76 results on '"Yamaguchi, Masayuki"'
Search Results
2. Retrospective details of false-positive and false-negative results in non-invasive prenatal testing for fetal trisomies 21, 18 and 13
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Suzumori, Nobuhiro, Sekizawa, Akihiko, Takeda, Eri, Samura, Osamu, Sasaki, Aiko, Akaishi, Rina, Wada, Seiji, Hamanoue, Haruka, Hirahara, Fumiki, Sawai, Hideaki, Nakamura, Hiroaki, Yamada, Takahiro, Miura, Kiyonori, Masuzaki, Hideaki, Nakayama, Setsuko, Kamei, Yoshimasa, Namba, Akira, Murotsuki, Jun, Yamaguchi, Masayuki, Tairaku, Shinya, Maeda, Kazuhisa, Kaji, Takashi, Okamoto, Yoko, Endo, Masayuki, Ogawa, Masaki, Kasai, Yasuyo, Ichizuka, Kiyotake, Yamada, Naoki, Ida, Akinori, Miharu, Norio, Kawaguchi, Satoshi, Hasuo, Yasuyuki, Okazaki, Tetsuya, Ichikawa, Mayuko, Izumi, Shunichiro, Kuno, Naohiko, Yotsumoto, Junko, Nishiyama, Miyuki, Shirato, Nahoko, Hirose, Tatsuko, and Sago, Haruhiko
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- 2021
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3. Control of optical and mechanical properties of poly(methyl methacrylate) by introducing lithium salt
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Ito, Asae, Maeno, Ryota, and Yamaguchi, Masayuki
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- 2018
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4. Birefringence control of solution-cast film of cellulose triacetate
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Kiyama, Ayumi, Nobukawa, Shogo, and Yamaguchi, Masayuki
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- 2017
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5. Flow property at capillary extrusion for ethylene–tetrafluoroethylene copolymer
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Kotera, Seigo and Yamaguchi, Masayuki
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- 2015
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6. Rheological characterization on thermal degradation of ethylene-tetrafluoroethylene copolymer
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Kotera, Seigo and Yamaguchi, Masayuki
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- 2014
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7. Incorporation of low-mass compound to alter the orientation birefringence in cellulose acetate propionate
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Abd Manaf, Mohd Edeerozey, Miyagawa, Azusa, Nobukawa, Shogo, Aoki, Yoshihiko, and Yamaguchi, Masayuki
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- 2013
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8. Preparation of highly dispersible and tumor-accumulative, iron oxide nanoparticles: Multi-point anchoring of PEG- b-poly(4-vinylbenzylphosphonate) improves performance significantly
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Ujiie, Kodai, Kanayama, Naoki, Asai, Kei, Kishimoto, Mikio, Ohara, Yusuke, Akashi, Yoshimasa, Yamada, Keiichi, Hashimoto, Shinji, Oda, Tatsuya, Ohkohchi, Nobuhiro, Yanagihara, Hideto, Kita, Eiji, Yamaguchi, Masayuki, Fujii, Hirofumi, and Nagasaki, Yukio
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- 2011
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9. Interdiffusion of dangling chains in weak gel and its application to self-repairing material
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Yamaguchi, Masayuki, Ono, Susumu, and Okamoto, Kenzo
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- 2009
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10. Growth pressure dependence of neighboring mask interference in densely arrayed narrow-stripe selective MOVPE for integrated photonic devices
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Sudo, Shinya, Yokoyama, Yoshitaka, Nakazaki, Tadashi, Mori, Kazuo, Kudo, Koji, Yamaguchi, Masayuki, and Sasaki, Tatsuya
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- 2000
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11. Pegbelfermin in Patients With Nonalcoholic Steatohepatitis and Compensated Cirrhosis (FALCON 2): A Randomized Phase 2b Study.
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Abdelmalek, Manal F., Sanyal, Arun J., Nakajima, Atsushi, Neuschwander-Tetri, Brent A., Goodman, Zachary D., Lawitz, Eric J., Harrison, Stephen A., Jacobson, Ira M., Imajo, Kento, Gunn, Nadege, Halegoua-DeMarzio, Dina, Akahane, Takemi, Boone, Bradly, Yamaguchi, Masayuki, Chatterjee, Arkendu, Tirucherai, Giridhar S., Shevell, Diane E., Du, Shuyan, Charles, Edgar D., and Loomba, Rohit
- Abstract
Pegbelfermin is a polyethylene glycol–conjugated analog of human fibroblast growth factor 21, a nonmitogenic hormone that regulates energy metabolism. This phase 2b study evaluated 48-week pegbelfermin treatment in patients with nonalcoholic steatohepatitis (NASH) with compensated cirrhosis. FALCON 2 (NCT03486912) was a randomized (1:1:1:1), double-blind, placebo-controlled study. Eligible adults had biopsy-confirmed NASH and stage 4 fibrosis. Pegbelfermin (10, 20, or 40 mg) or placebo was injected subcutaneously once weekly. The primary endpoint was 1 or more stages of improvement in the NASH Clinical Research Network fibrosis score without NASH worsening at week 48; pegbelfermin dose response was assessed using a Cochran–Armitage trend test across proportions (1-sided α =.05). Additional endpoints included histologic and noninvasive measures of steatosis, fibrosis, and liver injury/inflammation. Overall, 155 patients were randomized, and 154 patients received treatment. At week 48, 24% to 28% of the pegbelfermin arms had primary endpoint responses vs 31% of the placebo arm (P =.361). Nonalcoholic fatty liver disease activity score improvements were more frequent with pegbelfermin vs placebo and were driven primarily by reduced lobular inflammation. Numerically higher proportions of the pegbelfermin arms had liver stiffness (magnetic resonance elastography) and steatosis (magnetic resonance imaging-proton density fat fraction) improvements vs placebo; these differences were not statistically significant. Mean N-terminal type III collagen propeptide, alanine aminotransferase, and aspartate aminotransferase values were numerically lower in the 20- and/or 40-mg pegbelfermin arms compared with placebo. Serious adverse events were more frequent with pegbelfermin vs placebo, although none were treatment related. One patient (40-mg pegbelfermin) discontinued treatment because of a treatment-emergent adverse event (worsening ascites). FALCON 2 did not meet its primary endpoint of 1 or more stages of improvement in the NASH Clinical Research Network fibrosis without NASH worsening assessed via biopsy. Pegbelfermin generally was well tolerated in this advanced NASH population. [Display omitted] [ABSTRACT FROM AUTHOR]
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- 2024
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12. Pegbelfermin in Patients With Nonalcoholic Steatohepatitis and Stage 3 Fibrosis (FALCON 1): A Randomized Phase 2b Study.
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Loomba, Rohit, Sanyal, Arun J., Nakajima, Atsushi, Neuschwander-Tetri, Brent A., Goodman, Zachary D., Harrison, Stephen A., Lawitz, Eric J., Gunn, Nadege, Imajo, Kento, Ravendhran, Natarajan, Akahane, Takemi, Boone, Bradly, Yamaguchi, Masayuki, Chatterjee, Arkendu, Tirucherai, Giridhar S., Shevell, Diane E., Du, Shuyan, Charles, Edgar D., and Abdelmalek, Manal F.
