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Recent progress of the theoretical interpretation for the X-ray magnetic circular dichroism (XMCD) at the rare-earth (RE) L2,3 absorption edges is reviewed. We discuss the XMCD spectra of RFe2 (R = RE) in the Laves phase based on the tight-binding approximation for RE 5d and Fe 3d conducting states. A variety of the XMCD spectra can be attributed to (i) the electric dipole and (ii) the electric quadrupole transitions. For (i), the polarization of the RE 5d electrons, being indispensable for XMCD, is dominated by the RE intra-atomic exchange interaction, which also yields the enhancement of the 2p–5d dipole matrix element. In addition, the hybridization with the spin-polarized Fe 3d states plays a distinctive role. For (ii), the multiplet couplings among the 4f electrons and the 2p core hole determine the XMCD spectra. We also consider XMCD in the mixed valence compound CeFe2, taking many-body interactions into account based on the impurity Anderson model combined with a cluster approximation. [Copyright &y& Elsevier]

Pays tribute to Norio Kato, professor emeritus of Nagoya University in Japan, who died on April 5, 2002. Educational background; Contributions of Kato to the study of x-ray diffraction topography; Affiliations of Kato.

Magnetic properties of S=1 antiferromagnetic spin chains with alternating nearest-neighbor and competing next-nearest-neighbor interactions are studied, using the strong coupling expansion as well as numerical methods. Characteristic features of this system such as magnetization plateau, field-induced long-range ordering and incommensurate behavior are discussed in connection with the dimer gap, focusing on a novel role of the anisotropy. [Copyright &y& Elsevier]

Abstract: In liver tissue engineering, the development of appropriate extracellular matrix (ECM) is important because hepatocytes are anchorage-dependent cells and they rapidly lose liver-specific functions and viability in vitro. Therefore, it is very important to regulate galactose-mediated hepatocyte recognition to enhance selective interactions between galactose-carrying polymers and hepatocytes and liver-specific functions. In this review, to regulate hepatocyte behaviors by galactose-carrying polymers, the effect of physico-chemical properties of galactose-carrying polymers, cellular environment, medium composition and dynamic culture system were explained. Moreover, to understand the regulation mechanism of hepatocyte behaviors by galactose-carrying polymers, intracellular signal transduction in the hepatocytes by galactose-carrying polymers was also discussed. [Copyright &y& Elsevier]

Abstract: We calculate X-ray magnetic circular dichroism (XMCD) spectra in the Lu edge of ferromagnetic compounds Lu2Fe14B and LuFe2, and in the Ce edge of a mixed valence compound CeFe2. The calculated results are in good agreement with the available experimental ones, although spectral structures are mostly smeared out by the large lifetime broadening of the core hole. We then calculate the spectrum of – resonant X-ray emission spectroscopy (RXES) and its MCD (MCD-RXES) for these materials, and predict theoretically that the experimental observation of excitation spectra of MCD-RXES is a powerful tool to detect fine structures of XMCD beyond the lifetime broadening of the core hole. [Copyright &y& Elsevier]

An increase in interleukin (IL)-18 production from epidermal cells has been reported in an atopic dermatitis (AD) mouse model, and subsequent topical application of Staphylococcus aureus results in severe dermatitis. To reveal the relationship between S. aureus colonization of skin lesions and keratinocyte IL-18 production, particularly in AD with relatively low serum IgE levels. We also aimed to establish a simple and noninvasive method of assaying IL-18 produced by epidermal keratinocytes to evaluate local skin inflammation and therapeutic effects in patients with AD. IL-18 in the horny layer of the skin was collected via a tape-stripping method and measured in 95 patients with AD and 40 healthy controls by enzyme-linked immunosorbent assay (ELISA). Clinical severity, blood data and S. aureus skin colonization were evaluated before and after treatment. IL-18 levels in the horny layer were significantly higher in the skin lesions of patients with AD than in healthy controls and correlated with SCORAD, levels of serum IL-18, IgE, lactate dehydrogenase, thymus and activation-regulated chemokine, blood eosinophils and transepidermal water loss. In the AD group with serum IgE < 1500 IU mL, significantly higher IL-18 levels were observed in the horny layer of patients colonized with S. aureus compared with those who were not. Epidermal IL-18 production was associated with the severity of AD. Staphylococcus aureus colonization seems to contribute to this IL-18 production, especially in the AD group with relatively low IgE production. Tape stripping provides an easy and noninvasive method to assess epidermal IL-18 production by ELISA. [ABSTRACT FROM AUTHOR]

