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Japanese medaka is specified as a model fish in the OECD Test Guidelines. Recently, populations of Japanese medaka in Japan were divided into two species, the northern Oryzias sakaizumii and the southern O. latipes. Previously, we reported that induction concentrations for sex reversal by exposure to 17a-methyltestosterone differed significantly between these two species, indicating that they respond differently to endocrine-disrupting chemicals. In the present study, we examined the effects of exposure to two more endocrine-disrupting chemicals (bisphenol A and 17β-trenbolone) in O. sakaizumii, and compared the results to those previously reported for O. latipes. Both bisphenol A and 17β-trenbolone exposure induced testis-ova formation or sex reversal in O. sakaizumii. 17β-trenbolone exposure also increased gonadal soma-derived factor (gsdf) expression. Least-observed-effect concentrations for gonadal sex differentiation and gsdf expression were lower for O. latipes than for O. sakaizumii upon exposure to bisphenol A, and were lower for O. sakaizumii than for O. latipes upon exposure to 17β-trenbolone. These results demonstrate that O. sakaizumii and O. latipes respond differently to androgenic and estrogenic endocrine-disrupting chemicals. This article is protected by copyright. All rights reserved. Environ Toxicol Chem 2022;00:0-0. © 2022 SETAC.

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The acidity of acetylene CH is stronger than that of alkane CH, and the attractive interaction between an acetylene CH with π-electrons, which shows a clear hydrogen bond property, is called activated CH/π interaction. In this study, cooperative enhancement of the activated CH/π interaction has been probed through the cluster size dependence of the red shift of the acetylene CH stretching vibrational band in neutral phenol-(acetylene)n (∼16 ≤ n ≤ ∼30) and (acetylene)n+ (10 ≤ n ≤ 70). In both the clusters, the characteristic asymmetric (red-shaded) shape of the CH stretch band has been observed. This band shape means that the magnitude of the activated CH/π interaction is enhanced by its cooperativity in the interior moiety of the cluster. The red-shifted component of the band extends with increasing cluster size, and the edge of this component seems to reach to the CH stretch band position of crystalline acetylene at the size of n = 20-30, indicating that dozens of molecules need to interact each other to maximize cooperativity in the activated CH/π interaction of acetylene. On the other hand, the peak position of the band does not converge to that of crystalline acetylene in the observed size range. The present result suggests that the spectral convergence of acetylene clusters to the bulk may occur in the cluster size range of hundreds or larger.

Highlights • We determined C5/C6/C7 myotomes from patients with MRI-confirmed single-root radiculopathy. • The brachioradialis was mainly innervated by C5. • C6 muscles were the pronator teres and extensor carpi radialis brevis., Objective There are many myotome charts in the literature, but few studies have presented actual data to support their identification. We aimed to determine C5/C6/C7 myotomes based on clinical and EMG data of patients with cervical spondylotic radiculopathy (CSR) having a single-root lesion confirmed by MRI. Methods Medical Research Council (MRC) scores and EMG findings were retrospectively reviewed for patients enrolled from our EMG database. Results Enrolled were 25 patients (10 C5, 6 C6, and 9 C7 CSR). In C5 CSR, weakness or denervation potentials in EMG, or both, were observed in the deltoid (Del) and infraspinatus (Isp) muscles for all patients, and in the biceps brachii (BB) and brachioradialis (BR) muscles for 9/10 and 8/9 patients, respectively. In C6 CSR, weakness of the wrist extensor and/or denervation of the extensor carpi radialis longus (ECRL)/extensor carpi radialis brevis (ECRB), and those of the pronator teres (PT) were observed for all patients. Weakness was not observed for any other muscle in C6 CSR. Denervation potentials of ECRL were found in 5/8 and 3/5 patients with C5 and C6 CSR, respectively, whereas those of ECRB were found in 1/5, 6/6, and 2/5 patients with C5, C6 and C7 CSR, respectively. In C7 CSR, weakness/denervation of the triceps brachii (TB) and denervation potentials of the flexor carpi radialis (FCR) were observed for all patients. Denervation potentials in PT and weakness/denervation of the extensor digitorum (ED) were observed in 2/9 and 4/9 patients, respectively. Conclusion Suggested dominant myotomes are: C5 for the Del, Isp, BB, and BR, C5/6 for the ECRL, C6 > C7 for the ECRB and PT, and C7 for the TB and FCR. Significance The current study identified dominant myotomes that differ from the existing literature.

Osimertinib is the only EGFR-tyrosine kinase inhibitor (TKI) capable of overcoming EGFR-T790M–mutated NSCLC, but osimertinib-resistant EGFR triple mutations (Del19/T790M/C797S or L858R/T790M/C797S) have been reported. Although allosteric EGFR TKIs (e.g., EAI-045) that potentially overcome L858R/T790M/C797S have been identified, there are no effective inhibitors against Del19/T790M/C797S. In this study, we identified CH7233163 as having the potential to overcome EGFR-Del19/T790M/C797S. CH7233163 showed potent antitumor activities against tumor with EGFR-Del19/T790M/C797S in vitro and in vivo. In addition to EGFR-Del19/T790M/C797S, the characterization assays showed that CH7233163 more selectively inhibits various types of EGFR mutants (e.g., L858R/T790M/C797S, L858R/T790M, Del19/T790M, Del19, and L858R) over wild type. Furthermore, crystal structure analysis suggested that CH7233163 is a noncovalent ATP-competitive inhibitor for EGFR-Del19/T790M/C797S that utilizes multiple interactions with the EGFR's αC-helix-in conformation to achieve potent inhibitory activity and mutant selectivity. Therefore, we conclude that CH7233163 is a potentially effective therapy for osimertinib-resistant patients, especially in cases of EGFR-Del19/T790M/C797S.

