National Institutes for Quantum and Radiological Science and Technology
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Single shot all-optical switching in artificial ferrimagnetic Co/Gd/CoFeB trilayer
No full textManipulation of magnetization is one of the most central topics in the field of spintronics because of its essentiality from both fundamental and technological viewpoints. Among the various ways of magnetization manipulation, all-optical switching (AOS) which involves manipulating magnetization using laser pulse with the absence of magnetic field is attracting an increasing interest, due to its ultrafast switching process down to picosecond scale as well as low energy consumption which are desirable to future logical and memory devices. In this study, a new type of artificial ferrimagnetic multilayers contains a CoFeB layer which is popularly used in MTJs was developed for the purpose of AOS study. The samples investigated in this study have a stacking structure of Ta(3 nm)/Pt(3 nm)/Co(0.8 nm)/Gd(x nm)/CoFeB(y nm)/MgO(2 nm)/Ta(5 nm), which were deposited on thermally oxidized Si substrate at room temperature by magnetron sputtering. The ferrimagnetic coupling in Co/Gd/CoFeB tirlayer is confirmed by element-specified hysteresis loop measurement using XMCD. Hysteresis loops suggest a well-defined PMA is established in our sample, and the entirely overlapping feature of the hysteresis loops suggest Co, Gd and CoFeB layers are antiferromagnetically exchange-coupled to each other. The AOS experiment was performed by using a home-made femtosecond laser integrated magneto-optic Kerr effect (MOKE) microscope. A linearly polarized laser pulse (wavelength: 1033 nm; width: 253 fs) was irradiated to the sample surface at normal incidence. MOKE images were taken before and after the laser irradiation, and then the differential images were processed to check the laser irradiation induced magnetization change. For pulse energy density around 5.1 mJ/cm2~7.8 mJ/cm2, deterministic AOS was observed. The reversal area increases with the pulse energy which can be interpreted by the spatial Gaussian shape of the laser pulse. Below this energy range, magnetization reversal was found to be not sufficient. Above this energy range, complex AOS behaviors involve deterministic AOS at the out-edge and random multidomain formation at the center region was observed. Through a systematic AOS study on a double-thickness-wedge sample, we found rather than the total magnetization, but the individual magnetization of Gd and CoFeB layers play a critical role in determining the AOS in Co/Gd/CoFeB, which can be well interpreted in terms of a purely thermal toggle process. This newly developed CoFeB-based artificial ferrimagnet will provide a new building block for developing MTJs with both ultrafast optically switching and large magnetoresistance.第73回応用物理学会春季学術講演会conference presentatio
ガス媒質における軟Ｘ線高次高調波発生
No full text薄ディスクYb:YAGレーザーと光パラメトリックチャープパルス増幅器を用いた高強度フェムト秒赤外光源の開発とそれを用いた水の窓を超える軟X線高次高調波発生と応用研究について発表する。第1回ISSP-IMSS研究会conference presentatio
133Cs+20Ne反応における149Tbの製造と化学分離
No full textタンデム加速器実験課題「133Cs+20Ne反応による149Tbの製造」での研究成果として、加速器で製造する医療用RIであるTb-149の製造と化学分離に関する実験結果に基づいて、製造に基礎データとなる励起関数測定に成功したこと、並びに照射済みCsターゲットから簡便に無担体のTbトレーサーを得る手法を確立したことを報告する。東海・重イオン科学シンポジウムータンデム加速器成果報告会ーconference poste
ルテチウム-177標識前立腺特異的膜抗原特異的リガンド（177Lu-PSMA-617）注射液を用いた核医学治療に係る医療実態調査報告書
No full text要旨： 前立腺特異的膜抗原（prostate specific membrane antigen: PSMA）陽性去勢抵抗性前立腺癌に対して用いられるルテチウム-177標識前立腺特異的膜抗原特異的リガンドは，今後薬事承認されたのちに臨床使用されることが予想される．現在，核医学治療を行い，かつ，計画的な治療管理を行った場合の算定として，放射性同位元素内用療法管理料が設定されているが，本剤を用いた場合にも同様の管理料を設定する必要がある．日本核医学会は，本治療の医療実態を調査するため，本剤の治験に参加した医療機関を対象に調査を行った．調査の結果，外科系学会社会保険委員会連合生体検査試案第7.4版に基づく1症例あたりの治療管理に必要な費用は，1,752,860円と算出された．本剤は，6週間ごとに最大6回の投与を行うこととされており，1回投与あたりの当該治療管理料は292,143円，診療報酬としては1症例1回投与あたり29,214点が妥当であると考えられた．また，治療適応可否判断の為に必要なPSMA-PET診断には，溶出・調製作業などが必要となる．溶出・調製管理費用として，1症例あたり123,083円の診療報酬の設定が必要であり，1回投与あたり12,308点が妥当であると考えられた．journal articl
Intrathoracic 90Y-NZ-16 therapy improves efficacy and reduces toxicity in pleural mesothelioma mice
