National Institutes for Quantum and Radiological Science and Technology
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Encoding of odor information and reward anticipation in anterior cortical amygdaloid nucleus
No full textOlfactory information directly reaches the amygdala through the olfactory cortex, without the involvement of thalamic areas, unlike other sensory systems. The anterior cortical amygdaloid nucleus (ACo) is one of the olfactory cortices that receives olfactory sensory input, and is part of the olfactory cortical amygdala, which relays olfactory information to the amygdala. To examine its electrophysiological features, we recorded individual ACo neurons during the odor-guided go/no-go task to obtain a water reward. Many ACo neurons exhibited odor-evoked go cue-preferred activity during the late phase of nose-poking supporting the population dynamics that differentiate go/no-go responses before executing the odor-evoked behaviors. We observed two types of neurons with different anticipation signals: one neuron type exhibited gradual increases of activity toward reward delivery, while another type exhibited a phasic go cue-preferred activity during nose-poking as well as another phasic anticipatory activity for rewards. These results suggest that the ACo may be involved in reward-related behavioral learning by associating the olfactory information with reward anticipation.journal articl
Self-powered gamma-ray detector based on high-radiation-tolerant CuInGaSe solar cell
No full textFor radiation detection, a solar cell device has been introduced as a self-powered dosimeter that outputs a radiation-induced current signal without requiring an external voltage but using a built-in potential. As CuInGaSe (CIGS) solar cells have very high radiation tolerance, they likely allow to detect radiation stably over long periods in a high-dose environment. However, the radiation detection characteristics of CIGS solar cells should be further clarified. We focus on the current response of CIGS solar cells in a gamma-ray environment and characterize the dosimeter behavior. In addition, we propose a method to construct a photodetector that leverages the characteristics of solar cells, and another method to enhance the device durability using radiation degradation prediction based on the formulation for space solar cells. The CIGS solar cell device exhibits stable operation without degradation even in a Co-60 gamma-ray environment of 1 MGy, and its detection characteristics allow measuring dose rates from 100 mGy/h to 100 kGy/h with an approximate resolution of 10 mGy/h with a fast response of approximately 2 ms. We derive radiation detection characteristics of CIGS solar cells from their high external quantum efficiency and high parallel resistance. Overall, we found that conventional solar cell technologies may enable the development of high-performance dosimeters.journal articl
Bi2Sr2Ca2Cu3O10+δ単結晶におけるNV中心を用いた高圧力下磁気測定
No full textBi2Sr2Ca2Cu3O10+δ (Bi2223)は常圧下において超伝導転移温度 Tc = 110 K 以下で超伝導を示す。最適ドープ試料の Tc の圧力依存性は、交流帯磁率測定によって調べられており、その他の銅酸化物超伝導体同様にドーム型の傾向を示すが、24 GPa を超えると Tc が再び上昇し始めると報告されている。一方、高圧力下電気抵抗測定においては、Tcオンセットこそドーム型の依存性を示すものの、高圧力領域ではゼロ電気抵抗温度は低温側にシフトし、電気抵抗の温度依存性も半導体的な振る舞いへと変化する。これらの相違は、圧力媒体の種類に起因すると考えられている。本研究では、圧力媒体の違いが超伝導転移に与える影響を調べるために、窒素-空孔(NV)中心を用いた光検出磁気共鳴（ODMR）による高圧力下磁気測定を実施した。圧力発生にはダイヤモンドアンビルセルを用い、[111]配向 1b ダイヤモンドアンビルにイオン注入・アニーリングすることでキュレット表面に NV 中心を形成した。試料には最適ドープ Bi2223 単結晶試料を用いた。赤色発光強度の検出には EMCCD カメラを用い、試料室内部の磁場イメージングを行った。図 1a に EMCCD カメラで得られた試料室の蛍光マップを示す。ゼロ磁場冷却後に 1.9 mT の磁場を印加した場合の 59±4 K における各地点の ODMR スペクトルを図 1b に示す。磁場は[111]方向に印加している。また、ODMR の共鳴周波数から決定した試料室内の圧力はおよそ 4 GPa である。Bi2223 試料直上では、超伝導転移を示唆する反磁性を観測した。当日は実験の詳細およびその他の結果についても報告する。第73回応用物理学会 春季学術講演会conference poste
Establishment of a low dose rate 133Ba γ-ray calibration field for photon energy in the 300–400 keV range
