6 results on '"Koya Kubo"'
Search Results
2. Crystal field excitation in the chiral helimagnet YbNi$_3$Al$_9$
- Author
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Mitsuru Tsukagoshi, Suguru Kishida, Kenshin Kurauchi, Daichi Ito, Koya Kubo, Takeshi Matsumura, Yoichi Ikeda, Shota Nakamura, and Shigeo Ohara
- Subjects
Condensed Matter - Strongly Correlated Electrons ,Strongly Correlated Electrons (cond-mat.str-el) ,FOS: Physical sciences - Abstract
Crystal field level scheme of a uniaxial chiral helimagnet YbNi$_3$Al$_9$, exhibiting a chiral magnetic soliton lattice state by Cu substitution for Ni, has been determined by inelastic neutron scattering. The ground and the first excited doublets are separated by 44 K and are simply expressed as $\alpha|\pm 7/2\rangle + \beta |\mp 5/2\rangle$ with $\alpha$ and $\beta$ nearly equal to $\pm 1/\sqrt{2}$. The easy axis of the crystal field anisotropy is the $c$ axis when the excited levels are populated at high temperatures and high magnetic fields. On the other hand, the magnetism at low temperatures and low magnetic fields, where only the ground doublet is populated, is described by an easy plane anisotropy which may be treated as an $S=1/2$ system with an anisotropic $g$-factor, $g_{xy}=3.02$ and $g_z=1.14$. An orbital dependent exchange interaction is also discussed to explain the temperature dependence of the magnetic susceptibility based on this level scheme., Comment: 9 pages, 7 figures, 2 figures in the supplemental material, accepted for publication in Phys. Rev. B
- Published
- 2023
3. Crocetin protects ultraviolet A-induced oxidative stress and cell death in skin in vitro and in vivo
- Author
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Kazuhiro Tsuruma, Naofumi Umigai, Mitsue Ishisaka, Takuya Ohba, Saori Tsujii, Takao Iwawaki, Koya Kubo, Masamitsu Shimazawa, and Hideaki Hara
- Subjects
Male ,0301 basic medicine ,Programmed cell death ,Ultraviolet Rays ,ved/biology.organism_classification_rank.species ,Crocetin ,Radiation-Protective Agents ,Pharmacology ,medicine.disease_cause ,Antioxidants ,Crocin ,Mice ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Crocus sativus ,Autophagy ,medicine ,Animals ,Vitamin A ,Skin ,chemistry.chemical_classification ,Reactive oxygen species ,Cell Death ,biology ,ved/biology ,Crocus ,Endoplasmic Reticulum Stress ,biology.organism_classification ,Carotenoids ,Oxidative Stress ,030104 developmental biology ,chemistry ,Gardenia ,Biochemistry ,Apoptosis ,030220 oncology & carcinogenesis ,Lipid Peroxidation ,Reactive Oxygen Species ,Oxidative stress - Abstract
Crocetin, the aglycone of crocin, is a carotenoid found in fruits of gardenia (Gardeina jasminoides Ellis) and saffron (Crocus sativus L.). We investigated the protective effects of crocetin against ultraviolet-A (UV-A)-induced skin damage and explored the underlying mechanism. Human skin-derived fibroblasts cells (NB1-RGB) were damaged by exposure to UV-A irradiation (10J/cm(2)). Crocetin protected these cells against cell death and reduced the production of reactive oxygen species induced by UV-A irradiation. Crocetin treatment also suppressed induction of caspase-3 activation by UV-A irradiation. The effects of crocetin against oxidative stress were also examined by imaging of Keap1-dependent oxidative stress detector (OKD) mice. UV-A irradiation upregulated oxidative stress in the OKD mice skin, while crocetin administration (100mg/kg, p.o.) ameliorated this oxidative stress. Crocetin administration also decreased lipid peroxidation in the skin. These findings suggest that crocetin its observed protective effects against UV-A induced skin damage by reducing reactive oxygen species production and cell apoptosis.