- Abstract
Pegbelfermin is a polyethlene glycol–conjugated analog of human fibroblast growth factor 21, a nonmitogenic hormone that regulates energy metabolism. This phase 2b study evaluated 48-week pegbelfermin treatment in patients with nonalcoholic steatohepatitis (NASH) and stage 3 (bridging) fibrosis. The FALCON 1 study (NCT03486899) was a multicenter, randomized (1:1:1:1), double-blind, placebo-controlled study. Patients with biopsy-confirmed NASH and stage 3 fibrosis (N = 197) received weekly subcutaneous pegbelfermin (10, 20, or 40 mg) or placebo injections for 48 weeks. The week 24 primary endpoint was a ≥1-point decrease in fibrosis score without NASH worsening or NASH improvement without fibrosis worsening; pegbelfermin dose response was assessed using a Cochran-Armitage trend test across proportions (1-sided α = 0.05). Secondary/exploratory endpoints included histological and noninvasive measures of steatosis, fibrosis, and liver injury/inflammation. At week 24, the primary endpoint was met by 14% (placebo) vs 24%–31% (pegbelfermin arms); statistical significance was not reached due to lack of pegbelfermin dose response (P =. 134). At weeks 24 and 48, more patients who received pegbelfermin had ≥30% relative reductions in hepatic fat fraction (magnetic resonance imaging-proton density fat fraction) vs placebo, although no differences reached statistical significance. In the pegbelfermin arms, improvements in liver fibrosis (magnetic resonance elastography and N-terminal type III collagen propeptide) and liver injury/inflammation (alanine aminotransferase, aspartate aminotransferase) were observed vs placebo. Adverse events occurred at similar frequencies across arms. No treatment-related serious adverse events were observed. The FALCON 1 study did not meet its primary endpoint; a ≥1-point decrease in fibrosis score without NASH worsening or NASH improvement without fibrosis worsening assessed via biopsy. Pegbelfermin was generally well tolerated during 48 weeks of treatment. [Display omitted] [ABSTRACT FROM AUTHOR]
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- 2024
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13. Successful treatment of advanced squamous cell carcinoma arising from mature cystic teratoma of the ovary with homologous recombination deficiency: A case report.
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Tamura, Ryo, Yamaguchi, Masayuki, Kitani, Yohei, Nishikawa, Nobumichi, Kawasaki, Takashi, and Kikuchi, Akira
- Abstract
Squamous cell carcinoma (SCC) arising from mature cystic teratoma of the ovary (MCT-SCC) has a poor prognosis at advanced stages. Although the relationship between homologous recombination deficiency (HRD) and platinum-based chemotherapy sensitivity or poly (ADP ribose) polymerase (PARP) inhibitor efficacy in epithelial ovarian cancer has been demonstrated in clinical trials, the significance of HRD status in MCT-SCC has not previously been described. A 73-year-old woman underwent emergency laparotomy due to ovarian tumor rupture. The ovarian tumor was strongly adherent to the surrounding pelvic organs and could not be completely resected. The postoperative diagnosis was stage IIIB MCT-SCC (pT3bNXM0) of the left ovary. After surgery, we conducted the myChoice CDx. The genomic instability (GI) score of 87 was remarkably high, and there was no BRCA1 / 2 pathogenic mutation. After six courses of combination therapy with paclitaxel and carboplatin, the residual tumors had shrunk by 73 %. We performed interval debulking surgery (IDS), and the residual tumors were completely resected. Subsequently, the patient underwent two courses of the combination of paclitaxel, carboplatin, and bevacizumab, followed by maintenance therapy with olaparib and bevacizumab. Twelve months after IDS, no recurrence has been observed. The present case suggests that there are some HRD cases among MCT-SCC patients and that IDS and maintenance therapy with PARP inhibitors may be effective in such cases, as in epithelial ovarian cancer. Although the frequency of HRD-positive status in MCT-SCC remains unknown, HRD testing may provide appropriate treatment options for advanced MCT-SCC. • Squamous cell carcinoma arising from mature cystic teratoma of the ovary (MCT-SCC) has a poor prognosis at advanced stages. • The significance of the homologous recombination deficiency status in MCT-SCC remains unclear. • We presented the case of an MCT-SCC patient with a remarkably high genomic instability score who was successfully treated. [ABSTRACT FROM AUTHOR]
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- 2023
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14. A case–control study of risk factors for placenta previa accreta
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Yamaguchi, Masayuki, Hyuga, Taeko, Yoshida, Kunihiko, Itsukaichi, Mina, Nonaka, Taro, Haino, Kazufumi, Enomoto, Takayuki, and Takakuwa, Koichi
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- 2016
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15. Analysis of pregnant women with inflammatory bowel disease in our hospital
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Yoshida, Kunihiko, Hyuga, Taeko, Sugino, Kentaro, Yamaguchi, Manako, Tamura, Tomoko, Nonaka, Taro, Haino, Kazufumi, Yamaguchi, Masayuki, Takakuwa, Koichi, and Enomoto, Takayuki
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- 2016
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16. Pharmacokinetic Modeling to Simulate the Concentration-Time Profiles After Dermal Application of Rivastigmine Patch.
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Nozaki, Sachiko, Yamaguchi, Masayuki, and Lefèvre, Gilbert
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ACETYLCHOLINESTERASE inhibitors , *PHARMACOKINETICS , *TRANSDERMAL medication , *MEDICATION safety , *DRUG absorption , *COMPUTER simulation - Abstract
Rivastigmine is an inhibitor of acetylcholinesterases and butyrylcholinesterases for symptomatic treatment of Alzheimer disease and is available as oral and transdermal patch formulations. A dermal absorption pharmacokinetic (PK) model was developed to simulate the plasma concentration-time profile of rivastigmine to answer questions relative to the efficacy and safety risks after misuse of the patch (e.g., longer application than 24 h, multiple patches applied at the same time, and so forth). The model comprised 2 compartments which was a combination of mechanistic dermal absorption model and a basic 1-compartment model. The initial values for the model were determined based on the physicochemical characteristics of rivastigmine and PK parameters after intravenous administration. The model was fitted to the clinical PK profiles after single application of rivastigmine patch to obtain model parameters. The final model was validated by confirming that the simulated concentration-time curves and PK parameters (C max and area under the drug plasma concentration-time curve) conformed to the observed values and then was used to simulate the PK profiles of rivastigmine. This work demonstrated that the mechanistic dermal PK model fitted the clinical data well and was able to simulate the PK profile after patch misuse. [ABSTRACT FROM AUTHOR]
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- 2016
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17. Self-repairing property of polymer network with dangling chains
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Yamaguchi, Masayuki, Ono, Susumu, and Terano, Minoru
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- 2007
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18. Clinical usefulness of 2-hydroxyglutarate as a biomarker in IDH-mutant chondrosarcoma.