No full textTo evaluate the therapeutic efficacy and safety of intrathoracic administration of 90Y-labeled anti-podoplanin antibody NZ-16 in a pleural mesothelioma murine model, in comparison with conventional intravenous administration.journal articl
Improvement of the Quench Detection System for the PF Coils of JT-60SA
No full textThe JT-60SA superconducting coil system comprises 6 Equilibrium Field coils, 4 Central Solenoid modules, and 18 Toroidal Field coils. Detecting a quench correctly in superconducting coils is essential to avoid damage of the coil. During the last integrated commissioning test, spike-shaped voltage fluctuations were observed on the EF and CS quench detection (QD) voltages. The voltage fluctuations occurred when the currents in the EF and CS coils rapidly changed. Following a circuit analysis of the EF coils, it was found that the spike voltage originated at the input of the QD differential amplifier from a slight mismatch of the time constants of the resistance-capacitance (RC) noise filter circuit. The RC filter circuit had to be adjusted precisely to achieve the same time constant between the winding and the pickup coil. The reduction of spike noise was experimentally confirmed by adjusting the variable capacitor or resistor in the filter circuit.journal articl
DA-Raf synergistically binds to the plasma membrane and Ras to suppress ERK signaling
No full textThe small GTPase Ras on the plasma membrane (PM) activates the ERK pathway (Raf–MEK–ERK signaling pathway) to regulate a variety of cellular, physiological, and pathological events. DA-Raf1 (DA-Raf) is a splicing isoform of A-Raf and contains the Ras-binding domain and the Cys-rich domain but lacks the conserved region 2 (CR2) and CR3 containing the kinase domain. Accordingly, DA-Raf dominant-negatively regulates Raf proteins to prevent the Ras–ERK pathway. We elucidate here the mechanisms of how DA-Raf conducts its dominant-negative function on Raf proteins. Because DA-Raf lacks the CR2 and CR3, it was incapable of adopting the autoinhibitory closed conformation and thereby favorable for PM localization. Basic amino acids in DA-Raf Ras-binding domain, and those in the Cys-rich domain, were essential for the interaction with phosphatidylserine in the PM. This interaction favored the cooperative binding of DA-Raf to active Ras, which predominated over that of Raf proteins, leading to the stable PM association of DA-Raf. Consequently, DA-Raf exerts its dominant-negative function on Raf proteins to prevent the Ras–ERK pathway.journal articl
Low-Dose Chronic Radiation Exposure Does Not Induce DNA Oxidative Damage in Pinus densiflora a Decade After the Fukushima Dai-Ichi Nuclear Power Plant Accident
No full textIt is well established that radiation effects on wild organisms from nuclear power plant accidents primarily depend on the dose received at the accident; however, impacts of prolonged low-dose exposure remain poorly understood. In this study, oxidative DNA damage in Pinus densiflora, assessed via 8-OHdG levels, was compared between inside (0.87–7.74 μSv/h) and outside (0.094–0.16 μSv/h) the difficult-to-return zone 10 years after the Fukushima accident. Leaf 8-OHdG levels varied among the sites but were unrelated to the absorbed dose. In buds, 8-OHdG levels were very low. An irradiation experiment on 2-year seedlings using Cs-137 at three dose rates (44.8, 461, 1738 mGy/h) also found no association between dose rate and 8-OHdG levels; only sampling points correlated with 8-OHdG levels. In contrast, both dose rate and 8-OHdG levels negatively affected seedling survival after the irradiation experiment. Even without irradiation, samples with >0.04% 8-OHdG did not survive. These results suggest 8-OHdG status indicates seedling health and that environmental stress induces oxidative stress via photosynthesis disruption. Additionally, microsatellite mutation rate in megagametophytes was assessed in 1136 seeds using nine markers, detecting only one mutation in contaminated areas, not statistically significant. This mutation rate was too low for sufficient statistical power. In this study, no evidence was found that low-dose chronic exposure affects oxidative DNA damage or mutation rate in P. densiflora. To understand the impact of low-dose chronic radiation exposure on wild plants, further studies incorporating environmental stress and using endpoints other than mutations, such as genome methylation levels and/or responses to oxidative stress, are necessary.journal articl
