National Institutes for Quantum and Radiological Science and Technology
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Functionalized Fluorescent Nanodiamonds with Millisecond Spin Relaxation Times
No full textFluorescent nanodiamonds (FNDs) containing nitrogen-vacancy (NV) defects are useful probes for biological imaging and nanoscale sensing applications. Here, we explore the effect of chemical surface modifications and core−shell structures on the T1 relaxation times of 100 nm FNDs hosting nitrogen- vacancy ensembles. The results show that surface oxidation and silica coating of FNDs using the Stöber method can dramatically increase the spin relaxation time from T1 =320± 9 μs to T1 =1.00± 0.06 ms. Using FT-IR and NEXAFS measurements conducted on air oxidized particles, we find that changes to surface functional group sand sp2 carbon density may be responsible for the observed enhancements to the spin relaxation rate. Finally, we use a Monte Carlo model to numerically investigate the relationship between chemical sensitivity and shell thickness and find that a shell thickness on the order of 1 nm should provide the highest sensitivity. Our findings demonstrate that the surface of FNDs can be engineered to exhibit bulk-like T1 relaxation times, in the absence of complex quantum control sequences, which is crucial to advancing biosensing and imaging applications where surface spin noise currently limits measurement precision.journal articl
Current comparator for both AC and DC ratio measurements with 10-8-level accuracy
No full textAccurate measurements of alternating current (AC) and direct current(DC) ratios are fundamental to electric power metrology. However, conventional current comparators for AC and DC typically rely on distinct technologies-electromagnetic induction for AC and superconducting quantum interference devices for DC. This technological divide leads to a fragmented and complex traceability system. Bridging this gap is critical for developing unified current standards that meet the demands of emerging power technologies. In this work, we present a compact, room-temperature AC/DC current comparator that integrates a diamond-based magnetometer using nitrogen-vacancy centers. The device achieves an accuracy of 10-8 for both AC and DC signals and supports a system bandwidth up to 300 Hz, without the need for cryogenics. It surpasses the performance of typical AC comparators, offering ten-fold higher accuracy, and matches that of state-of-the-art DC comparators. This unified, cryogenics-free solution not only enhances precision and versatility but also expands the applicability of the system to DC resistance bridges in quantum electrical standards.journal articl
Dealing with ambiguity in the context of psychological stress resilience
No full textProvide a narrative summary of what is contained in this registration or how it differs from prior registrations. If this project contains documents for a preregistration, please note that here.This registration gives a general overview over a research project on ambiguity and resilience. While the project as a whole investigates ambiguity and resilience, the individual analyses for the different constructs represent separate research questions and will likely result in separate publications. Thus, separate registrations for the individual research questions will be created within the project. For details, please refer to these individual registrations.conference pape
Development of noninvasive measurement for monoacylglycerol lipase activity in the brain using positron emission tomography
No full textObjectives: Monoacylglycerol lipase (MAGL) is well known as a key enzyme for regulation of endocannabinoid system which retrogradely controlled glutamatergic neurons. So far, a lot of efforts have successfully resulted in developments of some useful covalent inhibitors for MAGL [1]. Simultaneously, some positron emission tomography (PET) probes with irreversible brain kinetics were developed for MAGL imaging. Of these, the radiotracer containing azetidine carbamate showed an unexpected clearance of radioactivity from brain in the manner of the reversible-type radiotracer. Here, we forecasted in vivo behavior of azetidine carbamate radiotracer by referring a previous report [1], demonstrating it by the in vitro assessment. Additionally, utilizing a unique brain kinetic of azetidine carbamate radiotracer, we attempted noninvasive measurement of MAGL activity using PET.Methods: To confirm production of [11C]CO2 derived from hydrolyzation of [11C]azetidine carbamate radiotracer via MAGL, we conducted in vitro assessments using [11C]QST-0837 (Fig. 1B), an azetidine carbamate radiotracer for MAGL [2], and rat brain homogenates. As an opponent, [11C]HPPC, a piperidine carbamate radiotracer [2], was also used. PET imaging with [11C]QST-0837 was carried out using four healthy rats and hydrolysis rate (KH) of [11C]QST-0837 via MAGL was estimated by mono-exponential fitting on time-activity curves of the regions of interests (ROIs).Results: In vitro assessments showed the generation of [11C]CO2 as the final product derived from hydrolysis of [11C]QST-0837 via MAGL, whereas [11C]HPPC has not seen that. In PET study with [11C]QST-0837 using healthy rat, KH values in the brain were successfully estimated around 0.7 /h in each ROI.Conclusions: We successfully developed the method for noninvasive quantifying hydrolysis rate of MAGL using PET with [11C]QST-0837. References: [1] Butler CN, et al., J. Med. Chem. 2017, 60, 9860–9873. [2] Yamasaki T, et al. Brain. Commun. 2024, 6, fcae172.iSRS2025conference poste
