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193 results on '"Nakayama, Atsuyoshi"'

53. Chemical modification of chitosan. Part 15: Synthesis of novel chitosan derivatives by substitution of hydrophilic amine using N-carboxyethylchitosan ethyl ester as an intermediate

Author

Sashiwa, Hitoshi, primary, Kawasaki, Norioki, additional, Nakayama, Atsuyoshi, additional, Muraki, Einosuke, additional, Yajima, Hirofumi, additional, Yamamori, Naoki, additional, Ichinose, Yoshifumi, additional, Sunamoto, Junzo, additional, and Aiba, Sei-ichi, additional

Published
2003
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54. Chemical Modification of Chitosan. 13. Synthesis of Organosoluble, Palladium Adsorbable, and Biodegradable Chitosan Derivatives toward the Chemical Plating on Plastics

Author

Sashiwa, Hitoshi, primary, Kawasaki, Norioki, additional, Nakayama, Atsuyoshi, additional, Muraki, Einosuke, additional, Yamamoto, Noboru, additional, Zhu, Hong, additional, Nagano, Hiroshi, additional, Omura, Yoshihiko, additional, Saimoto, Hiroyuki, additional, Shigemasa, Yoshihiro, additional, and Aiba, Sei-ichi, additional

Published
2002
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88. Rapid determination of 4-aminobutyric acid and L-glutamic acid in biological decarboxylation process by capillary electrophoresis-mass spectrometry.

Author

Takeda, Sahori, Yamano, Naoko, Kawasaki, Norioki, Ando, Hisanori, and Nakayama, Atsuyoshi

Abstract

4-Aminobutylic acid (GABA) is a monomer of plastic polyamide 4. Bio-based polyamide 4 can be produced by using GABA obtained from biomass. The production of L-glutamic acid (Glu) from biomass has been established. GABA is produced by decarboxylation of Glu in biological process. High-performance liquid chromatography (HPLC) with derivatization is generally used to determine the concentration of GABA and Glu in reacted solution samples for the efficient production of GABA. In this study, we have investigated the rapid determination of GABA and Glu by capillary electrophoresis-mass spectrometry (CE-MS) without derivatization. The determination was achieved with the use of a shortened capillary, a new internal standard for GABA, and optimization of sheath liquid composition. Determined concentrations of GABA and Glu by CE-MS were compared with those by pre-column derivatization HPLC with phenylisothiocyanate. The determined values by CE-MS were close to those by HPLC with pre-column derivatization. These results suggest that the determination of GABA and Glu in reacted solution is rapid and simplified by the use of CE-MS. [ABSTRACT FROM AUTHOR]

Published
2012
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91. Studies on Poly[acrylamide-co-(ɛ-caprolactone)]: Synthesis, Characterization and Biodegradability

Author

Kawasaki, Norioki, Nakayama, Atsuyoshi, Higashi, Takashi, Maeda, Yasukatsu, Yamamoto, Noboru, and Aiba, Sei-ichi

Abstract

The synthesis, characterization, hydrolysis and biodegradation of a copoly(ester amide), poly[acrylamide-co-(ɛ-caprolactone)], are described. The hydrogen transfer copolymerization of acrylamide (AA) with ɛ-caprolactone (CLN) in the presence of butyllithium or calcium hydride as initiators has been investigated. The calcium hydride was effective for the synthesis of the copoly(ester amide) in a wide range of polymer composition (AA/CLN =  10 : 90 to 90 : 10). The copoly(ester amide) was readily hydrolyzed in the presence of hydrochloric acid (0.1 n) at 125°C in an autoclave (e. g. AA/CLN =  59 : 41, degradation 93%). Furthermore, the copoly(ester amide) was hydrolyzed enzymatically by lipase from Rhizopus arrhizus. The behavior of the enzymatic hydrolysis differed to the non-enzymatic hydrolysis. The enzymatic hydrolyzability was remarkable in the range of the AA repeating unit (β-alanine unit) from 10 to 40 mol-% (e. g. AA/CLN =  27 : 73, degradation 44%), while, the degradability for the non-enzymatic hydrolysis rose with increasing AA repeating unit content. The biodegradation of the copoly(ester amide) was evaluated using a standard activated sludge (e. g. AA/CLN =  27 : 73 biodegradation 45%). The relationship between the biodegradation and the polymer composition was similar for the standard activated sludge and the enzymatic hydrolysis.