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Nakagawa, Makoto, Yamaguchi, Masayuki, Endo, Makoto, Machida, Yukino, Hattori, Ayuna, Tanzawa, Fumie, Tsutsumi, Shinji, Kitabayashi, Issay, Kawai, Akira, and Nakatani, Fumihiko
- Abstract
• 2-HG is expected to be a useful biomarker for diagnosing and treating IDH-mutant tumors. • Both intratumoral and serum levels of 2-HG were significantly higher in IDH-mutant tumors. • Serum 2-HG levels were correlated with tumor volume and tumor progression. • MR spectroscopy (MRS) detected 2-HG peaks in a xenograft model of IDH-mutant chondrosarcoma. • In vivo MRS can be a useful tool for determining the therapeutic effect of mutant IDH inhibitors. Chondrosarcoma is a common form of malignant bone tumor with limited treatment options. Approximately half of chondrosarcomas harbor gain-of-function mutations in isocitrate dehydrogenase (IDH), and mutant IDH produces 2-hydroxyglutarate (2-HG), which is an oncometabolite that contributes to malignant transformation. Therefore, inhibiting 2-HG production is a novel and promising treatment for advanced chondrosarcoma. 2-HG is also expected to be a useful biomarker for the diagnosis and treatment of IDH-mutant tumors. However, few studies have confirmed this using chondrosarcoma clinical specimens. Non-invasive monitoring of 2-HG levels is useful to infer that mutant IDH inhibitors reach therapeutic targets and to confirm their therapeutic efficacy in clinical practice. To evaluate the clinical utility of 2-HG as a surrogate biomarker for diagnosis and therapeutic efficacy, we measured intra-tumor and serum levels of 2-HG using frozen tissues and peripheral blood from patients with chondrosarcoma. We also developed a non-invasive method to detect intra-tumor 2-HG signals in vivo using magnetic resonance spectroscopy (MRS) Both intratumoral and serum 2-HG levels were significantly elevated in IDH-mutant tumors, and these levels correlated with decreased survival. Furthermore, we detected intratumoral 2-HG peaks using MR spectroscopy in a xenograft model of IDH-mutant chondrosarcoma, and observed that 2-HG peak signals disappeared after administering an inhibitor of mutant IDH1. Our findings suggest that both intratumoral and serum 2-HG levels represent potentially useful biomarkers for IDH-mutant tumors and that the 2-HG signal in MR spectra has potential value as a non-invasive biomarker. Taken together, these findings may positively impact the clinical development of mutant IDH inhibitors for the treatment of advanced chondrosarcoma. [ABSTRACT FROM AUTHOR]
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- 2022
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19. Flow instability for binary blends of linear polyethylene and long-chain branched polyethylene
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Mieda, Naoya and Yamaguchi, Masayuki
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POLYETHYLENE , *RHEOLOGY , *POLYMERS , *SHEAR (Mechanics) , *FRACTURE mechanics , *ANGLES - Abstract
Abstract: The rheological properties and flow instability are studied for binary blends composed of a long-chain branched polyethylene and a linear polyethylene. It is found that the blends containing a linear-polyethylene with high shear viscosity exhibit higher oscillatory moduli, drawdown force, and strain-hardening behavior. The blends showing the anomalous rheological phenomena show sharkskin failure in low shear rate region as compared with a pure linear polyethylene. Moreover, the blends exhibit severe gross melt fracture at low output rate. Enhanced strain-hardening in elongational viscosity and large entrance angle at a die entry will be responsible for the severe gross melt fracture for the blends. [ABSTRACT FROM AUTHOR]
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- 2011
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20. Modification of orientation birefringence of cellulose ester by addition of poly(lactic acid)
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Yamaguchi, Masayuki, Lee, SoYoung, Manaf, Mohd Edeerozey Abd, Tsuji, Manami, and Yokohara, Tadashi
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DOUBLE refraction , *CELLULOSE esters , *LACTIC acid , *PROPIONATES , *ANISOTROPY , *PHASE separation method (Engineering) , *BIOMASS chemicals , *BIOPOLYMERS - Abstract
Abstract: Effect of the addition of poly(lactic acid) (PLA) to cellulose acetate propionate (CAP) on the optical anisotropy is studied considering the morphology and molecular orientation. It is found that PLA is miscible with CAP when the amount of PLA is less than 3 wt.%. The dissolution of PLA chains having large intrinsic birefringence into CAP phase enhances the orientation birefringence of a stretched film, although the viscosity and thus the relaxation time of PLA is significantly shorter than those of CAP. The high level of orientation of PLA chains without relaxation is attained by the cooperative alignment with CAP chains. As a result, a retardation film having appropriate birefringence can be designed by polymer blends composed of biomass-based materials. When the amount of PLA is more than 3 wt.%, however, phase separation occurs. In the case of the blends with phase-separated morphology, the orientation birefringence is not greatly enhanced by blending PLA, because the molecular orientation of PLA in PLA phase relaxes immediately as compared with that of CAP. [ABSTRACT FROM AUTHOR]
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- 2010
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21. Plywood-like structure of injection-moulded polypropylene
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Yamaguchi, Masayuki, Irie, Yuta, Phulkerd, Panitha, Hagihara, Hiroki, Hirayama, Soichiro, and Sasaki, Shintaro
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POLYPROPYLENE , *NUCLEATION , *INJECTION molding of plastics , *MOLECULAR structure , *MECHANICAL properties of polymers , *LAYER structure (Solids) - Abstract
Abstract: Injection-moulded products having unique structure, in which the direction of molecular orientation in the skin layer is perpendicular to that in the core layer, are developed employing isotactic polypropylene with a nucleating agent. The extraordinary three-layered structure with β trigonal crystal form in the core layer, which shows higher impact strength than the conventional α monoclinic form, leads to high level of toughness. Moreover, an injection-moulded product having five-layered structure is also demonstrated in this paper. Because of the complicated crack propagation nature due to the abrupt change of molecular orientation, which avoids fractured pieces with sharp-edge, the products with plywood-like structure will be employed in various applications to improve the safety. [ABSTRACT FROM AUTHOR]
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- 2010
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22. Role of Rigid–Amorphous chains on mechanical properties of polypropylene solid using DSC, WAXD, SAXS, and Raman spectroscopy.
