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268 results on '"Yoshikawa, Isao"'

10. Active control of molecular stacking types in a congeneric library of dihalogenated salicylideneaniline crystals and their solid solutions.

Author

Yoshikawa, Isao, Zhang, Zaixiang, Suzuki, Masahiro, Ikedo, Hana, Yin, Qiuxiang, and Houjou, Hirohiko

Subjects
*MOLECULAR crystals, *MELTING points, *CRYSTALS, *MOLECULAR structure, *CRYSTAL structure, *SOLID solutions, *STACKING interactions
Abstract

Intentional crystal packing modification is a crucial subject in crystal engineering to achieve functional modulation. In this study, we report a series of congeneric N-(4′-halosalicylidene)-4-haloanilines (4XY, where X and Y = C or B for Cl or Br substitution, respectively). 4BB afforded three polymorphic crystals in which, the isostructural layers were stacked differently, also called polytypes. The structural differences resulted from the different types of interhalogen contacts between the layers. 4CC-y, 4BC, and 4CB crystals were isostructural to one of the 4BB polytypes, reflecting the preferred type of interhalogen contacts depending on the halogen atoms involved. A similar polytypism was found for the 5′-substituted compounds 5XY. By changing the ratio of the 4XY compositions, we obtained a series of binary solid solutions that exhibited various stacking arrangements and melting points while retaining their fundamental molecular structures and properties. The present work serves as a successful example of controlling crystal structures by means of systematic change of constituent atoms in molecular crystals. [ABSTRACT FROM AUTHOR]

Published
2023
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25. Photochromism of 2-(Phenylazo)imidazoles

Author

Otsuki, Joe, Suwa, Kazuya, Narutaki, Koichi, Sinha, Chittaranjan, Yoshikawa, Isao, and Araki, Koji

Subjects
Photochromic materials -- Electric properties, Imidazole -- Electric properties, Absorption spectra -- Research, Chemicals, plastics and rubber industries
Abstract

An investigation of the isomerization behaviors of 2(phenylazo)imidazole (Pai-H) and 1-N-methyl-2-(phenylazo)imidazole (Pao-Me) was conducted. It was suggested that metal ions can modulate the absorption spectrum of Pai-Me without a loss of the gross photochromic behavior.

Published
2005

29. Imported leishmaniasis in dogs, US Military Bases, Japan

Author

Kawamura, Yuta, Yoshikawa, Isao, and Katakura, Ken

Subjects
Dogs -- Diseases, Leishmaniasis -- Diagnosis -- Care and treatment, Health
Abstract

To the Editor: Leishmaniasis is found in canids in ≅ 50 of the 88 countries where leishmaniases are found in humans (1). In Japan, 2 cases of imported canine leishmaniasis [...]

Published
2010
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35. Experimental and theoretical studies on constitutional isomers of 2,6-dihydroxynaphthalene carbaldehydes. Effects of resonance-assisted hydrogen bonding on the electronic absorption spectra

Author

Houjou, Hirohiko, Motoyama, Takatoshi, Banno, Seisaku, Yoshikawa, Isao, and Araki, Koji

Subjects
Aldehydes -- Chemical properties, Hydrogen bonding -- Analysis, Naphthalene -- Chemical properties, Naphthalene -- Structure, X-ray crystallography -- Usage, Biological sciences, Chemistry
Abstract

The preparation and x-ray structural characterization of a series of mono- and dicarbaldehydes of 2,6-dihydroxynaphthalene that have potential resonance-assisted hydrogen bonding (RAHB) units are described. The findings from the study offer insight into the optimization of electronic structure of mono- and diformyl derivatives that could be used in the development of new drugs and materials.

Published
2009

36. Material design for piezochromic luminescence: Hydrogen-bond-directed assemblies of a pyrene derivative

Author

Sagara, Yoshimitsu, Mutai, Toshiki, Yoshikawa, Isao, and Araki, Koji

Subjects
Luminescence -- Analysis, Hydrogen bonding -- Research, Polycyclic aromatic hydrocarbons -- Optical properties, Chemistry
Abstract

A novel design principle was adopted to incorporate two strongly demanding factors for molecular packing, a planar aromatic core and multiple hydrogen-bonding sites into a single molecule structure. The designed molecule, an amide-substituted tetraphenylpyrene derivative C6TPPy, successfully showed a piezochromic luminescence by pressure-induced alteration of the molecular packing and subsequent heating-induced restoration.

