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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of geometry 5 (1974), S. 101-107 
    ISSN: 1420-8997
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, we give necessary and sufficient conditions for embedding a given metric space in Euclidean space. We shall introduce the notions of flatness and dimension for metric spaces and prove that a metric space can be embedded in Euclidean n-space if and only if the metric space is flat and of dimension less than or equal to n.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 3 (1987), S. 107-111 
    ISSN: 1432-0789
    Keywords: Oniscus asellus ; Leaf litter ; Acer negundo ; A. saccharum ; Fagus grandifolia ; Picea rubens ; Tsuga canadensis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Feeding by the isopod, Oniscus asellus, produced changes in the sulfur constituents of leaf litter substrates (Acer negundo, A. saccharum, Fagus grandifolia, Picea rubens, and Tsuga canadensis). Isopod consumption of leaf litter generally accelerated the mineralization of carbon-bonded S and increased the formation of ester sulfate in all substrates. After the isopod egestion of A. negundo leaves, fecal decomposition over 6 weeks increased total S concentration from 68 to 120 μmol S/g due to the catabolism of organic carbon. During the same period sulfate decreased from 34 to 20 μmol S/g and carbon-bonded S increased from 34 to 100 μmol S/g. Thus the total S pool in aged feces became enriched with organic S (83% of total S). Macroinvertebrate consumption accelerated the transformation of S constituents and the carbon-bonded S concentration approached that of the Oa organic horizon of a northern hardwood forest.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 7 (1989), S. 239-246 
    ISSN: 1432-0789
    Keywords: Nutrient cycling ; Oniscus asellus ; Hardwood forest soil ; Leaching ; Macrofauna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Oniscus asellus produced changes in the nutrients leached from Oie and Oa horizons of a hardwood forest soil. Soil with isopods lost more K+ (54%) from the Oie horizon and more Ca2+ (25%), Mg2+ (40%), and water-extractable S (23%) from the Oa horizon than soil without isopods. In contrast, soils with isopods lost less Ca2+ (39076) from the Oie horizon and less dissolved C-bonded S (33%) from the Oa horizon than soil without isopods. In addition, the Oia and Oa horizons exhibited different nutrient dynamics. When isopods were present, the Oa horizon leachates accumulated more Na+ K+, Ca2+, Mg2+, NO3 − , water-soluble SO4 2−, and dissolved C-bonded S, and the Oie horizon retained more of these nutrients. The type of leaching solution also had a major effect on nutrients. Leaching with a simulated soil solution resulted in smaller nutrient losses for K+ and Mg2+ in both horizons and for Na+, Ca2+, and NO3 − in the Oa horizon than leaching with distilled water.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Earth, moon and planets 13 (1975), S. 259-276 
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Cosmic ray exposure ages of lunar samples have been used to date surface features related to impact cratering and downslope movement of material. Only when multiple samples related to a feature have the same rare gas exposure age, or when a single sample has the same81Kr-Kr and track exposure age can a feature be considered reliably dated. Because any single lunar sample is likely to have had a complex exposure history, assignment of ages to features based upon only one determination by any method should be avoided. Based on the above criteria, there are only five well-dated lunar features: Cone Crater (Apollo 14) 26 m.y., North Ray Crater (Apollo 16) 50 m.y., South Ray Crater (Apollo 16) 2 m.y., the emplacement of the Station 6 boulders (Apollo 17) 22 m.y., and the emplacement of the Station 7 boulder (Apollo 17) 28 m.y. Other features are tentatively dated or have limits set on their ages: Bench Crater (Apollo 12) ⩽99 m.y., Baby Ray Crater (Apollo 16) ⩽2 m.y., Shorty Crater (Apollo 17) ≈ 30 m.y., Camelot Crater (Apollo 17) ⩽140 m.y., the emplacement of the Station 2 boulder 1 (Apollo 17) 45–55 m.y., and the slide which generated the light mantle (Apollo 17) ⩾50 m.y.
