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  • 1
    Electronic Resource
    Electronic Resource
    O2-Sensing and O2-dependent gene regulation in facultatively anaerobic bacteria (1995)
    Springer
    Archives of microbiology 164 (1995), S. 81-90 
    Details
    ISSN: 1432-072X
    Keywords: Key words FNR ; Anaerobic gene regulation ; Oxygen ; Facultative anaerobic metabolism ; Anaerobic respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Availability of O2 is one of the most important regulatory signals in facultatively anaerobic bacteria. Various two- or one-component sensor/regulator systems control the expression of aerobic and anaerobic metabolism in response to O2. Most of the sensor proteins contain heme or Fe as cofactors that interact with O2 either by binding or by a redox reaction. The ArcA/ArcB regulator of aerobic metabolism in Escherichia coli may use a different sensory mechanism. In two-component regulators, the sensor is located in the cytoplasmic membrane, whereas one-component regulators are located in the cytoplasm. Under most conditions, O2 can readily reach the cytoplasm and could provide the signal in the cytoplasm. The transcriptional regulator FNR of E. coli controls the expression of many genes required for anaerobic metabolism in response to O2. Functional homologs of FNR are present in facultatively anaerobic Proteobacteria and presumably also in gram-positive bacteria. The target genes of FNR are mostly under multiple regulation by FNR and other regulators that respond to O2, nitrate, or glucose. FNR represents a ’one-component' sensor/regulator and contains Fe for signal perception. In response to O2 availability, FNR is converted reversibly from the aerobic (inactive) state to the anaerobic (active) state. Experiments suggest that the Fe cofactor is bound by four essential cysteine residues. The O2-triggered transformation between active and inactive FNR presumably is due to a redox reaction at the Fe cofactor, but other modes of interaction cannot be excluded. O2 seems to affect the site-specific DNA binding of FNR at target genes or the formation of an active transcriptional complex with RNA polymerase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050238
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  • 2
    Electronic Resource
    Electronic Resource
    Cyclic-oxidation behavior of TiAl and of TiAl alloys (1993)
    Springer
    Oxidation of metals 39 (1993), S. 93-106 
    Details
    ISSN: 1573-4889
    Keywords: cyclic oxidation ; TiAl ; TiAl alloys ; scale spallation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The cyclic-oxidation behavior of (in w/o) Ti-36Al, Ti-35Al-0.1C, Ti-35Al-1.4V-0.1C and Ti-35Al-5Nb-0.1C was studied between 800 and 1000° C in air. A few experiments were also performed in oxygen. Scale spallation after oxidation in air occurs during cooling on TiAl, TiAl-C, and TiAl-V at or close to the metal/scale interface when a critical scale thickness has been achieved. This process repeats and can lead to a stratified scale. These three materials form scales composed of an inward-growing fine-grain mixture of TiO2-Al2O3 and an outward-growing coarse-grain TiO2 layer or TiO2+Al2O3 mixture. The TiAl-Nb alloy had a significantly different behavior. The scale on this material grew very slowly because a protective Al2O3 layer formed at the metal/scale interface. This behavior resulted in much better resistance to spallation because the critical scale thickness was reached only after a much longer time, and is different from the behavior of the other three alloys. Oxidation in air leads to slight nitridation of the subsurface zone beneath the scale. In comparison to oxidation in air, oxidation in oxygen improves the cyclicoxidation behavior. Whereas the scale formed in air was uniformly thick over the entire surface, the scale grown in oxygen varied locally in structure and thickness. A large fraction of the surface was covered with a thin Al2O3 layer, while the remaining part formed a two-layer scale similar to that formed in air. The results are discussed briefly in the light of a recently published model for scale spallation under compressive stress, however, quantitative estimations are not possible due to a lack of relevant data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00666612
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  • 3
    Electronic Resource
    Electronic Resource
    Mechanism of isothermal oxidation of the intel-metallic TiAl and of TiAl alloys (1992)
    Springer
    Oxidation of metals 38 (1992), S. 425-464 
    Details
    ISSN: 1573-4889
