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    ISSN: 0992-7689
    Keywords: Meteorology and atmospheric dynamics ; (middle atmosphere dynamics; thermospheric dynamics; waves and tides)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A meteor radar located at Sheffield in the UK has been used to measure wind oscillations with periods in the range 10–28 days in the mesosphere/lower-thermosphere region at 53.5°N, 3.9°W from January 1990 to August 1994. The data reveal a motion field in which wave activity occurs over a range of frequencies and in episodes generally lasting for less than two months. A seasonal cycle is apparent in which the largest observed amplitudes are as high as 14 ms−1 and are observed from January to mid-April. A minimum in activity occurs in late June to early July. A second, smaller, maximum follows in late summer/autumn where amplitudes reach up to 7–10 ms−1. Considerable interannual variability is apparent but wave activity is observed in the summers of all the years examined, albeit at very small amplitudes near mid summer. This behaviour suggests that the equatorial winds in the mesopause region do not completely prevent inter-hemispheric ducting of the wave from the winter hemisphere, or that it is generated in situ.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 35 (1976), S. 41-47 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The concentration and turnover of dissolved free amino acids were measured in samples from 25 and 100 m on three occasions at a station 6 miles off the California (USA) coast. Individual amino acid concentrations varied from undetectable (〈0.05 μg/l) to 3 μg/l, the total amino acid concentration from 1.8 to 8.5 μg/l. The greater concentration of total amino acids was always found at 25 m. The predominant amino acids were serine, lysine, aspartate, glutamate and alanine; reliable analyses could not be made for glycine because of a high blank. For the 10 individual amino acids studied, the rate of heterotrophic turnover ranged from undetectable to 1.2 μg/l day-1; serine, aspartate, alanine and glutamate showed the highest rates. In samples from 25 m, the rates were 15 to 20 times higher than those taken from 100 m. The total calculated flux of the amino acids studied varied from 0.015 to 3.2 μg/l day-1 and amounted to 1–10% of photosynthetic carbon dioxide fixation.
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  • 4
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The rate of primary production, excretion of photosynthetic products and turnover of glucose and amino acids was measured at a station in a coastal region in the Bahamas. Over the depths 0 to 50 m, total photosynthetic rates varied from 1.7 to 12.7 μgC fixed 1-1day-1, averaging 4.3. The extent of extracellular photosynthetic products ranged from undetectable to 23%, averaging 6.9%. Neither the field data nor studies with axenic cultures of Dunaliella tertiolecta, Skeletonema costatum, and Monochrysis lutheri showed any evidence of an increase in the percentage excretion at low population densities or low photosynthetic rates. Rates of amino acid turnover varied from 21 to 168% day-1, and that of glucose from 8.3 to 41% day-1. Light seems to have little effect on the uptake and respiration of these substrates by the planktonic population. There was a significant relationship between the fraction of the substrate used for respiration and that retained by the cell. On average, 42% of the glucose taken up was respired and 21% of the amino acid mixture. Tentative calculations suggest that the production of dissolved organic material as extracellular photosynthetic products would be insufficient to supply the heterotrophic population, and it was concluded that some other route(s) must be of major importance.
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  • 5
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between release of organic substances by phytoplankton and their utilization by heterotrophic bacteria has been measured by means of differential filtration in parallel Steemann Nielsen and Parsons and Strickland incubations. In Southampton Waters (UK), between March and September, the values for bacterial production measured in the above manner varied between 1 and 30%, the total primary production being taken as 100%. Even when low bacterial production occurs during the light period of incubation, a significant increase takes place during the following dark period. Thus, a close correlation between primary algal and the resultant bacterial production can be demonstrated. Quantitative data on bacterial production may be obtained from the conventional productivity experiments by simple double filtration.
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  • 6
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microheterotrophic dissolved free amino acid (DFAA) utilization, and microbial community and bacterial community carbon production and growth were studied using 3H-labeled organics as tracers in marine surface-film and subsurface (10 cm) waters off Baja California in November 1983. DFAA utilization was generally more rapid during the day (0.14 to 0.38 nM h-1) than at night (0.04 to 0.14 nM h-1) in surface-film and subsurface waters, but the percent of utilized amino acid which was respired was always greater during the night (22 to 57%) compared to the day (14 to 18%). Utilization of DFAA-carbon was estimated to range from 0.3 to 5.3 μg C l-1 d-1 for all stations studied. In six of the 8 samples examined, the percentage of microbial carbon accounted for by the bacterial component of the population (1.4 to 5.9%) was strikingly similar to the percentage of microbial carbon production accounted for by bacterial carbon production (1.9 to 5.1%). In all of these six samples, total microbial specific-growth rates and bacterial specific-growth rates were approximately equivalent (0.9 to 2.2 d-1 for the microbial community; 0.7 to 1.9 d-1 for bacteria). The two exceptions were samples apparently influenced by transient flagellate populations migrating into the surface or subsurface waters at night. These observations support the conclusion that surface films contain unique and highly active microbial populations.