Development and Performance Evaluation of Ferromagnetic-Resonance Instruments with NanoVNA
No full textIn our daily lives, electromagnetic waves such as visible light, microwaves, and X-rays have become indispensable. One of the key phenomena related to the microwave absorption of magnetic materials is ferromagnetic resonance (FMR). FMR measurements are essential for understanding magnetization dynamics and crucial for developing spintronics devices. This study aims to enable the observation of FMR cost-effectively. Recently, vector network analyzers (VNA) have been widely used for broadband FMR measurements; however, VNAs are prohibitively expensive. To address this issue, we developed an FMR measurement system using NanoVNA, an affordable vector network analyzer readily available on platforms such as Amazon. The NanoVNA is capable of measuring up to 3 GHz, making it suitable for many FMR experiments. Although NanoVNA’s application to physical property measurements, such as high-frequency permittivity, is still in its infancy [1], it holds significant potential. In this study, FMR measurements were performed on Y₃Fe₅O₁₂ (YIG) thin films with a thickness of approximately 2 μm grown on Gd₃Ga₅O₁₂ (GGG) substrates. Fig. 1 shows magnetic field dependence of FMR spectra of the YIG thin film measured using NanoVNA. The measurements were conducted at room temperature, with the magnetic field applied in the film plane. A dip in the transmission coefficient (S21) corresponding to absorption was observed, which shifted to higher frequencies with increasing magnetic field. This confirms that the observed phenomenon is FMR. In this presentation, we will also introduce cost-reducing strategies, including the use of 3D-printed components.[1] A. Erkoreka and J. Martinez-Perdiguero, Rev. Sci. Instrum. 95, 023903 (2024).Conference on Laser and Synchrotron Radiation Combination Experiment 2025 (LSC2025)conference presentatio
フラグメント分子軌道法による励起状態の解析法
No full text電子励起状態の性質を解析することは、光合成初期過程や有機光デバイスの機能を理解する上で極めて重要である。本研究では、フラグメント分子軌道（FMO）法に基づく励起状態計算から、全系の遷移密度行列（TDM）を再構築する手法を開発した。さらに、再構築されたTDMを特異値分解することにより、FMOの線形結合として全系の自然遷移軌道(NTO)を計算し、電子励起の集団性や非局在性を定量化できる手法を提案する。計算手法の検証として、ピレン二量体に対して本手法を適用し、FMOから再構築されたNTOがフラグメント分割近似なしの結果とよく一致することを示した。応用例として、ペンタセン集合体に対して本手法を適用した。まず、FMO法により得られる励起状態ハミルトニアンの近似として、フレンケル励起子状態とワニエ-モット励起子状態を導出する。これらの近似的な励起子状態とFMOから得られる実際の励起状態を、集団性と非局在性の観点から比較することにより、ペンタセン集合体の励起状態の性質を詳細に議論した。さらに、光合成反応中心に適用した例についても報告する。量子生命科学会第７回大会conference poste
Impacts of climate change in the North Pacific: which are the most important anthropogenic radionuclide tracers of oceanic change?
No full textIncreasing anthropogenic greenhouse gas emissions (mainly carbon dioxide and methane) into the atmosphere have accelerated global warming with serious impacts on Earth ecosystems. Changes in precipitation patterns have increased flooding, and draught events on the other sides resulted in melting of glaciers and sea level rise. Oceans have been experiencing serious changes, such as frequent marine heat waves on a global scale, which could slow the Global Meridional Overturning Circulation (GMOC), disrupting thus the ocean circulation with many accompanying changes in biogeochemical processes, including surface ocean acidification. Anthropogenic radionuclides, released to the marine environment mainly after atmospheric nuclear weapons tests, have been used as sensitive tracers, which could register some of the climate-change impacts on the world ocean (e.g., seawater circulation patterns) as well as on regional seas (e.g., processes in the water column). Climate change affects the time revolution and the distribution of anthropogenic radionuclides in the ocean. Therefore, anthropogenic radionuclides (3H, 14C, 90Sr, 137Cs, 129I, 236U, 237Np and Pu isotopes) have been useful tracers, providing important information on processes in the Pacific Ocean.The North Pacific Ocean (NPO) is a key area in the GMOC path because of the return of deep water to the surface. However, there is no clear picture of GMOC in NPO. The subarctic circulation (SAC) is the largest cyclonic circulation in the NPO, which is characterized as an upwelling region high in nutrients. On the other hand, the North Pacific Subtropical Gyre (NPSTG) is an