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  • 1
    Electronic Resource
    Electronic Resource
    Hydrogen adsorption states at the Pd/SiO2 interface and simulation of the response of a Pd metal–oxide–semiconductor hydrogen sensor (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 3947-3951 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The response of a Pd–SiO2–Si hydrogen sensor depends on the reaction kinetics of hydrogen on the Pd surface and on the hydrogen adsorption states at the Pd/SiO2 interface. In this work we show that besides the dominating hydrogen adsorption state located on the oxide side of the interface, a second state, resulting in opposite hydrogen polarization, exists. This state is possibly a reminiscence of the hydrogen adsorption state on a clean Pd surface. Taking both states into account, a simulation of the hydrogen response over more than ten decades in hydrogen pressures gives good agreement with published data. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367150
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  • 2
    Electronic Resource
    Electronic Resource
    Difference in hydrogen sensitivity between Pt and Pd field-effect devices (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4275-4280 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An explanation is given for the large differences in the hydrogen sensitivity in air observed for gas sensitive field-effect devices with palladium and platinum gates, respectively. It is demonstrated that this difference is mainly due to a difference in the hydroxyl formation rate between the two metals. The water production rates are, however, almost the same for the two metals. The considerably smaller sensitivity of platinum devices in air is then due to the much lower steady-state hydrogen atom concentration on the platinum surface compared with the palladium surface. This leads to a smaller coverage of hydrogen atoms at the metal–oxide interface and thus a smaller response of the device at a given hydrogen concentration in air. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1448874
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  • 3
    Electronic Resource
    Electronic Resource
    Methanol production from lignin-related substances by Phanerochaete chrysosporium (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 65 (1985), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Methanol production resulting from the demethoxylation of lignin-related substances by Phanerochaete chrysosporium K-3 was studied in the presence or absence of glutamic acid in order to determine if methanol formation involved the ligninolytic system of the fungus. The general pattern was that methanol formation, calculated as percentage of theoretical yield, decreased in the order guaiacyl 〉 syringyl 〉 veratryl (3,4-dimethoxy) compounds. Methoxyhydroquinone and vanillic acid were most easily demethoxylated, while methanol production decreased with increasing molecular weight for the same type of structure (i.e. guaiacyl). Glutamic acid inhibited the demethoxylation of many of the compounds tested. The demethoxylation of the 4-methoxy group of veratric acid was particularly inhibited by glutamic acid suggesting a participation of the ligninolytic system, while the 3-methoxy group was influenced to a lesser extent.The demethoxylating enzyme acting on lignin-related phenols is probably a peroxidase, while the identity of the enzyme demethoxylating dimethoxy compounds is not known with certainty, although a peroxidase type of enzyme reaction is anticipated also here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1985.tb02402.x
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  • 4
    Electronic Resource
    Electronic Resource
    Competition between freshwater fish and goldeneyes Bucephala clangula (L.) for common prey (1979)
    Springer
    Oecologia 41 (1979), S. 99-107 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Results of a descriptive field study showed that goldeneyes preferred lakes without fish to those with fish. Field experiments were carried out in order to investigate whether or not this preference could be ascribed to a higher food supply in the lakes devoid of fish, as goldeneyes and some freshwater fish (perch and roach in the studied lakes) to some extent feed on the same kinds of prey. Changes in the abundance of prey common to fish and goldeneyes and the use by goldeneyes of lakes after experimentally changed predation pressure from fish were studied. Some aquatic insect groups, Cloeon larvae, Odonata larvae, water bugs, dytiscids, and Chaoborus larvae, proved sensitive to predation from fish. Goldeneyes increased their use of an experimental lake after fish were removed, and they used this lake more than an adjacent control lake. It is suggested that fish are able to reduce the availability of foods common to the goldeneyes to such an extent that the selection by the ducks of feeding localities is affected, and that exploitation competition between freshwater fish and goldeneyes may occur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00344840
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  • 5
    Electronic Resource
    Electronic Resource
    Ecological mechanisms important for the biotic changes in acidified Lakes in Scandinavia (1989)
    Springer
    Archives of environmental contamination and toxicology 18 (1989), S. 201-206 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract We describe some mechanisms behind the biotic changes in acidified lakes in Scandinavia. Besides direct effects, such as reduced reproduction or survival of fish and invertebrates due to low pH or exposure to toxic metals, we emphasize the importance of indirect effects. Mechanisms involved are of an ecological character; such as a shift of top predatores from fish to invertebrates and a reduced decomposition rate due to decreased abundance of detrivores, as well as feed-back effects on the abiotic environment; such as reduced productivity and turnover rate of nutrients and an increase in water transparency. We include the aspects of how bird species in aquatic habitats may be indirectly affected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01056204
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  • 6
    Electronic Resource
    Electronic Resource
    Metal contents in liver tissues of non-fledged Goldeneye,Bucephala clangula, ducklings: A comparison between samples from acidic, circumneutral, and limed lakes in South Sweden (1989)
    Springer
