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310 results on '"Iwasaki, Yuichi"'

33. COVID-19 risk assessment at the opening ceremony of the Tokyo 2020 Olympic Games

Author

Murakami, Michio, primary, Miura, Fuminari, additional, Kitajima, Masaaki, additional, Fujii, Kenkichi, additional, Yasutaka, Tetsuo, additional, Iwasaki, Yuichi, additional, Ono, Kyoko, additional, Shimazu, Yuzo, additional, Sorano, Sumire, additional, Okuda, Tomoaki, additional, Ozaki, Akihiko, additional, Katayama, Kotoe, additional, Nishikawa, Yoshitaka, additional, Kobashi, Yurie, additional, Sawano, Toyoaki, additional, Abe, Toshiki, additional, Saito, Masaya M., additional, Tsubokura, Masaharu, additional, Naito, Wataru, additional, and Imoto, Seiya, additional

Published
2021
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39. Projecting future changes in element concentrations of approximately 100 untreated discharges from legacy mines in Japan by a hierarchical log-linear model

Author

Iwasaki, Yuichi, Fukaya, Keiichi, Fuchida, Shigeshi, Matsumoto, Shinji, Araoka, Daisuke, Tokoro, Chiharu, Yasutaka, Tetsuo, Iwasaki, Yuichi, Fukaya, Keiichi, Fuchida, Shigeshi, Matsumoto, Shinji, Araoka, Daisuke, Tokoro, Chiharu, and Yasutaka, Tetsuo

Abstract

Understanding future changes in the concentrations of elements such as Cd in mine drainages, which can cause severe environmental impacts, is crucial to strategically optimize the treatment and management of such drainages. In this study, on the basis of 17-year data (2003 & ndash;2019) for 99 untreated drainages from legacy mines in Japan, we developed a Bayesian hierarchical log-linear model that can capture temporal changes in the concentrations of seven elements including six metals (Cd, Pb, As, Cu, Zn, Fe, and Mn) in individual mine drainages. We also projected future changes to understand the prospective trends nationwide. The modeling results showed that, during 2003 & ndash;2019, although overall decreasing trends were observed for most elements across all the drainages evaluated, decreases in the concentrations of these elements were not evident in many mine drainages (5%& ndash;28% of drainages for individual elements); in addition, any rise in the number of mine drainages with element concentrations below nationwide drainage standards over the next 100 years will likely be limited (e.g., approximately 10 drainages for Zn and Fe at median estimates). These results have significant implications for future strategies to manage mine drainages: it is probably too optimistic to assume that the element concentrations of mine drainages will always decrease, or that these drainages will satisfy drainage standards (permits) in the not so distant future.

Published
2021

46. Hypermobile Anterior Horn of the Lateral Meniscus: A Case Report and Literature Review

Author

Nakashima, Hirotaka, Takahara, Yasuhiro, Uchida, Yoichiro, Kato, Hisayoshi, Itani, Satoru, Tsujimura, Yoshitaka, Nakamura, Makoto, and Iwasaki, Yuichi

Subjects
body regions, Article Subject, musculoskeletal system
Abstract

Hypermobile meniscus is known as one of the causes of knee pain and locking or limitation of the range of motion during knee flexion, even when there is no evidence of meniscus tear on magnetic resonance imaging (MRI). Most such cases show excessive hypermobility of the posterior part of the lateral meniscus. This case report presented a rare case of a hypermobile anterior horn of the lateral meniscus. An 18-year-old woman visited our hospital for left knee pain without trauma. Her physical examination showed a limited range of motion and tenderness in the lateral joint space. However, her MRI did not show any abnormalities. After conservative treatment failed, we performed arthroscopic surgery. The arthroscopic evaluation showed no meniscus and no other intraarticular injury. However, the anterior horn of the lateral meniscus was easily translated beyond the lateral condyle by using a probe. Thus, hypermobile anterior horn of the lateral meniscus was diagnosed. The meniscus was stabilized by the outside-in technique. Immediately after surgery, the catching symptom and pain were alleviated. After three-and-a-half months, she returned to work. The Lysholm score improved from 55, preoperatively, to 100, 1-year postoperatively. In conclusion, careful arthroscopic evaluation is essential for the diagnosis of a hypermobile anterior horn of the lateral meniscus. Arthroscopic meniscus stabilization provides a good outcome for hypermobile meniscus.

