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  • 1
    Electronic Resource
    Electronic Resource
    Strong electron correlations in cobalt valence tautomers (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 3681-3689 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have examined cobalt based valence tautomer molecules such as Co(SQ)2(phen) using density functional theory (DFT) and variational configuration interaction (VCI) approaches based upon a model Hamiltonian. Our DFT results extend earlier work by finding a reduced total energy gap (order 0.6 eV) between high-temperature and low-temperature states when we fully relax the coordinates (relative to experimental ones). Furthermore, we demonstrate that a charge transfer picture based upon formal valence arguments succeeds qualitatively while failing quantitatively due to strong covalency between the Co 3d orbitals and ligand p orbitals. With the VCI approach, we argue that the high-temperature, high spin phase is strongly mixed valent, with about 30% admixture of Co (III) into the predominantly Co(II) ground state. We confirm this mixed valence through a fit to the XANES spectra. Moreover, the strong electron correlations of the mixed valent phase provide an energy lowering of about 0.2–0.3 eV of the high-temperature phase relative to the low-temperature one. Finally, we use the domain model to account for the extraordinarily large entropy and enthalpy values associated with the transition. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1446023
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  • 2
    Electronic Resource
    Electronic Resource
    Hall effect for Kondo systems (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3896-3898 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have calculated the variations with temperature of the skew scattering contribution to the Hall effect for a Kondo-type ion. The conduction electron t matrix is calculated by using the single-ion Anderson model, and the 4f electrons' Green's function is evaluated by self- consistently solving a set of integral equations. Except for the asymptotic region T/Tk(very-much-greater-than)1, the Hall constant is not proportional to the susceptibility, nor does the constant change sign for realistic values of the parameters entering the theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340596
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  • 3
    Electronic Resource
    Electronic Resource
    Dynamic magnetic susceptibilities of valence-fluctuation Ce compounds (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3166-3168 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have computed dynamic susceptibilities of valence-fluctuating Ce compunds for temperatures between 0.01 and 40 T0, where T0 is the position of the many-body "Kondo resonance'' in the 4f density of states. Our calculations reproduce several results seen in neutron scattering and nuclear-magnetic-resonance experiments: (i) nonmonotonic behavior of the magnetic relaxation rate, (ii) non-Lorentzian behavior of the dynamic susceptibility for low temperatures, and (iii) high-temperature T1/2 behavior of the magnetic relaxation rate. Most of the magnetic relaxation data for valence-fluctuating Ce compunds are consistent with the Kondo resonance picture which has been applied successfully previously to thermodynamic and high-energy spectroscopy data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335137
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  • 4
    Electronic Resource
    Electronic Resource
    Transport properties of the Anderson lattice (1988)
    Springer
    The European physical journal 71 (1988), S. 321-340 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Transport properties including electrical resistivity, thermoelectric power, Lorenz number and a.c. conductivity are evaluated in an approximate fashion for the Anderson lattice model for six-fold degenerate Ce ions. Coherence (Bloch's theorem) is explicitly included while the effects of intersite interactions which may be responsible for magnetic and superconducting instabilities are neglected. The calculations utilize the AverageT-matrix Approximation (ATA) with the self-consistent Non-Crossing Approximation (NCA) perturbation theory employed to give the single siteT-matrix estimate. The resistivity peaks near the characteristic Kondo temperatureT 0, with high temperature logarithmic decrease and low temperatureT 2 behavior. The thermoelectric power is positive and similar to the impurity result except for low temperatures; sign changes in the thermopower are in principle possible with momentum dependent hybridization. Frequency and temperature dependent optical conductivity calculations are in qualitative agreement with experimental data, although a suitably defined optical effective mass and scattering rate do not agree at least for large orbital degeneracy. The behavior of these latter quantities is qualitatively different for twofold degeneracy. Unanswered questions arising from the experimental literature are summarized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01312492
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  • 5
    Electronic Resource
    Electronic Resource
    Antibody against ahosphorylated proteins (MPM-2) recognizes mitotic microtubules in endosperm cells of higher plant haemanthus (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 31 (1995), S. 34-44 
    Details
    ISSN: 0886-1544
    Keywords: microtubule ; MTOC ; mitosis ; MPM-2 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In diverse cell types, monoclonal antibody MPM-2 recognizes a class of phosphorylated proteins related to microtubule organizing centers and abundant during mitosis. We have used this antibody in an attempt to identify the spatial and temporal localization of putative microtubule organizing centers in endosperm cells of the higher plant Haemanthus. Our results show that MPM-2 recognized epitope is present in interphase cells and enriched in mitotic cells. In interphase the antibody usually stains cytoplasmic granules. During the interphase-prophase transition immunoreactive material appears in the nucleus, at the nuclear envelope, and in association with microtubules. Concomitantly, we observed an increase of immunoreactivity of the cytoplasm. During mitosis the phosphorproteins recognized by MPM-2 are detected in the cytoplasm, in association with microtubules of the spindle, the phragmoplast, and in the newly-formed cell plate. After completion of mitosis, only the cell plate and cytoplasmic granules are MPM-2 positive. Extraction of the cells with Triton X-100 prior to fixation removes staining of the cytoplasm by MPM-2. The detergent resistant immunoreactive material remains associated with surrounding the nucleus microtubules of the prophase spindle, the core of kinetochore fibers, and the phragmoplast. In the phragmoplast, however, segments of microtubules which are distal to the cell plate are depleted of MPM-2.These data demonstrate that microtubule arrays of endosperm cells are phosphorylated during mitosis. Thus, similar to animal cells, interphase and mitotic microtubules of higher plants have different properties. Additionally, the localization of detergent resistant MPM-2 antigen points to the difference in microtubule nucleation/organization between higher plant and animal cells.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970310105
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