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  • ENERGY PRODUCTION AND CONVERSION  (6)
  • PHYSICAL SCIENCES  (2)
  • dormancy  (2)
Collection
Keywords
Publisher
Years
  • 1
    Electronic Resource
    Electronic Resource
    Seed coat structure and dormancy (1992)
    Springer
    Plant growth regulation 11 (1992), S. 201-209 
    Details
    ISSN: 1573-5087
    Keywords: Seed coat structure ; dormancy ; permeability ; Dichrostachys cinerea ; natural dormancy-breaking factors ; inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An understanding of dormancy mechanisms is of ecological and economic importance. Identification of the level at which dormancy is imposed appears to be species specific. The variation brought about by this therefore requires that developmental studies be included in seed coat dormancy experiments. In most cases, a site of permeability can be identified during the developmental process, and this information can be utilized later to remove dormancy. Under natural conditions, the removal of seed coat dormancy requires the interaction of a number of ecological and physiological dormancy-breaking cues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00024559
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    The role of natural agents in the removal of coat-imposed dormancy in Dichrostachys cinerea (L.) Wight et Arn. seeds (1994)
    Springer
    Plant growth regulation 14 (1994), S. 51-59 
    Details
    ISSN: 1573-5087
    Keywords: bush encroachment ; Dichrostachys cinerea ; dormancy ; germination ; impermeability ; natural factors ; seed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstracts Dichrostachys cinerea seeds are impermeable to water and do not germinate readily. The plant, however, contributes to a bush encroachment problem, minimising visibility in wildlife reserves and reducing the area available for grazing. Natural dormancy-breaking conditions must therefore exist, promoting the germinability of these normally dormant seeds. Diurnal temperature fluctuations (50°C/15°C), especially when combined with moisture were found to break dormancy. High temperatures, such as those generated by fire, destroyed seeds. Seeds ingested by herbivorous browsers such as nyala, became permeable. Seed burial for 48 weeks, was a more effective treatment than storage in promoting permeability. Distribution of D. cinerea will therefore be restricted to areas in which these conditions or factors occur. Seeds germinated optimally at 30δC in the laboratory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00024141
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    Paper (German National Licenses)
    Fulltext
  • 3
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    Unknown
    Improved fuel cell (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Concept in fuel cell design has two cells, each with its own reactant flow fields bonded into single modular unit. Cells require fewer parts and occupy less space than conventional fuel cells, effecting easier assembly and maintenance.
    Keywords: PHYSICAL SCIENCES
    Type: MFS-23797 , NASA Tech Briefs (ISSN 0145-319X); 2; 4; P. 3
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Unknown
    Development of advanced fuel cell system, phase 3 (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A multiple task research and development program was performed to improve the weight, life, and performance characteristics of hydrogen-oxygen alkaline fuel cells for advanced power systems. Gradual wetting of the anode structure and subsequent long-term performance loss was determined to be caused by deposition of a silicon-containing material on the anode. This deposit was attributed to degradation of the asbestos matrix, and attention was therefore placed on development of a substitute matrix of potassium titanate. An 80 percent gold 20 percent platinum catalyst cathode was developed which has the same performance and stability as the standard 90 percent gold - 10 percent platinum cathode but at half the loading. A hybrid polysulfone/epoxy-glass fiber frame was developed which combines the resistance to the cell environment of pure polysulfone with the fabricating ease of epoxy-glass fiber laminate. These cell components were evaluated in various configurations of full-size cells. The ways in which the baseline engineering model system would be modified to accommodate the requirements of the space tug application are identified.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-134818 , PWA-5201
    Format: application/pdf
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  • 5
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    Increased fuel-cell cross-pressure limit (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Polytetrafluoroethylene (PTFE) impregnated support screen increases cross pressure on electrolyte-filled matrix in fuel-cell passive water-removed unit. This increases cell operating pressure limit which may improve performance and life characteristics of passive water-removal-type fuel cells.
    Keywords: PHYSICAL SCIENCES
    Type: MFS-25196 , NASA Tech Briefs (ISSN 0145-319X); 4; 4; P. 490
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Development of advanced fuel cell system (1978)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An experimental program was conducted continuing the development effort to improve the weight, life, and performance characteristics of hydrogen-oxygen alkaline fuel cells for advanced power systems. These advanced technology cells operate with passive water removal which contributes to a lower system weight and extended operating life. Endurance evaluation of two single cells and two, two-cell plaques was continued. Three new test articles were fabricated and tested. A single cell completed 7038 hours of endurance testing. This cell incorporated a Fybex matrix, hybrid-frame, PPF anode, and a 90 Au/10 Pt cathode. This configuration was developed to extend cell life. Two cell plaques with dedicated flow fields and manifolds for all fluids did not exhibit the cell-to-cell electrolyte transfer that limited the operating life of earlier multicell plaques.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-159443 , FCR-0398
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Development of advanced fuel cell system (phase 4) (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: For abstract, see N76-23686.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-135030S , FCR-0194
    Format: application/pdf
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  • 8
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    Development of Advanced Fuel Cell System (Phase 4) (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A multiple-task research and development program was performed to improve the weight, life, and performance characteristics of hydrogen-oxygen alkaline fuel cells for advanced power systems. During Phase 4, the lowest stabilized degradation rate observed in all the testing completed during four phases of the program, 1 microvolt/hour, was demonstrated. This test continues after 5,000 hours of operation. The cell incorporates a PPf anode, a 90Au/10Pt cathode, a hybrid frame, and a Fybex matrix. These elements were developed under this program to extend cell life. The result demonstrated that the 80Au/20Pt cathode is as stable as a 90Au/10Pt cathode of twice the precious metal loading, was confirmed in full-scale cells. A hybrid frame two-cell plaque with dedicated flow fields and manifolds for all fluids was demonstrated to prevent the cell-to cell electrolyte transfer that limited the endurance of multicell plaques. At the conclusion of Phase 4, more than 90,900 hours of testing had been completed and twelve different cell designs had been evaluated. A technology base has been established which is ready for evaluation at the powerplant level.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-135030 , FCR-0165
    Format: application/pdf
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  • 9
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    Development of advanced fuel cell system, phase 2 (1973)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A multiple task research and development program was performed to improve the weight, life, and performance characteristics of hydrogen-oxygen alkaline fuel cells for advanced power systems. Development and characterization of a very stable gold alloy catalyst was continued from Phase I of the program. A polymer material for fabrication of cell structural components was identified and its long term compatibility with the fuel cell environment was demonstrated in cell tests. Full scale partial cell stacks, with advanced design closed cycle evaporative coolers, were tested. The characteristics demonstrated in these tests verified the feasibility of developing the engineering model system concept into an advanced lightweight long life powerplant.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-134721 , PWA-4984
    Format: application/pdf
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  • 10
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    Strip cell test and evaluation program (1978)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The performance characteristics of alkaline fuel cells to be used for space power systems were tested. Endurance tests were conducted on the cells during energy conversion operations. A feature of the cells fabricated and tested was the capability to evaporate the product water formed during the energy conversion reaction directly to space vacuum. A fuel cell powerplant incorporating these cells does not require a condenser and a hydrogen recirculating pump water separator to remove the product water. This simplified the fuel cell powerplant system, reduced the systems weight, and reduced the systems parasite power.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-159652 , FCR-0945
    Format: application/pdf
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