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  • Springer  (20)
  • Ovid Technologies  (5)
  • 2010-2014  (2)
  • 1990-1994  (18)
  • 1935-1939  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Textural evolution of the rapakivi granites, south Greenland —Sr, O and H isotopic investigations (1991)
    Springer
    Contributions to mineralogy and petrology 107 (1991), S. 459-471 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The development of rapakivi texture in feldspars from the Ketilidian granitoids of south Greenland has been investigated using Sr, O and H isotopes. A low temperature signature is found in the Sr and O data which seemingly contradicts some textural features that point to a magmatic origin of the plagioclase mantles around the K-feldspar ovoids. An origin for these mantles involving exsolution from an original alkali feldspar solid solution is proposed, which involves growth of mantles over a range of conditions determined by the mobility of the exsolving sodic feldspar. This mobility may be enhanced at high temperatures in the presence of melts or increased fluid pressures and at lower temperatures by the processes responsible for the transformation of K-feldspar to microcline. Rapakivi granites with both white and dark green feldspar occur in south Greenland but show no major isotopic differences, although the dark alkali feldspars contain significantly more fluid. Equivalent fluids in the white alkali feldspars may have escaped during plagioclase exsolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310680
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  • 2
    Electronic Resource
    Electronic Resource
    Formation of calcium deficient hydroxyapatite at near-physiological temperature (1992)
    Springer
    Journal of materials science 3 (1992), S. 299-305 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The formation of calcium deficient hydroxyapatite Ca9(HPO4)(PO4)5OH (HAp) at 25°C by reaction of tetracalcium phosphate (TetCP), monocalcium phosphate monohydrate (MCPM), and calcium hydroxide was investigated. Phase pure, calcium deficient hydroxyapatite was prepared in approximately 3.25 h at 25°C by the reaction of dilute suspensions. Variations in the solution pH, calcium, and phosphorus concentration were determined during the reactions. The solution conditions for all reactions investigated show similar behaviour. Isothermal calorimetry was carried out to determine the rates of heat evolution during reaction. Results indicate that significant reaction occurs in the first 15 min. During this period the solution pH ranges from 4.5 to 7.5 during three distinct stages of reaction. Early reaction occurs at low pH due to rapid MCPM dissolution. The presence of Ca(OH)2 effects the pH in the first 2 min of reaction in association with the proportion of MCPM. Brushite (CaHPO4 · 2H2O) is the predominant product formed until MCPM is consumed. X-ray diffraction analysis confirmed that brushite formed as an intermediate in the first few minutes. Brushite precipitated as thin plates having varying geometric shapes. A second stage is the reaction of brushite, tetracalcium phosphate, and Ca(OH)2 (if present) as the solution adjusts to invariant conditions while forming hydroxyapatite. A rise in pH occurs during this period. A third stage of reaction proceeds at relatively constant near-physiological pH conditions for the remainder of the reaction as brushite is consumed along with tetracalcium phosphate in forming hydroxyapatite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00705297
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  • 3
    Electronic Resource
    Electronic Resource
    Ca2+-activated K+ channels are involved in regulatory volume decrease in acinar cells isolated from the rat lacrimal gland (1994)
    Springer
    The journal of membrane biology 141 (1994), S. 193-201 
    Details
    ISSN: 1432-1424
    Keywords: Ca2+-activated K+ channels ; Cell volume ; Regulatory volume decrease ; Tetraethylammonium ; Lacrimal acinar cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The volumes of acinar cells isolated from rat lacrimal gland were measured on computer by video-imaging. Cells were found to swell on exposure to hypotonic solutions; they subsequently exhibited a regulatory volume decrease (RVD). RVD was inhibited in the absence of extracellular Ca2+, and by the K+ channel blocker tetraethylammonium chloride (2 mm TEA+). The possible involvement of K+ channels in RVD was further investigated in cell-attached patches. Exposing the cells to a hypotonic solution activated channels with a conductance of 141±6 pS (n=11). These channels were partially blocked by 0.5 mm TEA+, and channel activation was not observed in the absence of extracellular Ca2+. Experiments in the inside-out patch configuration demonstrated that the channels activated by hypotonie stress were “maxi” Ca2+-activated K+ channels. It is concluded that the opening of these channels plays an important role in RVD, by facilitating K+ loss from the cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238253
