Experimental Evidence for the Anisotropic Ostwald Ripening of β-Silicon Nitride

A powder mixture of α-Si₃N₄, Y₂O₃, and SiO₂ was heat-treated in a loose powder state in the temperature range of 1750°–1900°C for 2 h; then, the mixture was acid-rinsed to remove the glassy phase. The widths and lengths of the resulting β-Si₃N₄ crystals were analyzed quantitatively. The width–aspect-ratio distribution of the β-Si₃N₄ crystals initially showed a strong negative correlation, and then the aspect ratio of crystals with small widths quickly decreased. After a stage in which aspect ratio was almost constant, regardless of the width, the width-aspect-ratio distribution evolved to show a positive correlation in the final stage. This pattern of morphology evolution of the β-Si₃N₄ crystals was in good agreement with that predicted by the anisotropic Ostwald ripening model.     

Oxygen Content in ß-Si3N4 Crystal Lattice

ß-Si₃N₄ crystals were obtained through the heat treatment of alpha-Si₃N₄ powder with additives, Y₂O₃:SiO₂= 1:2 and 2:1, and subsequent acid treatments that removed the secondary phases. The lattice oxygen contents of these crystals were determined by the hot-gas extraction method to be 0.258 ± 0.006 and 0.158 ± 0.003 wt% for the additive compositions of Y₂O₃:SiO₂= 1:2 and 2:1, respectively. The oxygen dissolved in the ß-Si₃N₄ crystal lattice as much as in the alpha-Si₃N₄ crystral lattice prepared by the chemical vapor deposition process and in the AlN crystal lattice that exhibited high thermal conductivity.     

Overview of energy consumption and GHG mitigation technologies in the building sector of Japan

This paper outlines the energy consumption and greenhouse gas emission trends in the residential and commercial sectors in Japan. The results showed that the increase in residential energy consumption in Japan is mainly caused by the widespread use of heating equipment, hot water supply apparatus, and other household electrical appliances. On the other hand, it was indicated that the increase in commercial energy use is mainly due to the increase of the floor area of buildings, particularly hotels, hospitals, and department stores. The paper also describes political measures to promote energy conservation, including the building energy conservation standard, Comprehensive Assessment System for Building Environmental Efficiency, top runner programs, financial incentives, and the dissemination of the Cool Biz concept. Finally, the projections of CO₂ emissions until 2050 are presented.

An efficient algorithm for generating manipulator inertia matrix using the minimum set of dynamics parameters

This article presents an efficient algorithm for computing the inertia matrix of rigid serial manipulators. The derivation of the algorithm is based on the closed-form formulation of the force and moment exerted on a link using a minimum set of dynamic parameters of the manipulator model. The minimum set of dynamic parameters can be derived completely from the original dynamic parameters using the recursive re-grouping method before starting the simulation and the control. The proposed computation method is suitable for the control and the simulation based on parameter estimates because the minimum set of dynamic parameters is an identifiable parameter set. The computational efficiency of the proposed methods is compared with other published methods. It is shown that the proposed algorithm is the most efficient approach for serial manipulators. As an example, the number of computations for the inertia matrix of a manipulator with n rotational joints is 11n²+9 n − 35 multiplications and 7n²+ 23 n − 57 additions by reformulating the dynamic model using the minimum set of dynamic parameters. © 1996 John Wiley &, Sons, Inc.     

Thermal Conductivity of β-Si3N4: II, Effect of Lattice Oxygen

Dense β-Si₃N₄ with various Y₂O₃/SiO₂ additive ratios were fabricated by hot pressing and subsequent annealing. The thermal conductivity of the sintered bodies increased as the Y₂O₃/SiO₂ ratio increased. The oxygen contents in the β-Si₃N₄ crystal lattice of these samples were determined using hot-gas extraction and electron spin resonance techniques. A good correlation between the lattice oxygen content and the thermal resistivity was observed. The relationship between the microstructure, grain-boundary phase, lattice oxygen content, and thermal conductivity of β-Si₃N₄ that was sintered at various Y₂O₃/SiO₂ additive ratios has been clarified.     

Modeling and simulation of grain growth in Si3N4-II. The α–β transformation

The anisotropic Ostwald ripening model has been developed for completely faceted crystals. This model has been applied to the simulation of grain growth in β-Si₃N₄ with a highly anisotropic rod-like grain shape developed in the liquid phase. The reduction of aspect ratio after the phase transformation observed by previous studies is proved to be a consequence of the anisotropic Ostwald ripening. This model predicts a growth exponent n=3 for totally interfacial reaction controlled kinetics, and higher values when the diffusion constant approaches the interfacial reaction constants. This would explain the puzzling results reported by previous works that growth exponents n=3 or higher have been observed in the grain growth of faceted crystals. While the length distribution becomes wider with time, the reduced radius distribution approaches the shape that is known as the asymptotic distribution function derived from the LSW theory.     

