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204. Znの室温クリープにおける粒界近傍での転位挙動

Author

Takahashi, Kohei, Matsunaga, Tetsuya, Sato, Eiichi, and Kitazono, Koichi

Abstract

第22回宇宙構造・材料シンポジウム（2006年12月1日. 宇宙航空研究開発機構宇宙科学研究本部 (JAXA)(ISAS)）, 相模原市, 神奈川県, 22nd Symposium on Aerospace Structure and Materials (December 1, 2006. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan, 資料番号: SA6000019033

Published
2007

205. Development of N‐Phosphinomethyl‐Substituted NHC‐Nickel(0) Complexes as Robust Catalysts for Acrylate Salt Synthesis from Ethylene and CO2.

Author

Takahashi, Kohei, Cho, Kinryo, Iwai, Asaki, Ito, Tatsuyoshi, and Iwasawa, Nobuharu

Subjects
*ETHYLENE synthesis, *ACRYLATES, *SALTS, *ACRYLIC acid, *THERMAL stability, *CATALYSTS
Abstract

By using a nickel complex with an N‐phosphinomethyl‐N‐heterocyclic carbene ligand (NHC‐P), the reducing ability and thermal stability of the complex were improved considerably compared to the previously reported bipyridine and bisphosphine complexes, and acrylate salt was prepared from ethylene and CO2 with the highest TON ever reported for nickel systems even without using metallic zinc. Oxidative cyclization of ethylene and CO2 on the NHC‐P nickel complex was found to proceed very rapidly compared to previous systems. [ABSTRACT FROM AUTHOR]

Published
2019
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206. Development of N‐Phosphinomethyl‐Substituted NHC‐Nickel(0) Complexes as Robust Catalysts for Acrylate Salt Synthesis from Ethylene and CO2.

Author

Takahashi, Kohei, Cho, Kinryo, Iwai, Asaki, Ito, Tatsuyoshi, and Iwasawa, Nobuharu

Subjects
ETHYLENE synthesis, ACRYLATES, SALTS, ACRYLIC acid, THERMAL stability, CATALYSTS
Abstract

By using a nickel complex with an N‐phosphinomethyl‐N‐heterocyclic carbene ligand (NHC‐P), the reducing ability and thermal stability of the complex were improved considerably compared to the previously reported bipyridine and bisphosphine complexes, and acrylate salt was prepared from ethylene and CO2 with the highest TON ever reported for nickel systems even without using metallic zinc. Oxidative cyclization of ethylene and CO2 on the NHC‐P nickel complex was found to proceed very rapidly compared to previous systems. [ABSTRACT FROM AUTHOR]

Published
2019
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209. Crystallization of Strictly Linear Poly(ethylene-ran-acrylic acid) Copolymer: Impacts of Pendant Group Insertion and Hydrogen Bonding

Author

Zhou, Jian, Takahashi, Kohei, Nozaki, Kyoko, Yamamoto, Yuta, Katashima, Takuya, Yoshie, Naoko, and Nakagawa, Shintaro

Abstract

Functionalized polyolefins hold great promise as a material group for a future society. The hierarchical structure formation process during crystallization and melting of such polymers is greatly influenced by the inter- and intrachain interactions induced by functional groups. Herein, we report the comprehensive structural analysis of strictly linear poly(ethylene-ran-acrylic acid), i.e., polyethylene bearing pendant carboxyl (−COOH) groups randomly along the chain (PE-COOH), during the crystallization and melting processes. Additional use of the corresponding methyl ester (PE-COOMe) and polyethylene (PE) enabled us to separate the effects of hydrogen bonds (H-bonds) among the −COOH groups from those caused by the random insertion of pendant groups. The crystallizable methylene sequences were divided by the randomly inserted pendant groups, giving rise to the sequence-length selective crystallization. That is, longer sequences crystallized at higher temperatures and vice versa. This significantly hindered the crystallization rate, crystal thickness, and crystallinity and led to a strong melt memory effect. The H-bonding between −COOH groups acted as physical cross-linking for the PE chains and hindered the chain motion. This further slowed the crystallization and reinforced the melt memory effect. On the other hand, the H-bonds contributed to increased crystallinity and melting point of PE-COOH crystallized at high temperatures, compared to those of PE-COOMe. Thus, it was found that the H-bonding of −COOH groups stabilized the crystals formed at high temperatures. This work presents a unified view of the crystallization and melting behavior of strictly linear PE with interacting pendant groups, providing the possibility to precisely control the crystalline morphology in scales of both lamella and spherulite by altering the thermal history.

