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  • 1
    ISSN: 1432-0495
    Keywords: Key words Heavy metals ; Base metals ; Smelter ; Anthropogenic contamination ; Chemical partitioning ; Soil ; Particulate emissions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Trace element geochemistry of humus (〈0.425 mm) and till (〈0.002 mm) collected in the Flin Flon-Snow Lake area, northern Manitoba and Saskatchewan, provides a regional context for assessing smelter contamination in the environment. The area includes a Cu-Zn smelter known to discharge As, Cd, Cu, Fe, Hg, Pb, and Zn. In this study, sequential extraction analyses, scanning electron microscopy and x-ray diffraction analyses were used on a suite of samples to determine: (1) the chemical and physical characteristics of heavy metals in surficial sediments related to distance from the smelter, (2) criteria for assessing the relative contribution of these metals from natural and anthropogenic sources, and (3) the potential of these metals for remobilization in the environment. Humus geochemistry reflects the anthropogenic and natural component of heavy metal concentrations. Smelter-related elements show anomalously high values adjacent to the smelter, decreasing with distance until background values are reached at 70–104 km, depending on the element. In humus, Zn is associated primarily with labile phases; Hg with non-labile phases. Adjacent to the smelter, high proportions and concentrations of Zn and Hg in non-labile phases, indicative of smelter-derived particulates, are confirmed by SEM examination. The particles occur as spheres, irregular grains, and with organics. With increasing distance from the smelter, the geochemical response to bedrock composition is more obvious than the anthropogenic input. Till geochemistry reflects the natural variation imposed by bedrock composition. At highly contaminated sites (〈3 km from the smelter), increased percentages of smelter-related elements in labile phases suggests heavy metals are leached from humus to the underlying sediment.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 181 (1958), S. 133-134 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Mitochondrial preparations from the endosperms of germinating castor oil beans2 were diluted 8-10 times with ice-cold demineralized water and incubated at 0 for 30 min. to render the mitochondrial oxidase and reductase systems accessible to cytoehrome c. In the resulting preparations the ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 178 (1956), S. 593-594 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In the presence of reduced diphosphopyridine nucleotide and malic dehydrogenase, the oxalacetate is reduced to malate; oxalacetate + DPNH malate + DPN (2) The linked reaction, phosphoenolpyruvate + CO2 + DPNH malate + DPN + orthophosphate (3) may then be followed spectrophotometrically by ...
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 185 (1960), S. 690-691 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] What may be overlooked is that it is frequently possible to isolate an enzyme biochemically rather than physically by adding to an adequately dialysed mixture only that combination of substrates, co-enzymes and co-factors which is necessary for its activation. In these circumstances it may prove ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 210 (1966), S. 793-796 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] PHOTOPHOSPHORYLATION has been widely studied since its discovery in 19541'2. When supplied with inorganic phosphate and a co-factor such as phenazine methosulphate (PMS), illuminated chloroplasts will carry out 'cyclic' photophosphorylation (reaction 1) of exogenous adenosine diphosphate (ADP) at ...
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 226 (1970), S. 1204-1208 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Chloroplasts utilize light energy to convert carbon dioxide to sugars and other compounds. As this review article shows, work with isolated chloroplasts has done much to reveal how the necessary “reducing power” is generated, and to establish the importance of membranes in ...
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Global change biology 6 (2000), S. 0 
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Current land-cover classifications used for global modelling portray Arctic tundra as one or two classes. This is insufficient for analysis of climate–vegetation interactions. This paper presents a simple three-level vegetation-map legend system useful for modelling at global, regional, and landscape scales. At the highest level (global scale: 107−108 km2) the Tundra Zone is divided into four subzones based on vegetation response to temperature along the latitudinal temperature gradient from north to south: (1) Cushion-forb, (2) Prostrate Dwarf-shrub, (3) Erect Dwarf-shrub, and (4) Low Shrub subzones. The boundaries follow a modification of Yurtsev's phytogeographic subzones. Parent material and topography are also major considerations at global, regional, and landscape scales. Soil pH is a key variable for many ecosystem responses, and a division into acidic (pH 5.5 or less) and nonacidic soils is used. A conceptual mesotopographic gradient is used to characterize the influence of soil-moisture and snow regimes. The example legend framework focuses on the Northern Alaska floristic subprovince, and could be expanded to other floristic provinces using local expert knowledge and available literature. Dominant plant functional types within each habitat type within the four subzones are also presented. Modellers could include or ignore different levels of resolution depending on the purpose of the model. The approach resolves conflicts in terminology that have previously been encountered between the Russian, North American, and Fennoscandian approaches to Arctic zonation.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 1131-1135 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Direct measurement of the transfer function of hot-wire anemometers is needed whenever any turbulence frequencies approach the hot-wire frequency response. In particular, in high-speed applications it is not possible to obtain hot-wire frequency response sufficient to capture all of the turbulent kinetic energy. With knowledge of the hot-wire response, either an estimate of the turbulent integral scale or an approximation of the high-frequency part of the turbulent spectrum may be sufficient to correct measurements by post-detection frequency compensation. Described in this article are simple electronic circuits and a technique for obtaining sine-wave test frequency response of a hot-wire anemometer in a very short time without prohibitively high sampling rates.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biochemistry 39 (1970), S. 389-428 
    ISSN: 0066-4154
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Chemistry and Pharmacology , Biology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 4 (1981), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Unlike wheat chloroplasts, wheat protoplasts showed a pronounced restoration of the induction phase after a short period of darkness. This difference was used to investigate the relative roles of light-induced reductive activation of enzymes and the auto-catalytic increase in the level of substrates in the control of the rate of photosynthesis during induction. Light activation and dark inactivation of ribulose 5-phosphate kinase, fructose 1,6-biphosphatase and NADP+-specific glyceraldehydephosphate dehydrogenase were measured. In this respect there was no appreciable difference between protoplasts and chloroplasts. In contrast, the level of photosynthetic intermediates remained constant in darkened isolated chloroplasts, but declined rapidly in chloroplasts isolated from darkened protoplasts. When fructose 1,6-bisphosphatase was pre-activated by treating protoplasts with dithiothreitol the lag was only slightly shortened. These results are discussed in terms of control of the rate of the photosynthesis during the lag by substrates rather than limitation imposed by activity of any of the enzymes measured.
    Type of Medium: Electronic Resource
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