National Institutes for Quantum and Radiological Science and Technology
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Developmental changes in element-specific localization during seed maturation of Lotus japonicus
No full textIn dicotyledonous seeds, mineral elements are accumulated in specific tissues that support germination and early seedling growth. Although element-specific localization patterns in mature seeds have been reported, the dynamic changes in spatial distribution during seed maturation remain poorly understood. In this study, we investigated developmental changes in elemental localization during seed maturation using in-air micro-PIXE elemental imaging. Seeds of Lotus japonicus (accession Miyakojima MG-20) were collected at multiple maturation stages, and the spatial distributions of potassium (K), phosphorus (P), and calcium (Ca) were analyzed. At early and mid maturation stages, K and P were distributed relatively uniformly throughout the seed, whereas Ca began to accumulate preferentially at the seed surface during mid maturation. With further maturation and differentiation of internal structures such as cotyledons and the root / hypocotyl, P showed preferential accumulation in specific tissues. Ca exhibited a distinct transition, accumulating in both peripheral and internal tissues and forming a characteristic linear pattern in cotyledons of fully mature seeds. In contrast, K remained broadly distributed throughout maturation. These results demonstrate that mineral accumulation during seed maturation is dynamically regulated in coordination with tissue differentiation and follows element-specific accumulation strategies.conference pape
Novel criterion for W-Cu interlayer joint delamination in divertor target monoblock under heating through ANSYS-CZM parametric studies
No full textTo evaluate the possibility of delamination in the joint interface between the divertor target tungsten monoblock and the copper interlayer, the stress and displacement distributions around the joint interface under monotonic heat loading up to the equivalent level of the disruption (20 MW/m2) were investigated in this study, by the finite element analysis applying the Cohesive Zone Model (CZM). Parametric studies were performed regarding the strength and critical energy release rate of the joint interface. Each kinetic parameter was set so that not to exceed the corresponding one of the weaker base material (the copper or tungsten) in Mode I failure. The interfacial shear stress and displacement reached their thresholds respectively, while the normal stress showed compression (Mode II failure) regardless of inputs of CZM parameters (strength and critical energy release rate of the joint). Consequently, it is suggested that the dominant failure mode during heating is mode II. In addition, a conservative delamination criterion regarding the relation between strength and critical energy release rate of the joint interface was obtained based on the CZM parameters of mode I, which are lower than those of mode II. This criterion indicates an increased possibility of the delamination due to neutron irradiation, considering degradation of the critical energy release rate of tungsten and the strength of bulk copper as reported in previous studies.journal articl
First evaluation of a heteroepitaxial diamond ionization chamber operating at low voltage for diagnostic X-ray dosimetry
No full textPurpose: Real-time and high-sensitivity dosimetry in diagnostic radiology demands compact detectors that operate at low bias voltage, exhibit minimal energy dependence, and ensure stable charge collection. This study evaluates a heteroepitaxial diamond ionization chamber (HED-IC) fabricated on a 4 × 4 × 0.5 mm³ substrate for its performance under diagnostic X-ray conditions.Methods: The HED-IC, equipped with Ti/Au electrodes, was operated at bias voltages of −0 to −500 V and irradiated with diagnostic X-rays (effective energy: 25–45 keV). Dose linearity, sensitivity, energy dependence, and charge-collection stability were measured. The volumetric sensitivity was compared with that of a standard air-ionization chamber. Monte Carlo simulations using PHITS were performed to estimate the expected enhancement in energy-absorption density within diamond.Results: The HED-IC exhibited excellent dose linearity (R² > 0.997) even at bias voltages as low as −50 V. At −50 V to −100 V, its sensitivity was comparable to or higher than that of a standard air-ionization chamber despite a 1/830 smaller active volume. The volumetric sensitivity enhancement (4.5 × 10³–8.5 × 10³) was of the same order as the PHITS-calculated values (5 × 10³–6 × 10³), indicating consistent experimental and theoretical trends. The energy dependence across 25–45 keV remained within ±10 % without energy-compensation filters. After pre-irradiation (priming), the detector demonstrated negligible leakage current and reproducible charge-collection characteristics.Conclusions: The HED-IC provides a unique combination of high sensitivity, low-voltage operation, and minimal energy dependence, fulfilling key requirements for diagnostic X-ray dosimetry. Its scalability and cost-effectiveness enabled by heteroepitaxial diamond growth make it a promising candidate for compact, tissue-equivalent, real-time dosimetry and quality assurance in diagnostic radiology.journal articl
Development of a 553 nm light source for Ba isotope–selective excitation using a distributed feedback (DFB) laser and a periodically poled LiNbO₃ (PPLN) waveguide
No full textバリウム同位体は、イオントラップ型量子演算素子での量子ビットの候補となっている。本研究では、バリウムの同位体選択的励起と導入を目指して、553nmの励起用レーザー光源を、分布帰還型レーザーdistributed feedback (DFB) laserと周期的分極反転ニオブ酸リチウムperiodically poled LiNbO3 (PPLN)を用いて開発した。出力は、1107nmDFB基本波が86mW、第２高調波553nmが15mWと、導入に十分な強度が得られた。DFBレーザーの設定温度を変えることにより、出力波長を変化させることが可能である。これに基づき、シングルモードでモード飛びのない波長掃引が示された。これは、バリウムの同位体選択的励起に必要な開発項目であるjournal articl
Competitive transplantation in rat mammary tissue and its use for cell competition and tumor clonality assays