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  • 4
    Electronic Resource
    Electronic Resource
    Thin-skinned thrust mineralization in the Brasília fold belt: the example of the old Luziânia gold deposit (1992)
    Springer
    Mineralium deposita 27 (1992), S. 293-303 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Luziânia gold deposits in southern Goiás lie within the Late Proterozoic Brasília fold belt. The rocks that host the gold mineralization are a monotonous series of hydrothermally altered phyllites that have been subject to low grade regional metamorphism. The major controls on the gold mineralization are northeast trending and gently northwest dipping ductile-brittle, dextral-reverse shear zones associated with regional thin-skinned thrusting of the Canastra Group. From a preliminary fluid inclusion study it is deduced that low salinity, ⩽ 7 eq. wt% NaCl, moderately dense, H2O-CO2 ± CH4 ore fluids deposited gold at temperatures of 300 ± 75°C and pressures of 1.5 to 3 kb in the filling stage of the vein formation. Post-filling stage gold deposition probably occured by mixing of fluids at higher crustal levels (1.5–2 kb). During thrusting, prograde metamorphism released pore water which penetrated along thrust planes that acted as high permeability zones for the ponding and release, by hydraulic fracturing, of overpressured fluids. Later in the tectonic evolution and at shallower crustal levels, there was likely an incursion of near suface water into the fault zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00193400
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  • 5
    Electronic Resource
    Electronic Resource
    DNA variation in tissue-culture-derived rice plants (1990)
    Springer
    Theoretical and applied genetics 80 (1990), S. 673-679 
    Details
    ISSN: 1432-2242
    Keywords: Rice ; Tissue culture ; Somaclonal variation ; RFLP ; Methylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Regenerants of rice were examined by RFLP analysis to determine the occurrence and extent of somaclonal variation. DNA polymorphisms were observed both among plants regenerated from different callus cultures as well as among sibling plants derived from a single callus. Regardless of the basal medium, a higher degree of genetic instability was found among plants regenerated from callus cultures maintained for longer incubation periods (67 days) than among those from shorter incubation periods (28 days). Detailed analysis showed that in several regenerants, there was a close correlation among those plants exhibiting DNA rearrangements and those with apparent methylation changes. Such alterations were observed with both structural and housekeeping genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224228
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  • 6
    Electronic Resource
    Electronic Resource
    RFLP analysis of Zea mays callus cultures and their regenerated plants (1991)
    Springer
    Theoretical and applied genetics 81 (1991), S. 227-232 
    Details
    ISSN: 1432-2242
    Keywords: Callus cultures ; RFLP ; Zea mays ; Oryza sativa ; Regeneration ; Somaclonal variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Tissue culture of the Zea mays inbred line A188 resulted in the regeneration of plants having a high level of phenotypic variation compared to seed-grown control plants. To determine how such variation was induced and whether this could be related to specific in vitro culture methods, callus cultures were established and maintained on different, commonly used culture media. Plants were regenerated and the genomic DNA of callus cultures and regenerants analysed for RFLP differences. The results show that regardless of the gene probe used, callus formation resulted in significant deviations from the DNA pattern normally found in seed-grown control plants. Alterations in gene copy number also occurred. As differentiation and organogenesis began, the level of DNA variation fell, and most of the regenerated plants showed a genetic similarity to the controls; those with RFLP differences were the somaclonal variants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215727
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of single protoplasts and regenerated plants by PCR and RAPD technology (1993)
    Springer
    Molecular genetics and genomics 237 (1993), S. 311-317 
    Details
    ISSN: 1617-4623
