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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 64 (1992), S. 2735-2742 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    facet.materialart.
    Unknown
    Baltimore : Periodicals Archive Online (PAO)
    Human Biology. 64:2 (1992:Apr.) 263 
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  • 3
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Mehrere Formationen im unteren Teil der Appin Gruppe der Dalradians sind durch karbonatische und kalk-silikatische Lithologien gekennzeichnet. Amphibole treten in diesen metasedimentären Einheiten in verschiedener Ausbildung auf, als feinkörnige, disseminierte Kristalle, als radialstrahlige, die Gesteine durchwachsende Aggregate und in dunkelgrünen, zu mehr als 90% aus Amphibolen bestehenden Lagen. Elektronenstrahl-Mikrosondenuntersuchungen belegen einfache mineralchemische Zusammensetzungen, die Tremolite, tremolitische Hornblende und Magnesio-Hornblende umfaßt. Die einzige bedeutende Substitution ist die zwischen Tremolit und Alumino-Tschermakit [MgSi ⇌ AlviAliv] und zwischen Tremolit und Ferri-Tschermakit [MgSi ⇌ FeviAliv]. Im Gegensatz dazu zeigen Amphibole aus den nahegelegenen Metavulkaniten und intrusiven Metadoleriten vier Substitutionstrends von Tremolit zu Ferro-Akttinolith, Edenit, Alumino-Tschermakit und Ferri-Tschermakit. Diese unterschiedlichen Trends könnten auch anderswo bei der Unterscheidung zwischen Para- und Orthoamphiboliten behilflich sein. Tremolitische Amphibole machen normalerweise einen Großteil der kalk-silikatischen Gesteine aus, in denen ansonsten nur Quarz ± Phologpit auftritt. Karbonate fehlen bemerkenswerterweise. Dies weist auf Mg-reiche sedimentäre Protolithe, wie dolomitische Mergel mit möglicherweise etwas Magnesit, hin. Sedimentologische Überlegungen lassen die Ablagerung in abgeschnürten Küstenlagunen tropischer Breiten, die Teil eines weiträumigen stabilen Schelfes waren, vermuten.
    Notes: Summary Several formations within the lower part of the Dalradian Appin Group are characterised by calcareous and calc-silicate lithologies. Amphibole occurs in these metasedimentary units in a variety of habits, from fine-grained disseminated crystals, through radiating aggregates permeating the whole rock, to dark green layers consisting of over 90% amphibole. Electron microprobe analyses of these amphiboles exhibit simple compositional trends from tremolite, through tremolitic hornblende to magnesio-hornblende. The only significant substitutions are from tremolite towards alumino-tschermakite [MgSi ⇌ AlviAliv] and from tremolite towards ferri-tschermakite [MgSi ⇌ FeviAliv]. This is in marked contrast to amphiboles from nearby suites of metavolcanic rocks and intrusive metadolerites which exhibit four coupled substitutions, leading from tremolite towards the ferro-actinolite, edenite, alumino-tschermakite and ferritschermakite end-members. These distinctive compositional trends may aid the distinction between para- and ortho-amphibolites elsewhere. Tremolitic amphibole commonly constitutes a high proportion of the calc-silicate rocks, the only other phases present being quartz ± phlogopite. Carbonate minerals are notably absent. This suggests that the sedimentary protolith was high in Mg, such as a dolomitic marl, possibly containing some magnesite. Sedimentological considerations suggest deposition in tropical latitudes in restricted coastal lagoons forming part of an extensive stable shelf bordering a mature landscape.
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  • 4
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Mehrere Formationen im unteren Teil der Appin Gruppe der Dalradians sind durch karbonatische und kalk-silikatische Lithologien gekennzeichnet. Amphibole treten in diesen metasedimentären Einheiten in verschiedener Ausbildung auf, als feinkörnige, disseminierte Kristalle, als radialstrahlige, die Gesteine durchwachsende Aggregate und in dunkelgrünen, zu mehr als 90% aus Amphibolen bestehenden Lagen. Elektronenstrahl-Mikrosondenuntersuchungen belegen einfache mineralchemische Zusammensetzungen, die Tremolite, tremolitische Hornblende und Magnesio-Hornblende umfassen. Die einzige bedeutende Substitution ist die zwischen Tremolit und Alumino-Tschermakit [MgSi ⇌ AlviAliv] und zwischen Tremolit und Ferri-Tschermakit [MgSi = FeviAliv]. Im Gegensatz dazu zeigen Amphibole aus den nahegelegenen Metavulkaniten und intrusiven Metadoleriten vier Substitutionstrends von Tremolit zu Ferro-Aktinolith, Edenit, Alumino-Tschermakit und Ferri-Tschermakit. Diese unterschiedlichen Trends könnten auch anderswo bei der Unterscheidung zwischen Para- und Orthoamphiboliten behilflich sein. Tremolitische Amphibole machen normalerweise einen Großteil der kalk-silikatischen Gesteine aus, in denen ansonsten nur Quarz ± Phlogopit auftritt. Karbonate fehlen bemerkenswerterweise. Dies weist auf Mg-reiche sedimentäre Protolithe, wie dolomitische Mergel mit möglicherweise etwas Magnesit, hin. Sedimentologische Überlegungen lassen die Ablagerung in abgeschnürten Küstenlagunen tropischer Breiten, die Teil eines weiträumigen stabilen Schelfes waren, vermuten.
