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  • 1
    ISSN: 1432-2145
    Keywords: Pollen-pistil interference ; Prior self-pollination ; Tristyly ; Self-incompatibility Stylar senescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The potential inhibitory effects of incompatible pollen on outcrossed seed set were investigated in mass-flowering, self-incompatible, tristylous Pontederia sagittata. Prior application of self pollen, followed after 2, 4, or 6 h by compatible pollen, was conducted on five genotypes of each of the three style morphs under uniform glasshouse conditions. The greatest reductions in seed set occurred in pollinations of the long-styled (L) morph at the 6 h time interval. Smaller reductions were also found for this treatment in the mid-styled (M) morph. No significant reductions in seed set were observed in the short-styled (S) morph or in the other morphs at shorter time intervals. Observations of pollen germination and pollen tube growth indicated that the lack of inhibitory effects in the S morph may occur because relatively few pollen grains adhered to stigmas in selfpollinations. In the L and M morphs, early germination of self pollen may cause physical clogging of the stigma and style, resulting in a reduced number of compatible pollen tubes in styles. Observations of the structural integrity of styles indicated that prior germination of self pollen resulted in more rapid onset of pistil senescence, particularly in the L morph. These influences may contribute to the morph-specific differences in seed set observed following prior self-pollination of outcrossed flowers. The negative effects of incompatible pollen are likely to be most evident where ecological factors cause delays in the delivery of outcross pollen to stigmas.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A narrow feature recently observed in photoemission spectra of heavy rare earth metals at a binding energy of 5.5–6.2 eV has been interpreted as a many-electron satellite. We question this interpretation and suggest that this feature is due to H contamination.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Direct reaction of C60 with alkali-metal vapour in sealed pyrex tubes has been the predominant synthetic route to AXC60 (where A is K, Rb or Cs), but the lower vapour pressure and greater reactivity with pyrex are a severe problem for reactions with sodium. Therefore, we have ...
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 352 (1991), S. 522-524 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The experimental plant was the self-compatible annual water hyacinth, Eichhornia paniculata (Pontederiaceae). The species inhabits ephemeral pools and ditches in northeastern Brazil and the Caribbean, and exhibits a wide range of natural outcrossing rates12. The experiments reported here used ...
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  • 5
    Publication Date: 2013-08-31
    Description: 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.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: A-90231 , NAS 1.15:102847 , NASA-TM-102847
    Format: application/pdf
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  • 6
    Publication Date: 2018-12-01
    Description: 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.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 91-0610
    Format: text
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  • 7
    ISSN: 1573-5176
    Keywords: Isochrysis ; lipid ; mariculture ; mass culture ; microalgae ; Nannochloropsis ; nutrition ; Pavlova ; polyunsaturated fatty acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three species of microalgae were grown in mass culture to investigate the influence of culture technique and growth phase on the production of 20:5(n−3) and 22:6(n−3). These polyunsaturated fatty acids (PUFA) are considered to be essential in many marine animals diets for high growth and survival rates. The species of microalgae examined wereNannochloropsis oculata, Pavlova lutheri andIsochrysis sp. (clone T.Iso). All batch cultures (logarithmic and stationary phase) and semi-continuous cultures (logarithmic phase) examined contained high levels of the long-chain (n−3) PUFA, but production could be maximised by harvesting at specific times and growth phases. Maximum cellular content (pg cell-1) of long-chain PUFA was found in logarithmic phase batch cultures ofN. oculata and in stationary phase cultures ofP. lutheri. The cellular content of PUFA in cultures ofIsochrysis sp. did not change significantly with culture technique or growth phase. Alternatively, stationary phase cultures of all three species showed increased proportions (%) and cellular contents of triacylglycerols, and saturated and monounsaturated fatty acids with correspondingly decreased proportions of polar lipids and most PUFA relative to logarithmic phase cultures. The exception was the proportion and cellular content of 22:6(n−3) inP. lutheri which increased with triacylglycerol content. The mass of long-chain (n−3) PUFA per volume of culture was significantly higher in stationary phase cultures due to the higher cell counts per volume. These findings indicate that the opportunity exists to maximise PUFA production by microalgae with the potential to improve animal growth and reduce production costs in mariculture operations and may be of use in the large scale culture and harvesting of microalgae for the biotechnology industry.
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  • 8
    ISSN: 1573-5168
    Keywords: salmon ; eggs ; embryos ; larvae ; thyroid hormones ; development ; ontogeny ; pituitary gland ; thyrotropic cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Total organism content of L-thyroxine (T4) and triiodo-L-thyronine (T3) were measured in the early developmental stages of a stock of Lake Ontario coho salmon from the egg to the yolk absorption stage. Whole organism T4 levels were constant between the egg and pre-hatch embryo stages, but fell progressively during yolk absorption. T3 levels were low from egg to eye-pigment appearance, but then increased prior to hatch and fell again during the post-hatch yolk absorption period. When expressed as ng/tissue, T4 content of the body compartment rose progressively between days 67 and 87 post-fertilization, whilst T4 content of the yolk compartment fell progressively during the same period; the pattern was not evident for tissue T3 content. When expressed as ng/g dry weight of tissue, the inverse relationship was found for T4, and T3 content of the body and yolk compartments decreased progressively and increased progressively, respectively during the same period, suggesting that thyroid hormones were selectively retained in the yolk compartment. Intensely “immunostained” (using anti-human β-TSH antibody) thyrotropic cells were present in small numbers in the pars distalis of the embryonic pituitary at the eye-pigment appearance stage, and the numbers increased markedly until the pre-hatch period. Administration of either bovine thyrotropic hormone (bTSH) or ovine growth hormone (oGH) had no effect on thyroid hormone content of larvae challenged during the yolk absorption period, suggesting that the thyroid tissue was not responsive to exogenous bTSH challenge at this time, and that oGH-sensitive 5′-monodeiodination was either not present or at levels that were too low to cause an elevation in total T3 content, or that the substrate levels were insufficient to permit a measureable increase in whole body T3 content.
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  • 9
    Publication Date: 2019-07-12
    Description: Numerical results support predictions of simplified theories. Report discusses aspects of algebraic and numerical modeling of flow in infinite half space on one side of infinitely-large, flat plate, with sinusoidally oscillating free-stream velocity along one axis of plate. Flow has rich variety of behaviors, including strong gradients of pressure, points of inflection, and reversal.
    Keywords: MECHANICS
    Type: ARC-11858 , NASA Tech Briefs (ISSN 0145-319X); 14; 7; P. 73
    Format: text
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  • 10
    Publication Date: 1990-02-01
    Print ISSN: 0278-7407
    Electronic ISSN: 1944-9194
    Topics: Geosciences
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