    Archives of environmental contamination and toxicology 18 (1989), S. 255-260 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract The risk of increased exposure to metals for a vertebrate predator foraging on aquatic insects in acidified lakes was investigated through analyses of the content of Al, As, Ca, Cd, Cu, Fe, Hg, Mn, Pb, Ru, Se, and Zn in the liver tissue of 42 non-fledged Goldeneye,Bucephala clangula, ducklings from acidic, circumneutral, and limed lakes in South Sweden. No indications of significantly different concentrations in samples from acidic lakes in comparison with circumneutral lakes were detected for any metal, but among individual birds from acidic lakes there were high contents of Hg. Liming probably affects the exposure to some metals; lower contents of Hg were recorded from limed lakes in comparison with acidic lakes, while the reverse trend was recorded for Cd and Mn.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01056211
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  • 7
    Electronic Resource
    Electronic Resource
    Radiometric dating of recent lake sediments from a highly eroded area in semiarid Tanzania (1998)
    Springer
    Journal of paleolimnology 19 (1998), S. 377-383 
    Details
    ISSN: 1573-0417
    Keywords: Semiarid ; Tanzania ; erosion ; sediments ; chronologies ; radionuclides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Semiarid regions are vulnerable environments with a series of important and often discussed problems such as land degradation, water scarcity and desertification. These regions are dynamic and respond quickly to climatic and environmental changes. Unlike lakes in temperate zones, lakes in semiarid regions are yet poorly utilized as climatic and environmental indicators. In this study aquatic deposits are used to uncover the environmental history of a severely degraded area in central Tanzania. The 210Pb and 137Cs chronologies date a 360 cm long sediment sequence to 155 years. The sediments show that lake Haubi basin changed from a seasonally waterlogged depression to a lake at the turn of the century. Calculated sedimentation rates show that the catchment of the lake has been subject to varied and enhanced soil erosion during the last 155 years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007986402639
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  • 8
    Electronic Resource
    Electronic Resource
    Recent lake level variations in Lake Haubi, central Tanzania, interpreted from pollen and sediment studies (1999)
    Springer
    Journal of paleolimnology 22 (1999), S. 457-473 
    Details
    ISSN: 1573-0417
    Keywords: lake levels ; lake sediments ; palaeoclimate ; pollen ; Tanzania ; East Africa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Variations in pollen assemblages and in physical and chemical composition of a dated sediment record from the small Lake Haubi in north central Tanzania, reveal lake level fluctuations since the late 19th century. Lake Haubi changed from a seasonally inundated swamp to a lake in the beginning of the 20th century. With the exception of 1942-44, when it dried out completely, it remained water filled until 1994 when it again turned into a swamp. The lake level fluctuations in Lake Haubi are largely in phase with fluctuations of the larger East African lakes levels during the 20th century, and are therefore interpreted as being mainly controlled by regional climatic fluctuations. However, the initial formation of Lake Haubi at the turn of the century was likely due to local catchment specific causes, e.g. changes in land use, as the rapid increase in the water level at this time does not correspond to other lake level records from the region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008066726211
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  • 9
    Electronic Resource
    Electronic Resource
    The cyanobacterium Synechococcus sp. PCC 7942 possesses a close homologue to the chloroplast ClpC protein of higher plants (1996)
    Springer
    Plant molecular biology 31 (1996), S. 721-730 
    Details
    ISSN: 1573-5028
    Keywords: chaperone ; cyanobacteria ; gene expression ; heat shock ; protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Clp family consists of large, ubiquitous proteins that function as molecular chaperones and/or regulators of ATP-dependent proteolysis. A single copy gene coding for one of these proteins, ClpC, was cloned from the unicellular cyanobacterium Synechococcus sp. PCC 7942. The predicted polypeptide is most similar (ca. 88%) to the chloroplast-localized ClpC protein from higher plants. Using degenerate PCR primers specific for the two distinct ATP-binding domains characteristic of all ClpA-C proteins, partial sequences homologous to clpC from Synechococcus were also identified in five other cyanobacterial strains. The Synechococcus clpC gene is transcribed under standard growth conditions as a monocistronic message of around 2.7 kb. The level of this message, however, decreases slightly after a shift from 37 to 47.5°C for 2 h, similar to expression previously observed for clpC mRNA from heat-shocked higher plants. At the protein level, the amount of ClpC remains relatively unchanged during the high temperature shift, while that of the known heat shock protein GroEL rises considerably. In contrast, the constitutive level of ClpC in Synechococcus increases considerably under conditions of rapid growth, both with increasing light intensities or CO2 concentrations. This, and the fact that attempts to inactivate clpC expression fail to produce a viable phenotype, suggest that ClpC activity is essential for growth in this obligate photoautotrophic cyanobacterium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00019460
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  • 10
    Electronic Resource
    Electronic Resource
    Homologous and heterologous protein import into mitochondria isolated from the green alga Chlamydomonas reinhardtii (1997)
    Springer
    Plant molecular biology 35 (1997), S. 973-980 
    Details
    ISSN: 1573-5028
    Keywords: mitochondrial protein import ; protein targeting ; precursor protein ; presequence ; protein processing ; Chlamydomonas reinhardtii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have established a homologous system for studying mitochondrial protein import in Chlamydomonas reinhardtii, using C. reinhardtii precursor proteins and mitochondria isolated from C. reinhardtii. The precursors of the F1α ATP synthase subunit and the Rieske FeS protein were imported into mitochondria with high efficiency, while the F1β subunit precursor was imported with much lower efficiency. The import of heterologous precursor proteins from higher plants was also less efficient. The precursor of the C. reinhardtii PsaF chloroplast protein was converted into a protease-protected form upon incubation with mitochondria. In vitro processing studies revealed that in contrast to the situation in higher plants, the processing of the precursors was catalysed by a soluble, matrix-located peptidase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005878614878
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