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  • 5
    ISSN: 1432-2048
    Keywords: C3-C4 intermediate species (Flaveria, Moricandia, Panicum) ; C4 evolution ; Glycine decarboxylase (localization) ; Photorespiration ; Serine hydroxymethyltransferase (localization)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cell-specific distribution of the four subunit proteins (P, L, T and H) of glycine decarboxylase (GDC) and of serine hydroxymethyltransferase (SHMT) has been studied in the leaves of C3-C4 intermediate and C4 species of three genera (Flaveria, Moricandia and Panicum) using immunogold localization. Antibodies raised against these proteins from pea leaf mitochondria were used to probe Western blots of total leaf proteins of F. linearis Lag., M. arvensis (L.) DC and P. milioides Nees ex Trin. (C3-C4), and F. trinervia (Spring.) Mohr and P. miliaceum (L.) (C4). For all species, each antibody recognised specifically a protein of similar molecular weight to that in pea leaves. In leaves of M. arvensis the P protein was present in the mitochondria of the bundle-sheath cells but was undetectable in those of the mesophyll, whereas the L, T and H proteins and SHMT were present in both cell types. The density of immunogold labelling of SHMT on the mitochondria of mesophyll cells was less than that on those of the bundle-sheath cells, which correlates with the relative activities of SHMT in these cell types. These data reveal that the lack of functional GDC in the mesophyll cells of M. arvensis, which is the principal biochemical reason for reduced photorespiration in this species, is due to the loss of a single subunit protein. This lack of coordinate expression of the subunit proteins of GDC within a photosynthetic cell represents a clear difference between M. arvensis and other C3 and C3-C4 species. None of the GDC proteins was detectable in the mesophyll cells of the C3-C4 and C4 Flaveria and Panicum species but all were present in the bundle-sheath cells. The differences in the distribution of the GDC proteins in leaves of the C3-C4 species studied are discussed in relation to the evolution of photosynthetic mechanisms.
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  • 6
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Maintenance of estuarine zooplankton populations in large river-dominated estuaries with short residence times has been an intriguing subject of investigation. During three different hydrological seasons, autumn 1990, summer 1991, and spring 1992, we intensively sampled zooplankton populations in the estuarine turbidity maxima (ETM) region of the Columbia River estuary of Oregon and Washington, USA. One of the principal objectives was to investigate retention mechanisms of the predominant zooplankton species, the harpacticoid copepod Coullana canadensis and the epibenthic calanoid copepod Eurytemora affinis. In the ETM, C. canadensis densities mirrored those of turbidity gradients and were almost always greater at the river bed, while E. affinis densities were greater higher in the water column during the flood and lower in the water column during the ebb. Cross-correlation and time-series analyses determined that C. canadensis densities were highly positively correlated with turbidity and that most of the variability was explained by the lunisolar diurnal (K1) and principal lunar (M2) tidal components occurring once every 23.93  h and once every 12.42 h, respectively. This indicates that C. canadensis populations are most probably maintained in the estuary through the same near-bottom circulation features that trap and concentrate particles in the ETM. In contrast, densities of the more motile species E. affinis were highly correlated with negative velocities, or ebb tide, and most of the variability in population densities could be explained by the principal lunar tidal component; therefore, we hypothesize that this species is probably vertically migrating on a tidal cycle into different flow layers to avoid population losses out of the estuary.
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  • 7
    ISSN: 1432-2242
    Keywords: Key wordsBrassica napus  ;  Moricandia arvensis  ;  Somatic hybridisation  ;   intermediate  ;   Photorespiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The wild crucifer Moricandia arvensis is a potential source of alien genes for the genetic improvement of related Brassica crops. In particular M. arvensis has a intermediate photosynthetic mechanism which results in enhanced recapture of photorespired CO2 and may increase plant water-use efficiency. In order to transfer this trait into Brassica napus, somatic hybridisations were made between leaf mesophyll protoplasts from cultured M. arvensis shoot tips and hypocotyl protoplasts from three Brassica napus cultivars, ‘Ariana’, ‘Cobra’ and ‘Westar’. A total of 23 plants were recovered from fusion experiments and established in the greenhouse. A wide range of chromosome numbers were observed among the regenerated plants, including some apparent mixoploids. Thirteen of the regenerated plants were identified as nuclear hybrids between B. napus and M. arvensis on the basis of isozyme analysis. The phenotypes of these hybrids were typically rather B. napus-like, but much variability was observed, including variation in flower colour, leaf shape and colour, leaf waxiness, fertility and plant vigour. CO2 compensation point measurements on the regenerated plants demonstrated that 3 of the hybrids express the M. arvensis intermediate character at the physiological level. Semi-thin sections through leaf tissues of these 3 plants revealed the presence of a Kranz-like leaf anatomy characteristic of M. arvensis but not found in B. napus. This is the first report of the expression of this potentially important agronomic trait, transferred from Moricandia, in M. arvensis×B. napus hybrids.