Published
2007

43. 宇宙放射線と微小重力の相乗作用(複合影響)に関する研究

Author

Ikenaga, Mitsuo, Kato, Tomohisa, Han, Zhen-Bo, Kitao, Hiroyuki, Todo, Takeshi, Niwa, Otsura, Uematsu, Tetsuo, Ishizaki, Kanji, Yoshikawa, Isao, Suzuki, Fumio, 池永 満生, 加藤 友久, 北尾 洋之, 藤堂 剛, 丹羽 太貫, 植松 哲生, 石崎 寛治, 吉川 勲, 鈴木 文男, Ikenaga, Mitsuo, Kato, Tomohisa, Han, Zhen-Bo, Kitao, Hiroyuki, Todo, Takeshi, Niwa, Otsura, Uematsu, Tetsuo, Ishizaki, Kanji, Yoshikawa, Isao, Suzuki, Fumio, 池永 満生, 加藤 友久, 北尾 洋之, 藤堂 剛, 丹羽 太貫, 植松 哲生, 石崎 寛治, 吉川 勲, and 鈴木 文男

Abstract

放射線と微小重力の相乗効果がヒト細胞でも認められるか否かを明らかにするために、ミスマッチDNA修復能を欠損しているヒト腫瘍細胞HCT116を用いて、マイクロサテライト座位の突然変異頻度を解析した。HCT116細胞をクリノスタットを用いて擬似微小重力環境で3日間培養すると、マイクロサテライト突然変異の頻度が有意に上昇した。同様に、遠心機による過重力の下で3日間培養した場合も、有意な突然変異の増加が認められた。このことから、重力変化単独でもヒト細胞にDNA塩基配列レベルの突然変異を誘発することが明らかになった。しかし、X線を照射した細胞に重力変化を負荷しても、放射線と擬似微小重力あるいは過重力の相乗効果は検出されなかった。重粒子によるハムスターSHE細胞の試験管内発癌については、重粒子のLETが100keV/μmでRBEが最大値の約7となることを見出した。, NASDA Special Publication, 宇宙開発事業団特別報告

Published
2015

44. Genetic effects of HZE and cosmic radiation

Author

Ikenaga, Mitsuo, Yoshikawa, Isao, Kojo, Moto, Kato, Yumiko, Ayaki, Toshikazu, Ryo, Haruko, Ishizaki, Kanji, Kato, Tomohisa, Yamamoto, Hanako, and Hara, Ryujiro

Subjects
致死遺伝子, ハエ, radiation sensitive strain, 羽毛, 突然変異, 宇宙飛行, lethal gene, chromosome, 宇宙放射線, 遺伝的影響, 野性株, space flight, wild type strain, 宇宙環境, 高エネルギー重荷電粒子, space shuttle, heavy charged particle ion, 長期宇宙滞在, germ cell, genetic effect, wing hair, スペースシャトル, 放射線感受性株, space environment, fly, 染色体, cosmic radiation, mutation, long term space journey, 生殖細胞
Abstract