Abstract: Theoretical interpretations of X-ray magnetic circular dichroism (XMCD) at rare-earth (called R hereafter) L23 absorption edges are reviewed using differing models, depending on the material under investigation. In the first chapter, we present an overview of recent developments for XMCD in XAS with a few general remarks, especially at R atom absorption edges. In , we first describe basic mechanism of XMCD at L23 edges of R systems, and then we essentially discuss two examples of XMCD spectra in: (i) R2Fe14B metallic compounds, with the help of a cluster model, and (ii) RFe2 Laves-phase compounds, using a tight-binding approximation for R 5d and Fe 3d conducting states. A good agreement between theory and experiment for R2Fe14B suggests that a cluster model provides a valuable method to quantitatively calculate XMCD spectra of R systems, even with quite complicated atomic arrangements. For RFe2 systems the XMCD spectral shape, especially for the L2 edge of heavy R elements, is more complicated than those of R2Fe14B systems, and this is explained by the competition of some different XMCD mechanisms. In , we focus on special series of Ce systems, related to XAS and XMCD studies at the Ce L23 edges. Two clearly differing cases are interpreted: (i) A well localized 4f1 system, i.e. CeRu2Ge2; (ii) A less localized 4f1 system, i.e. CeFe2, with a 3d partner. Then, from a more experimental point of view, we investigate the influence of substitution on the low temperature properties of CePd3 compounds, i.e. alloys where x is about 0.03, giving rise to ordered structure. We give another example: alloys with x taken up to about 0.25. Also the Ce L23 XMCD signal measured in pure CePd3 demonstrates that in the Ce based dense Kondo materials, only the 4f1 channel yields a magnetic response. [Copyright &y& Elsevier]

Abstract: Extracellular matrix (ECM) plays important roles in tissue engineering because cellular growth and differentiation, in the two-dimensional cell culture as well as in the three-dimensional space of the developing organism, require ECM with which the cells can interact. Especially, the bioartificial liver-assist device or regeneration of the liver-tissue substitutes for liver tissue engineering requires a suitable ECM for hepatocyte culture because hepatocytes are anchorage-dependent cells and are highly sensitive to the ECM milieu for the maintenance of their viability and differentiated functions. Galactose-carrying synthetic ECMs derived from synthetic polymers and natural polymers bind hepatocytes through a receptor-mediated mechanism, resulting in enhanced hepatocyte functions. Attachment and functions of hepatocytes were affected by physico-chemical properties including ECM geometry as well as the type, density and orientation of galactose. Also, cellular environment, medium composition and dynamic culture system influenced liver-specific functions of hepatocytes beside ECM. [Copyright &y& Elsevier]