    Notes: Summary Several formations within the lower part of the Dalradian Appin Group are characterised by calcareous and calc-silicate lithologies. Amphibole occurs in these metasedimentary units in a variety of habits, from fine-grained disseminated crystals, through radiating aggregates permeating the whole rock, to dark green layers consisting of over 90% amphibole. Electron microprobe analyses of these amphiboles exhibit simple compositional trends from tremolite, through tremolitic hornblende to magnesio-hornblende. The only significant substitutions are from tremolite towards alumino-tschermakite [MgSi ⇌ AlviAliv] and from tremolite towards ferri-tschermakite [MgSi ⇌ FeviAliv]. This is in marked contrast to amphiboles from nearby suites of metavolcanic rocks and intrusive metadolerites which exhibit four coupled substitutions, leading from tremolite towards the ferro-actinolite, edenite, alumino-tschermakite and ferritschermakite end-members. These distinctive compositional trends may aid the distinction between para- and ortho-amphibolites elsewhere. Tremolitic amphibole commonly constitutes a high proportion of the calc-silicate rocks, the only other phases present being quartz ± phlogopite. Carbonate minerals are notably absent. This suggests that the sedimentary protolith was high in Mg, such as a dolomitic marl, possibly containing some magnesite. Sedimentological considerations suggest deposition in tropical latitudes in restricted coastal lagoons forming part of an extensive stable shelf bordering a mature landscape.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 29 (1994), S. 5787-5793 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The failure of titanium metal-matrix composites (MMCs) strengthened with monofilament carbon-coated sigma SiC fibres has been studied following exposure at a temperature of 900
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of muscle research and cell motility 15 (1994), S. 369-389 
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary At low levels of activation, an isometrically-held myofibrillar preparation on the descending limb may exhibit persistent oscillations of period 1–6 s in tension and sarcomere lengths. We propose a sarcomeric theory of spontaneous oscillatory contraction, based on the phenomena of force creep and delayed length activation. The time delay leads to oscillations and controls their period. A computer model using these ideas simulates spontaneous oscillatory contraction for fixed-end fibres only if isometric tension capacity varies slightly along the fibre. The form of this inhomogeneity controls a diversity of spontaneous oscillatory contraction behaviour: the tension waveform can vary from large and sinusoidal to small-amplitude pulses or chaotic behaviour, and these variations are observed in slow-twitch soleus fibres from the same animal (rat). The model predicts that oscillatory and quiescent regions coexist in the fibre, with large-amplitude sawtooth waveforms in sarcomere length in the former as observed. It can also generate travelling-wave structures, similar to those found by the Tokyo group, in oscillating regions when there is a spatial gradient in isometric tension capacity. Phase discontinuities in sarcomere length occur near the oscillatory-quiescent boundary. Predictions for the Ca2+ concentrations and sarcomere lengths in which spontaneous oscillatory contraction occurs and for differences in the spontaneous oscillatory contraction frequencies of fast-and slow-twitch fibres compare well with experiment. Spontaneous oscillatory contraction is also predicted under isotonic conditions.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of muscle research and cell motility 11 (1990), S. 12-24 
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Mechanically skinned skeletal muscle fibres from the soleus and tibialis anterior muscles of the small marsupialSminthopsis macroura were activated by Ca2+ and Sr2+ so that their isometric force properties could be determined. The properties characterized were the shape, slope and positions of the curves generated by plotting isometric force vs. pCa (−log10[Ca2+]) and pSr (−log10[Sr2+]), the maximum Ca2+-activated and Sr2+-activated tension (Ncm−2) and the frequency of force oscillations of myofibrillar origin during submaximal activations. The effect of caffeine on force activation was also studied. Apart from the fibres which exhibited physiological characteristics similar to those observed previously in mammalian fibres, a large proportion of fibres exhibited characteristics or combinations of characteristics which have not previously been described from healthy adult mammals. The results from 32 soleus fibres showed that only 23 could be categorized as either typical fast-twitch or slow-twitch fibres. The rest possessed unusual physiological characteristics which suggested the co-existence in the same fibre of Ca2+-regulatory and contractile properties from different categories of fast-twitch and slow-twitch fibres. We could distinguish two major fast twitch populations of tibialis anterior fibres which occurred in similar proportions. There were significant differences in the maximum tension produced by some of these groups of fibres. The tibialis anterior population fibres produced the highest maximum tension (T o Ca 44.6±4.6 Ncm−2, n=7) while the soleus combined type fibres produced the lowest maximum tension (T o Ca 18.1±2.1 Ncm−2, n=8). Our physiological observations of the Ca2+-activation and Sr2+-activation properties of soleus fibres in this study provide new evidence that there can be combinations of characteristics in single fibres and a continuum of properties between fibre types in normal mammalian skeletal muscles. These animals can therefore be used as a source of fibres with a wide range of properties.
