Fabrication of pressureless sintered dense β-SiAlON via a reaction-bonding route with ZrO2 addition

A reaction-bonding and post-sintering process was applied to fabricate pressureless sintered β-Si_6?ZAl_ZO_ZN_8?Z (Z = 1–3) ceramics with monoclinic ZrO₂ added to the starting powder. Samples with ZrO₂ showed enhanced nitridation and achieved near theoretical density following post-sintering, although this could not be achieved in the samples produced without ZrO₂. Thus the ZrO₂ is effective in both enhancing the nitridation of Si and as a sintering additive for densification of β-SiAlON. Part of the added monoclinic ZrO₂ was transformed to tetragonal ZrO₂, and the ZrN phase was also formed due to reaction with nitrogen during the reaction-bonding process. After the post-sintering process, the ZrN phase remained only in the Z = 3 composition. In the other compositions the ZrN reacted with SiO₂ to form both tetragonal and monoclinic ZrO₂ phases. These differences are explained in terms of the increasing densification and grain growth for Al₂O₃ rich compositions and the ZrN being trapped inside such grains in the case of the Z = 3 sample.     

Stress Dependence of the Raman Spectrum of β-Silicon Nitride

The stress dependence of the Raman bands of β-silicon nitride,β-Si₃N₄, has been investigated. In the stress range examined (from-200 to +200 MPa), low-frequency shift bands (namely the 183, 205, and 226 cm⁻¹ lines) do not show any frequency change with the stress, whereas the high-frequency shift bands (862, 925, and 936 cm⁻¹) have been found to have a linear stress dependence. The pertinent piezo-spectroscopic coefficients have been determined and are found to depend strongly on the additives used to promote densification presumably being taken into solid solution into the β-Si₃N₄ phase.     

Detection of new spider toxins from a Nephilengys borbonica venom gland using on-line mu-column HPLC continuous flow (FRIT) FAB LC/MS and MS/MS

The Morris water maze is frequently used to screen mutant mice generated by gene targeting. Targeted ES-cells are often derived from 129/Sv or BALB/c mice, known as poor swimming navigation learners. After mating the founders with C57BL/6 mice, the F2 or F3 hybrid generation is typically used for behavioral testing. In hybrid 129/Sv x C57BL/6 mice, a modification of the betaAPP gene entails impaired swimming navigation learning. This is readily detected despite behavioral variability, because wild-type 129/Sv x C57BL/6 hybrids outperform either of the parental strains and provide a control sample with good baseline performance. However, after backcrossing to the 129/Sv(ev) strain, the mutation effects are no longer detectable, masked by the very poor performance of wild-type 129/Sv(ev) mice. We conclude that F2 and F3 generations of 129/Sv x C57BL/6 crosses provide a suitable genetic background for behavioral testing of transgenic mice, provided that the samples are large enough to compensate for genetic and epigenetic variability and provided that normal performance in the control group is verified by comparison against a large database of mice tested under identical conditions. Creating congenic lines by backcrossing to an inbred strain is unlikely to enhance the sensitivity of the Morris test. Backcrossing to 129/Sv(ev) may even reduce it.     

Preliminary Comparison of Radioactive Waste Disposal Cost for Fusion and Fission Reactors

The environmental and economic impact of radioactive waste (radwaste) generated from fusion power reactors using five types of structural materials and a fission reactor has been evaluated and compared. Possible radwaste disposal scenario of fusion radwaste in Japan is considered. The exposure doses were evaluated for the skyshine of gamma-ray during the disposal operation, groundwater migration scenario during the institutional control period of 300 years and future site use scenario after the institutional period. The radwaste generated from a typical light water fission reactor was evaluated using the same methodology as for the fusion reactors. It is found that radwaste from the fusion reactors using F82H and SiC/SiC composites without impurities could be disposed by the shallow land disposal presently applied to the low level waste in Japan. The disposal cost of radwaste from five fusion power reactors and a typical light water reactor were roughly evaluated and compared.     

Novel Conjugated Polymers Containing [2.2]Paracyclophane and Carbazole Units with Efficient Photoluminescence

Summary Novel through-space conjugated polymers based on PPE having [2.2]paracyclophane and N-alkylcarbazole units in the main chain were synthesized by Sonogashira-coupling reaction. All polymers were quite soluble in a variety of organic solvents. Transparent and uniform thin films of the polymers were obtained easily by casting or spin-coating from toluene solution. These polymers possessed good thermal stability. The polymers exhibited strong blue photoluminescence in solution and bluish-green photoluminescence in the solid state.     