Abstract: Analyses of hard X-ray resonant photoelectron emission spectroscopy (HAX-RPES) and related spectroscopies such as X-ray absorption spectroscopy (XAS) and resonant X-ray emission spectroscopy (RXES) are made for mixed valence Ce compounds with single impurity Anderson model. First, the spectra of Ce XAS ( XAS) and the conventional Ce 3d X-ray photoelectron emission spectroscopy (XPS) are analyzed for , taking into account the bulk/surface sensitivity in XPS. Then it is shown that the bulk properties are more directly obtained from the Ce 3d HAX-RPES spectra, in which the Ce 2p–5d excitation is followed by the Ce 2p3d5d Auger decay. Furthermore, the Ce 3d HAX-RPES can reveal some hidden structures in the Ce XAS. From the analysis of the Ce HAX-RPES for , we reveal the existence of the Ce contribution in the XAS, and confirm an important role of the Coulomb interaction between Ce 4f and 5d elctrons in the XAS structure. For ferromagnetic mixed valence Ce compound , the spectra of the XAS and its magnetic circular dichroism (MCD-XAS) are analyzed, and the effect of is also important in explaining the relative peak positions of the XAS and MCD-XAS. Finally, the MCD in RXES (MCD-RXES) is calculated for , and it is predicted theoretically that the excitation spectrum of MCD-RXES can also reveal the hidden structure of the configuration in the Ce XAS (and MCD-XAS) spectrum. [Copyright &y& Elsevier]

The static spin structure factor S ( Q ) of CuGeO 3 was determined above its spin-Peierls transition temperature by inelastic neutron scattering. At 20 K, S ( Q ) has a Lorentzian line shape centered at the antiferromagnetic (AF) zone center. With increasing temperature, however, it splits into two peaks with their centers at incommensurate wave vectors at higher temperatures (70 and 120 K). The observed results are consistent with the prediction by recent numerical studies on the S =1/2 Heisenberg AF chain with competing spin interactions [I. Harada and Y. Aoyama, (1999) "Static spin structure factor of CuGeO 3 above spin-Peierls transition temperature", J. Phys. Chem. Solids 60 , 1105; I. Harada, Y. Nishiyama, Y. Aoyama and S. Mori, (2000) "Spin correlation in the one-dimensional Heisenberg antiferromagnet with competing interactions", J. Phys. Soc. Jpn. 69 , (Suppl. A), 339]. [ABSTRACT FROM AUTHOR]

The magnetic circular dichroism (MCD) of the X-ray absorption spectra (XAS) and of the resonant X-ray emission spectra (RXES) at the rare-earth (RE) L2,3 edges of R2Fe14B (R=La–Lu) are studied based on the model, where the band nature of the RE 5d states and the Fe 3d states and the intra-atomic exchange interaction between the RE 4f and 5d states are taken into account. We show that the detailed information on the weak polarization of the RE 5d states can be obtained by analyzing XAS-MCD and RXES-MCD. [Copyright &y& Elsevier]

Magnetic circular dichroism (MCD) of the X-ray absorption spectroscopy (XAS) at the Ce L2,3 edges in a typical mixed valence compound, CeFe2, is theoretically studied by using the impurity Anderson model combined with a cluster approach. We find that the hybridization of Ce 5d states with spin-polarized Fe 3d states is responsible for the differences between XAS and MCD, while the Coulomb interaction of a photo-excited 5d electrons plays a novel role, in addition to the many body effects yielding the two-peak structure of XAS. [Copyright &y& Elsevier]

Abstract: The resistivity in magnetic materials has been theoretically shown to depend on the spin–spin correlation function which in turn depends on the magnetic field, the density of conduction electron, the magnetic ordering stability, etc. However, these theories involved a lot of approximations, so their validity remained to be confirmed. The purpose of this work is to show by newly improved extensive Monte Carlo (MC) simulation the resistivity of the spin resistivity from low-T ordered phase to high-T paramagnetic phase in ferromagnetic and antiferromagnetic films. We take into account the interaction between the itinerant spins and the localized lattice spins as well as the interaction between itinerant spins themselves. We show that in ferromagnets the resistivity shows a sharp peak at the magnetic phase transition in agreement with previous theories in spite of their numerous approximations. Resistivity in antiferromagnets on the other hand shows no peak for the SC, BCC and diamond lattices. Discussion on the origin of these resistivity behaviors is given. [ABSTRACT FROM AUTHOR]