Mössbauer study on indium tin oxides (ITO) doped with Fe

InSnFe mixed oxides were prepared by a sol–gel method, and were investigated by Mössbauer spectrometry and magnetization measurements. The magnetic relaxation peaks in addition to paramagnetic peaks were observed in Mössbauer spectra. Most of Fe^3?+? species (D1) occupy 24d site of bixbyite structure, and the other Fe^3?+? species (D2) occupy 8b site. The area intensity ratio of two doublets for sample with x?=?0.06 and y?=?0.06 was most perfectly consistent with the ratio of d/b site occupations (24/8); this sample showed the highest magnetization among these samples. Fired ash of In oxide (5%Fe), which showed ferromagnetism, consisted of γ Fe₂O₃ segregated oxides.     

Graft copolymerization induced by thermal reactions of the binary alkali salts of poly(carboxylic acid)–brominated carboxylic acid in bulk

Thermal reactions of the binary alkali salts of poly(carboxylic acid)–brominated carboxylic acid such as sodium or potassium poly(4-vinylbenzoate)-2-bromopropanoate [Na or K (PVBA-2-BPA)] in bulk were investigated. A methanol solution of binary acids was prepared by fixing the molar ratio of the repeating unit of polymeric acid to the fraction of brominated carboxylic acid. The binary salts were prepared by the neutralization of the binary acid solution. The product of the thermal reaction followed by esterification was identified as a graft copolymer containing PVBA in the main chain and polylactic acid in the side chain. The reaction of 1/15 K (PVBA-2-BPA) at 120 °C for 2 h yielded the highest percentage of grafting (300%). The grafting proceeded gradually for the initial 2 h and then somewhat. Reactivity of the K salt was higher than that of the corresponding Na salt. The thermal reaction of 1/10 K [polymethacrylate-2-BPA (PMA-2-BPA)] at 120 °C for 2 h also yielded a graft copolymer, and the percentage of grafting was 300%. However, reaction temperatures higher than 120 °C caused homopolycondensation of K 2-BPA prior to grafting, and homopolycondensation occurred prior to grafting in the reaction with Na (PMA-2-BPA). © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1877–1885, 2001     

Homotopically equivalent simple loops on 2-bridge spheres in 2-bridge link complements (I)

In this paper and its two sequels, we give a necessary and sufficient condition for two essential simple loops on a 2-bridge sphere in a 2-bridge link complement to be homotopic in the link complement. This paper treats the case when the 2-bridge link is a \((2,p)\) -torus link, where more cases of homotopy arise, and its sequels will treat the remaining cases.     

Effect and Mechanism of a New Photodynamic Therapy with Glycoconjugated Fullerene

When irradiated, fullerene efficiently generates reactive oxygen species (ROS) and is an attractive photosensitizer for photodynamic therapy (PDT). Ideally, photosensitizers for PDT should be water-soluble and tumor-specific. Because cancer cells endocytose glucose more effectively than normal cells, the characteristics of fullerene as a photosensitizer were improved by combining it with glucose. The cytotoxicity of PDT was studied in several cancer cell lines cultured with C₆₀-(Glc)1 (d -glucose residue pendant fullerene) and C₆₀-(6Glc)1 (a maltohexaose residue pendant fullerene) subsequently irradiated with UVA₁. PDT alone induced significant cytotoxicity. In contrast, PDT with the glycoconjugated fullerene exhibited no significant cytotoxicity against normal fibroblasts, indicating that PDT with these compounds targeted cancer cells. To investigate whether the effects of PDT with glycoconjugated fullerene were because of the generation of singlet oxygen (¹O₂), NaN₃ was added to cancer cells during irradiation. NaN₃ extensively blocked PDT-induced apoptosis, suggesting that PDT-induced cell death was a result of the generation of ¹O₂. Finally, to investigate the effect of PDT in vivo, melanoma-bearing mice were injected intratumorally with C₆₀-(Glc)1 and irradiated with UVA₁. PDT with C₆₀-(Glc)1 suppressed tumor growth. These findings indicate that PDT with glycoconjugated fullerene exhibits tumor-specific cytotoxicity both in vivo and in vitro via the induction of ¹O₂.     

