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  • 1
    Electronic Resource
    Electronic Resource
    Single-crystal hydrostatic compression of synthetic pyrope, almandine, spessartine, grossular and andradite garnets at high pressures (1999)
    Springer
    Physics and chemistry of minerals 27 (1999), S. 52-58 
    Details
    ISSN: 1432-2021
    Keywords: Key words High pressure ; Single-crystal diffraction ; Garnet ; Bulk modulus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The compression of synthetic pyrope Mg3Al2 (SiO4)3, almandine Fe3Al2(SiO4)3, spessartine Mn3Al2 (SiO4)3 grossular Ca3Al2(SiO4)3 and andradite Ca3Fe2 (SiO4)3 was studied by loading the crystals together in a diamond anvil cell. The unit-cell parameters were determined as a function of pressure by X-ray diffraction up to 15 GPa using neon as a pressure transmitting medium. The unit-cell parameters of pyrope and almandine were measured up to 33 and 21 GPa, respectively, using helium as a pressure medium. The bulk moduli, K T 0, and their first pressure derivatives, K T 0 ′, were simultaneously determined for all five garnets by fitting the volume data to a third order Birch-Murnaghan equation of state. Both parameters can be further constrained through a comparison of volume compressions between pairs of garnets, giving for K T 0 and K T 0 ′ 171(2) GPa and 4.4(2) for pyrope, 185(3) GPa and 4.2(3) for almandine, 189(1) GPa and 4.2 for spessartine, 175(1) GPa and 4.4 for grossular and 157(1) GPa and 5.1 for andradite, where the K T 0 ′ are fixed in the case of spessartine, grossular and andradite. Direct comparisons of the unit-cell volumes determined at high pressures between pairs of garnets reveal anomalous compression behavior for Mg2+ in the 8-fold coordinated triangular dodecahedron in pyrope. This agrees with previous studies concerning the compression behaviors of Mg2+ in 6-fold coordinated polyhedra at high pressures. The results show that simple bulk modulus–volume systematics are not obeyed by garnets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050240
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  • 2
    Electronic Resource
    Electronic Resource
    A murine CDC25/ras-GRF-related protein implicated in ras regulation (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 14 (1993), S. 339-346 
    Details
    ISSN: 0192-253X
    Keywords: ras ; CDC25 ; guanine nucleotide release factor ; signal transduction ; embryonic stem cell ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: A partial cDNA encoding a novel putative p2, ras guanine nucleotide release-inducing factor (GRF), GRF2, was amplified from murine embryonic stem cells. The presumptive catalytic region of GRF2 is related to the yeast Ras GRF encoded by CDC25. GRF2 is 80% identical to murine CDC25Mm/ras-GRF, but is more similar to yeast CDC25 than to other ras GRFs related to the Drosophila son of sevenless gene product. A 9-kb GRF2 messenger RNA was highly expressed in brain, but GRF2-specific antibodies recognized apparent GRF2 proteins in various mouse tissues in addition to brain. Thus GRF2 represents a novel widely-expressed protein that is highly related to CDC25Mm/ras-GRF, at least in its catalytic domain. Both GRF2 and CDC25Mm/ras-GRF are expressed in murine embryonic stem cells, suggesting that different Ras activators may regulate ras-dependent proliferation and differentiation in early mouse development. © 1993Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020140503
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  • 3
    Electronic Resource
    Electronic Resource
    Cumulus cell function during bovine oocyte maturation, fertilization, and embryo development in vitro (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 40 (1995), S. 338-344 
    Details
    ISSN: 1040-452X
    Keywords: Zygotes ; Cumulus-oocyte complexes ; Zona pellucida ; Gap junctions ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Several contemporary micromanipulation techniques, such as sperm microinjection, nuclear transfer, and gene transfer by pronuclear injection, require removal of cumulus cells from oocytes or zygotes at various stages. In humans, the cumulus cells are often removed after 15-18 hr of sperm-oocyte coincubation to assist the identification of the fertilization status. This study was designed to evaluate the function of cumulus cells during oocyte maturation, fertilization, and in vitro development in cattle. Cumulus cells were removed before and after maturation and after fertilization for 0,7,20, and 48 hr. The cumulus-free oocytes or embryos were cultured either alone or on cumulus cell monolayers prepared on the day of maturation culture. Percentages of oocyte maturation, fertilization, and development to cleavage, morula, and blastocyst stages and to expanding or hatched blastocysts were recorded for statistical analysis by categorical data modeling (CATMOD) procedures.Cumulus cells removed before maturation significantly reduced the rate of oocyte maturation (4-26% vs. 93-96%), fertilization (0-9% vs. 91-92%), and in vitro development at all stages evaluated. Cumulus cells removed immediately prior to in vitro fertilization (IVF) or 7 hr after IVF reduced the rates of fertilization (58-60% and 71%, respectively, vs. 91-92% for controls), cleavage development (40-47% and 53-54% vs. 74-78% for controls), and morula plus blastocyst development (15% and 24% vs. 45%, P 〈 0.05). Cumulus cell co-culture started at various stages had no effect on fertilization and cleavage development but significantly improved rates of embryo development to morula or blastocyst stages (P 〈 0.05). Cumulus cell removal at 20 hr after IVF resulted in similar development to controls (P 〉 0.05) at all stages tested in this study. The intact state of surrounding cumulus cells of oocytes or embryos appears to be beneficial before or shortly after insemination (at or before 7 hr of IVF) but not essential at 20 hr after IVF. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080400310
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