Published
2024
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212. Reactivity of a Ruthenium(0) Complex Bearing a Tetradentate Phosphine Ligand: Applications to Catalytic Acrylate Salt Synthesis from Ethylene and CO2

Author

Ito, Tatsuyoshi, Takahashi, Kohei, and Iwasawa, Nobuharu

Abstract

By using a zerovalent, electron-rich ruthenium complex bearing a tetradentate phosphine ligand, a five-membered ruthenalactone was generated by oxidative cyclization of ethylene and CO2. This ruthenalactone underwent thermal, reversible β-H elimination to afford an acrylato(hydrido)ruthenium(II) complex, which liberated acrylate salt on treatment with a base. The reaction was successfully applied to the first ruthenium-catalyzed synthesis of an acrylate salt from ethylene and CO2. This study demonstrated the feasibility of the electron-rich ruthenium(0) complex as a catalyst in CO2-fixation chemistry.

Published
2019
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218. Fatty Acid Conjugates of Water‐Soluble (±)‐trans‐Selenolane‐3,4‐diol: Effects of Alkyl Chain Length on the Antioxidant Capacity

Author

Iwaoka, Michio, primary, Sano, Nobukazu, additional, Lin, Ying‐Yin, additional, Katakura, Arisa, additional, Noguchi, Masato, additional, Takahashi, Kohei, additional, Kumakura, Fumio, additional, Arai, Kenta, additional, Singh, Beena G., additional, Kunwar, Amit, additional, and Priyadarsini, K. Indira, additional

Published
2015
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222. Listeria monocytogenesmeningoencephalitis in cerebrum

Author

Murakami, Takenobu, primary, Yoshida, Kenji, additional, Namatame, Sachiko, additional, Iikuni, Yoichiro, additional, Morimatsu, Akeshi, additional, Yamada, Akane, additional, Sugiyama, Urara, additional, Takahashi, Kohei, additional, Shirata, Akiko, additional, and Yamane, Kiyomi, additional

Published
2014
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232. Antidepressant-like effect of aripiprazole via 5-HT1A, D1, and D2receptors in the prefrontal cortex of olfactory bulbectomized mice

Author

Takahashi, Kohei, Nakagawasai, Osamu, Nemoto, Wataru, Odaira, Takayo, Sakuma, Wakana, and Tan-No, Koichi

Abstract

Olfactory bulbectomized (OBX) mice exhibit depressive-like behaviors and memory deficits. We have reported that aripiprazole (ARI) ameliorates the behavioral hyper-responsivity to dopamine agonists and memory deficits in OBX mice; however, it is unclear whether ARI affects OBX-induced depressive-like behavior. To address this question, we evaluated the effect of ARI on depressive-like behavior in OBX mice using the forced swim test (FST). In addition, we investigated the effect of ARI on c-Fos expression in the prefrontal cortex (PFC), striatum, and hippocampus of OBX mice using western blotting. OBX mice exhibited a longer immobility duration in the FST 14 days after surgery. Depressive-like behavior in OBX mice was reversed 30 min after administration of ARI (0.01 or 0.03 mg/kg). In addition, c-Fos expression was increased in the PFC, but not the striatum or hippocampus, 30 min after acute administration of ARI. These effects were inhibited by administration of the selective 5-HT1A, D1, and D2 receptor antagonists, WAY100635, SCH23390, and L-741,626, respectively. These findings suggest that ARI produces an antidepressant effect in OBX mice that may be mediated by 5-HT1A, D1, and D2receptors in the PFC.

Published
2018
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234. Donepezil prevents olfactory dysfunction and α-synuclein aggregation in the olfactory bulb by enhancing autophagy in zinc sulfate-treated mice.

Author

Takahashi, Kohei, Tsuji, Minoru, Nakagawasai, Osamu, Katsuyama, Soh, Hong, Lihua, Miyagawa, Kazuya, Kurokawa, Kazuhiro, Mochida-Saito, Atsumi, Takeda, Hiroshi, and Tadano, Takeshi

Subjects
*OLFACTORY bulb, *ALPHA-synuclein, *SMELL disorders, *GLUTAMATE decarboxylase, *AUTOPHAGY
Abstract