Interfacial tension of aqueous two-phase systems containing poly(ethylene glycol) and dipotassium hydrogenphosphate

Liquid-liquid equilibrium (LLE) compositions and interfacial tensions of the aqueous two-phase system containing poly(ethylene glycol) (PEG 4000, average Mr=3500; PEG 6000, average Mr=7500; and PEG 20000, average Mr =20000) and dipotassium hydrogenphosphate were experimentally determined by using a shaking flask method and a drop volume method at 288.15, 298.15 and 308.15 K, respectively.     

Search for Superconductivity in the Stress-Induced Ferromagnetic Phase of Sr3Ru2O7

To explore the possibility of the existences of superconductivity and ferromagnetism in Sr₃Ru₂O₇, we have performed resistivity measurements on a single crystalline sample under uniaxial stresses of 0–110 MPa along the c-axis (perpendicular to the conducting RuO₂ plane). In this stress region no superconductivity was so far detected down to at least 160 mK. At the same time an indication of ferromagnetism was not seen clearly in the resistivity, either. Technical difficulties yet to be overcome for further progress are discussed.     

Non-volatile one-transistor-cell multiple-valued CAM with a digit-parallel-access scheme and its applications

A new high-density non-volatile multiple-valued content-addressable memory (CAM) is proposed for highly parallel search operations. Multiple-valued stored data correspond to the threshold voltage of a floating-gate MOS transistor, so that the cell circuit can be designed using only a single transistor. Since a single match line in a one-word circuit is used for performing a multi-input wired AND operation, the magnitude comparison result between multi-digit data can be obtained simultaneously. As a result, a one-word magnitude comparison with n digits can be performed by just n steps in spite of a single-transistor cell circuit and single-match-line architecture, which makes the peripheral circuit of a CAM cell array small. Moreover, typical applications clearly demonstrate that the proposed non-volatile CAM is useful as a hardware accelerator for a high-speed comparison.     

Fine particle removal by a negatively-charged fine particle collector in silane plasma

To suppress inclusion of fine particles in amorphous silicon films, a negatively-charged fine particle (NFP) collector has been successfully installed in a silane plasma. Two modes of operation of the NFP collector biasing were examined: (i) turning on after the appearance of fine particles; and (ii) turning on from the very beginning of the plasma operation. While the former proved the effectiveness of the NFP collector in the removal of fine particles, apparently very small particles (<100 nm) removal in the latter reduced the degradation of the photo conductivity in deposited a-Si:H films by light soaking. This effect is accompanied by the increased density of SiH bonding, which can be related to the possible modification in the silicon networks in the amorphous film.     

Differential contribution of various adhesion molecules to leukocyte kinetics in pulmonary microvessels of hyperoxia-exposed rat lungs

To elucidate the differential role of various adhesion molecules in distorting leukocyte behavior in the microvasculature of hyperoxia-exposed rat lungs, we investigated fluorescein-labeled leukocyte and erythrocyte kinetics in isolated lungs taken from the animals exposed to 90% O2 for 48 h under conditions in which endothelial intercellular adhesion molecule-1 (ICAM-1) and P-selectin were inhibited by appropriate monoclonal antibodies (1A29 for ICAM-1 and ARP2-4 for P-selectin), while leukocyte L-selectin was restrained with fucoidin. Measurements of blood cell kinetics were made by a confocal laser luminescence microscope coupled with a high-speed video camera. In addition, we histologically examined leukocyte accumulation within the alveolar septa and ICAM-1 as well as P-selectin expressions in the lung. We found that P-selectin expression was sparsely enhanced only in arterioles, whereas ICAM-1 was significantly induced in both venules and capillaries. Firm adhesion of leukocytes was not identified in arterioles and venules, whereas leukocyte rolling was evident in both the vessels. Arteriolar rolling was regulated via a P-selectin- and ICAM-1-independent but L-selectin-dependent mechanism, whereas venular rolling was mediated via a P-selectin-independent but ICAM-1- and L-selectin-dependent pathway. Leukocyte sequestration within capillaries was augmented by an ICAM-1-related mechanism. These findings may suggest that, in hyperoxia-exposed lungs, induction of adhesion molecules and their obstacles to leukocyte behavior are qualitatively different among arterioles, venules, and capillaries.