Vacancy ordering in SmGe2-x and GdGe2-x (x = 0.33): structure and properties of two Sm3Ge5 polymorphs and of Gd3Ge5

The crystal structures and the magnetic properties of three new binary rare-earth intermetallic phases are reported. alpha-Sm3Ge5 and beta-Sm3Ge5 and Gd3Ge5 have been prepared from the corresponding elements through high-temperature reactions using the flux-growth method. The structures of the three compounds have been established using single-crystal X-ray diffraction: alpha-Sm3Ge5 crystallizes with its own type in the hexagonal space group P2c (No. 190) with cell parameters a = 6.9238(11) A, c = 8.491(3) A, and Z = 2, whereas beta-Sm3Ge5 adopts the face-centered orthorhombic Y3Ge5 type with space group Fdd2 (No. 43) and with cell parameters a = 5.8281(6) A, b = 17.476(2) A, c = 13.785(2) A, and Z = 8. The orthorhombic Gd3Ge5 with cell parameters a = 5.784(2) A, b = 17.355(6) A, and c = 13.785(5) A is isostructural with beta-Sm3Ge5. The structures of the title compounds can be described as AlB(2) and alpha-ThSi2 derivatives with long-range ordering of the germanium vacancies. Temperature-dependent DC magnetization (5-300 K) measurements show evidence of antiferromagnetic ordering below ca. 30 and 10 K for alpha-Sm3Ge5 and beta-Sm3Ge5, respectively. Gd3Ge5 undergoes two successive magnetic transitions below ca. 15 and 11 K. The temperature dependence of the resistivity and heat capacity of Gd3Ge5 are discussed as well.     

Heterostructured nanohybrid of zinc oxide-montmorillonite clay

We have synthesized heterostructured zinc oxide-aluminosilicate nanohybrids through a hydrothermal reaction between the colloidal suspension of exfoliated montmorillonite nanosheets and the sol solution of zinc acetate. According to X-ray diffraction, N2 adsorption-desorption isotherm, and field emission-scanning electron microscopic analyses, it was found that the intercalation of zinc oxide nanoparticles expands the basal spacing of the host montmorillonite clay, and the crystallites of the nanohybrids are assembled to form a house-of-cards structure. From UV-vis spectroscopic investigation, it becomes certain that calcined nanohybrid contains two kinds of the zinc oxide species in the interlayer space of host lattice and in mesopores formed by the house-of-cards type stacking of the crystallites. Zn K-edge X-ray absorption near-edge structure/extended X-ray absorption fine structure analyses clearly demonstrate that guest species in the nanohybrids exist as nanocrystalline zinc oxides with wurzite-type structure.     

Nuclear factor of activated T cells negatively regulates expression of the tumor necrosis factor receptor-related 2 gene in T cells

Tumor necrosis factor receptor-related 2 (TR2, HVEM or TNFRSF-14) plays an important role in immune responses, however, the mechanisms regulating its expression are unclear. To understand the control of TR2 gene expression, we studied the upstream region of the gene. Gel supershift assays revealed inducible binding of nuclear factor of activated T cells (NFAT) to a putative NFAT site within the TR2 promoter. Furthermore, cotransfection of a dominant negative NFAT construct, or siRNA for NFAT, resulted in increased expression of a TR2 reporter gene. Our findings demonstrate that NFAT negatively regulates TR2 expression in activated T cells.     

Alterations of HLA class I and II antigen expression in preinvasive, invasive and metastatic cervical cancers

HLA expression is altered in a large variety of human cancers. We performed immunohistochemical staining on tissues from normal, preinvasive, invasive and metastatic cervical cancer tissues using anti-HLA class I or class II antibody. In tissues from normal squamous epithelium, carcinoma in situ (CIS) and microinvasive carcinoma (MIC), the expressions of HLA-B, C heavy chains and class II heavy chain were significantly decreased as disease progressed. When the expression patterns were compared between primary and metastatic squamous cell carcinoma (SCC) lesions, statistically significant down-regulation of HLA class I and class II antigen in metastatic lesions was observed. The rates of HLA-B, C heavy chains and class II heavy chain expressions were all significantly down-regulated compared to the down-regulation rate of class I beta2-microglobulin (beta2m) in invasive squamous lesions, and the expressions of class II heavy chain in metastatic lesions was decreased further than that in primary lesions. Unlike SCC, the degree of HLA class I and class II loss was not evident as disease progressed in early stage of adenocarcinoma. In invasive adenocarcinoma lesions, only the expression of HLA-B, C heavy chains was decreased and no differences were seen in HLA-B, C heavy chain expression patterns between primary and metastatic lesions. These results suggest that alterations of HLA class I and II expressions seem to occur at a particular step in cervical cancer development and depend on tissue types: when the tumor becomes invasive and starts to metastasize.     

Cryptotanshinone but not tanshinone IIA inhibits angiogenesisin vitro

In the course of screening of angiogenesis inhibitor from natural products, cryptotanshinone from Salvia miltiorrhiza was isolated as a potent small molecule inhibitor of angiogenesis. Cryptotanshinone inhibits bFGF-induced angiogenesis of BAECs at ten micromolar ranges in vitro without cytotoxicity. Tanshinone IIA, another tanshinone isolated from S. miltiorrhiza, which is structurally very similar to cryptotanshinone except C-15 position of dihydrofuran ring does not inhibit angiogenesis induced by bFGF. These results demonstrate that cryptotanshinone is a new anti-angiogenic agent and double bond at C-15 position of the dihydrofuran ring plays a crucial role in the activity.     

Generalized Shioda–Inose structures on K3 surfaces

In this note, we study the action of finite groups of symplectic automorphisms on K3 surfaces which yield quotients birational to generalized Kummer surfaces. For each possible group, we determine the Picard number of the K3 surface admitting such an action and for singular K3 surfaces we show the uniqueness of the associated abelian surface. Received: 9 April 1998 / Revised version: 17 July 1998     

Study on the reentering rates of individual cooling towers installed on a building roof

In this paper, the averaged reentering rates of the densely built cooling towers, which form banks on the building roof in Seoul, Korea have been predicted by a numerical method according to various summer wind conditions and roof wall types. The averaged reentering rates of all the cooling towers are compared according to two wall types to study the effect of the intake outdoor air louver on the reentering rates. Consequently, two findings are drawn as follows. (1) With a curtain wall, the averaged reentering rates of the total cooling towers against the west and the south wind at ν = 5 m/s are 13.3 and 24.4%, respectively. Therefore, it is strongly needed to find a method to reduce the reentering of the discharged air from the cooling towers. (2) In the case of a louver wall, the averaged reentering rates of the cooling towers with the west and south wind at ν = 5 m/s are 2.5 and 9.74%, respectively, which have been estimated to be lower than those of the curtain wall. Therefore, the louver wall can be suitably adopted to reduce the reentering of the discharged air from the cooling towers in the present study.     

Hidden Caldeira-Leggett dissipation in a Bose-Fermi Kondo model

We show that the Bose-Fermi Kondo model (BFKM), which may find applicability both to certain dissipative mesoscopic qubit devices and to heavy-fermion systems described by the Kondo lattice model, can be mapped exactly onto the Caldeira-Leggett model. This mapping requires an ohmic bosonic bath and an Ising-type coupling between the latter and the impurity spin. This allows us to conclude unambiguously that there is an emergent Kosterlitz-Thouless quantum phase transition in the BFKM with an ohmic bosonic bath. By applying a bosonic numerical renormalization group approach, we thoroughly probe physical quantities close to the quantum phase transition.