Preparation and structural control of metal coordination-assisted supramolecular architectures of porphyrins. Nanocubes to microrods

We have successfully prepared metal coordination-assisted porphyrin assemblies such as nanocubes, nanorods and microrods by controlling the synthetic conditions. The internal structures and lifetimes of the excited states are also quantitatively discussed.     

Mode localization phenomena and stability of disordered trains and train-like articulated systems travelling in confined fluid

The possible existence of mode localization in a chain of flexibly interconnected cylinders, representing a high-speed train travelling in a tunnel is investigated, in the presence of some disorder in the chain. Specifically, imperfections in the mass and springs in the model are considered as possible sources of mode localization, and it is shown that in general they can do so. This is part of a broader study into the dynamics of high-speed trains running in a tunnel, or more generally of a train-like system travelling in a coaxial cylindrical tube and subjected to aerodynamic forces associated with lateral motions of the cylinders. Each cylinder in the model is coupled to the other cylinders and is supported by springs, such that it has both translational and rotational degrees of freedom. Two models are used: a lumped-parameter Euler-Bernoulli beam model (LEB) and a lumped-parameter Timoshenko-beam model (LTB). The results of this study show that Timoshenko beam effects of rotational inertia and shear deformation have a considerable influence on the mode localization phenomena and that imperfections in the supporting springs have a considerable influence on the stability of the LTB model.     

Controlling emission wavelength from InAs self-assembled quantum dots on InP (0 0 1) during MOCVD

We studied the growth of InAs quantum dots on InP (0 0 1) substrates in a low-pressure metalorganic chemical vapor deposition by using a so-called InP ‘double-cap’ procedure. With double-capping, a photoluminescence spectrum is modified into a series of multiple peaks, where the emission peaks arise from several quantum dot families with different heights changing in a step of integer number of an InAs monolayer. Cross-sectional transmission electron micrograph observations revealed that the shape of double-capped dots is dramatically changed into a thin plate-like shape with extremely flat upper and lower interfaces, being consistent with our interpretation of the photoluminescence spectrum. We showed that the procedure was extremely useful for controlling the emission wavelength from quantum dots in an InAs/InP (0 0 1) system.     

First-principles calculations of magnetic and electronic structures around surfaces and interfaces of magnetic multi-layered structure

Electronic and magnetic structures of ferromagnetic (FM)/non-magnetic (NM) and FM/antiferromagnetic (AF) bi-layer systems are calculated by the first principles approach. For the FM/NM system, we focus on the Co/Cu multi-layered structure whose interfacial layer is assumed to have a mixed composition of Co and Cu atoms, and show a possibility that Co atoms at the interface play a significant role as the spin-dependent scattering potentials. In the FM/AF system, we consider Fe or Co monolayer as FM layer and MnNi as AF layers. It is predicted that the Mn moments adjacent to FM layer are forced to align the FM moments, and those of under layer go gradually to anti-parallel alignment as in the bulk MnNi.     

Influence of polyethylenimine on the precipitation process of lead sulfate crystals

Crystals of lead sulfate were precipitated in a solution of polyethylenimine (PEI) using a double-jet crystallizer. PEI controlled both the nucleation rate and the growth rate, and enabled to produce fine monodispersed crystals. This effect is considered to be due to a complexation between PEI and lead ion. The on-line measurement of the variation in the lead ion concentration indicated PEI lost its effect when a certain amount of reactants was supplied. And the duration in which PEI could control the precipitation rate and the amount of PEI had a strong correlation. In addition, it was suggested that their relationship could be utilized in order to produce monodispersed particles.     

Model system of self-reproducing vesicles

Development of self-reproducing vesicle systems is the first step for autopoietic cycles. We established a model self-reproducing vesicle system without the membrane molecule synthesis route. The model vesicle composed of cylinder- and inverse-cone-shaped lipids formed inclusion vesicles inside the mother vesicle, and the inclusion vesicles were then expelled by a temperature cycling. By changing the vesicle composition, the mother vesicles showed a budding-type self-reproduction pathway. A key concept of this system is the coupling of the main-chain transition and the shape of lipids.