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  • 8
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Single fibres of different sarcomere length at rest have been isolated from the claw muscle of the yabby (Cherax destructor), a decapod crustacean. Fibres of either long (SL 〉 6 μm) or short (SL 〈 4 μm) sarcomere length have been mechanically skinned and were maximally activated by Ca2+ and Sr2+ under various experimental conditions (ionic strength, in the presence of 2,3 butanedione monoxime (BDM)) to determine differences in their contractile properties. Isometric force was measured simultaneously with either myofibrillar MgATPase or fibre stiffness in both fibre types. The ultrastructure of individual long- and short-sarcomere fibres was also determined by electron microscopy. The long-sarcomere fibres developed greater tension (30.48±1.72 N cm−2) when maximally activated by Ca2+ compared with the short-sarcomere fibres (18.60±0.80 N cm−2). The difference in the maximum Ca2+-activated force can be explained by the difference in the amount of filament overlap between the two fibre types. The maximum Ca2+-activated myofibrillar MgATPase rate in the short-sarcomere fibres (1.60±0.27 mmol ATP l−1 s−1) was higher, but not significantly different from the ATPase rate in fibres with long-sarcomeres (1.09±0.14 mmol ATP l−1 s−1). As the concentration of myosin is estimated to be higher only by a factor of 1.22 in the short-sarcomere preparations there is no evidence to suggest that the myofibrillar MgATPase activity is different in the long- and short-sarcomere preparations. The maximum Ca2+-activated force (P 0) of both short- and long-sarcomere fibres was quite insensitive to BDM compared with vertebrate muscle. Force decreased to 60.2±5.3% and 76.1±2.7% in the short- and long-sarcomere fibres respectively in the presence of 100 mmol l−1 BDM. The difference in the force depression between the. long- and short-sarcomere fibres is statistically significant (p〈0.05). Fibre stiffness during maximum Ca2+-activation expressed as percentage maximum force per nm per half sarcomere was higher by a factor of 3.5 in short-sarcomere fibres than in long-sarcomere fibres suggesting that the compliance of the filaments in the long-sarcomere fibres is considerably higher than in the short-sarcomere fibres. Sr2+ could not activate the contractile apparatus to the same level as that seen by Ca2+ in either fibre type: the maximum Sr2+-activated force was (20±3%) and (63±3%) of the maximum Ca2+-activated force response in short- and long-sarcomere fibres, respectively. The ratio between fibre stiffness in the maximum Sr2+-activating solution and the Ca2+-activating solution was very similar to the ratio between the maximum Sr2+-activated force and Ca2+-activated force in either type of fibres, suggesting that the number of attached crossbridges is lower in the fibres when maximally activated by Sr2+ than when maximally activated by Ca2+. The short-sarcomere fibres were also more sensitive to changes in ionic strength than long-sarcomere fibres. In conclusion these results indicate that while several important specific characteristics of the short- and long-sarcomere length fibres (ATPase, maximum Ca2+-activated force and fibre stiffness) can be explained solely on differences in the ultrastructure (length and density per cross-sectional area of myosin filaments) there are also differences in the properties of the proteins involved in the force production and regulation evidenced by the differential effect of Sr2+, BDM and ionic strength on contractile activation in the two fibre types.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 10 (1991), S. 699-700 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 10
    ISSN: 1432-1777
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The rump-white (Rw) mutation in the mouse was previously mapped as part of a cluster of spotting genes on Chromosome (Chr) 5 that includes the dominant spotting (W) and patch (Ph) loci. Recent studies have shown that the W locus encodes the KIT tyrosine kinase cell surface receptor and that Ph is a deletional mutation encompassing the platelet-derived growth factor receptor alpha subunit (Pdgfra) gene. However, the molecular basis of the Rw mutation remains to be established. We have analyzed an interspecific Mus spretus backcross segregating Rw and several loci proximal and distal to the W/Ph/Rw region to study the basis of this mutation. These studies indicated that loci within the En2 to Kit region of the chromosome do not recombine with one another even though they have been separated in other mapping studies presented here and elsewhere. We conducted a series of fluorescent in situ hybridization (FISH) studies with genomic probes to En2, Msx1, D5Buc1, and Kit to compare the physical order of these loci on the Rw and wild-type chromosomes. The Kit locus mapped to approximately the same region on both chromosomes of the Rw heterozygotes, while the positions of En2, Msx1, and D5Buc1 were reversed on the two chromosomes. Taken together, both the genetic and physical mapping data establish that the Rw mutation is associated with an inversion involving loci in the proximal region of Chromosome 5.
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