No full textA γ-ray calibration field using a sealed 133Ba source for photon energy in the 300–400 keV range was established at the Japan Atomic Energy Agency to evaluate radiation protection devices under low dose rate conditions. To suppress low-energy γ-ray components, a 2-mm lead filter was applied. The photon fluence spectrum was measured using a CdTe spectrometer and an unfolding method, yielding a spectrum with a mean energy of 321 keV. Reference air kerma rates were determined using ionization chambers calibrated in a 137Cs field, with energy correction factors applied. Spectrometry using a CeBr₃ scintillation spectrometer combined with the G(E) function method was employed to validate these corrections. Spectrum-averaged conversion coefficients were derived from the measured spectrum, indicating equivalence to the N-400 radiation quality. This field provided air kerma rates from 0.22 to 2.13 μGy h−1, suitable for testing devices used in environmental monitoring and nuclear emergency response.journal articl
Temporal-orbitofrontal pathway regulates choices across physical reward and visual novelty.
No full textExpectation of perceptual novelty shapes our daily decisions and has an impact on how we evaluate primary rewards. To identify the underlying circuitry, we trained subjects to choose between offers associated with varying probabilities of receiving large juice rewards and experiencing novel objects. Anticipated novelty modulated valuation by increasing both choice preference for and motivational value of large rewards. This novelty-reward interaction was reflected in a circuit comprising anterior ventral medial temporal cortex (AVMTC), implicated in detecting and predicting novelty, and orbitofrontal cortex (OFC), which receives AVMTC inputs and signals the reward value associated with visual objects. Novelty and reward signals were first detectable in AVMTC. However, OFC neurons' activity more closely reflected subjective preference across the reward-novelty offers in our task. Chemogenetic disruption of AVMTC→OFC altered the impact of expected novelty on reward valuation. These results suggest that the ventral visual system contributes to novelty-reward interactions during valuation through direct projections to prefrontal cortex.journal articl
Altered Brain Functional Connectivity and Neurometabolite Correlations in Orofacial Chronic Pain with Central Sensitization
No full textPurpose: Central sensitization (CS) is one of the causes of refractory chronic orofacial pain (COFP). Chronic pain reportedly alters resting-state functional connectivity (FC) in the brain. The salience network (SN) overlaps with brain regions involved in chronic pain. Moreover, excitatory and inhibitory neural activities can alter FC. This study investigated the correlations between FC of the SN and other neural circuits, neurometabolites in anterior cingulate cortex (ACC), and CS Inventory (CSI) scores.Patients and methods: Participants were 21 COFP patients and 21 healthy sex- and age-matched volunteers. We conducted a combined study of CSI scores, resting-state functional magnetic resonance imaging, and proton magnetic resonance spectroscopy of ACC.Results: FC between the nucleus accumbens within the mesolimbic system and SN regions was significantly stronger in patients compared with that in controls. In patients, the results revealed positive correlations between CSI scores and FC in four pairs of regions: ACC-right putamen and ACC-right globus pallidus, left insula-right putamen, and right anterior supramarginal gyrus-right lateral prefrontal cortex. Regarding correlations between neurometabolites in ACC and FC between ACC and other cortical regions, the results revealed that bilateral ACC-anterior insula FC was negatively correlated with glutamate, glutamine, and glutathione. Additionally, aspartate, an N-methyl-D-aspartic acid receptor agonist, was negatively correlated with FC of ACC-right parietal cortex in the default mode network. Regarding FC of bilateral ACC-posterior parietal cortex in the frontoparietal network, FC on the right side was positively correlated with glutathione associated with excitatory neuronal activity, whereas that on the left side was negatively correlated with gamma-aminobutyric acid / total creatine associated with inhibitory neural activity.Conclusion: Connectivity within the SN, and between the SN and the mesolimbic system and other networks, may be involved in CS in COFP. Neurometabolites in the ACC may modulate FC linked to the ACC.journal articl
Burst Intensification by Singularity Emitting Radiation in Laser Plasma
