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  • Springer  (281)
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  • 1
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Olivine crystals in basaltic andesites which crop out in the Abert Rim, south-central Oregon have been studied by high-resolution and analytical transmission electron microscopy. The observations reveal three distinct assemblages of alteration products that seem to correspond to three episodes of olivine oxidation. The olivine crystals contain rare, dense arrays of coherently intergrown Ti-free magnetite and inclusions of a phase inferred to be amorphous silica. We interpret this first assemblage to be the product of an early subsolidus oxidation event in the lava. The second olivine alteration assemblage contains complex ordered intergrowths on (001) of forsterite-rich olivine and laihunite (distorted olivine structure with Fe3+ charge balanced by vacancies). Based on experimental results for laihunite synthesis (Kondoh et al. 1985), these intergrowths probably formed by olivine oxidation between 400 and 800°C. The third episode of alteration involves the destruction of olivine by low-temperature hydrothermal alteration and weathering. Elongate etch-pits and channels in the margins of fresh olivine crystals contain semi-oriented bands of smectite. Olivine weathers to smectite and hematite, and subsequently to arrays of oriented hematite crystals. The textures resemble those reported by Eggleton (1984) and Smith et al. (1987). We find no evidence for a metastable phase intermediate between olivine and smectite (“M” — Eggleton 1984). The presence of laihunite exerts a strong control on the geometry of olivine weathering. Single laihunite layers and laihunite-forsteritic olivine intergrowths increase the resistance of crystals to weathering. Preferential development of channels between laihunite layers occurs where growth of laihunite produced compositional variations in olivine, rather than where coherency-strain is associated with laihunite-olivine interfaces.
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  • 2
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Monomineralic domains of chlorite, corundum and Cr muscovite coexist over a kilometer scale within ultramafic schists of the Harare greenstone belt (2.73 Ga). This exotic lithological association includes the conjunction of some of the most aluminous (Al2O3∼88 wt%) and potassic (K2O∼10 wt%) rocks known. The paragenetic sequence developed from chlorite→corundum→corundum+ diaspore: Cr muscovite variably overprinted both the corundum and chloritite domains. Terminal stages were marked by sporadic production of andalusite+quartz, and finally margarite. Chlorite (Cr2O3=0.31–2.65 wt%), corundum (0.79–2.66 wt%), and diaspore are all Cr-rich varieties. The chromian (Cr2O3∼3.86 wt%) paragonitic muscovite incorporates up to 17% of the paragonite molecule, and significant Mg and Fe substitutions. The suite of rocks are characterized by ‘chondritic’ Ti/Zr ratios (−x=107), systematically enhanced Cr (up to 14000 ppm) and Ni (up to 1200 ppm) abundances, low levels of the alteration-insensitive incompatible elements Th, Ta, Nb. Chlorite, corundum and Cr muscovite represent progressive stages in the incremental metasomatic alteration of a komatiite precursor. Mass balance calculations, constrained by the isochemical behaviour of Ti, Zr and Hf reveal that the komatiite chloritite transformation involved volumetric contractions of ∼60% by hydrothermal leaching of Si, Fe, Mn, Ca and Na. Reaction of chloritite to corundum involved further volumetric reductions of ∼50% due to essentially quantitative loss of Si, Fe, Mn, Mg, K and Ca. Conversion of corundum to muscovite required additions of Si, K, Fe, Mn, Mg, Rb and Ba at 50–200% dilation. K, Rb, Ba, Li and Cs are enriched by up to 2×103 over background abundances in ultramafic rocks, and the suite is also enriched in B, Se, Te, Bi, As, Sb and Au. REE were extensively leached during chloritite-corundum stages, whereas LREE additions accompany development of muscovite. Ti, Zr, Hf and Al were all concentrated by selective leaching of mobile components, but absolute additions of Al accompanied development of the corundum domains due to Al precipitation in response to depressurization. Corundum (δ 18O=3.5–4.8), muscovite (δ 18O=6.7–7.5‰) and chlorite (4.5–5.6‰) are isotopically uniform and formed at 380–520° C from a fluid where δ 18O=5.6–6.9‰. The corundum is 18O depleted relative to either igneous or anatectic counterparts (δOcor=7.6–8.2), or to gibbsitic laterites (δ 18O=12–17). Previous genetic schemes involving metamorphism of exhalites or bauxite, or Si-undersaturation of magmas, can all be ruled out from the data. The chloritite, corundum, Cr-muscovite association represents sequential alteration products of ultramafic rocks by high temperature, low pH hydrothermal solutions carrying LIL-elements, and in which excursions of pH and/or degree of quartz undersaturation account for the mineralogical transitions. A deep level acid epithermal system, or fluid advection across steep inverted thermal gradients in a thrust regime could account for required hydrothermal conditions.