    Keywords: oxidation mechanism ; TiAl ; TiAl alloys ; air ; oxygen ; nitridation ; Ti-Al-O phase diagram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of Ti36Al, Ti35Al-0.1C, Ti35Al-1.4V-0.1C, and Ti35 Al-5Nb-0.1C (mass-%) in air and oxygen has been studied between 700 and 1000°C with the major emphasis at 900°C. Generally an oxide scale consisting of two layers, an outward- and an inward-growing layer, formed. The outward-growing part of the scale consisted mainly of TiO2 (rutile), while the inward-growing part is composed of a mixture of TiO2 and α-Al2O3. A barrier layer of Al2O3 on TiAl between the inner and the outer part of the scale was visible for up to 300 hr. Under certain conditions, the Al2O3 barrier dissolved and re-precipitated in the outer TiO2 layer. This “shift” leads to an effect similar to breakaway oxidation. Only the alloy containing Nb formed a longlasting, protective Al2O3 layer, which was established at the metal/scale interface after an incubation period of 80–100 hr. During this time, Nb was enriched in the subsurface zone up to approximately 20 w/o. The growth of the oxide scale on TiAl-V obeyed a parabolic law, because no Al2O3 barrier layer formed; large Al2O3 particles were part of the outward-growing layer. A brittle α2-Ti3Al-layer rich in O formed beneath the oxide scale as a result of preferential Al oxidation particularly when oxidized in oxygen. Oxidation in air can lead also to formation of nitrides beneath the oxide scale. The nitridation can vary between the formation of isolated nitride particles and of a metal/Ti2AlN/ TiN/oxide, scale-layer system. Under certain conditions, nitride-layer formation seemed to favor protective Al2O23 formation at the metal/scale interface, however, in general nitridation was detrimental with the consequence that oxidation was generally more rapid in air than in oxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00665663
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  • 4
    Electronic Resource
    Electronic Resource
    Geometrieoptimierung kleiner Moleküle im Allvalenzelektronen-MO-Formalismus mit Hilfe der SIMPLEX- und Gradientenmethode (1977)
    Springer
    Colloid & polymer science 255 (1977), S. 1017-1017 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01776226
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  • 5
    Electronic Resource
    Electronic Resource
    Fractionation, hybridisation and magma-mixing in the Kialineq centre East Greenland (1986)
    Springer
    Contributions to mineralogy and petrology 92 (1986), S. 57-70 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The igneous rocks of the Kialineq centre on the coast of East Greenland at 67°N include a number of quartz syenite and granite plutons intruded 35my BP. These are subvolcanic bodies emplaced by cauldron subsidence and with ring-dike and bell-jar form. Associated with the major intrusions is an extensive acid-basic mixed magma complex. Two-liquid structures, chilling of basic against acid magma, pillows of basic in acid, and net-veining of basic by acid magma, are superbly displayed. The basic magma was of a transitional or alkaline type and underwent varying degrees of fractionation in a regime of repeated intrusions and diverse chambers. Heterogeneous hybrid rocks intermediate between basalt and quartz syenite are strongly developed and were formed by repeated mechanical mixing of contrasting magmas. The energy for this mixing probably came in the main from cauldron-block subsidence. The quartz syenite magma, which itself fractionated towards granite, has initial 87Sr/86Sr ratios the same as the basic magma and is itself believed to be a fractionation product of alkali basalt magma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373963
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  • 6
    Electronic Resource
    Electronic Resource
    Cryptoperthites and cooling rate in a layered syenite pluton: a chemical and TEM study (1983)
    Springer
    Contributions to mineralogy and petrology 82 (1983), S. 13-25 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Alkali feldspars in the Klokken layered syenite (South Greenland) are optically either coarse, turbid, deuteric patch perthites or clear, unaltered, fine braid microor cryptoperthites. Irregular, clear volumes can be found in most turbid grains. Electron microscopy shows that all clear crystals or volumes are cryptoperthites in which the periodicity of the exsolution lamellae increases systematically with distance from the roof of the intrusion, from ∼40 nm to ∼300nm. They are composed of low albite and diagonally associated maximum microcline. A secondary coarsening is responsible for optically visible braid microperthites. The layered series consists of interleaved, granular syenites and coarser grained, laminated syenites with mineral layering. Microprobe analyses show a downward decrease in Ca and Ba in the granular syenite feldspars consistent with chilling from the roof inwards. Most laminated syenite feldspars