Exploring Mutation Patterns of Rice Seeds and Seedlings following Carbon Ion Beam and Gamma Irradiation using Whole Genome Sequencing
No full textA potent technique for crop development, induced mutagenesis enables the creation of new genetic variants. In this work, we used whole genome sequencing (WGS) for high-resolution characterization to compare mutations in rice (Oryza sativa L. cv. Nipponbare) seeds and seedlings exposed to carbon ion beams and gamma rays. Single-base substitutions (SBSs), insertions, deletions, and structural variants were among the genetic changes brought about by both irradiation treatments; however, the frequency and distribution of these changes varied greatly between the two radiation types. At comparable survival-reducing dosages in dry seed irradiation, gamma rays (2.2×10-7/bp) produced more mutations than carbon ions (1.2×10-7/bp). Dry-seed irradiation produced more mutations than seedling irradiation (1.7×10-7/bp) in case of gamma irradiation. On average for dry-seed irradiation, each gamma-ray-irradiated M2 plant had 47.4 SBSs, 29.8 deletions, and 2.5 insertions; in contrast, C-ion-irradiated mutants had fewer, with 22.3 SBSs, 20.0 deletions, and 1.1 insertions, including both homozygous and heterozygous mutations. On the other hand, equivalent gamma-ray-irradiated seedlings had comparatively lower mutations with 38.4 SBSs, 17.6 deletions, and 2.2 insertions. In the case of seed irradiation, carbon ions are approximately eight times more lethal than gamma rays per dose, and gamma ray irradiation of seedlings is approximately six times more lethal than seed irradiation from the comparative study of LD50 for survival of Nipponbare rice.11th International Plant Tissue Culture & Biotechnology Conferenceconference poste
Carbon-ion beam irradiation combined with miR-17-5p/miR-17-3p inhibitors effectively kill osteosarcoma cells
No full textOsteosarcoma (OS) is the most common type of bone cancer and is highly resistant to conventional photon beam radiotherapy; however, carbon-ion radiotherapy (CIRT) is effective in treating OS. In this study, to investigate whether miR-17-5p/miR-17-3p inhibitors act as radiosensitizers for CIRT, U2OS and MG63 OS cells were treated with carbon-ion beam irradiation (IR) alone, X-ray IR alone, or with one of the IR treatments in combination with miR-17-3p inhibitors. Cell death and invasive and migratory abilities were analyzed using cell viability and cell Transwell migration and invasion assays. Apoptosis and autophagy-related protein expression and DNA double-strand break (DSB) induction was determined using western blotting and immunofluorescence staining. We found that carbon-ion beam IR combined with miR-17-5p/miR-17-3p inhibitors significantly inhibited OS cell proliferation, migration, and invasion and markedly increased apoptosis-related cleaved-caspase 3, cleaved-PARP, and Bax expression compared to carbon-ion beam IR and X-ray IR alone. Furthermore, carbon-ion beam IR combined with miR-17-5p/miR-17-3p inhibitors markedly promoted autophagy-related ATG7 and LC3B expressions. In addition, combination treatment with miR-17-5p/miR-17-3p inhibitors and carbon-ion beam IR significantly increased the number of gammaH2AX foci as well as its phosphorylation. Taken together, miR-17-5p/miR-17-3p inhibitors enhanced the carbon-ion beam radiosensitivity of OS cells, presenting a novel strategy for the development of carbon-ion beam combination therapy.journal articl