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Kida, Takumitsu and Yamaguchi, Masayuki
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CRYSTAL defects , *ANNEALING of crystals , *DIFFERENTIAL scanning calorimetry , *STRESS-strain curves , *CRYSTAL structure - Abstract
We evaluated the rigid–amorphous (RA) fraction of isotactic polypropylene (iPP) samples by various measurement techniques and investigated the role of the RA chains on the mechanical properties of iPP. The RA fraction was increased by annealing above the α -relaxation temperature, although the RA fraction was almost independent of the molecular weight. The RA fraction obtained by differential scanning calorimetry increased linearly with the number of consecutive helical chains with 12–14 monomer units, suggesting that the RA chains are attributable to crystalline defects. Moreover, the α -relaxation temperature varied linearly with the RA fraction; the RA chains present as crystalline defects were removed from the crystalline structure by α relaxation. The yielding region of the stress–strain curve became broad by increasing the RA fraction; the fragmentation strength of the lamellar crystals was widely distributed owing to the large number of crystalline defects. [Display omitted] • We evaluated the rigid–amorphous fraction of isotactic polypropylene. • A large number of rigid–amorphous chains were located in crystals as defects. • Rigid–amorphous chains are excluded from the crystals by annealing at 100 °C. • The yielding deformation broadened with increasing rigid–amorphous fraction. [ABSTRACT FROM AUTHOR]
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- 2022
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23. Anomalous molecular orientation of isotactic polypropylene sheet containing N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide
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Yamaguchi, Masayuki, Fukui, Takashi, Okamoto, Kenzo, Sasaki, Shintaro, Uchiyama, Yohei, and Ueoka, Chiaki
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MOLECULAR rotation , *POLYPROPYLENE , *NAPHTHALENE , *CRYSTALLIZATION , *NUCLEATION , *CRYSTAL growth - Abstract
Abstract: Small amount of N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide as a β-form nucleating agent is dissolved beyond 280°C in a molten isotactic polypropylene (iPP) and appears as needle crystals around at 240°C during cooling procedure. Further, iPP molecules crystallize on the surface of the needle crystals, in which c-axis of the β-form iPP crystals grows perpendicular to the long axis of the needle crystals. Under flow field at extrusion processing, the needle crystals orient to the flow direction prior to the crystallization of iPP. As a result, c-axis of the β-form iPP crystals orients perpendicular to the applied flow direction with a small amount of α-form iPP. Moreover, the vertical molecular orientation of the extruded sheet sample is responsible for unique mechanical anisotropy; the fracture occurs along the transversal direction. [Copyright &y& Elsevier]
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- 2009
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24. Control of optical anisotropy of cellulose esters and their blends with plasticizer
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Yamaguchi, Masayuki, Iwasaki, Takuya, Okada, Kyoko, and Okamoto, Kenzo
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DOUBLE refraction , *ANISOTROPY , *CELLULOSE esters , *PLASTICIZERS , *BIOPOLYMERS , *VISCOELASTICITY , *MIXING of plastics - Abstract
Abstract: Orientation birefringence of various cellulose esters, such as cellulose triacetate, cellulose acetate propionate and cellulose acetate butyrate, and their blends with a plasticizer are studied. It is found that propionyl and butyryl groups show positive orientation birefringence, whereas the acetyl group exhibits negative birefringence. These results indicate that a cellulose ester with an appropriate composition of ester groups shows no orientation birefringence, irrespective of the molecular orientation. Further, photoelastic birefringence of cellulose esters in the glassy state is also investigated, and is found to be more pronounced with increasing butyryl group content. Moreover, the addition of the plasticizer affects both the orientation and photoelastic birefringences. It should be noted that the magnitude of these birefringences is dependent on the plasticizer species. Plasticizers with a large solubility parameter enhance the birefringence, whereas those with a small solubility parameter decrease it. Moreover, infrared dichroic measurements suggest that the orientation birefringence is mainly determined by the polarizability anisotropy of the ester groups, which is affected by the plasticizer. [Copyright &y& Elsevier]
- Published
- 2009
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25. Structure and properties for biomass-based polyester blends of PLA and PBS
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Yokohara, Tadashi and Yamaguchi, Masayuki
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LACTIC acid , *LACTATES , *BUTENE , *RHEOLOGY , *CRYSTALLIZATION - Abstract
Abstract: Structure and properties are studied for binary blends composed of poly(lactic acid) (PLA) and poly(butylene succinate) (PBS). The rheological measurements in the molten state reveal that the entanglement molecular weight of PLA is lower than that of PBS. Further, the interfacial tension of the immiscible blend system is evaluated employing a rheological emulsion model and found to be 3.5 [mN/m]. Moreover, thermal analysis directly detects that addition of PBS enhances the crystallization of PLA even though PBS is in a molten state. Further, the cold-crystallization for quenched blends occurs at lower temperature than that for a quenched PLA. This would be attributed to the nucleating ability of PBS, leading to generation of PLA crystallites during the quench operation. [Copyright &y& Elsevier]
- Published
- 2008
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26. Birefringence control for binary blends of cellulose acetate propionate and poly(vinyl acetate)
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Yamaguchi, Masayuki and Masuzawa, Kenji
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CELLULOSE , *ACETATES , *PROPIONATES , *PHASE separation method (Engineering) , *BIOMASS - Abstract
Abstract: Structure and optical properties for binary blends composed of biomass-based cellulose acetate propionate (CAP) and poly(vinyl acetate) (PVAc) have been studied. It is found that the blends exhibit high level of transparency, although the dynamic mechanical analysis in the solid state suggests that phase separation occurs in the blend. Furthermore, the birefringence resulting from molecular orientation decreases with increasing the content of PVAc. In particular, the blend with approximately 50wt% of PVAc exhibits no birefringence even after stretching. [Copyright &y& Elsevier]
- Published
- 2007
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27. Effect of thermal degradation on rheological properties for poly(3-hydroxybutyrate)
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Yamaguchi, Masayuki and Arakawa, Keiichi
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RHEOLOGY , *TEMPERATURE , *VISCOSITY , *BONE fractures , *SCISSION (Chemistry) , *MOLECULAR weights , *RHEOMETERS - Abstract
Abstract: Thermal degradation at processing temperature and the effect on the rheological properties for poly(3-hydroxybutyrate) have been studied by means of oscillatory shear modulus and capillary extrusion properties, with the aid of molecular weight measurements. Thermal history at processing temperature depresses the viscosity because of random chain scission. As a result, gross melt fracture hardly takes place with increasing the residence time in a capillary rheometer. Moreover, it was also found that the molecular weight distribution is independent of the residence time, whereas the inverse of the average molecular weight is proportional to the residence time. Prediction of average molecular weight with a constant molecular weight distribution makes it possible to calculate the flow curve following generalized Newtonian fluid equation proposed by Carreau as a function of temperature as well as the residence time. [Copyright &y& Elsevier]
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- 2006
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28. Impact of processing history on rheological properties for branched polypropylene
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Yamaguchi, Masayuki and Wagner, Manfred H.
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RHEOLOGY , *POLYPROPYLENE , *AUTOCLAVES , *LOW density polyethylene , *THERMOPLASTICS - Abstract
Abstract: The impact of applied processing history and the post-processing annealing procedure on the rheological properties of long-chain branched polypropylene (B-PP) have been studied intensively as compared with conventional linear polypropylene (L-PP) and low-density polyethylene (LDPE) produced by autoclave process. It was found that drawdown force, as a measure of melt elasticity for B-PP, is greatly depressed even by the short-time processing in an internal batch mixer, whereas the rheological properties of L-PP are unchanged by the processing history. Considering that the drawdown force is recovered to the original value during the post-processing annealing, the phenomenon is ascribed to the conformation change related to the branch structure, i.e. the alignment of long branches to a backbone chain, which is known as ‘shear modification’. Further, it is demonstrated that the depression of the drawdown force for B-PP is more significant than that for LDPE. Moreover, it is also clarified that B-PP needs a longer post-processing annealing time to recover the drawdown force than LDPE. The difference in the recovery curves during the annealing suggests that B-PP has less relatively ‘short’ long branches. [Copyright &y& Elsevier]
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- 2006
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29. Relation between molecular structure and flow instability for ethylene/α-olefin copolymers
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Yamaguchi, Masayuki, Miyata, Hiroshi, Tan, Victor, and Gogos, Costas G.
