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  • Mexico  (3)
  • complexes  (3)
  • Springer  (6)
  • 1
    Digitale Medien
    Digitale Medien
    Crystal structure of the Λ-[4M] enantiomer of cis-diaqua-bis(1,3-dimethylpteridine-2,4(1H,3H)-dione-N5,O4) copper(II) perchlorate monohydrate (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 571-574 
    Details
    ISSN: 1572-8854
    Schlagwort(e): crystal structure ; complexes ; pteridine ; lumazine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Single-crystal X-ray diffraction studies have been performed on the complex cis-diaqua-bis(1,3-dimethylpteridine-2,4(1H,3H)-dione-O4,N5) copper(II) perchlorate monohydrate, [Cu(DLM)2(H2O)2](ClO4)2 · H2O. This compound crystallizes in the orthorhombic system, P212121 space group, Z = 4 with a = 8.749(1) Å, b = 14.213(1) Å, c = 21.200(2) Å, and V = 2636.2(4) Å3. The metal ion is surrounded in octahedral geometry by two mutually quasi-perpendicular N5,O4-coordinated lumazine chelators with the O4 atoms trans and the N5 atoms cis. The polyhedron is completed by two cis-coordinated water molecules. The absolute configuration of the complex can be described, following Bailar's nomenclature, as the enantiomer Λ of the stereoisomer 4M. A three-dimensional hydrogen-bond network is defined by water molecules, perchlorate anions, and the O2 of the pteridine A.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009548803103
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Gold(III)-pteridine compounds: synthesis, spectral, and X-ray diffraction studies on new adducts between sodium tetrabromoaurate(III) and lumazine derivatives (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 565-570 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; complexes ; pteridine ; lumazine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract In aqueous hydrobromic medium, Na[AuCl4] reacts with 1,3-dimethyllumazine (1,3-dimethyl-pteridine-2,4(1H,3H)-dione, DLM) or 1,3,6,7-tetramethyllumazine (DLMD) to give three adducts with simplified formulas Na[AuBr4](DLMD), Na[AuBr4](DLM), and Na[AuBr4](DLM)2. These compounds have been characterized by means of analytical techniques, and IR and NMR spectroscopies. Single-crystal x-ray diffraction studies have been made on the Na[AuBr4](DLM)2 compound. The crystals belong to the orthorhombic Pbca space group, with a = 15.249(1), b = 15.238(2), c = 21.563(2) Å, Z = 8, and R = 0.053. The structure consists of planar [AuBr4]− anions and Na+ cations weakly linked to two crystallographically independent DLM molecules. The Na+ cation interacts weakly with four oxygen and one nitrogen atoms from four different pteridine molecules, its environment may be described as a very distorted square pyramid.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1023252324268
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    A cobalt(II) complex with the N,N,O-tridentate ligand 6-amino-5-formyl-1,3-dimethyluracilato-benzoyl-hydrazone (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 283-286 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; complexes ; cobalt ; benzoylhydrazone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The crystal structure of bis-(6-amino-5-formyl-1,3-dimethyluracilato benzoylhydrazone)cobalt(II) dimethylformamide solvate is described. This compound crystallizes in the triclinic system, space group P1¯, Z = 2 with a = 9.7368(8), b = 12.346(1), c = 17.184(1) Å, α = 78.372(6), β = 74.585(6), γ = 71.113(5)°, and V = 1869.0(3) Å3. The coordination polyhedron around the metal ion displays a slightly flattened M(NNO)2 octahedral shape. Both ligands bind in a trident fashion through the benzoylic oxygen atom, the hydrazone nitrogen atom closer to the uracil ring, and the deprotonated nitrogen atom of the amino group. The two ligands exhibit quite different conformations: one of them is almost planar, whereas the other is severely twisted.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009565600126
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    The desert vegetation of El Pinacate, Sonora, Mexico (1987)
    Springer
    Plant ecology 71 (1987), S. 49-60 
    Details
    ISSN: 1573-5052
    Schlagwort(e): Classification ; Generalised linear model ; Mexico ; Ordination: direct ; Ordination: indirect ; Perennial ; Plant community type ; Plant distribution ; Sonoran Desert
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The Pinacate region is part of the Gran Desierto, one of the driest deserts in North America. The presence-absence of perennial plant species, together with soil and landform characteristics, were registered in 110 sampling sites within this region. A classification and ordination of plant communities showed soil and landform units to be good predictors of plant variation. Plant distribution and species richness were also strongly related to altitude and rockiness. A Generalised Linear Model was used to fit the response curves of individual species. The environmental factors related with plant distribution are indicators of the water regime within a given site. Plant communities repeat along topographic gradients the large-scale biogeographic variation of the Sonoran Desert. Microphyllous shrubs colonise the drier bajada slopes, while more diverse communities, dominated by cacti and drought-deciduous trees, grow on the wetter pediments and in pockets within rocky soils.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00048511
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Survival and growth of five species of Pinus seedlings after different approaches to competition control: “bridging” studies between Oregon and Mexico (1991)
    Springer
    New forests 5 (1991), S. 219-238 
    Details
    ISSN: 1573-5095
    Schlagwort(e): Site preparation ; herbicides ; manual weeding ; aspect ; Mexico ; Oregon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Two species of pine native to Oregon and three native to Mexico were reciprocally planted in southwest Oregon and northeastern Mexico. The Oregon study site has very dry, hot summers; the Mexican site has hot, dry springs, but has rainy summers. Total rainfall and native genera are similar on both sites. Site-preparation trials were carried out on north and south slopes at both locations. For all species on both sites, survival on south slopes was satisfactory only with site-preparation treatments that gave near-complete vegetation control. Overall survival was best on north slopes in Mexico, and herb control was not required. Woody cover decreased survival and growth at all locations and aspect combinations. Chemical control improved survival, but the standing dead shade did reduce growth slightly as compared to growth on the totally cleared sites. Clearing without chemical control gave poor results in Oregon, but permitted good seedling survival and growth at the location in northeastern Mexico. Overall, ponderosa pine (Pinus ponderosa Dougl. ex Laws.) was the least sensitive species to environmental stress, and Hartweg pine (Pinus hartwegii Engelm.), the most sensitive. Mexican pines appeared to require more protection from water stress than did ponderosa pine.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00028113
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Boa constrictor, an introduced predator threatening the endemic fauna on Cozumel Island, Mexico (1999)
    Springer
    Biodiversity and conservation 8 (1999), S. 957-963 
    Details
    ISSN: 1572-9710
    Schlagwort(e): boa ; Boa constrictor ; Cozumel Island ; conservation ; insular fauna ; introduced predator ; introduction ; invasion ; Mexico
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We present evidence indicating that the boa (Boa constrictor) was introduced onto Cozumel Island, Quintana Roo, Mexico, in 1971. This snake is now firmly established and has a wide distribution on Cozumel. We recorded an encounter rate of 1.8 boas per 100 km of forest surveyed. The introduction of the boa onto Cozumel, where it has few predators, is a threat to the existence of endemic and other native terrestrial vertebrates of the island. We recommend the following immediate actions: (1) undertake research to confirm the origin of the boa on Cozumel; (2) assess the effect of the boa on the biota of Cozumel; and, (3) if an anthropogenic origin is confirmed, an eradication programme for the boa on Cozumel should be undertaken, obtaining information on the biology and ecology of the species. Options for the destiny of the eradicated boas are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008815004072
    Standort Signatur Erwartet Verfügbarkeit
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