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result(s) for
"Yamaji, Akihiro"
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Thermal multiferroics in all-inorganic quasi-two-dimensional halide perovskites
by
Kawasaki, Tatsushi
,
Kurosawa, Shunsuke
,
Kageyama, Hiroshi
in
639/301/119/995
,
639/301/119/996
,
639/638/263/915
2024
Multiferroic materials, particularly those possessing simultaneous electric and magnetic orders, offer a platform for design technologies and to study modern physics. Despite the substantial progress and evolution of multiferroics, one priority in the field remains to be the discovery of unexplored materials, especially those offering different mechanisms for controlling electric and magnetic orders
1
. Here we demonstrate the simultaneous thermal control of electric and magnetic polarizations in quasi-two-dimensional halides (K,Rb)
3
Mn
2
Cl
7
, arising from a polar–antipolar transition, as evidenced using both X-ray and neutron powder diffraction data. Our density functional theory calculations indicate a possible polarization-switching path including a strong coupling between the electric and magnetic orders in our halide materials, suggesting a magnetoelectric coupling and a situation not realized in oxide analogues. We expect our findings to stimulate the exploration of non-oxide multiferroics and magnetoelectrics to open access to alternative mechanisms, beyond conventional electric and magnetic control, for coupling ferroic orders.
Multiferroics can possess multiple ferroic orders, for example, electric polarization and magnetism, and are of interest for new device applications. Here thermal control is shown to manipulate electric and magnetic orders in a single-phase quasi-two-dimensional halide perovskite.
Journal Article
Plutonium dioxide particle imaging using a high-resolution alpha imager for radiation protection
by
Hayashi, Masateru
,
Makita, Taisuke
,
Kurosawa, Shunsuke
in
631/1647/245
,
639/4077/4091/4092
,
639/624/1107/510
2021
The internal exposure of workers who inhale plutonium dioxide particles in nuclear facilities is a crucial matter for human protection from radiation. To determine the activity median aerodynamic diameter values at the working sites of nuclear facilities in real time, we developed a high-resolution alpha imager using a ZnS(Ag) scintillator sheet, an optical microscope, and an electron-multiplying charge-coupled device camera. Then, we designed and applied a setup to measure a plutonium dioxide particle and identify the locations of the individual alpha particles in real time. Employing a Gaussian fitting, we evaluated the average spatial resolution of the multiple alpha particles was evaluated to be 16.2 ± 2.2 μmFWHM with a zoom range of 5 ×. Also, the spatial resolution for the plutonium dioxide particle was 302.7 ± 4.6 µmFWHM due to the distance between the plutonium dioxide particle and the ZnS(Ag) scintillator. The influence of beta particles was negligible, and alpha particles were discernible in the alpha–beta particle contamination. The equivalent volume diameter of the plutonium dioxide particle was calculated from the measured count rate. These results indicate that the developed alpha imager is effective in the plutonium dioxide particle measurements at the working sites of nuclear facilities for internal exposure dose evaluation.
Journal Article
Crystal growth and characterization of 1-inch GTAGG: Ce single crystal for sub-micron resolution synchrotron radiation X-ray imaging
by
Bartosiewicz, Karol
,
Kurosawa, Shunsuke
,
Hanada, Takashi
in
639/301
,
639/301/1019
,
639/301/1019/1022
2025
A high-performance Ce
3+
-doped (Gd, Tb)
3
(Ga, Al)
5
O
12
(GTAGG: Ce) single crystal was engineered and characterized, demonstrating a high application potential for advanced X-ray imaging. A transparent 1-inch diameter single crystal was grown using the Czochralski method, demonstrating a significant advancement in large-scale scintillator production. Comprehensive characterization using X-ray diffraction and electron probe micro-analysis confirmed the crystal’s structural integrity. Photoluminescence and radioluminescence spectroscopy demonstrated efficient bidirectional energy transfer between Ce
3+
and Tb
3+
ions, a critical mechanism enhancing the performance of the scintillator. X-ray imaging tests were performed using crystals with a thickness of 100 μm at the Aichi Synchrotron Radiation Center. Comparison with the industry-standard LuAG: Ce scintillator showed that the GTAGG: Ce crystal produced 2.4 times higher light output and achieved a high spatial resolution of 0.85 μm. The results indicated that GTAGG: Ce is suitable for the next generation of high-performance X-ray imaging detectors in scientific and medical imaging applications.
