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  • 2015-2019  (24)
  • 2000-2004  (18)
  • 1990-1994  (30)
  • 1880-1889
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  • 1
    Publication Date: 2020-02-12
    Type: info:eu-repo/semantics/conferenceObject
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  • 2
    Publication Date: 2020-02-12
    Description: The Baumkirchen clay pit near Innsbruck, western Austria, is a well-known site in Alpine Quaternary stratigraphy. Lacustrine sediments from the last glacial cycle from within the Alps provide a unique opportunity to investigate the regional palaeoclimate. Recent drilling has extended the known sequence to a total length of at least 250 m consisting of almost entirely well-laminated clayey silt. Luminescence dating identified two lake sequences, separated by a hiatus of ca. 7000–15 000 years. Lake phase 1 spans the period ca. 77–55 ka, i.e. from about Marine Isotope Stage (MIS) 5/4 to the MIS 4/3 transition. Lake phase 2 extends from mid- to late MIS 3 between ca. 45 and 33 ka. Down-core X-ray fluorescence core scanning confirmed the presence of the lake phases in the sediment composition, suggesting different sediment sources and/or transport mechanisms during these two intervals. A unique section of exotic, angular, silt matrix-supported gravel at the top of lake phase 1 is interpreted as ice-rafted debris. Luminescence dating constrains this layer to ca. 55 ka, thus providing the first evidence of a late MIS 4 or early MIS 3 ice advance confined to the interior of the Eastern Alps. A conceptual model of the sedimentary history of the valley is presented.
    Type: info:eu-repo/semantics/article
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  • 3
    Publication Date: 2020-02-12
    Type: info:eu-repo/semantics/conferenceObject
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  • 4
    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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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 21 (1880), S. 537-537 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SOMETHING very like the “comb-like masses of ice” appears upon the surfaces of plaster-models such as dentists make, after they have been coated with a preparation called Liquid Silex; except that it is finer and woolly. It seems to be caused by the contraction of the models forcing out very ...
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  • 7
    ISSN: 1432-1939
    Keywords: Key words Fruit and seed set ; Narcissus assoanus ; Pollen limitation ; Reproductive ecology ; Seed:ovule ratios
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A recent literature review indicates that pollen limitation of female fertility is a common feature of flowering plants. Despite the ecological and evolutionary significance of pollen limitation, most studies have only examined fertility in a single population at one time. Here we investigate pollen limitation of fruit and seed set in five populations of Narcissus assoanus, a self- sterile, insect-pollinated geophyte, over 2–3 years in southern France. In common with many early spring flowering plants, pollinator visitation to N. assoanus is often infrequent. Supplemental hand-pollination of flowers with outcross pollen significantly increased overall fruit and seed set by 11% and 19%, respectively. Four of the five populations experienced some pollen limitation during the study. For a given year, there was significant variation in pollen limitation among populations. Two of the populations were pollen limited in one year but not in other years in which they were studied. Seed:ovule ratios for open- and hand-pollinated flowers averaged 0.29 and 0.33, respectively. While hand pollination significantly increased the seed:ovule ratio, the low value obtained indicates that the majority of ovules in flowers do not mature seeds despite hand pollination. The role of genetic and environmental factors governing low seed:ovule ratios in N. assoanus is discussed.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 12 (2000), S. 203-208 
    ISSN: 1432-2145
    Keywords: Key words Tristyly ; Trimorphic incompatibility ; Pollen trimorphism ; Partial incompatibility ; Clonal aquatic plant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Eichhornia azurea (Pontederiaceae) is a mat-forming, clonal aquatic that inhabits lakes, marshes and river systems in many parts of the Neotropics. The species is tristylous with long-, mid-, and short-styled morphs commonly represented in natural populations. To investigate whether E. azurea possesses a trimorphic incompatibility system typical of tristylous species, we conducted a controlled pollination experiment on 15 clones representing the three style morphs from a natural population near Rosario, Argentina. Comparisons of fruit and seed set following self-, illegitimate, and legitimate pollinations clearly demonstrated the presence of trimorphic incompatibility in E. azurea. Self- and illegitimate pollinations produced significantly less fruit and seed than legitimate pollinations in all three style morphs. Pollen from the two anther levels within a flower exhibited contrasting compatibility relations in self-pollinations. In common with several other tristylous species in Pontederiaceae, the expression of self-incompatibility was weakest in the mid-styled morph and strongest in the short-styled morph. We discuss the ecological and evolutionary significance of the partial expression of trimorphic incompatibility in E. azurea.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 7 (1994), S. 273-281 
    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.
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  • 10
    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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