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  • 3
    ISSN: 1432-0789
    Keywords: Earthworms ; N mineralization ; Agroecosystems ; Soil structure ; Microbial biomass ; Lumbricus terrestris ; Aporrectodea tuberculata ; Soil cores
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influence of earthworms (Lumbricus terrestris and Aporrectodea tuberculata) on the rate of net N mineralization was studied, both in soil columns with intact soil structure (partly influenced by past earthworm activity) and in columns with sieved soil. Soil columns were collected from a well drained silt loam soil, and before the experiment all earthworms present were removed. Next, either new earthworms (at the rate of five earthworms per 1200 cm3, which was only slightly higher than field numbers and biomass) were added or they were left out. At five points in time, the columns were analyzed for NH 4 + , NO 3 − , and microbial biomass in separate samples from the upper and lower layers of the columns. N mineralization was estimated from these measurements. The total C and N content and the microbial biomass in the upper 5 cm of the intact soil columns was higher than in the lower layer. In the homogenized columns, the C and N content and the microbial biomass were equally divided over both layers. In all columns, the concentration of NH 4 + was small at the start of the experiment and decreased over time. No earthworm effects on extractable NH 4 + were observed. However, when earthworms were present, the concentration of NO 3 − increased in both intact and homogenized cores. The microbial biomass content did not change significantly with time in any of the treatments. In both intact and homogenized soil, N mineralization increased when earthworms were present. Without earthworms, both type of cores mineralized comparable amounts of N, which indicates that mainly direct and indirect biological effects are responsible for the increase in mineralization in the presence of earthworms. The results of this study indicate that earthworm activity can result in considerable amounts of N being mineralized, up to 90 kg N ha−1 year−1, at the density used in this experiment.
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  • 4
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
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  • 5
    ISSN: 1432-0789
    Keywords: Decomposition ; Litter ; Microarthropods ; Nitrogen ; 15N ; Litterbags ; Cornus florida ; Quercus prinus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Surface additions of (15NH4)2SO4 were used to measure the immobilization and subsequent movement of exogenous N added to two litter types of contrasting quality (Cornus florida and Quercus prinus). Litterbaskets were used to measure the litter mass loss and N dynamics and to follow the movement of the 15N label through litter, F layer, and soil pools. Half of the litterbaskets of each species were treated with naphthalene to reduce microarthropod densities. The faster decomposing C. florida litter maintained a higher excess atom % 15N, and a greater relative concentration of the labeled input (μg 15N g−1) than did Q. prinus litter. In both litter types the excess atom % 15N, relative concentration (μg 15N g−1), and absolute amount of label recovered in the litter declined over time. This occurred during a period of net accumulation of total litter N, implying simultaneous release of the initial input and immobilization of N from other sources. The concentration of 15N in the soil increased over time, while the F layer apparently acted as an intermediary in the transfer of 15N from litter to soil. Naphthalene effectively reduced microarthropod numbers in all horizons of the litterbaskets and significantly reduced the decay rates of Q. prinus, but not C. florida litter. Naphthalene did not appear to affect total N dynamics in the litter. However, with all horizons taken together, the naphthalene-treated litterbaskets retained more total 15N than the control litterbaskets. Naphthalene also changed the vertical distribution of 15N within litterbaskets, so that the litter retained less of the 15N-labeled input and the F layer and soil horizons retained more of the labeled input than in control litterbaskets. Our major conclusions are: (1) the N pool of decomposing litter is dynamic, with simultaneous N release and immobilization activating N turnover even during the net accumulation phase; (2) litter quality is an important determinant of immobilization and retention of exogenous N inputs and, therefore, turnover of the litter N pool; and (3) microarthropod activity can significantly affect the incorporation and retention of exogenous N inputs in decomposing litter, although these changes are apparently not reflected in net N accumulation or release during the 1st year of decomposition. However, the naphthalene may have affected microbially mediated N dynamics and this possibility needs to be considered in interpreting the results.