- Published
- 2016
4. Crocetin reduces the oxidative stress induced reactive oxygen species in the stroke-prone spontaneously hypertensive rats (SHRSPs) brain
- Author
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Fumihiko Yoshino, Ayaka Yoshida, Masaichi-Chang-il Lee, Naofumi Umigai, and Koya Kubo
- Subjects
antioxidant ,Antioxidant ,brain ,medicine.medical_treatment ,Clinical Biochemistry ,Crocetin ,Medicine (miscellaneous) ,chemistry.chemical_element ,medicine.disease_cause ,Oxygen ,chemistry.chemical_compound ,medicine ,oxidative stress ,electron spin resonance (ESR) ,chemistry.chemical_classification ,Reactive oxygen species ,Nutrition and Dietetics ,biology ,Spin trapping ,biology.organism_classification ,chemistry ,Biochemistry ,Gardenia ,Biophysics ,crocetin ,Original Article ,Hydroxyl radical ,Oxidative stress - Abstract
Crocetin is a natural carotenoid compound of gardenia fruits and saffron, which has various effects in biological systems. In this study, we investigated the antioxidant effects of crocetin on reactive oxygen species such as hydroxyl radical using in vitro X-band electron spin resonance and spin trapping. Crocetin significantly inhibited hydroxyl radical generation compared with the control. Moreover, we performed electron spin resonance computed tomography ex vivo with the L-band electron spin resonance imaging system and determined the electron spin resonance signal decay rate in the isolated brain of stroke-prone spontaneously hypertensive rats, a high-oxidative stress model. Crocetin significantly reduced oxidative stress in the isolated brain by acting as a scavenger of reactive oxygen species, especially hydroxyl radical, as demonstrated by in vitro and ex vivo electron spin resonance analysis. The distribution of crocetin was also determined in the plasma and the brain of stroke-prone spontaneously hypertensive rats using high-performance liquid chromatography. After oral administration, crocetin was detected at high levels in the plasma and the brain. Our results suggest that crocetin may participate in the prevention of reactive oxygen species-induced disease due to a reduction of oxidative stress induced by reactive oxygen species in the brain.
- Published
- 2011
5. Chiral Soliton Lattice Formation in Monoaxial Helimagnet Yb(Ni1-xCux)3Al9
- Author
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Takeshi Matsumura, Koya Kubo, Yusuke Kousaka, Shinji Michimura, Shigeo Ohara, Yugo Yoshikawa, Yosuke Kita, Toshiya Inami, and Katsuya Inoue
- Subjects
Physics ,Antisymmetric exchange ,Condensed matter physics ,Magnetic structure ,Spins ,Strongly Correlated Electrons (cond-mat.str-el) ,General Physics and Astronomy ,FOS: Physical sciences ,02 engineering and technology ,Electron ,Crystal structure ,021001 nanoscience & nanotechnology ,01 natural sciences ,Magnetic field ,Condensed Matter - Strongly Correlated Electrons ,0103 physical sciences ,Twist ,010306 general physics ,0210 nano-technology ,Magnetic dipole - Abstract
Helical magnetic structures and its responses to external magnetic fields in Yb(Ni$_x$Cu$_{1-x}$)$_3$Al$_9$, with a chiral crystal structure of the space group $R32$, have been investigated by resonant X-ray diffraction. It is shown that the crystal chirality is reflected to the helicity of the magnetic structure by a one to one relationship, indicating that there exists an antisymmetric exchange interaction mediated via the conduction electrons. When a magnetic field is applied perpendicular to the helical axis ($c$ axis), the second harmonic peak of $(0, 0, 2q)$ develops with increasing the field. The third harmonic peak of $(0, 0, 3q)$ has also been observed for the $x$=0.06 sample. This result provides a strong evidence for the formation of a chiral magnetic soliton lattice state, a periodic array of the chiral twist of spins, which has been suggested by the characteristic magnetization curve. The helical ordering of magnetic octupole moments, accompanying with the magnetic dipole order, has also been detected., Comment: 13 pages, 18 figures, accepted for publication in J. Phys. Soc. Jpn
- Published
- 2017
6. Chiral Soliton Lattice Formation in Monoaxial Helimagnet Yb(Ni1-xCux)3Al9.
- Author
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Takeshi Matsumura, Yosuke Kita, Koya Kubo, Yugo Yoshikawa, Shinji Michimura, Toshiya Inami, Yusuke Kousaka, Katsuya Inoue, and Shigeo Ohara
- Abstract
Helical magnetic structures and their responses to external magnetic fields in Yb(Ni
1-x Cux )3 Al9 with a chiral crystal structure of the space group R32 have been investigated by resonant X-ray diffraction. It is shown that the crystal chirality is reflected in the helicity of the magnetic structure by a one-to-one relationship, indicating that an antisymmetric exchange interaction mediated via the conduction electrons exists. When a magnetic field is applied perpendicular to the helical axis (c-axis), the second-harmonic peak of ð0; 0; 2qÞ develops with increasing field. The third-harmonic peak of ð0; 0; 3qÞ has also been observed for the x = 0.06 sample. This result provides strong evidence for the formation of a chiral magnetic soliton lattice state, a periodic array of chiral twist of spins, which has been suggested by the characteristic magnetization curve. The helical ordering of magnetic octupole moments accompanying the magnetic dipole order has also been detected. [ABSTRACT FROM AUTHOR]- Published
- 2017
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