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ETHYLENE , *ALKENES , *COPOLYMERS - Abstract
Surface instabilities in a capillary extrusion have been studied for various ethylene/α-olefin copolymers. It is found that the onset stress of shark-skin failure for ethylene/1-hexene copolymer (EHR) decreases rapidly with increasing 1-hexene content, whereas that of ethylene/propylene copolymer (EPR) is independent of propylene content in the experimental region. Consequently, EHR with high 1-hexene content exhibits shark-skin at low stress level compared to EPR. Lower rubbery plateau modulus, leading to higher Deborah number at the same stress level, is attributed to the lower onset stress. Further, the low entanglement density will cause cracks at lower stress level like glassy polymers, which is also responsible for the low onset stress for shark-skin. [Copyright &y& Elsevier]
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- 2002
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30. Effect of water absorption on the structure and properties of isosorbide-based polycarbonate.
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Miyashita, Maho and Yamaguchi, Masayuki
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POLYCARBONATES , *GLASS transition temperature , *YOUNG'S modulus , *YIELD stress , *REFRACTIVE index , *CARBONYL group - Abstract
The structure and properties of isosorbide-based polycarbonate (ISB-PC), and its responses to water absorption were investigated. Although the glass transition temperature of an ISB-PC film decreased as its water content increased, its Young's modulus increased as the strain at break decreased. The tensile yield stress of the polymer decreased following water absorption. Optical properties such as the refractive index and the photoelastic coefficient in the glassy state were also affected by water absorption. The refractive index increased with the water content, although the refractive index of water is lower than that of the polymer. The photoelastic coefficient reached a maximum at a specific water content. These phenomena can be explained by the interaction between water molecules and the carbonyl groups in the polymer, which affect the segmental mobility and polarizability anisotropy of ISB-PC. Basic properties such as entanglement molecular weight were also determined. Image 1 • Basic properties such as Me of isosorbide-based polycarbonate were clarified. • An increase in water content reduced the strain at break and increased the Young's modulus. • The yield stress decreased with increasing the water content. • The stress-optical coefficient is a function of water content. • Interaction with water molecules affects the chain mobility and polarizability anisotropy. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
31. Pronounced shear-induced crystallization of polypropylene by addition of poly(methyl methacrylate).
- Author
-
Kitabatake, Shion, Janchai, Khunanya, and Yamaguchi, Masayuki
- Subjects
- *
METHYL methacrylate , *CRYSTALLIZATION , *POLYPROPYLENE , *MOLECULAR weights , *POLYMER blends , *HIGH temperatures - Abstract
The shear-induced crystallization of polypropylene (PP) in immiscible blends with poly(methyl methacrylate) (PMMA) was studied using three types of PMMA samples with different molecular weights. The addition of low-molecular-weight PMMA greatly enhanced the shear-induced crystallization of PP. Because the low-molecular-weight PMMA had low viscosity at high temperatures, the PMMA droplets dispersed in the PP were deformed in the flow direction and subsequently turned fibrous. As the temperature decreased, the viscosity of PMMA increased greatly prior to PP crystallization. Consequently, the deformed PMMA dispersions were hardly deformed further in the molten PP. It provided excess stress for PP in the flow direction, leading to a large Rouse-Weissenberg number. They thereby accelerated shear-induced crystallization of the PP. Because of the pronounced shear-induced crystallization, the orientation of the PP chains, which causes high rigidity, was greatly enhanced. [Display omitted] • PMMA with low molecular weight promoted shear-induced crystallization of PP. • Deformed PMMA droplets solidified during cooling and acted as rigid fibers. • Because of pronounced shear-induced crystallization, PP orientation was enhanced. • PMMA with high molecular weight barely affected shear-induced crystallization of PP. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
32. Effect of lithium salt addition on the structure and optical properties of PMMA/PVB blends.
- Author
-
Tsugawa, Naoya, Ito, Asae, and Yamaguchi, Masayuki
- Subjects
- *
LITHIUM , *ALKALI metals , *METHYL methacrylate , *OPTICAL fibers , *GAMMA rays - Abstract
The effect of the lithium trifluoromethanesulfonate (LiCF 3 SO 3 ) addition on the structure and properties for binary blends of poly(methyl methacrylate) (PMMA) and a random copolymer composed of vinyl butyral and vinyl alcohol, that is denoted as PVB in this paper, was evaluated. Although PMMA and PVB are immiscible, the LiCF 3 SO 3 addition enhances the compatibility/miscibility by the ion-dipole interaction between lithium cation and both polymer chains. Only single peak ascribed to the glass-to-rubber transition is detected in the tensile loss modulus curve for PMMA/PVB/LiCF 3 SO 3 (70/30/20), although there are distinct double peaks for PMMA/PVB (70/30). This result demonstrates that the salt, LiCF 3 SO 3 , acts as a compatibilizer. Furthermore, the salt addition enhances the storage modulus in the glassy region and the heat resistance due to the high-temperature-shift of glass transition temperature. The blend containing LiCF 3 SO 3 is highly transparent and shows a significantly small value of the stress-optical coefficient in the glassy state, which are required for various optical films used for display, such as polarizer protective film. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
33. Modification of melt memory effect by addition of poly(butylene terephthalate) to thermoplastic polyester elastomer.
- Author
-
Yamada, Takumi, Kida, Takumitsu, and Yamaguchi, Masayuki
- Subjects
- *
POLYBUTENES , *POLYESTERS , *THERMOPLASTIC elastomers , *GLASS transition temperature , *MELTING points , *PHASE separation , *BUTENE , *MEMORY - Abstract
The structure and properties of a thermoplastic polyester elastomer (TPEE) containing a small amount of poly(butylene terephthalate) (PBT) were investigated by focusing on the residual crystals in the molten state. When the pure TPEE was extruded at a slightly higher temperature than its melting point, the crystallization rate increased. This phenomenon has been called the melt memory effect and has been attributed to unmolten crystals that act as nuclei. The addition of PBT widened the temperature range of the melt memory effect, because PBT crystals were present at the higher temperatures. Moreover, the addition of PBT induced phase separation, leading to a decrease in the dissolution of hard segments in the soft matrix. As a result, the glass transition temperature of the soft matrix decreased. Furthermore, the modulus at room temperature increased with good rubber elasticity. [Display omitted] • Melt memory effect of a thermoplastic polyester elastomer (TPEE) was investigated. • The addition of PBT widened the temperature range that showed melt memory effect. • Tg shifted to low temperature owing to well-developed phase separation. • The modulus of strands increased by the melt memory effect. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
34. A case report of placenta previa percreta with massive hemorrhage in early pregnancy.
- Author
-
Yamaguchi, Masayuki, Yoshida, Kunihiko, Haino, Kazufumi, Takakuwa, Koichi, and Enomoto, Takayuki
- Published
- 2013
- Full Text
- View/download PDF
35. Effect of mixing temperature on the carbon nanofiller distribution in immiscible blends of polycarbonate and polyolefin.