contain ∼1% An increasing to ∼5% in mafic layers. The periodicity of the exsolution lamellae in the laminated syenite feldspars is consistently up to twice that in adjacent granular syenites. Periodicity is not influenced by Ab:Or or An content, but high-An feldspars have continuous zig-zag intergrowths, while others are more lozengeshaped. Lamellar periodicities largely reflect cooling rate in the pluton. Cooling times in the exsolution interval were probably about 103–104 years at the top of the series, whereas existing experimental data suggest that the periodicities would be reached in a few days or years. The periodicities at the top of the granular series are only slightly greater than experimentally determined initial wavelengths for spinodal decomposition, suggesting that little or no coarsening occurred despite the long cooling times. Coarsening did occur lower in the pile. Framework ordering and twinning must slow or stop coarsening. The difference in periodicity between the granular and laminated syenite series may be caused by differences in amount of water incorporated in the feldspar structure from the magma. The exsolution of this water at low temperatures could be the cause of the deuteric unmixed patch perthites. Small volumes of cryptoperthite which have escaped deuteric unmixing may be common in igneous rocks in general and may be useful relative indicators of cooling rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371171
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  • 7
    Electronic Resource
    Electronic Resource
    The Prince of Wales Formation – post-flood basalt alkali volcanism in the Tertiary of East Greenland (1996)
    Springer
    Contributions to mineralogy and petrology 123 (1996), S. 424-434 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  In the nunataks of the Prince of Wales Mountains the tholeiite flood basalts of the East Greenland Tertiary Province are unconformably overlain by alkaline lavas. The majority of the alkaline lavas are strongly porphyritic picrites, ankaramites and hawaiites. These rocks have lower 143Nd/144Nd and higher 87Sr/86Sr than the tholeiitic flood basalts and are isotopically akin to ocean island basalts. The alkaline lavas also have high concentrations of incompatible elements which on normalised plots have a pattern which is similar in shape to that of enriched oceanic island basalts. The isotopic and chemical characteristics of these late-stage representatives of the East Greenland volcanic activity are attributed to their derivation from the peripheral regions of the East Greenland plume, the axial region of which was moving progressively eastwards relative to the westwards drift of the Greenland plate. It is proposed that the incompatible element contents of the magmas so produced were dominated by small degree melts formed beneath a cap of continental lithosphere in the marginal regions of the plume.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050166
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  • 8
    Electronic Resource
    Electronic Resource
    Mikrochemische Untersuchung der Ascusmembran als ein Beitrag zur Phylogenie des Ascus (1927)
    Springer
    Planta 4 (1927), S. 573-583 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01938193
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  • 9
    Electronic Resource
    Electronic Resource
    Childhood leukemia in Belarus before and after the Chernobyl accident (1996)
    Springer
    Radiation and environmental biophysics 35 (1996), S. 75-80 
    Details
    ISSN: 1432-2099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Childhood leukemia (ICD 204–208 [1]) incidence rates in the different regions of Belarus are reported for a period before and after the Chernobyl accident (1982–1994). There are, at this point, no recognizable trends towards higher rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02434028
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  • 10
    Electronic Resource
    Electronic Resource
    Infant leukemia in Belarus after the Chernobyl accident (1998)
    Springer
    Radiation and environmental biophysics 37 (1998), S. 53-55 
    Details
    ISSN: 1432-2099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Petridou et al. [1] have reported an increase in infant leukemia in Greek children born between 1/7/86 and 31/12/87 and have linked this increase to in utero radiation exposure due to the Chernobyl accident. Subsequently, Michaelis et al. [2] have reported a similar trend for Germany but found that it was not correlated to the levels of contamination. For Belarus, which was much more severely affected, a similar but much weaker trend is found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004110050092
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