Journal Article
Brachialis Muscle Rupture in a Pediatric Patient Followed Up by Ultrasound Examinations: A Rare Case Report
by
Ichimura, Harumitsu
,
Yamazaki, Masashi
,
Yamaji, Akihiro
in
Case Report
,
Case reports
,
Children
2022
Isolated brachial muscle injuries are relatively rare injuries and reportedly occur during forced elbow extension. Though commonly conservative treatment approach is adopted, the treatment criteria remain unclear. Here, we report the case of a patient who experienced functional recovery after conservative treatment for an isolated brachial muscle injury. The patient was an 8-year-old boy whose chief complaint was left elbow pain. The injury occurred when the patient fell while playing on gymnastics bars and bruised the palmar side of his left elbow on the bar. Owing to the pain in the left elbow, the patient came to our institution. There were no clear signs of deformities or swelling in the left elbow and no obvious tenderness. X-ray and computed tomography (CT) imaging examinations revealed no signs of a fracture or dislocation, and the patient was diagnosed with left brachialis muscle rupture based on magnetic resonance imaging (MRI). Although the brachialis muscle was complete ruptured, a healing tendency was seen on body surface ultrasound examinations over time, and the patient was treated conservatively. After 3 weeks of cast immobilization, the patient underwent range of motion exercises. Two months after the injury, there were no issues with elbow joint function in daily life activities and no limitations in range of motion. Here, MRI was used to diagnose brachialis muscle rupture, and ultrasound examinations were utilized to make treatment decisions.
Journal Article
Crystal Growth and Energy Transfer Study in Ce3+ and Pr3+ Co-Doped Lu2Si2O7
2025
Ce-doped Lu2Si2O7 has a high density, high luminescence efficiency even at high temperatures, and a high effective atomic number, making it a promising candidate for use as a radiation detector in medical devices and resource exploration equipment. In this study, we grow and characterize Pr3+ and Ce3+-doped Lu2Si2O7 single crystals by systematically varying the Ce3+ to Pr3+ ratio to further improve scintillation properties. The optical characterization results show a bidirectional energy transfer: from the Pr3+ 5d levels to the Ce3+ 5d levels and from the Ce3+ 5d levels to the Pr3+ 4f levels. Consistently with this result, the PL decay time of emission from the Pr3+ 5d–4f transition tends to become faster as the Ce3+/Pr3+ ratio increases, due to the energy transfer from the Pr3+ 5d levels to the Ce3+ 5d levels. Additionally, (Ce0.0022 Pr0.0016 Lu0.9962)2Si2O7 exhibits a high light yield comparable to Ce-doped Lu2Si2O7 and a slightly faster decay time than Ce-doped Lu2Si2O7.
Journal Article
Thermoelectric Properties of Nb-Doped SrTiO3/TiO2 Eutectic Solids Fabricated by Unidirectional Solidification
by
Horii, Shigeru
,
Kurosawa, Shunsuke
,
Ogino, Hiraku
in
Crystal lattices
,
Electrical resistivity
,
Grain boundaries
2019
Undoped and Nb-doped SrTiO3/TiO2 (STO/TO) eutectic solids were fabricated from the melt at a eutectic point of STO and TO by unidirectional solidification. Fabricated undoped and Nb:STO/TO eutectic solids were composed of the TiO2 rod-like and the SrTiO3 matrix phases, and the periodic and uniform eutectic morphology could be achieved in the Nb:STO/TO eutectic solids by stable control of the liquid–solid interface during the fabrication. The thermal conductivity of the Nb:STO/TO eutectic solid was less than half of that of the Nb:STO single crystal owing to the decrease of the lattice thermal conductivity by phonon scattering at the grain boundaries. The figures of merit ZT’s of the Nb:STO/TO eutectic solid, parallel and perpendicular to the growth direction, were ∼ 0.007 and ∼ 0.0004, respectively. The small ZT’s are attributable to the higher electrical resistivity originating from the insufficient carrier doping and high electrical resistivity of the TO phase.
Journal Article
Fabrication and Properties for Thermal Neutron Detection of 6LiCl/Rb2CeCl5 Eutectic Scintillator
by
Kurosawa, Shunsuke
,
Sasaki, Rei
,
Hanada, Takashi
in
Absorption cross sections
,
Bridgman method
,
Cathodoluminescence
2024
The 3He gas is commonly used for the detection of thermal neutrons. However, with the depletion of 3He gas, there is a need to develop new solid scintillators for thermal neutron detection. Solid scintillators containing 6Li, which have large neutron capture cross-sections and a large amount of energy released by transmutation reactions, are commonly used as alternative candidates. However, only single-crystal scintillators are currently used, and their 6Li concentration is limited by their chemical composition. In this study, we designed, grew, and evaluated a new eutectic scintillator, Rb2CeCl5/LiCl, which can improve the 6Li concentration compared with single-crystal scintillators. Rb2CeCl5, which was selected as the scintillator phase, has excellent scintillator properties (light yield: 36,000 photons/MeV, decay time: mostly 24 ns, slightly 153 ns), and is less deliquescent than other halide scintillators. The crystal grown using the vertical Bridgman method exhibited a eutectic phase composed of Rb2CeCl5 and LiCl. The eutectic crystals exhibited Ce3+ 5d-4f emissions, with a peak between 360 and 370 nm. The Rb2CeCl5 phase was identified as the luminescent phase via cathodoluminescence mapping, and 16,000 photons/neutron of the light yield and 56.1 ns of the decay time were observed. This study indicates that the Rb2CeCl5/LiCl eutectic scintillator is a promising candidate for use in thermal neutron detectors.