- Author
-
Fan, Bowen, Wiwattananukul, Rujirek, and Yamaguchi, Masayuki
- Subjects
- *
MULTIWALLED carbon nanotube testing , *POLYCARBONATES , *POLYETHYLENE , *POLYMER blend analysis , *CARBON-black - Abstract
We studied the selective localization of carbon nanofillers, such as multi-walled carbon nanotube (MWCNT) and graphene nanoplatelet (GNP), in immiscible polymer blends composed of polycarbonate (PC) and polyethylene (PE) or ethylene-propylene copolymer (EPR). It was found that the distribution state of the carbon nanofillers in the composites is greatly affected by the mixing temperature and the species of nanofillers. MWCNTs resided in the PE or EPR phase in the composites, which cannot be explained by the difference in the interfacial tension. A similar morphology was detected in the PC/GNP/PE composite prepared at 300 °C. In contrast, the PC/GNP/PE composite prepared at the low temperature (250 °C) and the PC/GNP/EPR composites have the carbon nanofillers mostly in the PC phase. The selective localization in the PE or EPR phase is attributed to the surface adsorption of PE or EPR chains on the carbon nanofillers, which is more obvious for PE and at the high mixing temperature. These results demonstrate that both the species of carbon nanofillers and the mixing temperature affect the carbon nanofiller distribution in the immiscible blends. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
36. Improvement of rigidity for rubber-toughened polypropylene via localization of carbon nanotubes.
- Author
-
Wiwattananukul, Rujirek, Fan, Bowen, and Yamaguchi, Masayuki
- Subjects
- *
GEOMETRIC rigidity , *RUBBER , *POLYPROPYLENE , *CARBON nanotubes , *MULTIWALLED carbon nanotubes , *IMMISCIBILITY , *POLYMER blends , *ISOTACTIC polymers - Abstract
A methodology for controlling the localization of multi-walled carbon nanotubes (MWCNTs) was studied using an immiscible polymer blend composed of isotactic polypropylene (PP) and ethylene- co -propylene rubber (EPR). We found that the MWCNTs were localized in EPR domains within the composite, which was prepared at 280 °C. EPR molecules bonded to the MWCNT surface are responsible for the localization in EPR. Conversely, MWCNTs preferentially resided in the matrix when the composite was prepared at 190 °C along with nitrogen gas purging. Because of the selective localization of the MWCNTs in the matrix, the composite obtained via mixing at the lower temperature exhibited a higher Young's modulus and yield strength. These findings demonstrate that mixing conditions greatly affect the MWCNT distribution and thus the mechanical properties of PP/EPR blends. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
37. Monolithically integrated multi-wavelength MQW-DBR laser diodes fabricated by selective metalorganic vapor phase epitaxy
- Author
-
Sasaki, Tatsuya, Yamaguchi, Masayuki, and Kitamura, Mitsuhiro
- Published
- 1994
- Full Text
- View/download PDF
38. Migration-controlled narrow-stripe selective MOVPE for high-quality [formula omitted] MQWs
- Author
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Kudo, Koji, Sasaki, Tatsuya, and Yamaguchi, Masayuki
- Published
- 1997
- Full Text
- View/download PDF
39. Development of microporous structure and its application to optical film for cellulose triacetate containing diisodecyl adipate.
- Author
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Shimada, Hikaru, Nobukawa, Shogo, and Yamaguchi, Masayuki
- Subjects
- *
MICROPOROSITY , *OPTICAL films , *CELLULOSE acetate , *PHASE separation , *BIREFRINGENCE , *ORGANIC solvents , *DISPERSION (Chemistry) - Abstract
Phase separation in plasticized cellulose triacetate (CTA) films is investigated to produce a microporous film that can be used in optical devices. Hot-stretched CTA films containing diisodecyl adipate (DIDA) show negative orientation birefringence similar to the hot-stretched pure CTA. After extracting DIDA from the stretched films by immersion into an organic solvent, however, the films exhibit positive birefringence. Moreover, the magnitude of the birefringence increases with the wavelength, known as extraordinary dispersion, which is an essential property in the preparation of an ideal quarter-wave plate. Numerous ellipsoidal pores with micro-scale were detected in the film after the immersion, indicating that DIDA were segregated and formed ellipsoidal domains in the CTA matrix during annealing and stretching. These results indicate that extraordinary wavelength dispersion is given by the combinations of orientation birefringence from CTA and form birefringence from micropores. Furthermore, it was found that annealing time and stretching condition affect the phase separation as well as the shape and size of pores. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
40. Localization of nanofibers on polymer surface using interface transfer technique
- Author
-
Doan, Vu Anh, Nobukawa, Shogo, and Yamaguchi, Masayuki
- Subjects
- *
NANOFIBERS , *INTERFACES (Physical sciences) , *POLYPROPYLENE , *POLYMER melting , *POLYMERIC composites , *QUENCHING (Chemistry) , *HIGH density polyethylene , *SURFACES (Technology) - Abstract
Abstract: A new method to localize polymer nanofibers on a polymer surface was verified using interface transfer technique of nanofibers between immiscible polymer pairs. Nanofibers of poly(butylene terephthalate) (PBT) were prepared in a molten polypropylene (PP) by melt-stretching and subsequent quenching. The obtained composite of PP containing PBT nanofibers was compressed into a flat sheet and piled with a sheet of high-density polyethylene (HDPE). During annealing procedure of the piled sheets at the temperature between melting points (Tm’s) of PP and PBT, PBT nanofibers were transferred from PP to HDPE. Consequently, PBT fibers was confirmed on the surface of HDPE. Similarly, polytetrafluoroethylene (PTFE) nanofibers dispersed in a molten poly(lactic acid) (PLA), which were obtained by mechanical blending process, were found to immigrate to PP during annealing procedure at the temperature between Tm’s of PLA and PTFE. This movement leads to the modification of surface tension for PP. Furthermore, the piled sheets of PP/PBT and HDPE as well as those of PLA/PTFE and PP were easily separated each other because of the immiscible nature. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
41. Isolation of cancer stem-like cells from a side population of a human glioblastoma cell line, SK-MG-1
- Author
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Fukaya, Raita, Ohta, Shigeki, Yamaguchi, Masayuki, Fujii, Hirofumi, Kawakami, Yutaka, Kawase, Takeshi, and Toda, Masahiro
- Subjects
- *
CANCER cells , *BRAIN tumors , *NEURAL stem cells , *CELL lines , *TUMOR growth , *FLOW cytometry , *BIOMARKERS , *EPIDERMAL growth factor - Abstract