Published
2020
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47. Coupling mixture reference models with DGT-perceived metal flux for deciphering the nonadditive effects of rare earth mixtures to wheat in soils

Author

Gong, Bing, He, Erkai, Peijnenburg, Willie J.G.M., Iwasaki, Yuichi, Van Gestel, Cornelis A.M., Cao, Xinde, Zhao, Ling, Xu, Xiaoyun, Qiu, Hao, Gong, Bing, He, Erkai, Peijnenburg, Willie J.G.M., Iwasaki, Yuichi, Van Gestel, Cornelis A.M., Cao, Xinde, Zhao, Ling, Xu, Xiaoyun, and Qiu, Hao

Abstract

The risk assessment of mixtures of rare earth elements (REEs) is hampered by a lack of fundamental understanding of their interactions in different soil types. Here, we assessed mixture interactions and toxicity to Triticum aestivum of Y and Ce in four different soils in relation to their bioavailability. Mixture toxicity was modelled by concentration addition (CA) and independent action (IA), in combination with different expressions of exposure: three equilibrium-based doses (total soil concentrations [M]tot, free ion activity in soil solution {M3+}, and the fraction (f) of metal ions bound to the biotic ligands (BLs)) and one kinetically controlled dose ([M]flux) metrics. Upon single exposure, REE toxicity was increasingly better described when using exposure expressions based on deepened understanding of their bioavailability: [M]flux > f > {M3+} > [M]tot. The mixture analyses based on [M]tot and {M3+} displayed deviations from additivity depending on the soil type. With the parameters derived from single exposures, the BLM approach gave better predictions of mixture toxicity (R2 ~ 0.70) than when using CA and IA based on either [M]tot or {M3+} (R2 < 0.64). About 30% of the variance in toxicity remained unexplained, challenging the view that the free metal ion is the main bioavailable form under the BLM framework based on thermodynamic equilibrium. Toxicity was best described when accounting for changes in the size of the labile metal pool by using a kinetically controlled dose metric (R2 ~ 0.80). This suggests that dynamic bioavailability analysis could provide a robust basis for modeling and reconciling the interplays and toxicity of metal mixtures in different soils.

Published
2020
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49. Comparison of Species Sensitivity Distributions for Sediment‐Associated Nonionic Organic Chemicals Through Equilibrium Partitioning Theory and Spiked‐Sediment Toxicity Tests with Invertebrates.

Author

Hiki, Kyoshiro, Iwasaki, Yuichi, Watanabe, Haruna, and Yamamoto, Hiroshi

Subjects
*TOXICITY testing, *SPECIES distribution, *CHEMICAL equilibrium, *ORGANIC compounds, *ENVIRONMENTAL toxicology, *INSECTICIDES, *PYRETHROIDS
Abstract

Equilibrium partitioning (EqP) theory and spiked‐sediment toxicity tests are useful methods to develop sediment quality benchmarks. However, neither approach has been directly compared based on species sensitivity distributions (SSDs) to date. In the present study, we compared SSDs for 10 nonionic hydrophobic chemicals (e.g., pyrethroid insecticides, other insecticides, and polycyclic aromatic hydrocarbons) based on 10–14‐day spiked‐sediment toxicity test data with those based on EqP theory using acute water‐only tests. Because the exposure periods were different between the two tests, effective concentrations (i.e., median effective/lethal concentration) were corrected to compare SSDs. Accordingly, we found that hazardous concentrations for 50% and 5% of species (HC50 and HC5, respectively) differed by up to a factor of 100 and 129 between the two approaches, respectively. However, when five or more species were used for SSD estimation, their differences were reduced to a factor of 1.7 and 5.1 for HC50 and HC5, respectively, and the 95% confidence intervals of HC50 values overlapped considerably between the two approaches. These results suggest that when the number of test species is adequate, SSDs based on EqP theory and spiked‐sediment tests are comparable in sediment risk assessments. Environ Toxicol Chem 2022;41:462–473. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Published
2022
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