Poly(ADP-ribose) Polymerase 1 Mediates Rab5 Inactivation after DNA Damage

Parthanatos is programmed cell death mediated by poly(ADP-ribose) polymerase 1 (PARP1) after DNA damage. PARP1 acts by catalyzing the transfer of poly(ADP-ribose) (PAR) polymers to various nuclear proteins. PAR is subsequently cleaved, generating protein-free PAR polymers, which are translocated to the cytoplasm where they associate with cytoplasmic and mitochondrial proteins, altering their functions and leading to cell death. Proteomic studies revealed that several proteins involved in endocytosis bind PAR after PARP1 activation, suggesting endocytosis may be affected by the parthanatos process. Endocytosis is a mechanism for cellular uptake of membrane-impermeant nutrients. Rab5, a small G-protein, is associated with the plasma membrane and early endosomes. Once activated by binding GTP, Rab5 recruits its effectors to early endosomes and regulates their fusion. Here, we report that after DNA damage, PARP1-generated PAR binds to Rab5, suppressing its activity. As a result, Rab5 is dissociated from endosomal vesicles, inhibiting the uptake of membrane-impermeant nutrients. This PARP1-dependent inhibition of nutrient uptake leads to cell starvation and death. It thus appears that this mechanism may represent a novel parthanatos pathway.     

Synthesis of Porous Ceramics with Complex Pore Structure by Freeze-Dry Processing

Porous ceramics with complex pore structure were synthesized by a freeze-dry process. Freezing-in of a water-based ceramics slurry was done while controlling the growth direction of the ice. Sublimation marks of the ice were generated by drying under reduced pressure. Porous ceramics having a complex pore structure were obtained by sintering the green body: aligned macroscopic open pores contained micropores in their internal walls. The pore structure was substantially affected by the starting slurry concentration and sintering temperature. The pore formation mechanism is discussed in relation to these effects.     

Polyether-segmented nylon hemodialysis membrane. V. Evaluation of blood compatibility of polyether-segmented nylons

The biocompatibility of poly(propylene oxide)-segmented nylon610 (PPO-Ny610), poly(ethylene oxide)-segmented nylon610 (PEO-Ny610), poly(ethylene oxide)-segmented nylonM10 (PEO-NyM10), and poly(ethylene oxide)-segmented nylon69/M10 (PEO-Ny69/M10) hollow fibers were investigated in terms of the transient leukopenia by the extracorporeal circulation in a rabbit. PPO-Ny610 and PEO-Ny610 hollow fibers showed that the minimum leukocyte counts during the circulations were > 80% against the initial count of leukocyte. These results indicate that these polymers have good blood compatibility. In PEO-NyM10 and PEO-Ny69/M10, the remarkable decreases of the leukocyte count were observed and the minimum counts were in the range of 45–50%. From the evaluation results of homo nylons (Ny610 and NyM10) hollow fibers, the low blood compatibilities observed in PEO-NyM10 and PEO-Ny69/M10 are not attributed to the chemical structure of the nylon blocks. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1253–1257, 1998     

Model polypeptide of mussel adhesive protein. I. Synthesis and adhesive studies of sequential polypeptides (X‐Tyr‐Lys)n and (Y‐Lys)n

The sequential polytripeptides and polydipeptides, (X‐Tyr‐Lys)_n, (XGly, Ala, Pro, Ser, Leu, Ile, Phe), (Y‐Lys)_n, (YGly, Tyr), and (Gly‐Tyr)_n, which imitate a mussel adhesive protein, have been synthesized. The molecular weights of the polypeptides were estimated to be 7,200 ∼ 13,400 (19 ∼ 42 repeating units), and the polypeptides were found to have satisfactory amino acid sequences. The polypeptides were crosslinked by tyrosinase, and the optimal pH in the crosslinking reaction was 7.4 in the case of the polytripeptide, (Gly‐Tyr‐Lys)_n. The optimal tyrosinase amount for the adhesive strength of (Gly‐Tyr‐Lys)_n was 0.34 unit/mg (polypeptide) at pH 7.4. The shear adhesive strength of the polytripeptide increased with an increase in the polytripeptide concentration, and was not influenced by the third amino acid, X. The shear adhesive strengths of polytripeptides (X‐Tyr‐Lys)_n were equal to one of the synthetic polydecapeptides, (Ala‐Lys‐Pro‐Ser‐Tyr‐Pro‐Pro‐Thr‐Tyr‐Lys)_n and (Gly‐Pro‐Lys‐Thr‐Tyr‐Pro‐Pro‐Thr‐Tyr‐Lys)_n which were the model polydecapeptides for blue mussel and Californian mussel, respectively. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 929–937, 2000