Abstract: Accumulating evidence suggests that in several types of brain tumors, including glioma, only a phenotypic subset of tumor cells called brain cancer stem cells (BCSCs) may be capable of initiating tumor growth. Recently, the isolation of side population (SP) cells using Hoechst dye has become a useful method for obtaining cancer stem cells in various tumors. In this study, we isolated cancer stem-like cells from human glioma cell lines using the SP technique. Flow cytometry analysis revealed that SK-MG-1, a human glioblastoma cell line, contained the largest number of SP cells among the five glioma cell lines that were analyzed. The SP cells had a self-renewal ability and were capable of forming spheres in a neurosphere culture medium containing EGF and FGF2. Spheres derived from the SP cells differentiated into three different lineage cells: neurons, astrocytes and oligodendrocytes. RT-PCR analysis revealed that the SP cells expressed a neural stem cell marker, Nestin. The SP cells generated tumors in the brains of NOD/SCID mice at 8weeks after implantation, whereas the non-SP cells did not generate any tumors in the brain. These results indicate that SP cells isolated from SK-MG-1 possess the properties of cancer stem cells, including their self-renewal ability, multi-lineage differentiation, and tumorigenicity. Therefore, the SP cells from SK-MG-1 may be useful for analyzing BCSCs because of the ease with which they can be handled and their yield. [Copyright &y& Elsevier]
- Published
- 2010
- Full Text
- View/download PDF
42. Carbon nanotube imprinting on a polymer surface
- Author
-
Yoon, Howon, Okamoto, Kenzo, and Yamaguchi, Masayuki
- Subjects
- *
CARBON nanotubes , *MOLECULAR imprinting , *SURFACE chemistry , *POLYCARBONATES , *POLYPROPYLENE , *ELECTRIC conductivity - Abstract
Abstract: Imprinting of multi-walled carbon nanotubes (CNTs) on the surface of a polymer sheet was demonstrated using interphase CNT transfer from one polymer to another. A pure polycarbonate (PC) sheet was placed on top of a sheet of a polypropylene (PP)/CNT composite and annealed at either 200 or 300°C. It was found that CNTs move from the PP/CNT composite to the PC during annealing. The sheets of PP/CNT and PC were easily separated because of the large interfacial tension between PP and PC. The formation of a thin CNT-rich layer on the surface of the separated PC sheet produces electrical conductivity. Consequently, a conductive sheet is obtained with 2wt.% of CNTs only in the thin surface layer. Since the CNT transfer is attributed to Brownian motion, the annealing conditions such as temperature and time are responsible for the diffusion. The polymer species decides the ability of the CNTs to transfer. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
43. Locally administered T cells from mice immunized with lipopolysaccharide (LPS) accelerate LPS-induced bone resorption
- Author
-
Ozaki, Yukio, Ukai, Takashi, Yamaguchi, Masayuki, Yokoyama, Miho, Ayón Haro, Esperanza R., Yoshimoto, Mayumi, Kaneko, Takashi, Yoshinaga, Miho, Nakamura, Hirotaka, Shiraishi, Chiaki, and Hara, Yoshitaka
- Subjects
- *
T cells , *LABORATORY mice , *BONE resorption , *BONE fractures , *OSTEOCLASTS , *POLYSACCHARIDES , *TUMOR necrosis factors - Abstract
Abstract: T cells play important roles in bone destruction and osteoclastogenesis and are found in chronic destructive bone lesions. Lipopolysaccharide (LPS) is one of several pathological factors involved in inflammatory bone destruction. We previously described the importance of T cells in the inflammatory bone resorption that occurs after repeated LPS administration. However, whether local or systemic T cells are important for inflammatory bone resorption and whether immunization of host animals influences bone resorption remain unclear. The present study examines the effects of local extant T cells from LPS-immunized mice on LPS-induced bone resorption. T cells from LPS-immunized or non-immunized mice were injected together with LPS into the gingival tissues of mice with severe combined immunodeficiency disease that lack both T and B cells. We histomorphometrically evaluated bone resorption at sites of T cell injections and examined the influence of T cells from LPS-immunized mice on osteoclastogenesis in vitro. We found that locally administered T cells from LPS-immunized but not non-immunized mice accelerated LPS-induced bone resorption in vivo. Moreover, T cells from LPS-immunized mice increased osteoclastogenesis in vitro induced by receptor activator of NF-κ B ligand and LPS and anti-tumor necrosis factor (TNF)-α antibody inhibited this increase. These results demonstrated that local extant T cells accelerate inflammatory bone resorption. Furthermore, T cells from LPS-immunized mice appear to elevate LPS-induced bone resorption using TNF-α. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
44. Trend of system level design and an approach to C-based design
- Author
-
Kambe, Takashi, Yamada, Akihisa, and Yamaguchi, Masayuki
- Subjects
- *
ARCHITECTURAL design , *SYSTEM analysis - Abstract
System level design study group in EDA technical committee of JEITA has researched the trends of system level design technologies from various aspects of views so as to define an ideal design flow and methodology. The results of the investigations consist of (1) problems and requirements from system level designers (needs), (2) current status of system level design tools (seeds), (3) standardization activities for system level design languages, and so on. They also proposed a desirable system level design flow taking account of the needs and the seeds.In this paper, we introduce the summary of their works. After that, I describe an approach to a C-based architecture design, called Bach, which we have developed. The features of the Bach system are (1) C-based user language with untimed semantics which is suitable for large-scale circuit design, (2) a fast bit-accurate simulator at the C level, (3) a high level synthesizer which can compile a program describing the untimed behavior of hardware into RTL VHDL. Using the example of an MPEG-4 video codec design, we summarize its design flow and effects. [Copyright &y& Elsevier]
- Published
- 2002
- Full Text
- View/download PDF
45. Effect of thermal history on the structure and mechanical properties of a thermoplastic polyester elastomer.
- Author
-
Yamada, Takumi, Kida, Takumitsu, and Yamaguchi, Masayuki
- Subjects
- *
THERMOPLASTIC elastomers , *CRITICAL temperature , *DYNAMIC mechanical analysis , *CRYSTAL structure , *YIELD stress , *RUBBER - Abstract
An appropriate processing protocol was proposed to improve the rubber elasticity of a thermoplastic polyester elastomer (TPEE). Rheology measurements at the processing temperature and thermal measurements determined the critical temperature at which small numbers of crystals exist. It was found from dynamic mechanical analyses, wide- and small-angle X-ray measurements, and electron microscope observations that cooling from the critical temperature markedly promoted the crystallization of hard segments. Moreover, tensile tests revealed that the modulus and yield stress increased. Most importantly, compared with films obtained by cooling from high temperatures, the residual strain at a fixed stress was low—i.e., the rubber elasticity was improved owing to its well-developed crystalline structure. These effects were accelerated by a more optimized process—i.e., subsequent heating at slightly below the critical temperature. The technique is noteworthy because a TPEE with high modulus generally shows poor elasticity. [Display omitted] • The rubber elasticity of a thermoplastic polyester elastomer (TPEE) was evaluated. • Melt processing was available for the TPEE at 220 °C, although it had a few crystals. • The crystals at 220 °C acted as nuclei, leading to well-developed crystalline structure. • The effect was accelerated by the 2nd heating process at 200 °C. • The well-developed crystals were responsible for improvement of rubber elasticity. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