anticyclonic circulation, which is characterized as a downwelling region low in nutrients. Assuming that the subarctic circulation is an outlet of deep water for the GMOC, a weakened deep-water formation in the North Atlantic and Antarctic Oceans would lead to a decline of upwelling of deep water in the NPSAC, which can weaken the cooling of surface waters and supply of nutrients. Therefore, it is important to better understand the changes in NPSAC and NPSTG accompanied by climate change. Although Pu has been recognized as a useful tracer of biogeochemical processes because of its high chemical reactivity, it has also been an important tool to trace the motion of water masses. Plutonium isotopes in the Pacific Ocean were primarily injected by global fallout from 1961-62 large-scale atmospheric nuclear tests carried out by the Soviet Union in the Arctic at Novaya Zemlya Island, although a significant amount of Pu was also released owing to close-in fallout from the US thermonuclear tests in the Pacific Proving Grounds (PPG) conducted in the 1950s mainly on Bikini and Enewetak Atolls. Global fallout Pu was deposited mainly in the NPSAC, whereas PPG the Pu of PPG origin was injected mainly in the NPSTG. Since the 240Pu/239Pu isotope ratio (0.18) of global fallout was different from that of PPG (0.33), the 240Pu/239Pu isotope ratio and Pu activity concentrations in seawater and sediment have been tracking the time revolution of the water masses in the North Pacific Ocean.the 8th International Conference on Environmental Radioactivityconference presentatio
カテキンの平面構造化によるラジカル消去活性増強と癌細胞傷害効果
No full text体内で過剰に産生される活性酸素種（ROS）は、神経変性疾患や心血管疾患、がんなど、非常に多くの疾患の発症及びその増悪に関与することが指摘されている。従って、過剰産生されたROSの効率的な除去が、疾患の防止とそれに伴う健康寿命の延伸につながることが期待されている。カテキンは緑茶に多く含まれる天然由来抗酸化物質であり、抗酸化効果のほかにも老化抑制作用や抗がん効果があることが知られている。しかし、カテキンは生体吸収量が低いことから、より高機能なカテキン誘導体を用いることで、効率的なROS消去効果が期待できる。我々はこれまでに、(+)-カテキンをベースにした平面構造を有する平面型カテキン誘導体を合成し、そのラジカル消去活性が元の(+)-カテキンの10倍になることを明らかにしてきた。本研究では、平面型カテキンの癌細胞傷害効果について検討した。 平面型カテキンと(+)-カテキンをラット由来胃癌細胞株RGK1に曝露したところ、平面型カテキンは元の(+)-カテキンに比べて顕著な細胞傷害性を示した。また、平面型カテキンはミトコンドリア膜電位の低下を引き起こすとともに活性型カスパーゼ3の発現増加を誘導したことから、ミトコンドリアを介したアポトーシスによる癌細胞死を引き起こすことが示唆された。さらに、平面型カテキンの抗酸化効果における活性点と考えられるヒドロキシ基をアセチル化したアセチル化平面型カテキンを合成し、癌細胞傷害効果を検討したところ、アセチル化によって細胞傷害性が著しく向上した。また、ROS消去活性を電子スピン共鳴法によって測定したところ、アセチル化によってROS消去活性が減弱したものの、エステラーゼ処理によって強いROS消去活性を示した。以上より、アセチル化による平面型カテキンの癌細胞傷害性の増強には、アセチル化による活性点の保護と細胞内エステラーゼによるアセチル基の脱保護を介した活性の復活が示唆された。量子生命科学会 第7回大会conference poste
窒化ガリウムにイオン注入したプラセオジムの電子状態と配位構造
No full text窒化ガリウム(GaN)中の孤立したプラセオジム(Pr)イオンは、ナノスケールの空間分解能で高感度に環境をセンシングできる量子センサーとして利用できる。イオン注入法によって特定の位置・数のPrイオンを注入できるが、注入後のPrイオンの電子状態の正確な状態を観測した例は少なく、詳細な理解は得られていない。Spring-8 BL14B1エネルギー分散型XAFS装置を用いて、GaNにイオン注入したPrの電子状態・周辺原子構造について解析したところ、注入後のPrはすべて+3価の状態でGaサイトを置換しているが、周辺の長距離秩序が乱れており、それが高温熱処理によって再配列することで非発光遷移過程が減少することがわかった。第41 回希土類討論会プログラムconference presentatio
Measurement of spatial polarization distributions of inverse Compton scattered gamma rays
No full textIn the UVSOR synchrotron facility, gamma rays with a maximum energy of 6.6 MeV are generated by 90-degree inverse Compton scattering (ICS) between a 750 MeV electron beam and a Ti:Sa laser with a wavelength of 800 nm. The gamma rays are used for atomic-scale defect analysis using gamma-ray-induced positron an-nihilation spectroscopy and for evaluation of polarized gamma-ray detectors. The generation of polarized gamma rays is one of the key features for ICS. It is well known that polarized gamma rays are generated by using linearly and circularly polarized lasers, but their polarization state varies with the position of the gamma-ray beam cross section. For example, the polarization axis of linearly polarized gamma rays changes with the position of the cross section. Moreover, the degree of circular polarization of circularly polarized gamma rays varies with the scattering angle and changes to linear polarization in the region outside the cross section. On the other hand, ICS using lasers with polarization states different from linear or circular could generate gamma rays with novel polarization states. We have developed a Compton polarimeter capable of measuring the two-dimensional polarization distribution of ICS gamma rays. In this conference, we will present the measurement results of the spatial polarization distribution of gamma rays generated using linearly, circularly, and axially symmetric polarized lasers. It was clearly observed that the polarization axis of linearly polarized gamma rays changed with the position of the cross section. We also demonstrated that the gamma rays generated by a circularly polarized laser transitioned to linear polarization in the outer region with the polarization axis aligning along the azimuthal direction. Furthermore, the gamma rays generated by an axially symmetric polarized laser were randomly polarized around the central axis and azimuthally polarized in the outer region.The 5th Nuclear Photonics Conferenceconference presentatio