No full textBurst Intensification by Singularity Emitting Radiation (BISER) appears as a bright temporally and spatially coherent Extreme Ultraviolet (XUV) and x-ray source driven by compact multi-terawatt femtosecond lasers in gas targets. There BISER originates from relativistic plasma singularities, so that the emission source size has a nanometer scale. The BISER x-ray yield quadratically depends on the driving laser power. BISER spectra have hundreds of electronvolt (eV) bandwidth embracing the 'water window' region (284 – 543 eV). Simulations predict that BISER pulses have durations close to the transform limit, which promises pulses shorter than the atomic unit of time (24 attoseconds). Based on the BISER brightness at ~20 terawatt laser power and the quadratic scaling, the brightness of BISER driven by petawatt-class lasers is predicted to exceed XUV free electron lasers. The BISER concept creates a new framework for a wide range of media emitting travelling waves capable of constructive interference, including acoustic and gravitational waves. Here we review the BISER experimental discovery, its explanation based on the relativistic laser plasma simulations and catastrophe theory, experimental validation of the theoretical BISER model, proposal for imaging fast moving singularities, driving laser requirements, and future prospects emphasizing the driving laser wavelength scalability and possibility of terawatt attosecond coherent x-ray pulse generation.journal articl
Survey on physicians’ perceptions of occupational radiation exposure management: differences in perceptions by sex
No full textWith the increase in the diagnostic and therapeutic techniques involving radiation, investigating the radiation-protection behavior of physicians and healthcare workers is becoming increasingly important. In this study, sex differences in physicians’ Knowledge, Attitudes, and Practices (KAPs) were examined regarding occupational radiation protection in Japan. A cross-sectional survey was conducted, and the responses were analyzed using logistic regression, principal component analysis (PCA), and cluster analysis. Logistic regression analysis showed that female physicians had a higher likelihood of consistent personal dosimeter wearing than male physicians after adjusting for age and clinical department; this finding warrants cautious interpretation given the small female subsample. PCA extracted four principal components representing distinct dimensions: (1) perceived organizational support for radiation protection, (2) understanding of and intention to practice protective behavior, (3) personal dose management behavior, and (4) awareness of rule violations by others. A cluster analysis based on these components identified five distinct patterns of radiation protection awareness and behavior. Differences in sex, age, and clinical department were observed across clusters, indicating the influence of both individual and institutional contexts. These results indicate that physicians’ KAPs for radiation protection are shaped not only by professional knowledge but also by their roles, environments, and personal experiences. Although the self-reported, cross-sectional survey design limits causal inference and generalizability, the observed patterns highlight specific targets for improvement. These insights can aid the development of practical interventions that can enhance radiation protection among healthcare professionals.journal articl
Applicability of simplified alpha spectroscopy for radionuclidic purity tests at 225Ac production sites
No full textThis study evaluated the feasibility of a simplified alpha spectroscopy method using a collimator for radionuclidic purity testing at 225Ac production sites. Monte Carlo radiation transport simulations indicated that the full width at half maximum for the peak due to alpha particles with 4.8 MeV emitted from 226Ra, a potential impurity in cyclotron-produced 225Ac, could be under 300 keV. Experimental results confirmed that this peak was distinctly separated from the primary alpha particle peaks of 225Ac and its progeny. Further simulations were implemented to evaluate the minimum detectable activity for 226Ra in an 225Ac solution with activity between 100 Bq and 10 000 Bq. The findings suggested that at least 0.5% contamination of 226Ra (activity ratio) can be detected by measuring an 225Ac solution over 3600 s. This simplified alpha spectroscopy method shows promise as a viable measurement technique to support future criteria for radionuclidic purity testing at 225Ac production sites.journal articl
