Browsing by Author "Takahashi K."

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    CMB spectrum in unified EFT of dark energy: scalar-tensor and vector-tensor theories
    (2024-07-01) Aoki K.; Gorji M.A.; Hiramatsu T.; Mukohyama S.; Pookkillath M.C.; Takahashi K.; Aoki K.; Mahidol University
    We study the cosmic microwave background (CMB) radiation in the unified description of the effective field theory (EFT) of dark energy that accommodates both scalar-tensor and vector-tensor theories. The boundaries of different classes of theories are universally parameterised by a new EFT parameter αV characterising the vectorial nature of dark energy and a set of consistency relations associated with the global/local shift symmetry. After implementing the equations of motion in a Boltzmann code, as a demonstration, we compute the CMB power spectrum based on the wCDM background with the EFT parameterisation of perturbations and a concrete Horndeski/generalised Proca theory. We show that the vectorial nature generically prevents modifications of gravity in the CMB spectrum. On the other hand, while the shift symmetry is less significant in the perturbation equations unless the background is close to the ΛCDM, it requires that the effective equation of state of dark energy is in the phantom region w DE<-1. The latter is particularly interesting in light of the latest result of the DESI+CMB combination as the observational verification of w DE>-1 can rule out shift-symmetric theories including vector-tensor theories in one shot.
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    Development and evaluation of a new intraoral voice assist device called the voice retriever
    (2024-01-01) Yamada T.; Yamaguchi K.; Horike A.; Takahashi K.; Amornsuradech S.; Nakagawa K.; Yoshimi K.; Tohara H.; Yamada T.; Mahidol University
    Objective: Patients lose their voice after laryngectomy for laryngeal cancer or aspiration prevention surgery for severe dysphagia. To assist such patients, we developed and verified the utility of a novel vocalization method using a device termed the voice retriever (VR), in which the sound source is placed in the mouth. Methods: We investigated the effectiveness of the VR in patients. The VR consists of a mouthpiece with a built-in speaker and a dedicated application that serves as the sound source. We compared the speech intelligibility and naturalness in normal participants using VR and an electrolarynx (EL) for the first time as well as the voice-related quality of life (V-RQOL) in patients with dysphonia before and after using the VR. Results: The VR produced significantly higher 100-syllable test scores as well as fluency, amount of additional noise, intonation, intelligibility and overall long reading test ratings in the first-time VR and EL users. Furthermore, the VR use significantly improved the V-RQOL of participants with dysphonia. Conclusion: Compared to EL, VR allows more effective speech improvement in participants without experience using an alternative vocalization method and improves the V-RQOL in patients with dysphonia. Level of Evidence: Step 4.
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    Health Effects of Occupational and Environmental Exposures to Nuclear Power Plants: A Meta-Analysis and Meta-Regression
    (2024-01-01) Lin R.T.; Boonhat H.; Lin Y.Y.; Klebe S.; Takahashi K.; Lin R.T.; Mahidol University
    Purpose of Review: Numerous epidemiological studies have shown increased health risks among workers and residents living near nuclear power plants exposed to radiation levels meeting regulatory dose limits. This study aimed to evaluate the association between radiation exposure and disease risks among these populations exposed to radiation levels meeting the current regulatory dose limits. Recent Findings: We searched four databases (Cochrane Library, PubMed, ScienceDirect, and Web of Science) for studies published before August 2023, screened eligible studies (inclusion and exclusion criteria based on population, exposure, comparator, and outcome framework), and collected data on exposure indicators and disease risks. We applied random-effects models of meta-analysis to estimate the pooled effects and meta-regression to assess the dose-response relationship (radiation dose rate for workers and distance for residents). We identified 47 studies, 13 with worker and 34 with resident samples, covering 175 nuclear power plants from 17 countries, encompassing samples of 480,623 workers and 7,530,886 residents. Workers had a significantly lower risk for all-cancer and a significantly higher risk for mesothelioma. Residents had significantly higher risks for all-cancer, thyroid cancer, and leukemia. Notably, children under 5 years old showed the highest risk for all-cancer. Our meta-regression showed a significantly positive dose-response relationship between cumulative dose of radiation exposure and risk for circulatory disease among workers. Summary: Our findings demonstrated higher risks for mesothelioma for workers and all-cancer, thyroid cancer, and leukemia for residents exposed to low-dose radiation from nuclear power plants. Some included studies did not adjust for cancer risk confounders, which could overestimate the association between radiation exposure and cancer risk and increase the risk of bias.