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  • 1
    Electronic Resource
    Electronic Resource
    Interdiffusion in diluted magnetic PbTe/Pb1−xMnxTe quantum well structures (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 97-106 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An x-ray diffraction study of the growth of Pb1−xMnxTe/PbTe (x=0.022–0.037) multi-quantum well (MQW) structures of period lengths 205–950 A(ring) is presented. In order to obtain a reliable Mn diffusion coefficient at the growth temperature T=270 °C, computed diffusion profiles are used as input for the calculation of diffractograms using kinematical diffraction theory. The satellites of the symmetric (222) Bragg reflections are compared to measurements. The analysis is based on a numerical solution of the diffusion equation which considers explicitly the effect that the boundary at the surface of the growing epitaxial layer moves during growth. Thus for the as-grown MQWs Mn interdiffusion is considered to occur already during the growth process. In addition, the Mn diffusion profiles of one sample which is isothermally annealed 4, 16, and 64 min at T=270 °C, are simulated using fixed boundary conditions. From comparison to both boundary conditions, the Mn diffusion coefficient of 8×10−17 cm2/s at T=270 °C is determined within an accuracy of a factor two. The results are well adapted to our special growth conditions, but the numerical model is applicable in generality. It uses only two essential input parameters: the diffusion coefficient and the growth rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352102
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of the BaF"2 substrate preparation on the structural perfection of epitaxially grown IV-VI compounds
    Amsterdam : Elsevier
    Journal of Crystal Growth 102 (1990), S. 933-938 
    Details
    ISSN: 0022-0248
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0022-0248(90)90863-G
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  • 3
    Electronic Resource
    Electronic Resource
    Interdiffusion in Pb"1"-"xEu"xSe/PbSe multi-quantum-well structures
    Amsterdam : Elsevier
    Journal of Crystal Growth 113 (1991), S. 593-598 
    Details
    ISSN: 0022-0248
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0022-0248(91)90095-M
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  • 4
    Electronic Resource
    Electronic Resource
    High vacuum molecular beam epitaxy for the growth of IV-VI compounds
    Amsterdam : Elsevier
    Journal of Crystal Growth 126 (1993), S. 293-304 
    Details
    ISSN: 0022-0248
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0022-0248(93)90036-V
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  • 5
    Electronic Resource
    Electronic Resource
    Microinjection of profilins from different sources into the green algaMicrasterias causes transient inhibition of cell growth (1997)
    Springer
    Protoplasma 199 (1997), S. 124-134 
    Details
    ISSN: 1615-6102
    Keywords: Actin ; Actin-binding proteins ; Gelsolin ; Micrasterias ; Microinjection ; Profilin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Recombinant profilins from different sources (Betula verrucosa, Schizosaccharomyces pombe, Acanthamoeba castellani, or man) cause marked effects on cell growth and morphogenesis when microinjected into growing cells of the green algaMicrasterias denticulata. Whereas control injections with β-lactoglobulin only result in a slight delay of cell growth, when profilin is injected cell differentiation ceases and only resumes about 1 to 2 h after the injection, depending on the dose. The resulting cell does not show any malformations, but is reduced in size and retarded in differentiation compared to controls. As a consequence of the profilin microinjection the pattern of cytoplasmic streaming and cytoplasmic structure are also altered. Gelsolin, injected for comparison, leads to minor retardation of cell development but produces less marked effects than profilin. Microinjection of fluorescently labeled profilin shows even distribution throughout the cytoplasm and more intense fluorescence in the nucleus. Electron microscopical investigations of cells fixed immediately after profilin injection show a normal distribution of dictyosomes, ER cisternae, microtubules, and secretory vesicles compared to noninjected controls at the same developmental stage. Our results indicate that disturbance of the natural actin turnover by the injection of actin-binding proteins strongly affects development ofMicrasterias, corroborating a key role of actin in the morphogenetic process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294501
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  • 6
    Electronic Resource
    Electronic Resource
    Profilin is localized in the nucleus-associated microtubule and actin system and is evenly distributed in the cytoplasm of the green algaMicrasterias denticulata (2000)
    Springer
    Protoplasma 212 (2000), S. 197-205 
    Details
    ISSN: 1615-6102
    Keywords: Actin-binding protein ; Green algae ; Immunolocalization ; Micrasterias denticulata ; Profilin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Profilin is detected by means of immunoblotting in the green algaMicrasterias denticulata at a molecular mass of about 14 kDa with antibodies against celery root profilin, recombinant tobacco profilin, and recombinant birch profilin. Poly-L-proline purification ofM. denticulata extracts leads to a single band at 14 kDa. By means of immunoelectron microscopy first evidence is provided for the presence of profilin in a microtubule center associated with the migrating nucleus in high-pressure-frozen and freeze-substituted cells. Colocalization with a particular filamen-tous-actin aggregation in the same area suggests a role of profilin in the process of nuclear migration. Moreover staining is visible in several areas of the nucleus including the nucleolus, heterochromatin, and nuclear-pore complexes. An even distribution of profilin is found throughout the cytoplasm at the confocal-microscopy level as well as by immunogold labeling. Occasionally also areas at the surface of the chloroplast are stained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01282920
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  • 7
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    Ecophysiology, secondary pigments and ultrastructure of Chlainomonas sp. (Chlorophyta) from the European Alps compared with Chlamydomonas nivalis forming red snow (2016)
    Oxford University Press
    Details
    Publication Date: 2016-04-02
    Description: Red snow is a well-known phenomenon caused by microalgae thriving in alpine and polar regions during the melting season. The ecology and biodiversity of these organisms, which are adapted to low temperatures, high irradiance and freeze–thaw events, are still poorly understood. We compared two different snow habitats containing two different green algal genera in the European Alps, namely algae blooming in seasonal rock-based snowfields ( Chlamydomonas nivalis ) and algae dominating waterlogged snow bedded over ice ( Chlainomonas sp.). Despite the morphological similarity of the red spores found at the snow surface, we found differences in intracellular organization investigated by light and transmission electron microscopy and in secondary pigments investigated by chromatographic analysis in combination with mass spectrometry. Spores of Chlainomonas sp. show clear differences from Chlamydomonas nivalis in cell wall arrangement and plastid organization. Active photosynthesis at ambient temperatures indicates a high physiological activity, despite no cell division being present. Lipid bodies containing the carotenoid astaxanthin, which produces the red color, dominate cells of both species, but are modified differently. While in Chlainomonas sp. astaxanthin is mainly esterified with two fatty acids and is more apolar, in Chamydomonas nivalis , in contrast, less apolar monoesters prevail.
