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  • FLUID MECHANICS AND HEAT TRANSFER  (4)
  • Sustainability Science  (3)
  • Behavior  (1)
  • Editorials  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Pollinator foraging behavior and pollen collection on the floral morphs of tristylous Pontederia cordata L. (1987)
    Springer
    Oecologia 74 (1987), S. 347-351 
    Details
    ISSN: 1432-1939
    Schlagwort(e): Pontederia cordata ; Bombus ; Tristyly ; Pollination ; Behavior
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The foraging behavior of the pollinators of tristylous Pontederia cordata was studied to determine if differences in floral morphology would lead to preferential visitation of the floral morphs. Although nectar production is not different in the three floral morphs, differences in the production and size of pollen grains produced by the three anther levels results in the morphs offering variable amounts of resources to pollen-collecting insects. Bumblebees (Bombus spp.) and the solitary bee Melissodes apicata used P. cordata primarily as a nectar source and therefore did not seem to exhibit any morph preference. In contrast, honeybees visited flowers mainly for pollen and preferred to forage on long-level anthers of the short-and mid-styled morphs. An analysis of the composition of corbicular pollen loads indicated that, relative to the frequency of production in the population: 1) honeybees collected an excess of pollen from long-level anthers; 2) bumblebees collected the three types of pollen without any apparent preference; and 3) M. apicata preferentially collected pollen from the short-level anthers — presumably because their proboscides are modified by the presence of tiny hairs. The results suggest that P. cordata in Ontario is serviced by a diverse, unspecialized pollinator fauna which is not co-adapted to the tristylous floral polymorphism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00378928
    Standort Signatur Erwartet Verfügbarkeit
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    Artikel (Nationallizenzen)
    Volltext
  • 2
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    Avoiding disastrous climate change is possible but not inevitable [Commentary] (2011)
    National Academy of Sciences
    Details
    Publikationsdatum: 2011-07-20
    Beschreibung: What the world does or does not do about climate change will have profound implications. If the world fails to act, we may cross a climate tipping point, with disastrous consequences all around. No country by itself can prevent this, but a substantial number of countries working together can avert disaster. Collectively, we know what we need to do. However, can we agree on what each of us should do? Can we be assured that, if we act, others will fulfill their pledges? An experimental paper in PNAS (1) provides reasons for optimism and despair, optimism because, with communication, outcomes...
    Schlagwort(e): Sustainability Science
    Print ISSN: 0027-8424
    Digitale ISSN: 1091-6490
    Thema: Biologie , Medizin , Allgemeine Naturwissenschaft
    Publiziert von National Academy of Sciences
    Standort Signatur Erwartet Verfügbarkeit
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    AKTUELLE ARTIKEL
  • 3
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    Aquaculture and resilience [Sustainability Science] (2014)
    National Academy of Sciences
    Details
    Publikationsdatum: 2014-09-17
    Beschreibung: Aquaculture is the fastest growing food sector and continues to expand alongside terrestrial crop and livestock production. Using portfolio theory as a conceptual framework, we explore how current interconnections between the aquaculture, crop, livestock, and fisheries sectors act as an impediment to, or an opportunity for, enhanced resilience in the...
    Schlagwort(e): Sustainability Science
    Print ISSN: 0027-8424
    Digitale ISSN: 1091-6490
    Thema: Biologie , Medizin , Allgemeine Naturwissenschaft
    Publiziert von National Academy of Sciences
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
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    Choices in the climate commons (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publikationsdatum: 2018-12-14
    Schlagwort(e): Editorials
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Geologie und Paläontologie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
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    Climate negotiations under scientific uncertainty [Sustainability Science] (2012)
    National Academy of Sciences
    Details
    Publikationsdatum: 2012-10-24
    Beschreibung: How does uncertainty about “dangerous” climate change affect the prospects for international cooperation? Climate negotiations usually are depicted as a prisoners’ dilemma game; collectively, countries are better off reducing their emissions, but self-interest impels them to keep on emitting. We provide experimental evidence, grounded in an analytical framework, showing that...
    Schlagwort(e): Sustainability Science
    Print ISSN: 0027-8424
    Digitale ISSN: 1091-6490
    Thema: Biologie , Medizin , Allgemeine Naturwissenschaft
    Publiziert von National Academy of Sciences
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
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    Direct simulation of a turbulent oscillating boundary layer (1987)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The turbulent boundary layer driven by a freestream velocity that varies sinusoidally in time around a zero mean is considered. The flow has a rich behavior including strong pressure gradients, inflection points, and reversal. A theory for the velocity and stress profiles at high Reynolds number is formulated. Well-resolved direct Navier-Stokes simulations are conducted over a narrow range of Reynolds numbers, and the results are compared with the theoretical predictions. The flow is also computed over a wide range of Reynolds numbers using a new algebraic turbulence model; the results are compared with the direct simulations and the theory.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA-TM-89460 , A-87220 , NAS 1.15:89460
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
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    A one-equation turbulence transport model for high Reynolds number wall-bounded flows (1991)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: A one-equation turbulence model that avoids the need for an algebraic length scale is derived from a simplified form of the standard-k-epsilon model equations. After calibration based on well established properties of the flow over a flat plate, predictions of several other flows are compared with experiment. The preliminary results presented indicate that the model has predictive and numerical properties of sufficient interest to merit further investigation and refinement. The one-equation model is also analyzed numerically and robust solution methods are presented.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA PAPER 91-0610
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
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    A one-equation turbulence transport model for high Reynolds number wall-bounded flows (1990)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: A one-equation turbulence model that avoids the need for an algebraic length scale is derived from a simplified form of the standard k-epsilon model equations. After calibration based on well established properties of the flow over a flat plate, predictions of several other flows are compared with experiment. The preliminary results presented indicate that the model has predictive and numerical properties of sufficient interest to merit further investigation and refinement. The one-equation model is also analyzed numerically and robust solution methods are presented.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA-TM-102847 , A-90231 , NAS 1.15:102847
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 9
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    Direct simulation of a turbulent oscillating boundary layer (1987)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-27
    Beschreibung: The turbulent boundary layer driven by a freestream velocity that varies sinusoidally in time around a zero mean is considered. The flow has a rich behavior including strong pressure gradients, inflection points, and reversal. A theory for the velocity and stress profiles at high Reynolds number is formulated. Well-resolved direct Navier-Stokes simulations are conducted over a narrow range of Reynolds numbers, and the results are compared with the theoretical predictions. The flow is also computed over a wide range of Reynolds numbers using a new algebraic turbulence model; the results are compared with the direct simulations and the theory.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Symposium on Turbulent Shear Flows; Sept. 7-9, 1987; Toulouse; France
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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