HZE(高エネルギー重荷電粒子)および宇宙放射線の遺伝的影響を調べるため、ショウジョウバエ(Drosophila melanogaster)の成虫雄と幼虫をスペースシャトル/エンデバー号(STS-47)に搭載し、雄の生殖細胞(精子やその元となる精原細胞など)に起こる伴性劣性致死突然変異と、幼虫の翅原基体細胞に起こる染色体のつなぎかえによる突然変異を調べた。用いた系統は、標準的な野生株(Canton-S)と放射線高感受性株(mei-41)である。各系統で、成虫雄は200匹ずつ、幼虫は約6000匹ずつを搭載し宇宙環境に曝すとともに、ほぼ同数を地上対照群として、宇宙飛行群と同じ環境条件(温度と湿度)で飼育した。宇宙飛行は約8日間であった。帰還した雄のハエは、伴性劣性致死突然変異を調べるため、検出用系統の処女雌に交配し、次々世代で致死遺伝子を保有しているX染色体を検出した。宇宙飛行群の致死遺伝子をもった染色体頻度は、地上対照群の頻度に比べて、野生株では2倍、放射線高感受性株では3倍高かった。幼虫は、帰還時にほとんどが蛹になっており、翌日より徐々に羽化が始まった。羽化した成虫は、順次70%アルコールで貯蔵し、後に翅標本を作成して、染色体突然変異由来の翅毛変異スポットを調べた。野生株では、宇宙飛行群と地上対照群の頻度は、ほぼ同じであった。放射線高感受性株から分離してくるMuller-5個体における頻度は、地上対照群に比べて宇宙飛行群では、1.5倍高かった。しかし、放射線高感受性個体における宇宙飛行群の頻度は、地上対照群に比べて有意に低い頻度を示した。地上対照群に比べて、宇宙飛行群の劣性致死突然変異の高頻度は、生殖細胞において、放射線と微小重力の突然変異誘発作用への相乗効果を示唆している。しかし、この相乗効果は、体細胞の染色体突然変異誘発作用に対しては観察されなかった。, For examining the genetic effects of High Energy Heavy ions (HZE) and cosmic radiation, adult males and larvae of fruit flies (Drosophila melanogaster) were loaded on the Space Shuttle, Endeavor (STS-47), and sex-linked recessive lethal mutation in the male germ cells (spermatozoa and spermatogonia that produce them) and chromosome-recombination-derived mutation on the larva wing basal somatic cells were investigated. The strains used were a standard wild type strain (Canton-S) and a radiation sensitive strain (mei-41). Two-hundred adult males and about 6000 larvae of each strain were loaded and exposed to the cosmic environment. At the same time, almost the same number of adult flies and larvae were bred in the same environmental condition (temperature and humidity) as ground control groups. The flight period was about eight days. The returned male flies were mated with virgin female flies from a detection strain for investigating sex-linked recessive lethal mutation. X chromosomes with lethal genes were detected on the second generation. In the returned flies, the frequency of chromosomes with lethal genes was two times higher in the wild type strain and three times higher in the radiation sensitive strain than that of the ground control groups. Most of the returned larvae were in the pupal stage on the return day, and began to emerge on the next day. The emerged adult flies were stored in 70 percent alcohol solutions, and their wing samples were prepared for investigating the wing mutation spots derived from chromosome mutation. Mutation frequency in the wild type strain was almost the same between the flight and ground groups. The frequency in the Muller-5 individuals separated from the radiation sensitive strain was one and half times higher in the flight group than in the ground control group. However, the frequency in the radiation sensitive strain was significantly lower in the flight group than the ground group. The higher recessive lethal mutation frequency in the flight group suggests the synergistic effect of radiation and minute gravity on mutation induction in germ cells. However, this synergy effect was not observed on the chromosome mutation induction in somatic cells., 資料番号: AA0004115012, レポート番号: NASDA-TMR-940002 V.1

Published
1994

50. Effects of interaction between the chelate rings and π-conjugated systems in fused salphen complexes on UV-Vis-NIR spectra.

Author

Houjou, Hirohiko, Yagi, Keisuke, Yoshikawa, Isao, Mutai, Toshiki, and Araki, Koji

Subjects
CHELATES, METAL complexes, BIOCONJUGATES, NEAR infrared spectroscopy, ISOMERS
Abstract

Dinuclear (Zn2, Ni2, and NiZn) complexes of fused salphen with acene-type annelation were synthesized from 3,7-diformyl-2,6-dihydroxynaphthalene. The spectroscopic properties of these complexes were compared with those of their constitutional isomers with phene-type annelation. The acene-type complexes exhibited a characteristic absorption band in the near-infrared region that showed a noticeable solvent effect. Time-dependent density functional theory calculations suggested that the absorption arose from a π → π* transition localized at the naphthalene ring, which was perturbed by the adjoining chelate rings. Effects of the connection topology in the fused salphen complexes are discussed by comparison with those of polycyclic aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

Published
2017
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