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31.
Yuki Nakashima You Zhou Keisuke Tanabe Souhei Arima Kiyoshi Hirao Tatsuki Ohji Norimitsu Murayama Manabu Fukushima 《Journal of the American Ceramic Society》2023,106(2):1139-1148
Silicon nitride (Si3N4) was prepared from silicon by a sintered reaction-bonded silicon nitride method using yttria and magnesia as sintering additives. Post-sintering (PS) of nitrided compacts was carried out at 1850°C under a nitrogen pressure of 1 MPa. Effect of PS time on microstructure and dielectric breakdown strength (DBS) of the prepared Si3N4 ceramics was evaluated. The DBS was measured using specimens with four different thicknesses (0.30, 0.20, 0.10, and 0.05 mm) in order to examine the thickness dependence. The porosity of the sintered Si3N4 decreased by prolonging the PS time, and the full density could be achieved at the PS time of over 6 h. After full densification, rod-like β-Si3N4 grains grew up, and their maximum grain size increased from 45.1 to 154.7 μm by prolonging the PS time from 6 to 48 h. The DBS of the thick Si3N4 substrates (0.30 mm) showed little variation from 35.4 to 47.0 kV/mm, regardless of the PS time. On the other hand, that of the thin ones (0.05 mm) dramatically decreased from 99.5 to 9.8 kV/mm with increased the PS time from 6 to 48 h. Because the DBS sharply decreased at the thin substrate sintered for longer time in which some large-elongated grains might span the substrate thickness-wise throughout, it was inferred that the interface between β-Si3N4 grains and grain boundary phase/intergranular glassy films might be a path of the dielectric breakdown. 相似文献
32.
Satoru Shindo Irma Josefina Savitri Takenobu Ishii Atsushi Ikeda Roodelyne Pierrelus Alireza Heidari Keisuke Okubo Shin Nakamura Umadevi Kandalam Mohamad Rawas-Qalaji Elizabeth Leon Maria Rita Pastore Patrick Hardigan Toshihisa Kawai 《International journal of molecular sciences》2022,23(6)
Effects of the antiosteoblastogenesis factor Semaphorin 4D (Sema4D), expressed by thrombin-activated platelets (TPs), on osteoblastogenesis, as well as osteoclastogenesis, were investigated in vitro. Intact platelets released both Sema4D and IGF-1. However, in response to stimulation with thrombin, platelets upregulated the release of Sema4D, but not IGF-1. Anti-Sema4D-neutralizing monoclonal antibody (mAb) upregulated TP-mediated osteoblastogenesis in MC3T3-E1 osteoblast precursors. MC3T3-E1 cells exposed to TPs induced phosphorylation of Akt and ERK further upregulated by the addition of anti-sema4D-mAb, suggesting the suppressive effects of TP-expressing Sema4D on osteoblastogenesis. On the other hand, TPs promoted RANKL-mediated osteoclastogenesis in the primary culture of bone-marrow-derived mononuclear cells (BMMCs). Among the known three receptors of Sema4D, including Plexin B1, Plexin B2 and CD72, little Plexin B2 was detected, and no Plexin B1 was detected, but a high level of CD72 mRNA was detected in RANKL-stimulated BMMCs by qPCR. Both anti-Sema4D-mAb and anti-CD72-mAb suppressed RANKL-induced osteoclast formation and bone resorptive activity, suggesting that Sema4D released by TPs promotes osteoclastogenesis via ligation to a CD72 receptor. This study demonstrated that Sema4D released by TPs suppresses osteogenic activity and promotes osteoclastogenesis, suggesting the novel property of platelets in bone-remodeling processes. 相似文献
33.
Sashihara T Sueki N Furuichi K Ikegami S 《International journal of food microbiology》2007,120(3):274-281
Lactobacillus gasseri OLL2809, a probiotic lactic acid bacterium, strongly stimulates interleukin (IL)-12 (p70) production by murine splenocytes; therefore, it is expected to ameliorate allergic diseases. Although many studies have investigated characteristics of the immunostimulatory activity of probiotics, little is known about how bacterial growth conditions affect the activity. In this study, we investigated the effects of the growth conditions of L. gasseri OLL2809 on the stimulation of IL-12 (p70) production. L. gasseri OLL2809 was grown under various culture conditions including different cultivation periods, media, and culture pH, and IL-12 (p70) production by murine splenocytes stimulated with these bacterial cells was determined. The results revealed that IL-12 (p70) production (i) increased with the growth of the bacterial cells and was higher in stationary-phase cells than in logarithmic-phase cells; (ii) it was higher in the cells grown in acidic pH; and (iii) it decreased when the cells were incubated in a buffer at neutral pH prior to heat treatment. These observations indicated that stimulation of IL-12 (p70) production is affected by culture medium pH. In addition, the observations of a difference in the stimulation of IL-12 (p70) production by L. gasseri OLL2809 grown under various conditions are consistent with the characteristics of autolysis. Therefore, it was deduced that the integrity of the bacterial cells is necessary for the stimulatory effect on IL-12 (p70) production and that acidic pH and heat treatment contributed to the stimulation by inhibiting the activity of autolysins indigenous to the bacteria. Our result suggests that cultivation until the stationary phase under acidic pH is required for the effective production of probiotics with immunostimulatory activity. 相似文献
34.