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  • 8
    ISSN: 1432-2242
    Keywords: Key words Brassica napus ; C3-C4 intermediate photosynthesis ; Glycine decarboxylase ; Intergeneric hybrid ; Moricandia arvensis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  An intergeneric hybrid plant was produced between the C3-C4 intermediate species Moricandia nitens and the C3 species Brassica napus by sexual hybridization and in vitro embryo rescue. The hybrid nature of the plant was apparent in its morphology and flower pigmentation and was confirmed by leaf isozyme patterns. The overall plant morphology and the shape and thickness of leaves of the hybrid plant were intermediate between those of the parent species. However, the bundle-sheath cells of the hybrid resembled those of the C3 parent and lacked the organelle development of the C3-C4 intermediate parent. Immunogold labelling for the presence of the P subunit of the mitochondrial glycine decarboxylase complex revealed a very similar labelling density on mitochondria in bundle-sheath and mesophyll cells in B. napus, while in  M. nitens the P subunit was only detectable in bundle sheath cells. In the hybrid the labelling density on mesophyll cell mitochondria was almost half of that on the bundle-sheath mitochondria. The CO2 compensation point of the hybrid was significantly less than that of the C3 parent but was not as low, nor as responsive to changes in light intensity, as for the C3-C4 parent.
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  • 9
    ISSN: 1432-2242
    Keywords: Brassica napus ; Moricandia arvensis ; Somatic hybridisation ; C3-C4 intermediate ; Photorespiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The wild crucifer Moricandia arvensis is a potential source of alien genes for the genetic improvement of related Brassica crops. In particular M. arvensis has a C3-C4 intermediate photosynthetic mechanism which results in enhanced recapture of photorespired CO2 and may increase plant water-use efficiency. In order to transfer this trait into Brassica napus, somatic hybridisations were made between leaf mesophyll protoplasts from cultured M. arvensis shoot tips and hypocotyl protoplasts from three Brassica napus cultivars, ‘Ariana’, ‘Cobra’ and ‘Westar’. A total of 23 plants were recovered from fusion experiments and established in the greenhouse. A wide range of chromosome numbers were observed among the regenerated plants, including some apparent mixoploids. Thirteen of the regenerated plants were identified as nuclear hybrids between B. napus and M. arvensis on the basis of isozyme analysis. The phenotypes of these hybrids were typically rather B. napus-like, but much variability was observed, including variation in flower colour, leaf shape and colour, leaf waxiness, fertility and plant vigour. CO2 compensation point measurements on the regenerated plants demonstrated that 3 of the hybrids express the M. arvensis C3-C4 intermediate character at the physiological level. Semi-thin sections through leaf tissues of these 3 plants revealed the presence of a Kranz-like leaf anatomy characteristic of M. arvensis but not found in B. napus. This is the first report of the expression of this potentially important agronomic trait, transferred from Moricandia, in M. arvensis x B. napus hybrids.
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  • 10
    ISSN: 1432-2242
    Keywords: Key words Rhizobium ; Transformation ; Nodule occupancy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  By introducing Bacillus thuringiensis subspecies tenebrionisδ-endotoxin genes (cryIIIA) into Rhizobium leguminosarum we have produced strains for the biological control of Sitona larvae. Comparisons between a transgenic and the parent strain show that transformation has induced changes not associated with the intended function of the transgene. Although growth rates in laboratory cultures are similar for both strains, the ability to compete for nodule occupancy is greater in the transgenic than in the non-transformed parent strain. This result demonstrates the importance of studying ecological and agronomic characters of transgenic micro-organisms that could have a bearing on the safety and success of their release into the environment, even if they are not thought to be connected with the transgenes introduced.
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