Series/Parallel Switching for Increasing Power Extraction from Thermoelectric Power Generators.

We propose a method for increasing power extraction from a thermoelectric generator (TEG) by switching between series/parallel circuit configurations of thermoelectric elements, which can adjust the internal impedance of the TEG. The power characteristics of the TEG can be adjusted to the load characteristics of the connected device and the relevant ambient temperature. In this paper, we analyzed the change in the TEG characteristics with the series/parallel switching function. We evaluated the power supply to the connected devices at different ambient temperatures and different series/parallel configurations and confirmed that the extracted power could be increased. By theoretically analyzing the circuit configuration of the thermoelectric devices, the switching required to improve the power extraction, and the temperature difference at which switching occurred, we devised a design method for a TEG with circuit switching in order to increase power extraction with any device. We demonstrated the configuration of switching by using a system in which a TEG supplied power to an external wireless transmitter circuit. In this system, the optimal configuration differed at temperature differences of 3.0 K and 4.0 K. At a temperature difference of 3.0 K, the 2-series/1-parallel configuration provided 10% more power to the external circuit than the 1-series/2-parallel configuration. On the other hand, at the temperature difference of 4.0 K, the 1-series/2-parallel configuration provided 23% more power than the 2-series/1-parallel configuration.

Monte Carlo simulations of organ and effective doses and dose-length product for dental cone-beam CT.

OBJECTIVES: The use of dental cone-beam CT (CBCT) has increased in recent years. We aimed to calculate the organ and effective doses in dental CBCT using Monte Carlo simulation (MCS) and to correlate the effective dose with the dose-length product (DLP), which is a radiation dose index. METHODS: Organ and effective doses were calculated by MCS using the adult male and female reference phantoms of the International Commission on Radiological Protection publication 110 in a half-rotation scan of the CBCT scanner Veraviewepocs 3Df. The simulations were performed by setting nine protocols in combination with the field-of-view (FOV) and imaging region. In addition, DLPs were calculated by MCS using the virtual CT Dose Index (CTDI) and CBCT phantoms, with the same protocol. RESULTS: The effective doses were 55 and 195 µSv at the minimum FOV of Φ40 × H40 mm and maximum FOV of Φ 80 × H80 mm, respectively. The organs with the major contribution to the effective dose were the red bone marrow (11.0‒12.8%), thyroid gland (4.0‒12.7%), salivary gland (21.8‒33.2%), and remaining tissues (35.1‒45.7%). Positive correlations were obtained between the effective dose and calculated DLP using the CTDI and CBCT phantoms. CONCLUSIONS: Organ and effective doses for each protocol of dental CBCT could be estimated using MCS. There was a positive correlation between the effective dose and DLP, suggesting that DLP can be used to estimate the effective dose of CBCT.

Are Online Simulations for Radiation Emergency Medical Preparedness Less Effective in Teaching Than Face-to-Face Simulations?

OBJECTIVE: The study clarified differences in understanding and satisfaction between face-to-face and online training on radiation emergency medical preparedness (REMP) training. METHODS: The training was held at Hirosaki University between 2018 and 2022, with 46 face-to-face participants and 25 online participants. RESULTS: Face-to-face training was significantly more understandable than online for the use of the Geiger counter (P < 0.05), but the educational effect of virtual reality (VR) was not significantly different from the actual practice. For the team exercise of taking care of the victims, online resulted in a significantly higher understanding (P < 0.05). CONCLUSIONS: Interactive exercises can be done online with equipment sent to learners, and VR is also as effective. The use of videos was more effective for first-timers to learn the practical process from a bird's-eye view, especially for team-based medical procedures.

Origami-Type Flexible Thermoelectric Generator Fabricated by Self-Folding.