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  • 6
    ISSN: 1432-0975
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Caribbean species of Halimeda from the steep slopes of San Salvador Island, Bahamas, were collected along vertical transects between 25 and 255 m, on the northeast, northwest, west, southwest and south sides of the island, using the Harbor Branch Oceanographic Institution's submersible Johnson Sea Link I. The characteristics delineating species (segment and utricle size) were assessed for selected species, and the depth and western Atlantic distributions of the species reviewed. Halimeda copiosa was found to show a variation of surface utricle diameter with depth, with the deeper plants having 15% larger diameter utricles than the shallower plants. Of the seven species, one variety and one form of Halimeda studied from our submersible dive sites, H. copiosa, H. cryptica and H. gracilis grew to the greatest depths, from 120 to 150-m depths. H. lacrimosa var. globosa was found growing to 91 m, and H. tuna f. platydisca and H. discoidea to a depth of 73 m. Those of lesser depth, to 61 m, were H. goreauii, H. tuna f. tuna and H. lacrimosa var. lacrimosa. These represent substantial increases in depth distribution of the nine taxa found.
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  • 7
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Familial cylindromatosis is an autosomal dominant predisposition to multiple neoplasms of the skin appendages. The susceptibility gene has previously been mapped to chromosome 16q12–q13 and has features of a recessive oncogene/tumour suppressor gene. We have now evaluated 19 families with this disease by a combination of genetic linkage analysis and loss of heterozygosity in cylindromas from affected individuals. All 15 informative families show linkage to this locus, providing no evidence for genetic heterogeneity. Recombinant mapping has placed the gene in an interval of approximately 1 Mb. There is no evidence, between families, of haplotype sharing that might be indicative of common founder mutations.
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  • 8
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Hereditary sensory neuropathy type I (HSN-I) is an autosomal dominant peripheral neuropathy affecting sensory and motor neurons. The disease involves distal sensory loss, distal muscle wasting and weakness, and variable neural deafness. The HSN1 locus has been mapped to a genetic interval of 3-4 cM on chromosome 9q22.1-q22.3 and is flanked by markers D9S1781 and FB19B7. This interval contains the gene NFIL3, a transcription factor that is regulated by the cytokine IL-3. Northern blot analysis of NFIL3 showed a ubiquitously expressed 2.2-kb mRNA. Expression was highest in the lung, with lower levels of expression in the brain and spinal cord. Mutation analysis by direct sequencing of reverse transcription/polymerase chain reaction products from HSN-I patients excluded the coding region of the NFIL3 from being involved in the pathogenesis of HSN-I.
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  • 9
    ISSN: 1432-1157
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Early diagenetic properties of Amazon shelf muds are dominated by nonsulfidic Fe and Mn cycling, resulting in relatively little S deposition compared to previously studied marine margin environments. Despite abundant potential reactants typical of sulfidic deposits, authigenic sulfides represent only ~ 10% of diagenetically reduced Fe, and DOP (degree of pyritization) is only ~0.02. The average C/S (wt wt−1) ratio of buried sediment below the zone of SO4 2- reduction is ~ 7.4, ~ 2.6 times more than the commonly assumed modern shelf average of ~ 2.8. The deltaic burial rate forΣS is ~ 0.65 × 106 tons yr−1. Relatively lowΣS deposition is promoted by terrestrial weathering that delivers reactive oxide debris, but apparently depends most strongly on reoxidation and rapid burial by intense physical reworking and fluid-mud formation. Diagenetic models of S distributions demonstrate rapid sediment reworking (~ 10–100 cm yr−1 as apparent advection), substantialΣS reoxidation (84–98%), and in one case, massive sediment deposition of up to ~ 5 m of sediment in ~ 1 year. Extremely low DOP coupled with dominance by nonsulfidic reduced-Fe minerals and lack of biogenic sedimentary structures may be an indicator in marine organic-rich muds of intense physical reworking under oxygenated waters.
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  • 10
    ISSN: 1432-2242
    Keywords: Wheat ; HMW glutenin subunits ; Bread-making quality ; Gene ; Protein sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A gene encoding the high-molecular-weight (HMW) subunit of glutenin 1Ax1 was isolated from bread wheat cv Hope. Comparison of the deduced amino acid sequence with that previously reported for an allelic subunit, 1Ax2*, showed only minor differences, which were consistent with both subunits being associated with good bread-making quality. Quantitative analyses of total protein extracts from 22 cultivars of bread wheat showed that the presence of either subunit 1Ax1 or 1Ax2*, when compared with a null allele, resulted in an increase in the proportion of HMW subunit protein from ca. 8 to 10% of the total. It is suggested that this quantitative increase in HMW subunit protein may account for the association of 1Ax subunits with good quality.
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