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  • 1
    Electronic Resource
    Electronic Resource
    Noncollinear phase of TbDy alloys (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5987-5989 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: TbxDy1−x is probably the simplest example of a magnetic system with competing anisotropy. Tb and Dy are both low-temperature easy-plane ferromagnets with well-characterized anisotropy energies, such that Tb moments prefer the b axis in the hcp structure, while Dy moments prefer the a axis. It has been predicted, by a two-subnetwork approximation, that the low-temperature phase of the alloys with x between 0.86 and 0.76 exhibits a nonsymmetry direction of magnetization, a noncollinear spin structure, and 12th-order anisotropy. However, the two-subnetwork approximation is suspect when used to describe magnetic structure in alloys near phase boundaries, such as those between the ferromagnetic and the noncollinear phase. Using a probability distribution for site occupation, we have calculated the fluctuations of the spin orientation and the spin-spin correlation function as a function of composition in the noncollinear phase. The mean-square fluctuation in spin orientation is proportional to (xb−x)1/2, where xb is the critical concentration which separates the b axis ferromagnet from the noncollinear magnet. The average orientation also varies as (xb−x)1/2. Therefore, the simple two-subnetwork model is not valid near the phase boundaries. In fact, we find that the fluctuations from the average site occupation increase the range of stability of the noncollinear phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346037
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  • 2
    Electronic Resource
    Electronic Resource
    Evidence of a new isotopic anomaly from titanium isotopic ratios in meteoric materials (1979)
    [s.l.] : Nature Publishing Group
    Nature 278 (1979), S. 704-707 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Titanium isotopic ratios in some terrestrial and meteoritic materials have been measured. Most have the same ratios within the experimental precisions. Some inclusion materials from the Allende meteorite have a statistically significant enhancement of the order of 1‰ in the 50/49 ratio, ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/278704a0
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  • 3
    Electronic Resource
    Electronic Resource
    Crystal structures of caesium and rubidium chlorochromates, CsCrO3Cl and RbCrO3Cl (1974)
    Springer
    Journal of chemical crystallography 4 (1974), S. 149-164 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structures of CsCrO3Cl and RbCrO3Cl have been determined from MoKα1diffractometer data and refined anisotropically toR = 0.029 andR = 0.033 respectively for 769 and 590 statistically significant reflections. CsCrO3Cl, which has a structure of the BaSO4 type, crystallizes in the orthorhombic space groupPnma, witha = 9.928,b = 6.043,c = 8.712 Å andZ = 4. RbCrO3Cl is isostructural with KCrO3C1 and NH4CrO3Cl and crystallizes in the monoclinic space groupP21/c witha = 7.857,b = 7.711,c = 8.055 Å, β = 90.43 ° andZ = 4. The geometry of the approximately tetrahedral CrO3Cl− groups is very similar in both structures, and the Cr-Cl and average Cr-O bond distances, corrected for thermal vibration of the terminal atoms, are 2.197 and 1.612 Å in CsCrO3Cl and 2.194 and 1.606 Å in RbCrO3Cl. Caesium ions are in 12-fold coordination and rubidium ions in irregular 11-fold coordination to chlorine and oxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01197910
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  • 4
    Electronic Resource
    Electronic Resource
    Rb-Sr ages of clasts from within Boulder 1, Station 2, Apollo 17 (1975)
    Springer
    Earth, moon and planets 14 (1975), S. 445-462 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Rb, Sr and87Sr/86Sr have been determined for fragments of matrix and clasts from three of the hand-specimens of Boulder 1, 72275, 72255, and 72215. Total-rock and certain plagioclase samples from a crushed norite clast (Civet Cat) define an age of 4.17±0.05AE (2σ) for the pre-Serenitatis igneous differentiation of the norite. Pyroxene and other mineral separates were affected by a later event at about 3.9±0.1AE. An unshocked clast of pigeonite basalt has a well-fitted mineral isochron of 4.01±0.04AE. Samples of the competent breccia matrix comparatively rich in small clasts of highly radiogenic microgranite define a mixing line equivalent to 4.03±0.03AE, which denotes the age of the microgranite. Other samples of the matrix dominated by small anorthosite clasts define a 4.4AE mixing-line and demonstrate that Sr isotope equilibration between plagioclase and matrix did not occur during the high-temperature event that indurated the matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00569675
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  • 5
    Electronic Resource
    Electronic Resource
    Unsupported radiogenic Pb in zircon: a cause of anomalously high Pb-Pb, U-Pb and Th-Pb ages (1984)
    Springer
    Contributions to mineralogy and petrology 88 (1984), S. 322-327 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Ion microprobe U-Th-Pb isotopic analyses of zircons from a granodioritic orthogneiss from the Napier Complex, Mount Sones, Enderby Land, Antarctica, have identified an unambiguous example of unsupported radiogenic Pb in a 3,950 Ma-old crystal. At one 40 μm spot on the crystal an unusually large heterogeneity in Pb content was found, the concentration of radiogenic Pb ranging from 5 to 50 percent higher than could have been generated in 3,950 Ma by radioactive decay of the co-existing U and Th. This relative excess of radiogenic Pb is attributed to Pb gain rather than to U and Th loss because first, the Pb content varied by more than the U or Th contents and secondly, changes in the Pb/U, Pb/Th and Pb isotopic composition correlated directly with changes in the Pb concentration. The individual 207Pb/206Pb apparent ages ranged from 4,000 Ma to 4,145 Ma, all greater than the inferred age of the crystal. A correlation between 207Pb/206Pb and Pb/U shows that the Pb excess has not resulted from recent Pb movement. The spot apparently gained radiogenic Pb about 2,500 Ma ago, at the same time as the majority of the other zircons in the rock suffered substantial Pb loss. The Pb movement occurred in response to a discrete geologic event. Reverse discordance is a phenomenon that must be considered when interpreting zircon U-Pb ages, especially 207Pb/206Pb ages of single crystals or portions of crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00376756
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of the t-butyl substituent on polymer properties in homopolymer systems (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 2753-2764 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of a bulky substituent on properties of different homopolymers has been examined. The substituent is the t-butyl moiety attached to a benzene ring found in the repeat units of the homopolymers of polyesters, polyarylates, polyamides, and polyaramides. These polymers have been prepared by melt, solution, or interfacial techniques. The source of the t-butyl group is mainly from 5-t-butylisophthalic acid (5TBIA) and comparisons are generally made with corresponding homopolymers based on isophthalic acid. The effect of the t-butyl group is shown by comparison of the properties of these homopolymers. Thermal and mechanical (tensile and impact) properties, density, water absorption, solubility, and processability are discussed. Differences in these properties are attributed to the t-butyl group and are based on intermolecular and intramolecular interactions that include increased free volume, chain stiffening, and conformational changes.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080281014
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