Cationic chitosan (CT) and anionic dextran sulfate (Dex) were layer-by-layer (LbL) assembled from aqueous solutions containing
1 M NaCl on a quartz crystal microbalance (QCM) substrate, and the original films ((CT-Dex)3-CT)) were end-capped with LbL assembly from CT solutions containing 1 M NaCl and Dex solutions without NaCl. The enzymatic
degradation of films by chitosanase was quantitatively analyzed by QCM in terms of numbers of end-capping steps. The degradation
of films end-capped with (Dex-CT)3 was considerably prolonged when compared to those end-capped with other end-capping steps. A mechanism for the prolonged
degradation was proposed by quantitative QCM data and zeta potential results. 相似文献
35.
Matsui T Matsumura K Hagisawa K Ishihara M Ishizuka T Suzuki M Kurita A Kikuchi M 《IEEE transactions on bio-medical engineering》2002,49(6):621-623
The purpose of this study is to investigate the vascular wall with a thermally self-regulating, cylindrical stent made of a low Curie temperature ferromagnetic alloy. Physiologic saline was circulated in the silicone model vessel implanted with the stent. The stent-temperature remained nearly constant for variable saline flows, saline temperatures, and magnetic flux densities. Stent implants of this type in human blood vessels could potentially enable thermotherapy and temperature determination without catheterization. 相似文献
36.
We demonstrate a novel method of equalizing a laser diode (LD) beam into a circular beam. This method uses the twist effect of graded index (GI) fiber optics. An asymmetric LD beam with beam qualities of M2 = 500 in the slow axis and M2 = 4 in the fast axis is converted successfully into a symmetric circular beam with a beam quality of M2 = 175. The circular-output beam with 92% coupling efficiency from the fiber input to the fiber output is obtained with a 5-m-long GI1200 (1200 means a core diameter of 1200 microm) fiber for a 2-W LD array. We extend the experiments to a higher-power source with higher asymmetric beam qualities of M2 = 3000 and M2 = 4. By slightly bending the GI10000 (10000 means a core diameter of 10,000 microm) fiber, we have succeeded in generating a symmetric beam with a improved beam quality of M2 = 2000. The average beam quality is preserved when the asymmetric ratio is not high, and the beam quality degradation ratio is investigated up to asymmetric ratios of 750. 相似文献
37.
Keisuke Omae In-Tae Bae Muneyuki Naito Manabu Ishimaru Yoshihiko Hirotsu James A. Valdez Kurt E. Sickafus 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2006,250(1-2):300-302
We have performed high-dose Fe ion implantation into Si and characterized ion-beam-induced microstructures as well as annealing-induced ones using transmission electron microscopy (TEM) and grazing-incidence X-ray diffraction (GIXRD). Single crystals of Si(1 0 0) substrate were irradiated at 623 K with 120 keV Fe+ ions to a fluence of 4 × 1017 cm−2. The irradiated samples were then annealed in a vacuum furnace at temperatures ranging from 773 K to 1073 K. Cross-sectional TEM observations and GIXRD measurements revealed that a layered structure is formed in the as-implanted specimen with ε-FeSi, β-FeSi2 and damaged Si, as component layers. A continuous β-FeSi2 layer was formed on the topmost layer of the Si substrate after thermal annealing. 相似文献
38.
Keisuke Hachisuka Teruhito Takeda Yusuke Terauchi Ken Sasaki Hiroshi Hosaka Kiyoshi Itao 《Microsystem Technologies》2005,11(8-10):1020-1027
Intra-body communication is a wireless means of exchanging information within a personal area network (PAN) between wearable electronic sensors and devices. The feasibility of intra-body communication is confirmed through several experiments on signal propagation within the human body, and a human phantom is designed and used to obtain reproducible results over repeated experiments. Based on the results of these experiments, a prototype transmission system is constructed using aluminum electrodes powered by 3 V DC and operating in the 10.7 MHz frequency modulation (FM) band. This prototype is demonstrated to be capable of transmitting analog signals through the human subjects in the presence of external noise. Digital data transmission at 9600 bps is also achieved using newly fabricated 10.7 MHz frequency shift keying (FSK) transmitter and receiver devices. The carrier frequency of 10.7 MHz is the intermediate frequency of FM radio receivers, meaning that the proposed system can make use of a wide selection of inexpensive, commercial radio frequency devices. 相似文献
39.
Daisuke Nagamatsu Masanori Maeda Keisuke Hashimoto Kenji Okumoto Hiroshi Kageyama Yasuhiko Shirota 《Journal of the Society for Information Display》2005,13(5):399-404
Abstract— A novel emitting vinyl polymer, poly[4‐(7‐{4‐[N,N‐bis(9,9‐dimethylfluoren‐2‐yl)amino]phenyl}‐2,1,3‐benzothiadiazol‐4‐yl)phenylethylene] (PVFABT), was designed and synthesized. The new vinyl polymer was found to form smooth amorphous films with a high glass‐transition temperature of 199°C. The polymer possesses bipolar character with both electron‐donating and accepting properties. It undergoes reversible anodic oxidation and cathodic reduction to give stable cation and anion radicals. It exhibits intense orange fluorescence in solution and as film. A multilayer organic electroluminescent device using PVFABT as an emitting material emitted orange light, exhibiting high performance. 相似文献
40.
Kurita H. Shimizu T. Yokoyama H. 《IEEE journal of selected topics in quantum electronics》1996,2(3):508-513
We investigated the detailed characteristics of synchronization of mode-locked laser diodes (MLLD's) by subharmonic optical pulse injection. It was shown that optical harmonic injection mode-locking was not very sensitive to injection pulse shapes. In the time domain, subharmonic injection pulses were multiplexed inside the MLLD and these multiplexed pulses effectively modulated the absorbance of the saturable absorber at the MLLD's repetition frequency. It was also found in the spectral domain that injection pulse trains should have optical spectrum components broader than the MLLD's intermode spacing, and injection spectral components should couple to at least two modes of the MLLD 相似文献