46. Improvement of mechanical and impact performance of poly(lactic acid) by renewable modified natural rubber.
- Author
-
Tessanan, Wasan, Chanthateyanonth, Ratana, Yamaguchi, Masayuki, and Phinyocheep, Pranee
- Subjects
- *
RUBBER , *LACTIC acid , *LATEX , *SCANNING electron microscopy , *PARTICULATE matter - Abstract
Enhancement of mechanical properties of biodegradable and compostable poly(lactic acid) is remarkably achieved by melt-blending with particular modified natural rubber. The modified natural rubber is prepared by a two-step process using hydrogenation, followed by an epoxidation reaction, in latex phase, which is sustainably derived from the rubber trees. The as-prepared epoxidized hydrogenated natural rubber is used (10% by weight) for the first time, as a toughening agent, in a mixture with poly(lactic acid). The structure modification of the rubber containing hydrogenated and epoxide moieties provides improved compatibility between rubber and poly(lactic acid). The results demonstrate the maximum increment in impact performance and elongation at break of the modified natural rubber/poly(lactic acid) blend with the values of 32.43 kJ/m2 and 348%, respectively. The results reveal that the impact resistance and elongation at break of PLA blend can increase approximately ninefold and forty-ninefold, respectively, compared to the neat PLA. Meanwhile, there is an improvement in tensile strength (41.79 MPa) and modulus (2.02 GPa) of the blend when compared to the unmodified natural rubber/poly(lactic acid) blend (31.39 MPa tensile strength and 1.57 GPa modulus). Furthermore, the microstructure, evidenced by scanning electron microscopy, reveals the presence of the fine rubber particles and the appearance of some fibrils on the impact-fractured surface of the blends. Therefore, the modification of natural rubber improves its compatibility with poly(lactic acid) and enhances the mechanical and impact properties of poly(lactic acid). The successful preparation of natural rubber-based toughening agent using an environmental-friendly latex system paves the way for broadening and diversifying the use of natural rubber and also poly(lactic acid), in which both derived from renewable resources with the truly-sustainable developments and sustainability. Image 1 • High mechanical performance poly(lactic acid) is gained by modified natural rubber. • Epoxidized hydrogenated natural rubber is an efficient plastic toughening agent. • Compatibility between modified rubber and poly(lactic acid) is well observed. • The lower glass-transition temperature indicates the compatibility of the blends. • Thermal behavior of poly(lactic acid) is improved by modified natural rubber. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
47. Improvement of mechanical toughness of poly(lactic acid) by addition of ethylene-vinyl acetate copolymer.
- Author
-
Kugimoto, Daisuke, Kouda, Shingo, and Yamaguchi, Masayuki
- Subjects
- *
VINYL acetate , *ETHYLENE-vinyl acetate , *LACTIC acid , *BRITTLE fractures , *PARTICULATE matter , *INTERFACIAL tension - Abstract
We investigated the structure and properties of binary blends comprising poly(lactic acid) (PLA) as a matrix and ethylene–vinyl acetate copolymer (EVA), by considering the effect of the vinyl acetate (VAc) content in EVA. The interfacial tension with PLA was found to decrease with increasing the VAc content. Therefore, blends comprising EVA with a high VAc content have fine EVA particles, and exhibit marked mechanical toughness and good transparency. Although pure PLA is prone to brittle fractures, the addition of EVA leads to shear yielding, which is prominent when the matrix ligament thickness is shorter than a critical value. The cavitation process in the dispersed EVA particles is also responsible for the mechanical toughness, which is obvious in EVA with a high VAc content. • EVA addition improves mechanical toughness of PLA greatly. • Massive shear yielding and cavitation are responsible for the improvement. • EVA with a high VAc content shows a marked modification performance. • Fine morphology is detected in the blends with EVA having a high VAc content. • The blend shows good transparency due to refractive index matching. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
48. Anomalous viscosity decrease of polycarbonate by addition of polystyrene.
- Author
-
Sako, Takumi, Date, Jitsuhiro, Hagi, Misaki, Hiraoka, Tatsuhiro, Matsuoka, Shinji, and Yamaguchi, Masayuki
- Subjects
- *
POLYSTYRENE , *VISCOSITY , *POLYCARBONATES , *SHEARING force , *POLYMER blends , *CAPILLARY flow - Abstract
Abstract The shear viscosity of binary blends comprising polycarbonate (PC) and low-molecular-weight polystyrene (L-PS) was examined. It was found that the viscosity of PC significantly decreases by the addition of L-PS. Although the dynamic mechanical properties indicated that L-PS is immiscible with PC, the morphology observation of the extruded strand clarified that shear-induced phase-mixing occurs. Furthermore, the viscosity decrease was found to be pronounced in the high shear stress condition, which is much more obvious than that by the addition of low-molecular-weight PC. Consequently, the addition of L-PS improves the flowability at injection-molding greatly. Graphical abstract Image 10992 Highlights • A blend of polycarbonate and polystyrene shows flow-induced phase-mixing. • Addition of polystyrene greatly decreases the shear viscosity of polycarbonate. • Because of the viscosity drop, the blend shows high flowability at injection-molding. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
49. Birefringence and strain-induced crystallization of stretched cellulose acetate propionate films.
- Author
-
Nobukawa, Shogo, Nakao, Akichika, Songsurang, Kultida, Pulkerd, Panitha, Shimada, Hikaru, Kondo, Misaki, and Yamaguchi, Masayuki
- Subjects
- *
BIREFRINGENCE , *CRYSTALLIZATION , *CELLULOSE acetate , *PROPIONATES , *THERMAL analysis - Abstract
We have investigated the wavelength dependence of the birefringence (Δ n ) for cellulose acetate propionate (CAP) films stretched at various draw ratios (DRs) and strain rates (SRs) by comparing with the result of cellulose triacetate (CTA). CAP exhibits extraordinary wavelength dispersion of Δ n although CTA shows ordinary dispersion, indicating that Δ n of CAP is determined by the acetyl and propionyl groups. For CAP, the extraordinary dispersion becomes stronger at higher DR and SR. Thermal analysis suggests that hot stretching induces crystallization of CAP and the crystal size increases with increasing DR and SR. Furthermore, the two-dimensional X-ray diffraction patterns of CAP and CTA (a semicrystalline polymer) exhibit orientation of the induced crystal. These results mean that the acetyl orientation in CAP becomes stronger than the propionyl orientation. This conclusion is reasonable because the acetyl group is more tightly confined to the pyranose ring than the propionyl group. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
50. Interphase transfer of plasticizer between immiscible rubbers.
- Author
-
Kuhakongkiat, Nawaphorn, Wachteng, Viyada, Nobukawa, Shogo, and Yamaguchi, Masayuki
- Subjects
- *
CELL cycle , *PLASTICIZERS , *PLASTIC additives , *RUBBER - Abstract
Interphase transfer of di-2-ethylhexyl adipate (DOA) between ethylene-propylene copolymer (EPR) and polyisobutylene (PIB) in the laminated sheets was studied. It was found that the amount of DOA in each phase is determined by the ambient temperature. DOA moved to EPR from PIB at −20 °C and vice versa at 40 °C, when the DOA content before lamination was 10 phr. This is attributed to the change of interaction parameters between DOA and each rubber as a function of temperature. Because of the DOA transfer, the glass transition temperature of each rubber phase changes with the ambient temperature. The phenomenon can be applicable to an all-season tire, when a matrix polymer contains more plasticizer at low temperature and vice versa in a blend with sea-island structure. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
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