The flexibility of thermoelectric generators (TEGs) is important for low-contact thermal resistance to curved heat sources. However, approaches that depend on soft materials, which are used in most existing studies, have the problem of low performance in terms of the substrate's thermal conductivity and the thermoelectric conversion efficiency of the thermoelectric (TE) elements. In this study, we propose a method to fabricate "Origami-TEG", a TEG with an origami structure that enables both flexibility and the usage of high-performance rigid materials by self-folding. By applying the principle of the linkage mechanism to self-folding, we realized a fabrication process in which the TE element-mounting process and the active-material-addition process were separated in time. The fabricated origami-TEG showed similar internal resistance and maximum output power when attached to heat sources with flat and curved surfaces. Furthermore, it exhibited high-performance stability against both stretching and bending deformations.

Training of Medical Responders to Nuclear Disaster: Hybrid Program in the COVID-19 Pandemic.

OBJECTIVE: The spread of COVID-19 has made it difficult to provide training in medical treatment in a radiation disaster. In this study, we will examine the effects and challenges of using a hybrid approach that combines online and face-to-face components. METHODS: A total of 5 face-to face and 25 online medical staff participated in the training program. This program was conducted by using multiple cameras for live coverage, while protective clothing and decontamination kits had been sent in advance to the participants so that they could experience face-to-face and online learning at the same time. RESULTS: Participants reported a high level of satisfaction and achievement with the style of delivery. They also experienced problems such as fatigue due to long hours, and dissatisfaction with the debriefing. CONCLUSIONS: In designing new online training, it is necessary to consider the quantity and content of the program, and to take participant fatigue into consideration.

The Effect of High-Dose-Rate Pulsed Radiation on the Survival of Clinically Relevant Radioresistant Cells.

We demonstrated that low dose pulsed radiation (0.25 Gy) at a high-dose-rate, even for very short intervals (10 s), decreases cell survival to a greater extent than single exposure to a similar total dose and dose rate. The objective of this study was to clarify whether high-dose-rate pulsed radiation is effective against SAS-R, a clinically relevant radioresistant cell line. Cell survival following high-dose-rate pulsed radiation was evaluated via a colony assay. Flow cytometry was utilized to evaluate γH2AX, a molecular marker of DNA double-strand breaks and delayed reactive oxygen species (ROS) associated with radiation-induced apoptosis. Increased cytotoxicity was observed in SAS-R and parent SAS cells in response to high dose rate pulsed radiation compared to single dose, as determined by colony assays. Residual γH2AX in both cells subjected to high-dose-rate pulsed radiation showed a tendency to increase, with a significant increase observed in SAS cells at 72 h. In addition, high-dose-rate pulsed radiation increased delayed ROS more than the single exposure did. These results indicate that high-dose-rate pulsed radiation was associated with residual γH2AX and delayed ROS, and high-dose-rate pulsed radiation may be used as an effective radiotherapy procedure against radioresistant cells.

Short tau inversion recovery in breast diffusion-weighted imaging: signal-to-noise ratio and apparent diffusion coefficients using a breast phantom in comparison with spectral attenuated inversion recovery.

OBJECTIVE: This study aimed to compare the signal-to-noise ratios (SNRs) and apparent diffusion coefficients (ADCs) obtained using two fat suppression techniques in breast diffusion-weighted imaging (DWI) of a phantom. MATERIALS AND METHODS: The breast phantom comprised agar gels with four different concentrations of granulated sugar (samples 1, 2, 3, and 4). DWI with short tau inversion recovery (STIR-DWI) and that with spectral attenuated inversion recovery (SPAIR-DWI) were performed using 3.0-T magnetic resonance imaging, and the obtained SNRs and ADCs were compared. ADCs were also compared between the right and left breast phantoms. RESULTS: For samples 3 and 4, SNRs obtained using STIR-DWI were lower than those obtained using SPAIR-DWI. For samples 2, 3, and 4, overall ADCs obtained using STIR-DWI were significantly higher than those obtained using SPAIR-DWI (p < 0.001 for all), although no significant difference was observed for sample 1 (p = 0.62). STIR-DWI shows a positive bias and wide limits of agreement in Bland-Altman plot. The coefficients of variance of overall ADCs were good in STIR-DWI and SPAIR-DWI. For all samples, STIR-DWI demonstrated slightly larger percentage differences in ADCs between the right and left phantoms than SPAIR-DWI. CONCLUSION: SNRs and ADCs obtained using STIR-DWI are influenced by the T 1 value; a shorter T 1 value decreases SNRs, overestimates ADCs, and induces the measurement error in ADCs. STIR-DWI showed a larger difference in ADCs between the right and left phantoms than SPAIR-DWI.