Alzheimer's disease is associated with marked olfactory dysfunction observed in the early stages. Clinical studies reported that acetylcholinesterase inhibitor donepezil (DNP) attenuated this deficit; however, the underlying mechanism remains unclear. Herein, we aimed to examine the effects and underlying mechanisms of DNP on olfactory deficits in zinc sulfate (ZnSO 4) nasal-treated mice, which were used as a model of reversible olfactory impairment. We evaluated olfactory function using the buried food finding test and neurogenesis in the subventricular zone (SVZ) using immunohistochemistry. Finally, we measured the expression of doublecortin (DCX), neuronal nuclear antigen (NeuN), olfactory marker protein, tyrosine hydroxylase (TH), tryptophan hydroxylase 2, glutamic acid decarboxylase 67, p-α-synuclein (Ser129), α-synuclein, p-AMPK, p-p70S6 kinase (p70S6K) (Thr389), LC3 Ⅱ/Ⅰ, and p-p62 in the olfactory bulb (OB) by western blotting. On day 7 after treatment, ZnSO 4 -treated mice exhibited prolonged time to find the buried food, cell proliferation enhancement in the SVZ, increased NeuN, p-α-synuclein (Ser129), and α-synuclein levels, and decreased DCX and TH levels in the OB; except for TH, these changes normalized on day 14 after treatment. Repeated administration of DNP prevented the ZnSO 4 -induced changes on day 7 after treatment. Moreover, DNP increased p-AMPK and LC3 Ⅱ/Ⅰ, and decreased p-p70S6K and p-p62 (Ser351) levels in the OB, suggesting that DNP enhances autophagy in the OB. These findings indicate that DNP may help prevent olfactory dysfunction by autophagy that reduces α-synuclein aggregation via the AMPK/mTOC1 pathway. • Donepezil (DNP) prevented zinc sulfate (ZnSO 4)-induced olfactory deficit. • DNP prevented ZnSO 4 -induced cell proliferation in the subventricular zone. • DNP prevented ZnSO 4 -induced maturation of neurons in the olfactory bulb (OB). • DNP prevented ZnSO 4 -induced abnormal aggregated α-synuclein in the OB. • DNP enhanced autophagy in the OB through the p-AMPK/mTORC1 pathway. [ABSTRACT FROM AUTHOR]

Published
2023
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240. Alterations in behavioral responses to dopamine agonists in olfactory bulbectomized mice: relationship to changes in the striatal dopaminergic system.

Author

Takahashi, Kohei, Nakagawasai, Osamu, Nemoto, Wataru, Nakajima, Takeharu, Arai, Yuichiro, Hisamitsu, Tadashi, and Tan-No, Koichi

Subjects
*DOPAMINE agonists, *OLFACTORY bulb, *DOPAMINERGIC mechanisms, *MENTAL depression, *LABORATORY mice
Abstract

Background: Olfactory bulbectomy (OBX) in rodents is considered a putative animal model of depression. It has been reported that some abnormal behaviors observed in this animal model of depression involve dopaminergic neurons of the mesolimbic pathway. Therefore, we examined changes in the dopaminergic system in the caudate putamen (CPu), nucleus accumbens core (NAcC), and shell (NAcSh) of OBX mice and whether or not these alterations were reversed by chronic administration of imipramine. Methods: We observed climbing behavior, which is a dopamine (DA) receptor-associated behavior, to demonstrate changes in the dopaminergic system of the mesolimbic pathway, when mice were administrated either the nonselective DA agonist apomorphine only or were pre-treated with the selective D antagonist SCH23390, with the selective D antagonist sulpiride, or with the D/D partial agonist aripiprazole (ARI). Moreover, we examined tyrosine hydroxylase (TH) and D- and D-like receptor levels in the CPu, NAcC, and NAcSh using immunohistochemistry and autoradiography. Results: The OBX group exhibited significantly enhanced apomorphine-induced climbing behavior, and this enhanced behavior was reversed by administration of sulpiride, ARI, and imipramine but not SCH23390. Moreover, we found a reduction in TH levels in the CPu, NAcC, and NAcSh of OBX mice and an increase in D receptor densities in the NAcC of OBX mice. The increased D receptor density observed in OBX mice was reversed by imipramine administration. Conclusions: These findings reveal that OBX mice display enhanced DA receptor responsiveness, which may relate to some of the behavioral abnormalities reported in this animal model. [ABSTRACT FROM AUTHOR]

Published
2016
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243. Exploiting No-SQL DB for Implementing Lifelog Mashup Platform.

Author

Takahashi, Kohei, Matsumoto, Shinsuke, Saiki, Sachio, and Nakamura, Masahide

Abstract

To support efficient integration of heterogeneous lifelog service, we have previously proposed and implemented a lifelog mashup platform consisting of the lifelog common data model (LLCDM) and the lifelog mashup API (LLAPI) to access the standardized data. The LLCDM has standardized columns which is application-independent. And it has application-specific data (i.e. JSON format text of API response of a lifelog service) in the column as a plain text. But because the LLCDM repository is implemented using the relational database, we can't access to the column data directory, and select out a particular field of it via the LLAPI. To cope with these problems, we exploited the lifelog mashup platform with the document-oriented No-SQL database MongoDB for the LLCDM repository. And, we conduct a case study developing an application of retrieving Twitter's posts involving URLs. [ABSTRACT FROM AUTHOR]

Published
2014
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