    Print ISSN: 0168-6496
    Electronic ISSN: 1574-6941
    Topics: Biology
    Published by Oxford University Press
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  • 8
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    The green alga Zygogonium ericetorum (Zygnematophyceae, Charophyta) shows high iron and aluminium tolerance: protection mechanisms and photosynthetic performance (2016)
    Oxford University Press
    Details
    Publication Date: 2016-06-17
    Description: Streptophyte green algae, ancestors of Embryophytes, occur frequently in terrestrial habitats being exposed to high light intensities, water scarcity and potentially toxic metal cations under acidic conditions. The filamentous Zygogonium ericetorum synthesizes a purple vacuolar ferrous pigment, which is lost after aplanospore formation. However, it is unknown whether this cellular reorganization also removes excessive iron from the protoplast and how Z. ericetorum copes with high concentrations of aluminium. Here we show that aplanospore formation shifts iron into the extracellular space of the algal filament. Upon germination of aplanospores, aluminium is bound in the parental cell wall. Both processes reduce iron and aluminium in unpigmented filaments. Comparison of the photosynthetic oxygen production in response to light and temperature gradients in two different Z. ericetorum strains from an Austrian alpine and a Scottish highland habitat revealed lower values in the latter strain. In contrast, the Scottish strain showed a higher optimum quantum yield of PSII during desiccation stress followed by rehydration. Furthermore, pigmented filaments of both strains exhibited a higher light and temperature dependent oxygen production when compared to the unpigmented phenotype. Our results demonstrate a high metal tolerance of Z. ericetorum , which is crucial for surviving in acidic terrestrial habitats.
    Print ISSN: 0168-6496
    Electronic ISSN: 1574-6941
    Topics: Biology
    Published by Oxford University Press
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  • 9
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    Single Glucose Biofuel Cells Implanted in Rats Power Electronic Devices (2013)
    Springer Nature
    Details
    Publication Date: 2013-03-23
    Description: We describe the first implanted glucose biofuel cell (GBFC) that is capable of generating sufficient power from a mammal's body fluids to act as the sole power source for electronic devices. This GBFC is based on carbon nanotube/enzyme electrodes, which utilize glucose oxidase for glucose oxidation and laccase for dioxygen reduction. The GBFC, implanted in the abdominal cavity of a rat, produces an average open-circuit voltage of 0.57 V. This implanted GBFC delivered a power output of 38.7 μW, which corresponded to a power density of 193.5 μW cm−2 and a volumetric power of 161 μW mL−1. We demonstrate that one single implanted enzymatic GBFC can power a light-emitting diode (LED), or a digital thermometer. In addition, no signs of rejection or inflammation were observed after 110 days implantation in the rat. Scientific Reports 3 doi: 10.1038/srep01516
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
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  • 10
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    Formation of lipid bodies and changes in fatty acid composition upon pre-akinete formation in Arctic and Antarctic Zygnema (Zygnematophyceae, Streptophyta) strains (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-28
    Description: Filamentous green algae of the genus Zygnema (Zygnematophyceae, Streptophyta) are key components of polar hydro-terrestrial mats where they face various stressors including UV irradiation, freezing, desiccation and osmotic stress. Their vegetative cells can develop into pre-akinetes, i.e. reserve-rich, mature cells. We investigated lipid accumulation and fatty acid (FA) composition upon pre-akinete formation in an Arctic and an Antarctic Zygnema strain using transmission electron microscopy and gas chromatography coupled with mass spectrometry. Pre-akinetes formed after 9 weeks of cultivation in nitrogen-free medium, which was accompanied by massive accumulation of lipid bodies. The composition of FAs was similar in both strains, and α-linolenic acid (C18:3) dominated in young vegetative cells. Pre-akinete formation coincided with a significant change in FA composition. Oleic (C18:1) and linoleic (C18:2) acid increased the most (up to 17- and 8-fold, respectively). Small amounts of long-chain polyunsaturated FAs were also detected, e.g. arachidonic (C20:4) and eicosapentaenoic (C20:5) acid. Pre-akinetes exposed to desiccation at 86% relative humidity were able to recover maximum quantum yield of photosystem II, but desiccation had no major effect on FA composition. The results are discussed with regard to the capability of Zygnema spp. to thrive in extreme conditions.
    Print ISSN: 0168-6496
    Electronic ISSN: 1574-6941
    Topics: Biology
    Published by Oxford University Press
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