The Effect of Ultraviolet B on Fibrillin-1 and Fibrillin-2 in Human Non-pigmented Ciliary Epithelial Cells In Vitro.

The ciliary zonules link the lens to the ciliary body in the eye, controlling the thickness of the lens for focusing through their characteristic elasticity. The ciliary zonules are composed of oxytalan fibers. Physiological or pathological damage to the ciliary zonules, including exposure to ultraviolet (UV)-A and UV-B components, can lead to lens dislocation. However, no studies have shown whether UV affects the ciliary zonule. Here, we assessed the effects of UV light on human nonpigmented ciliary epithelial cells (HNPCECs). HNPCECs were cultured for 4 weeks, and expression of fibrillin-1 and fibrillin-2 was confirmed. In control cultures (0 mJ/cm2), some fibrillin-1-positive fibers were merged with fibrillin-2. After UV-A irradiation, the appearance of both fibrillin-1- and fibrillin-2-positive fibers was unchanged. However, after UV-B irradiation, fibrillin-1-positive fibers became thin at an irradiation level of 100 mJ/cm2, and the fiber structure became amorphous at 150 mJ/cm2. Fibrillin-2-positive fibers lost their continuity and disappeared after being exposed to 150 mJ/cm2 UV-B. UV-B irradiation did not affect cell viability, possibly because of the sensitivity of fibrillin-1 and fibrillin-2 to UV-B. Thus, dislocation of the lens with age may be attributable to cumulative exposure to UV-B.

Impact of time interval and dose rate on cell survival following low-dose fractionated exposures.

Enhanced cell lethality, also known as hyper-radiosensitivity, has been reported at low doses of radiation (≤0.5 Gy) in various cell lines, and is expected to be an effective cancer therapy. We conducted this study to examine the impact of time interval and dose rate of low-dose fractionated exposures with a short time interval. We evaluated the cell-survival rates of V79 and A549 cells using clonogenic assays. We performed fractionated exposures in unit doses of 0.25, 0.5, 1.0 and 2.0 Gy. We exposed the cells to 2 Gy of X-rays (i) at dose-rates of 1.0, 1.5 and 2.0 Gy/min at 1-min intervals and (ii) at a dose-rate of 2.0 Gy/min at 10-s, 1-min and 3-min intervals by fractionated exposures. Apoptosis and cell cycle analyses were also evaluated in the fractionated exposures (unit dose 0.25 Gy) and compared with single exposures by using flow cytometry. Both cell-type survival rates with fractionated exposures (unit dose 0.25 Gy) with short time intervals were markedly lower than those for single exposures delivering the same dose. When the dose rates were lower, the cytotoxic effect decreased compared with exposure to a dose-rate of 2.0 Gy/min. On the other hand, levels of apoptosis and cell cycle distribution were not significantly different between low-dose fractionated exposures and single exposures in either cell line. These results indicate that a stronger cytotoxic effect was induced with low-dose fractionated exposures with a short time interval for a given dose due to the hyper-radiosensitivity phenomenon, suggesting that dose rates are important for effective low-dose fractionated exposures.

Ascorbic acid does not reduce the anticancer effect of radiotherapy.