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  • 7
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Gairloch Schist Belt in the Archaean to Early Proterozoic Lewisian Complex of north-west Scotland is largely composed of amphibolite facies metabasites and metagreywackes. These are associated with a distinctive suite of metamorphosed volcanic-exhalative sediments including quartz-magnetite rocks, garnet-grunerite rocks and compositionally variable, siliceous calcite- and dolomite-bearing lithologies. The carbonate horizons are locally rich in sulphide and carry Cu-Zn-Au mineralization. Meta-exhalites occur within parts of metavolcanic units characterized by metamorphosed tuffs and tuffs mixed with exhalative material. Quartz-magnetite and carbonate horizons were dismembered and underwent mylonitic recrystallization during regional compression. The associated metabasic rocks in the shear zones have suffered extensive phyllonitization. This style and degree of deformation are not developed elsewhere in the immediate area which suggests that ductile shear zones in the Gairloch Schist Belt were preferentially initiated near and localized around the meta-exhalative horizons.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Mineralium deposita 23 (1988), S. 247-255 
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Metasomatic tourmaline-quartz-hydromuscovite/phengite-fluorite rocks which locally contain in excess of 40% disseminated arsenopyrite and lesser amounts of pyrrhotite, chalcopyrite, pyrite, molybdenite, rutile, ilmenite and Fe-rich chlorite, occur near the village of Inistioge in SE Ireland. They are developed within Lower Palaeozoic phyllites close to the northwest margin of the southern termination of the Leinster batholith. The mineralization occurs within a belt of anomalously high (Caledonian) strain which was active during batholith-intrusion and which is essentially a product of heterogeneous shortening. Tourmaline constitutes up to 60% of the volume of the metasomatic material and although the lithology exhibits bed-parallel lamination, both detailed field and textural relationships demonstrate its origin to be epigenetic. The mineralization is spatially related to pegmatitic (K-feldspar, fluorite and muscovite-bearing) quartz veins with greisen alteration envelopes composed of coarse-grained muscovite, fluorite, apatite and tourmaline. The mineralized rocks were produced during alteration of aluminous metasediments by magmatic and/or meteoric fluids which were channelled through the high strain zone during cooling of the batholith.
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  • 9
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Au-Ag mineralization in the Mt-Shamrock — Mt. Ophir area of SE Queensland is related to a geographically-isolated calc-alkaline igneous centre consisting of high level plutonic and minor intrusions emplaced into the eroded remains of a silicic volcanic ediface and its basement. Mineralization occurs in both the igneous rocks and in the Permian siltstone country rocks and is controlled by a NE-trending structure parallel to Late Triassic lineaments. This structure is unrelated to, and younger than the exposed intrusions. Au-Ag-As-rich, Cu-Mo-poor mineralization occurs in breccias and veinlet networks within pervasively altered rocks characterized by silicification and H (sericite), CO2 (calcite-ankerite), Na (albite), B (tourmaline), and S (pyrite) metasomatism. Secondary mineral compositions suggest that most of this alteration occurred at temperatures between 350 ° and 400 °C. The alteration was complex in detail and characterized by multiple hydrothermal events and space and/or time variations of physico-chemical conditions. Although some of these features are similar to prophyry deposits the chemical character of the alteration and mineralization is not typical of Cu-Mo-Au porphyries and has more in common with tectonometamorphic Au deposits formed at considerably greater depths.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 24 (1997), S. 231-238 
    ISSN: 1432-0789
    Keywords: Key words N2O ; Mechanistic model ; Nitrification ; Denitrification ; Michaelis-Menten kinetics ; Grassland ; Spatial variablity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Seasonal and annual N2O fluxes from urine-affected pasture were approximated with a mechanistic model based on Michaelis-Menten kinetics. The model combined the effects of soil nitrate-N, soil ammonium-N, soil temperature and soil moisture (all from the top 5cm) to calculate N2O emissions from nitrification (F nit ) and denitrification (F den ), with total N2O emission being the sum of the two (F tot =F nit +F den ). Best results were obtained when different kinetic parameters were used for periods of constant soil moisture conditions and after heavy rainfalls when a rapid change of the soil moisture status occurred. Modelled N2O emissions over a year were within the range of uncertainties of measured N2O emissions. Results indicate that the spatial variability of N2O emissions at times when all the model inupt variables were constant may be related to microorganism growth dynamics or enzyme production rates.
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