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  • 1
    Electronic Resource
    Electronic Resource
    Melting and melt segregation in the aureole of the Glenmore Plug, Ardnamurchan (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of metamorphic geology 23 (2005), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Contact metamorphism caused by the Glenmore plug in Ardnamurchan, a magma conduit active for 1 month, resulted in partial melting, with melt now preserved as glass. The pristine nature of much of the aureole provides a natural laboratory in which to investigate the distribution of melt. A simple thermal model, based on the first appearance of melt on quartz–feldspar grain boundaries, the first appearance of quartz paramorphs after tridymite and a plausible magma intrusion temperature, provides a time-scale for melting. The onset of melting on quartz–feldspar grain boundaries was initially rapid, with an almost constant further increase in melt rim thickness at an average rate of 0.5–1.0 × 10−9 cm s−1. This rate was most probably controlled by the distribution of limited amounts of H2O on the grain boundaries and in the melt rims.The melt in the inner parts of the aureole formed an interconnected grain-boundary scale network, and there is evidence for only limited melt movement and segregation. Layer-parallel segregations and cross-cutting veins occur within 0.6 m of the contact, where the melt volume exceeded 40%. The coincidence of the first appearance of these signs of the segregation of melt in parts of the aureole that attained the temperature at which melting in the Qtz–Ab–Or system could occur, suggests that internally generated overpressure consequent to fluid-absent melting was instrumental in the onset of melt movement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.2005.00560.x
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  • 2
    Electronic Resource
    Electronic Resource
    The pressure–temperature–time path of migmatites from the Sikkim Himalaya (2004)
    Oxford, UK : Blackwell Science Inc
    Journal of metamorphic geology 22 (2004), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A combined metamorphic and isotopic study of lit-par-lit migmatites exposed in the hanging wall of the Main Central Thrust (MCT) from Sikkim has provided a unique insight into the pressure–temperature–time path of the High Himalayan Crystalline Series of the eastern Himalaya. The petrology and geochemistry of one such migmatite indicates that the leucosome comprises a crystallized peraluminous granite coexisting with sillimanite and alkali feldspar. Large garnet crystals (2–3 mm across) are strongly zoned and grew initially within the kyanite stability field. The melanosome is a biotite–garnet pelitic gneiss, with fibrolitic sillimanite resulting from polymorphic inversion of kyanite. By combining garnet zoning profiles with the NaCaMnKFMASHTO pseudosection appropriate to the bulk composition of a migmatite retrieved from c. 1 km above the thrust zone, it has been established that early garnet formed at pressures of 10–12 kbar, and that subsequent decompression caused the rock to enter the melt field at c. 8 kbar and c. 750 °C, generating peritectic sillimanite and alkali feldspar by the incongruent melting of muscovite. Continuing exhumation resulted in resorption of garnet. Sm–Nd growth ages of garnet cores and rim, indicate pre-decompression garnet growth at 23 ± 3 Ma and near-peak temperatures during melting at 16 ± 2 Ma. This provides a decompression rate of 2 ± 1 mm yr−1 that is consistent with exhumation rates inferred from mineral cooling ages from the eastern Himalaya. Simple 1D thermal modelling confirms that exhumation at this rate would result in a near-isothermal decompression path, a result that is supported by the phase relations in both the melanosome and leucosome components of the migmatite. Results from this study suggest that anatexis of Miocene granite protoliths from the Himalaya was a consequence of rapid decompression, probably in response to movement on the MCT and on the South Tibetan detachment to the north.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.2004.00511.x
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  • 3
    Electronic Resource
    Electronic Resource
    C-terminal truncation of the transcriptional activator encoded by areA in Aspergillus nidulans results in both loss-of-function and gain-of-function phenotypes (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 7 (1993), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Mutations truncating as many as 143 C-terminal residues from the transcriptional activator encoded by the areA gene, mediating nitrogen metabolite repression in Aspergillus nidulans, do not significantly reduce the ability of the areA product to activate expression of most genes under areA control. Such mutations can even have a gain-of-function, derepressed phenotype, consistent with a critical role for this region in modulating the activity of the areA protein. However, expression of a few genes under areA control is substantially impaired by such C-terminal truncations, indicating that regions of an activator protein can play differing roles in the control of different structural genes. This underlines the advantages of being able to monitor effects of areA mutations on expression of large numbers of structural genes. Additionally, it is shown that truncation of as many as 153 C-terminal residues, virtually all amino acids C-terminal to the DNA-binding region, is compatible with retention of some areA function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1993.tb01099.x
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  • 4
    Electronic Resource
    Electronic Resource
    C-terminal truncation of the transcriptional activator encoded by area in Aspergillus nidulans results in both loss-of-function and gain-of-function phenotypes (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 7 (1993), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1993.tb01195.x
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  • 5
    Electronic Resource
    Electronic Resource
    Mutational analysis of the C-terminal region of AREA, the transcription factor mediating nitrogen metabolite repression in Aspergillus nidulans (1996)
    Springer
    Molecular genetics and genomics 250 (1996), S. 106-114 
    Details
    ISSN: 1617-4623
    Keywords: Key words areA ; Aspergillus nidulans ; Nitrogen metabolite repression ; GATA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  In Aspergillus nidulans the positive-acting, wide domain regulatory gene areA mediates nitrogen metabolite repression. Previous analysis demonstrated that the C-terminal 153 residues of the areA product (AREA) are inessential for at least partial expression of most genes subject to regulation by areA. Paradoxically, areA r 2, a −1 frameshift replacing the wild-type 122 C-terminal residues with a mutant peptide of 117 amino acids, leads to general loss of function. To determine the basis for the areA r 2 mutant phenotype, and as a means of delineating functional domains within the C-terminal region of AREA, we have selected and characterised areA r 2 revertants. Deletion analysis, utilising direct gene replacement, extended this analysis. A mutant areA product truncated immediately after the last residue of the highly conserved GATA (DNA-binding) domain retains partial function. The areA r 2 product retains some function with respect to the expression of uaZ (encoding urate oxidase) and the mutant allele is partially dominant with respect to nitrate reductase levels. Consistent with the areA r 2 product having a debilitating biological activity, we have demonstrated that a polypeptide containing both the wild-type DNA-binding domain and the mutant C-terminus of AREA2 is able to bind DNA in vitro but no longer shows specificity for GATA sequences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02191830
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