No full textCompetitive transplantation is a valuable technique in experimental biology, although its use in mammary gland biology has been limited to mouse models. We aim to implement this technique in rats, an alternative model relevant to the human breast. Mammary cells were obtained from wild-type or transgenic rats expressing green or red fluorescent protein and transplanted into the cleared fat pads of recipients. Tissue clearing was implemented for the rat mammary gland to evaluate fluorescent proteins by confocal imaging. Transgenic rats were used as recipients because wild-type recipients rejected transgenic cells. A competitive assay between radiation-exposed and nonexposed cells expressing different fluorescence revealed no effect of high-dose radiation on the repopulating ability. A polyclonal nature was identified in adenomas developing in recipients that received a mixture of fluorescent and nonfluorescent cells and were exposed to carcinogens. Thus, we developed a method to track multiple cell lineages in the rat mammary gland.journal articl
Mesoscopic cavity quantum electrodynamics with phase-disordered emitters in a Kerr nonlinear resonator
No full textThe field of cavity quantum electrodynamics (QED) has seen a recent resurgence of interest in few- and many-body physics owing to the realization that the breaking of symmetries and the presence of disorder can give rise to entirely new phenomena. Here we demonstrate a few-emitter cavity QED system capable of realizing new Hamiltonians in quantum optics based on breaking of symmetries and the realization of an in situ Kerr nonlinearity. Our experiment relies on a high-finesse silicon carbide whispering gallery mode resonator hosting an ensemble of silicon vacancy color centers. The simultaneous presence of spectral and spatial disorder of the mesoscopic atom system gives rise to emergent chirality, and the optical nonlinearity of the silicon carbide host crystal enables the observation of atom-photon correlations induced by a four-photon nonlinear process. This work demonstrates the potential for solid state defect systems to realize emerging proposals and to study fundamental physics in quantum electrodynamics.journal articl
Detection of negative charge state luminescence from nitrogen vacancy centers under electron beam excitation: effects of extrinsic and intrinsic factors
No full textElectrically driven optical emission from the negatively charged nitrogen-vacancy (NV−) centers is essential for the realization of diamond-based quantum devices. Attempts have been made to achieve electrical excitation using complex device structures and electric fields, but no clear success has been achieved. The zero-phonon line (ZPL) of NV− centers is rarely observed under electrical excitation. The absence of NV− ZPL under electrical excitation may be attributed to an increased ionization rate of the NV− centers due to high-energy electron/hole injection. To realize electrically driven NV− centers, it is crucial to understand and control the luminescence mechanism of NV− centers under high-energy electron/hole injection. Cathodoluminescence (CL) based on electron beam excitation can generate numerous electron-hole pairs, enabling rapid evaluation of NV− centers without requiring electric fields and device structures. In this study, we investigated the luminescence properties of NV− centers by investigating intrinsic materials factors (substitutional nitrogen concentration, negative and neutral NV centers concentrations) and extrinsic measurement conditions (temperature, excitation power, etc.) using the CL method.journal articl
Prostate dose escalation may positively impact survival in patients with clinically node-positive prostate cancer definitively treated by radiotherapy: surveillance study of the Japanese Radiation Oncology Study Group (JROSG).
No full textTo retrospectively analyze outcomes of patients who received definitive pelvic irradiation for clinically pelvic node-positive (cT1-4N1M0) prostate cancer (PCa).journal articl
Nuclear, Thermal, and Shielding Design of Test Cell in A-FNS
No full textSignificant quantities of neutrons and gamma rays deduce the nuclear heating on the shielding walls of the test cell (TC) in the A-FNS. This study presents nuclear and thermal analyses of the shielding wall in the A-FNS to evaluate its radiation-shielding effectiveness and cooling capacity. Previous designs incorporated cooling water pipes embedded in the concrete shielding wall for thermal management. However, we determined that this approach failed to maintain concrete temperatures within specified limits due to the low thermal conductivity of concrete and the challenge of ensuring adequate contact between the concrete and piping. We developed a new shielding wall design that eliminates the need for cooling pipes inside the concrete. This updated design integrates an 85 cm of stainless steel 316 L (SS316L) structure containing 20 % cooling water positioned in front of the concrete, which maintains concrete temperatures within acceptable limits. In addition, nuclear assessments of this revised shielding wall structure were conducted to verify its radiation shielding capacity. Results indicate that the effective dose criteria are met at thicknesses of 255 cm for heavy concrete and 335 cm for ordinary concrete when the 85 cm of combing structure of SS316L/water (20 % water) is included.journal articl
Forced Oscillation of Circadian Transcriptional Circuits
No full textCircadian rhythms are based on transcriptional circuits by clock genes. Accumulating evidence indicates an existence of unidentified oscillator independent of the clock genes, although the mechanism has been unclear. Here, we show that circadian Ca2+ rhythms mediate forced oscillations of the transcriptional circuits. Circadian Ca2+ oscillation is observed in the cells lacking Bmal1 or Cry1/2. Newly developed non-rhythmic cell models revealed that clock gene expression was insufficient to generate autonomous oscillations of transcription and Ca2+. Importantly, transcriptional oscillations of Per2 and Bmal1 were sustained by artificial induction of daily Ca2+ signaling. CaMKII-CLOCK axis is a basic pathway for oscillations of the transcriptional circuits by circadian Ca2+ signaling. These results illustrate a novel clock model that the circadian transcriptional circuits are driven by Ca2+-dependent forced oscillation.journal articl