The present study hypothesized that the therapeutic use of ascorbic acid (AsA) in combination with radiation may reduce therapy-related side effects and increase the antitumor effects. The aim of the study was to examine the association between the scavenged activity of AsA and the biological anticancer effect of hydroxyl (OH) radicals generated by X-ray irradiation. Cell survival, DNA fragmentation of human leukemia HL60 cells and the amount of OH radicals were investigated following X-ray irradiation and AsA treatment. The number of living cells decreased, and DNA fragmentation increased at AsA concentrations >1 mM. Electron spin resonance spectra revealed that X-ray irradiation generated OH radicals, which were scavenged by AsA at concentrations >75 µM. The AsA concentration inside the cell was 75 µM when cells underwent extracellular treatment with 5 mM AsA, which significantly induced HL60 cell death even without irradiation. No increase in the number of viable HL60 cells was observed following AsA treatment with irradiation when compared to irradiation alone. In conclusion, the disappearance of the radiation anticancer effects with AsA treatment in combination with radiotherapy for cancer treatment is not a cause for concern.

Image quality assessment of single-shot turbo spin echo diffusion-weighted imaging with parallel imaging technique: a phantom study.

OBJECTIVE: This study aimed to evaluate the image quality and apparent diffusion coefficient (ADC) values of single-shot turbo spin echo (TSE) diffusion-weighted (DW) images obtained using a parallel imaging (PI) technique. METHODS: All measurements were performed on a 3.0-T whole-body MRI system and 32-channel phased-array coil. Signal-to-noise ratio (SNR) and ADC values were measured with a DW imaging (DWI) phantom comprising granulated sugar and agar. The SNRs were calculated using a subtraction method and compared among TSE-DW images at acceleration factors (AFs) of 1-4. Image blur was visually assessed on TSE-DW images of a pin phantom at AFs of 1-4. The ADC values were calculated using DW images with b = 0 and 1000 s mm(-2). The ADC values of TSE-DW images and echo-planar imaging EPI-DW images were compared. RESULTS: The SNRs decreased as AFs increased, despite selecting the shortest echo time. A lower AF caused increased image blur in the phase-encoding direction. The ADC values of TSE-DWI tended to be lower than those of EPI-DWI, and AFs of 3 and 4 yielded variable ADC values on TSE-DW images. CONCLUSION: TSE-DWI with an AF of 3 or 4 yielded reduced SNRs; in addition, the image noise and artefacts associated with PI technique may have affected ADC measurements, despite improving image blur in the phase-encoding direction. ADVANCES IN KNOWLEDGE: Optimizing the imaging parameters of TSE-DWI is useful for providing good image quality and accurate ADC measurements.

Effects of X­ray irradiation in combination with ascorbic acid on tumor control.

Our previous studies demonstrated that the combination of treatment with ascorbic acid (AsA) and X­ray irradiation results in increased apoptosis in HL60 cells. The present study was performed to investigate the effects of the combined use of AsA and X­ray irradiation on epithelial cancer and sarcoma cells, and its potential use in future clinical treatment. X­ray irradiation combined with AsA treatment resulted in increased suppression of cell growth of HT1080, SAS and A549 cells in vitro compared with X­ray irradiation alone. The combined treatment also suppressed tumor growth in implanted HT­1080 cells in vivo. Using annexin V/propidium iodide staining and the detection of activated caspase 3, it was found that X­ray irradiation increased the apoptotic rate of HT1080 cells and resulted in G2/M arrest. However, apoptosis in the HT1080 cells treated with 5 mM AsA remained unchanged, and no changes were observed in the G2/M fraction. By contrast, AsA treatment caused increased suppression of proliferation compared with X­ray irradiation. These results suggested that 5 mM AsA slowed the cell cycle and reduced tumor growth. Therefore, X­ray irradiation combined with AsA treatment may be effective against epithelial cancer and sarcoma cells.

Effect of ascorbic acid and X-irradiation on HL-60 human leukemia cells: the kinetics of reactive oxygen species.