    Keywords: PCR ; RAPD ; Somaclonal variation ; Tissue culture ; Transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We investigated the use of the polymerase chain reaction (PCR) and the associated random amplification of polymorphic DNA (RAPD) technique in the analysis of DNA and specific genes in plant cells at different stages of regeneration in in vitro cultures. We demonstrate that both procedures can be used to differentiate reproducibly between closely related species as well as to reveal levels of DNA polymorphism in regenerated plants. We also demonstrate that both procedures, using protocols that we have developed, are applicable at all tissue culture stages, from single isolated protoplasts to regenerated plants. Possible explanations for the variation levels detected in regenerated wheat plants are advanced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00279433
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  • 8
    Electronic Resource
    Electronic Resource
    Molecular changes in protoplast-derived rice plants (1990)
    Springer
    Molecular genetics and genomics 223 (1990), S. 324-328 
    Details
    ISSN: 1617-4623
    Keywords: Rice ; Protoplast ; RFLP ; Methylation ; Polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary To determine whether regeneration of rice plants from protoplast culture induces DNA polymorphisms, progeny plants from direct regenerants of such cultures were examined for restriction fragment length polymorphisms (RFLP analysis). Significantly increased levels of DNA polymorphism were found compared with those in non-tissue culture control plants. Analysis with gene sequences representative of different functional domains, revealed that such polymorphisms are apparently widespread and not associated with any particular region. Analysis by comparative digestion with both methylation-sensitive and insensitive restriction enzymes revealed that methylation changes cannot be regarded as a major factor in the induction of these DNA polymorphisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00265070
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  • 9
    Electronic Resource
    Electronic Resource
    Crystal structure of aluminium containing superconducting oxides: single crystal study of GdBa2Cu3−x AL x O6.88 (x=0.28) and ErBa2Cu3−y Al y O6.6 (y=0.14) (1990)
    Springer
    The European physical journal 80 (1990), S. 177-180 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Following the discovery of the high temperature super-conductivity in YBa2Cu3O7−δ (T c ≃93 K) [1] it has been found that Y atoms can be substituted entirely by almost all of the rare-earth elements, except for Ce, Pr, and Tb, without changing the superconducting properties appreciably [2, 3]. The magnetic moments carried by the rare-earth atoms have apparently no influence on the superconducting properties. In Nd-, Sm-, Gd-, Dy- and Er-based compounds the rare earth moments order at low temperatures (0.025–2.2 K) [4–8] and the ordered antiferromagnetic state coexists with the superconducting state. We have investigated the antiferromagnetic ordering of these compounds by neutron diffraction both on powder and single crystal samples obtained from several laboratories [8–10]. Magnetic structures of all these compounds consist of antiferromagnetic (001) planes stacked ferro- or antiferromagnetically. There have been some controversies as to the stacking of antiferromagnetic (001) planes in GdBa2Cu3O7−δ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01357499
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  • 10
    Electronic Resource
    Electronic Resource
    Environmental education in Sweden (1993)
    Springer
    The environmentalist 13 (1993), S. 221-227 
    Details
    ISSN: 1573-2991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Summary Schools and higher education institutions in Sweden have developed a wide range of innovative and demanding curricula to meet the objectives of Sweden's environmental policy. Environmental education in compulsory schools is taught principally through biological sciences, although social studies are beginning to occupy a substantial component of the environmental curriculum. Upper secondary schools offer more opportunities to develop environmental awareness, understanding and practical skills than comparable sixth form and post-secondary colleges in England. In Sweden there is a strong emphasis on practical work developed through projects based on contemporary environmental issues and their resolution. The development of environmental education has been well supported by a substantial input of new resources, especially materials developed by the Swedish Environmental Protection Agency and Industry. Universities have also begun to adopt new organisational structures to help develop inter-disciplinary teaching and research teams. Several universities are experimenting with ‘common core’ courses, parts of which comprise environmental elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01901384
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