés. Molinio-Arrhenatheretea Arrhenatheretalia Cynosurion Holco-Cynosuretum 1. Lolio-Cynosuretum 2. ?? Thymo-Festucetum 3. Nardo-Callunetea Nardetalia Nardo-Galion saxatilis Galio-Nardetum 4. On a relié les associations aux facteurs des silés et on a discuté la validité des groupes décrits.
    Notes: Summary The various types of pastures in a region of upland England were examined; the following is a conspectus of the communities. Molinio-Arrhenatheretea Arrhenatheretalia Cynosurion Holco-Cynosuretum 1. Lolio-Cynosuretum ?? Thymo-Festucetum 3. Nardo-Callunetea Nardetalia Nardo-Galion saxatilis Galio-Nardetum 4. The communities were related to site factors and the validity of the units described are briefly discussed.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-8477
    Keywords: Sit-and-wait predators ; predator distribution ; antlion larvae ; Myrmeleon immaculatus ; Kentucky ; invertebrate predation ; interference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We generated a computer model to analyse the effects of ‘shadow’ competition for sit-and-wait predators, particularly antlion larvae. The model used a simple foraging assessment rule to determine the quality of an antlion's location, and antlions relocated randomly in their habitat when a location proved to be of low quality. Shadow competition, or competition for food caused when one sit-and-wait predator intercepts moving prey before a second sit-and-wait predator is encountered, was incorporated into the model by restricting antlions to a bounded arena, and having prey for the antlions enter from the arena periphery. Antlions responded to shadow competition by relocating their pits to peripheral areas of their habitat. This peripheral accumulation of pits was most pronounced when antlion densities were high, and when prey availabilities were intermediate. An experimental test with the antlionMyrmeleon immaculatus supported the importance of shadow competition as a cause of observed pit distributions. Only the treatment which incorporated shadowing had pit distributions near the periphery, while the pit distributions in the control treatments did not differ from randomly generated distributions. We conclude that shadowing can influence sit-and-wait predator distributions when the prey distributions and movement patterns generate the conditions necessary for shadowing. But when prey availability is unpredictable, making assessment of patches difficult, or when prey do not originate in the periphery of the habitat, other factors, such as temperature or moisture, could be more important.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 45 (1990), S. 9-22 
    ISSN: 1573-5060
    Keywords: International Board for Plant Genetic Resources ; germplasm storage ; in vitro conservation, international survey ; databases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The availability of a wide genepool is a prerequisite for crop improvement and the material involved is usually conserved in collections. The genetic resources of most crops can be conserved as seed but some vegetatively propagated crops and those that produce recalcitrant seeds cannot. In vitro (tissue culture) storage methods including cryopreservation in liquid nitrogen are being developed to conserve such problem materials in a complementary way to the maintenance of whole plants in the field. To aid the effective utilization of plant genetic resources, it is essential that as much associated information as possible be available to potential users — the plant breeders. The International Board for Plant Genetic Resources (IBPGR) has taken the lead in genetic conservation work including related areas of information management. A significant example is the promotion of in vitro conservation. The IBPGR's In Vitro Programme includes the establishment of databases holding data on technological developments. An international survey of the in vitro research community is conducted by questionnaire every two years. Data are gathered on the crop under investigation, field of interest, propagation method, problem areas, characterization, disease indexing, exchange of cultures, and storage of material under normal or slow growth conditions or by cryopreservation. The survey returns are computerized into databases that are available for consultation by request. Such databases have been compiled for in vitro research carried out in 1980, 1983 and 1985. The 1985 database, for example, covers the work of 589 scientists who contributed information on 654 different species. The most recent phase of the project involved the circulation of a new questionnaire to approximately 2,500 scientists in over 70 countries. All databases are available for search requests.
    Type of Medium: Electronic Resource
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