Ascorbic acid (AsA) treatment is expected to be a potential cancer therapy strategy with few side-effects that can be used alone or in combination with chemotherapy. However, the combination of AsA, a free radical scavenger, with radiation is not clearly understood; conflicting data are reported for cancer cell death. We conducted this study to determine the effect of AsA treatment combined with X-irradiation and the role of reactive oxygen species (ROS) in HL-60 human promyelocytic leukemia cells. Additive cytotoxic effects were observed when the cells were exposed to 2 Gy X-irradiation after 2.5 mM AsA treatment. When catalase was added to the culture with AsA alone, the cytotoxic effects of AsA disappeared. X-irradiation increased intercellular ROS levels and mitochondrial superoxide levels. By contrast, AsA alone and in combination with X-irradiation decreased ROS levels. However, in the presence of catalase neutralizing H2O2, AsA alone or in combination with X-irradiation only slightly decreased the intercellular ROS. Moreover, AsA decreased the mitochondrial membrane potential, which is commonly associated with apoptosis. These results suggest that the reduction of ROS did not result from ROS scavenging by AsA, and AsA induced apoptosis through a ROS-independent pathway. This study reports that a combination of AsA with radiation treatment is effective in cancer therapy when considering ROS in cancer cells.

Effects of strong static magnetic fields used in magnetic resonance imaging on insulin-secreting cells.

The magnetic flux density of MRI for clinical diagnosis has been steadily increasing. However, there remains very little biological data regarding the effect of strong static magnetic fields (SMFs) on human health. To evaluate the effects of strong SMFs on biological systems, we cultured insulin-secreting cells under exposure to sham and SMF conditions (3-10 T of magnetic flux density, and 0-41.7 T/m of magnetic field gradient) for 0.5 or 1 h, and analyzed insulin secretion, mRNA expression, glucose-stimulated insulin secretion, insulin content, cell proliferation and cell number. Exposure to SMF with a high magnetic field gradient for 1 h significantly increased insulin secretion and insulin 1 mRNA expression. Exposure to SMF with a high magnetic flux density for 0.5 h significantly enhanced responsiveness to glucose stimulation. Exposure to SMF did not affect the insulin content, cell proliferation or cell number. Our results suggested that MRI systems with a higher magnetic flux density might not cause cell proliferative or functional damages on insulin-secreting cells, and that SMF with a high magnetic field gradient might be used clinically after thorough in vivo investigations are conducted.

Enhanced secretion of prostaglandin E2 from osteoblasts by exposure to a strong static magnetic field.

Exposure to static magnetic fields (SMFs) has been reported to promote osteoblast differentiation in vitro, and increase bone formation in vivo and in clinical studies. Prostaglandins respond early to exogenous mechanical loading, and play an important role in bone formation. In this study, we investigated whether exposure to a strong SMF affects prostaglandin E(2) (PGE(2)) secretion from a mouse osteoblastic cell line, MC3T3-E1. We also investigated the PGE(2)-synthesizing enzyme, cyclooxygenase 2 (Cox-2), and translocation of the transcription factor nuclear factor kappa B (NF-kappaB), which is involved in the induction of Cox-2 expression. In the SMF exposures, experiments were performed at the 10 T-exposure position, at which the magnetic flux density was highest, and at the 6 T-exposure position, at which the magnetic field gradient was highest (41.7 T/m). PGE(2) secretion was not affected by exposure at the 10 T-exposure position compared to sham-exposure, but was enhanced at the 6 T-exposure position (about 1.5-fold). Similarly, Cox-2 expression and NF-kappaB translocation were not enhanced at the 10 T-exposure position, but increased at the 6 T-exposure position (about twofold, two- to threefold, respectively). These findings suggested that exposure to a high magnetic field gradient induced secretion of PGE(2) and expression of the Cox-2 protein, which was mediated through increased translocation of NF-kappaB.