Published
2001
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92. Synthesis and characterization of novel biodegradable copolyesters by transreaction of poly(ethylene terephthalate) with copoly(succinic anhydride/ethylene oxide)

Author

Maeda, Yasukatsu, Maeda, Takuya, Yamaguchi, Kazumi, Kubota, Shizuo, Nakayama, Atsuyoshi, Kawasaki, Norioki, Yamamoto, Noboru, and Aiba, Seiichi

Abstract

Poly(ethylene terephthalate)/copoly(succinic anhydride/ethylene oxide) copolymers, (PET/PES copolymers) were synthesized by the transreaction between PET and PES and characterized with GPC, 1H NMR, and DSC. Most of the copolymers obtained were random copolymers. The films cast of these copolymers were transparent. The thermal, mechanical properties, and biodegradability of the copolymers obtained were studied with respect to the composition and lengths of aliphatic and aromatic units in the copolymers. In the copolymers having high PET content, the melting points, due to the PET segment, were observed by DSC measurement, although the fusion heats of the copolymers were small. The enzymatic hydrolyzability by a lipase from Rhizopus arrhizus and biodegradability by activated sludge of the copolymers decreased with an increase in PET content. When the length of succinic acid unit in the copolymer was below 2, the hydrolyzability of the copolymers decreased considerably. The tensile strengths of the cast films prepared from the copolymers synthesized by the transreaction increased with an increase in PET content, whereas, the elongations at break decreased. Their tensile strengths were half, and the elongations were double compared to those of PET homopolymer film. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4478–4489, 2000

Published
2000
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93. Synthesis and biodegradation of poly(γ-butyrolactone-co-<span style="font-variant:small-caps">l</span> -lactide)

Author

Nakayama, Atsuyoshi, Kawasaki, Norioki, Arvanitoyannis, Ioannis, Aiba, Seiichi, and Yamamoto, Noboru

Abstract

Abstract: Biodegradable polyesters were synthesized by ring-opening copolymerization of gamma-butyrolactone (BL) and its derivatives withl-lactide (LLA). Although tetraphenyl tin was the main catalyst used, other organometallic catalysts were used as well.1H and13C NMR spectra showed that poly(BL-co-LLA)s were statistical and that their number-average molecular weights were as high as 7×104. The maximum BL content obtained from copolymerization BL/LLA was around 17%. TheT m andT g values of the copolymers showed a gradual depression with an increase in BL content. NoT m was obtained for the copolymers containing more than 13 mol% BL. The biodegradability of the copolyesters was evaluated by enzymatic hydrolysis and nonenzymatic hydrolysis tests. The enzymatic hydrolysis was carried out at 37°C for 24 h using lipases fromRhizopus arrhizus andR. delemar. Hydrolyses by both lipases showed that an increase in BL content of the copolymer resulted in enhanced biodegradability. Nonenzymatic accelerated hydrolysis of copolymers at 70°C was found to increase proportionally to their exposure time. The hydrolysis rate of these copolymers was considerably faster than that of PLLA. The higher hydrolyzability was recorded for the BL-rich copolymers. The copolymerization of gamma-methyl-gamma-butyrolactone (MBL) or gamma-ethyl-gamma-butyrolactone (EBL) with LLA resulted in relatively LA-rich copolymers.

Published
1996
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94. Synthesis of Sterically Congested Cyclam Derivatives and Their Nickel(II) Complexes

Author

Kobiro, Kazuya, Nakayama, Atsuyoshi, Hiro, Toshitaka, Suwa, Mitsuhito, Kakiuchi, Kiyomi, Tobe, Yoshito, and Odaira, Yoshinobu

Abstract

A new class of cyclam, octamethylcyclam, and its related compounds bearing tetramethylethane, cis-cyclohexane, or trans-cyclohexane subunit(s) have been synthesized. Nickel(II) complexes with sterically congested ligands have been shown to be low-spin complexes in water, while those with less congested ligands to be mixtures of low-spin and high-spin ones. Nickel(II) complexes with sterically congested ligands have been also exhibited to have higher half-wave potentials (E1/2(NiII,III)) than those of the complexes with less congested ligands.

Published
1990
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97. Sound Velocity Measurements of Nuclear-Ordered Solid 3He in the Low Field Phase.

Author

Sasaki, Satoshi, Takagi, Daisuke, Nakayama, Atsuyoshi, Sasaki, Yutaka, and Mizusaki, Takao

Subjects
SOLID helium, MAGNETIC fields, SPEED of sound, FERROMAGNETIC materials, MAGNETIC domain, SPIN exchange, MAGNETIC susceptibility, NUCLEAR magnetism
Abstract

We have measured, along the melting curve, the magnetic-field dependences of the velocities of the longitudinal and two transverse sound modes in the low field phase (U2D2) of nuclear-ordered solid 3He crystals with a single magnetic domain. We determined the elastic-stiffness tensors cij(T,B) along the melting curve at T=0.5 mK. Since the U2D2 phase has a tetragonal symmetry, we extracted six components of the nuclear-spin elastic-stiffnesses tensor Δc ijN(0.5 mK,B). We obtained the generalized Grüneisen constants Γij1/χ for the magnetic susceptibility χ from ΔcijN(0.5 mK,B), which were proportional to B2. [ABSTRACT FROM AUTHOR]

Published
2006
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