Journal Article
Prognostic Factors for Respiratory Dysfunction for Cervical Spinal Cord Injury and/or Cervical Fractures in Elderly Patients: A Multicenter Survey
2024
Study design
Retrospective Cohort Study
Objective
The purpose of this study was to investigate the prognosis of respiratory function in elderly patients with cervical spinal cord injury (SCI) and to identify predictive factors.
Methods
We included 1353 cases of elderly cervical SCI patients collected from 78 institutions in Japan. Patients who required early tracheostomy and ventilator management and those who developed respiratory complications were defined as the respiratory disability group. Patients’ background characteristics, injury mechanism, injury form, neurological disability, complications, and treatment methods were compared between the disability and non-disability groups. Multiple logistic regression analysis was used to examine the independent factors. Patients who required respiratory management for 6 months or longer after injury and those who died of respiratory complications were classified into the severe disability group and were compared with minor cases who were weaned off the respirator.
Results
A total of 104 patients (7.8%) had impaired respiratory function. Comparisons between the disabled and non-disabled groups and between the severe and mild injury groups yielded distinct trends. In multiple logistic regression analysis, age, blood glucose level, presence of ossification of posterior longitudinal ligament (OPLL), anterior vertebral hematoma, and critical paralysis were selected as independent risk factors.
Conclusion
Age, OPLL, severe paralysis, anterior vertebral hematoma, hypoalbuminemia, and blood glucose level at the time of injury were independent factors for respiratory failure. Hyperglycemia may have a negative effect on respiratory function in this condition.
Journal Article
Fabrication and Characterization of K2CeCl5/6LiCl and CeCl3/SrCl2/6LiCl Eutectics for Thermal Neutron Detection
by
Kurosawa, Shunsuke
,
Sasaki, Rei
,
Hanada, Takashi
in
Bridgman method
,
Cathodoluminescence
,
Cerium
2022
In recent years, thermal neutron detection using scintillators has been used in a wide range of fields. Thus, the development of scintillators with a higher light yield, faster decay, and higher sensitivity for thermal neutrons is required. In this study, K2CeCl5/6LiCl and CeCl3/SrCl2/6LiCl were developed as novel eutectic scintillators for thermal neutron detection. LiCl was selected as the neutron capture phase and K2CeCl5 and CeCl3 were used as the scintillator phases. The eutectics of K2CeCl5/6LiCl and CeCl3/SrCl2/6LiCl were prepared using the Vertical Bridgman method and the phases were identified by scanning electron microscopy and powder X-ray diffraction measurements. The results of radioluminescence measurements under Ag source X-ray tube irradiation confirmed that the 5d-4f emission derived from Ce3+. The cathodoluminescence spectra and thermal neutron responses of the prepared eutectics were measured to evaluate their optical properties.
Journal Article
Prognosis of Cervical Diffuse Idiopathic Skeletal Hyperostosis-Related Spine Injuries in Elderly Patients: Analyses of Both Fracture and Spinal Cord Injury Without Fracture
2025
Study Design
Retrospective multicenter study.
Objective
The purpose of this study was to compare the prognosis of elderly patients with injuries related to cervical diffuse idiopathic skeletal hyperostosis (cDISH) to matched control for each group, with and without fractures.
Methods
The current multicenter study was a retrospective analysis of 140 patients aged 65 years or older with cDISH-related cervical spine injuries; 106 fractures and 34 spinal cord injuries without fracture were identified. Propensity score–matched cohorts from 1363 patients without cDISH were generated and compared. Logistic regression analysis was performed to determine the risk of early mortality for patients with cDISH-related injury.
Results
Patients with cDISH-related injuries with fracture did not differ significantly in the incidence of each complication and ambulation or severity of paralysis compared to matched controls. In patients with cDISH-related injury without fracture, those who were nonambulatory at discharge comprised 55% vs 34% of controls, indicating significantly poorer ambulation in those with cDISH-related injuries (P = .023). There was no significant difference in the incidence of complications and ambulation or paralysis severity at 6 months as compared with controls. Fourteen patients died within 3 months. Logistic regression analysis identified complete paralysis (odds ratio [OR] 36.99) and age (OR 1.24) as significant risk factors for mortality.
Conclusions
The current study showed no significant differences in the incidence of complications, ambulation outcomes between patients with cDISH-related injury with fracture and matched controls, and that the ambulation at discharge for patients with cDISH-related injury without fractures were significantly inferior to those of matched controls.
Journal Article