Chiba, T. and Nishimura, Y., 2020. Using diatom assemblages to infer topographical changes from storm-induced sandbar breaching in Horokayanto Lagoon, Hokkaido, Japan. Journal of Coastal Research, 36(4), 720–731. Coconut Creek (Florida), ISSN 0749-0208.The sandbar of Horokayanto Lagoon, a sandbar-fronted lagoon on the coast of eastern Hokkaido, Japan, was partly breached, and the bottom was partly exposed during severe weather in June 2016. After the breach, the mean lagoon level fell to about 1.2 m above Tokyo Peil, equivalent to the height of the mean higher-high tide level. Field surveys were conducted on 2, 23, and 30 June 2016 to examine topographical changes in the Horokayanto area. Four diatom-assemblage groups were identified from samples collected during this fieldwork: marsh, emerged lagoon bottom, lagoon bottom, and seashore groups. The assemblages showed good consistency with the salinity and sediment properties at each location. The high-tide-level indicator Pseudopodosira kosugii was recognized in the emerged lagoon-bottom assemblage, together with freshwater–brackish and brackish–marine species. Living P. kosugii colonies had previously been recognized only in the lower reaches of the Obitsu River, Chiba Prefecture, Japan, although the species is widespread in Holocene sediments in Japan and other countries. Reworked Neogene diatoms were also detected in the assemblages. These diatoms were presumably derived from nearby Neogene basement rocks, such as the Taiki Formation, which were eroded by current inflow into the lagoon during the severe weather. During the period of emergence, seawater might have been transported into Horokayanto Lagoon by high waves generated by an atmospheric low-pressure system. Water pressure or moisture changes caused by the emergence, changes in light quantum density and ultraviolet rays, or changes in water quality, such as in salinity and pH, or a mixture of these factors, may have influenced the increase in abundance of P. kosugii.

Nitzschia taikiensis sp. nov. is a brackish diatom species found in the Toberi River marsh, eastern Hokkaido, Japan. This species has characteristics similar to Nitzschia subamphioxoides Hustedt, which was originally described by Hustedt in 1959. In the present study, we conducted a comparative morphological analysis of N. taikiensis and N. subamphioxoides. The obtained results showed that they are different species. Sampling sites of N. taikiensis were located in salt marsh environments with very low salinity (1-5‰), acidic pH (5.2-5.9) and high mud content (95.0-97.5%). Identification of this species was relatively easy based on LM and SEM image analysis of its frustule features, such as the external form and stria density. This species has not been previously reported in Japan, which could be attributed to the reduction or loss of Japanese freshwater and salt marsh environments in the coastal areas, resulting from urban and industrial development.

Saliva sample can be self-collected and used in testing of SARS-CoV-2 nucleic acid amplification tests (NAATs) test in Japan. However, this may have difficulty collecting a proper specimen when collecting for the first time. We compared 2 collection methods, conventional methods and Direct Saliva Sample Collection method (DiSC) from 44 asymptomatic or symptomatic individuals who were in quarantine in Toho university hospital. RT-PCR by DiSC method showed about 70 % positive percent agreement compared to RT-PCR by conventional methods. In addition, comparing RT-PCR and TMA by DiSC method, TMA showed about 90 % positive percent agreement compared to RT-PCR. DiSC method is easy to perform by every person, does not have complicated restrictions/instructions and can be used in RT-PCR and TMA. This method allows for ease of saliva collection in certain patient populations.

Advances in food production technology and newer distribution systems have made it easier to obtain fresh ingredients from both within and outside of Japan. Although convenient, mass distribution of food over wide areas involves the risk of expanding the health damage caused by foods. Comprehensive management from production to consumption, using systems, such as hazard analysis and critical control point (HACCP), is required to ensure the safety of foods. Improved inspection methods are also required to detect the effects of environmental changes on food. In this paper, we demonstrate the use of "Methods of Analysis in Health Science 2020" for food hygiene and safety management.

ImportanceThere have been few studies on the heterogeneous interconnection of COVID-19 outbreaks occurring in different social settings using robust, surveillance epidemiological data.ObjectivesTo describe the characteristics of COVID-19 transmission within different social settings and to evaluate settings associated with onward transmission to other settings.Design, Setting, and ParticipantsThis is a case series study of laboratory-confirmed COVID-19 cases in Tokyo between January 23 and December 5, 2020, when vaccination was not yet implemented. Using epidemiological investigation data collected by public health centers, epidemiological links were identified and classified into 7 transmission settings: imported, nightlife, dining, workplace, household, health care, and other.Main Outcomes and MeasuresThe number of cases per setting and the likelihood of generating onward transmissions were compared between different transmission settings.ResultsOf the 44 054 confirmed COVID-19 cases in this study, 25 241 (57.3%) were among male patients, and the median (IQR) age of patients was 36 (26-52) years. Transmission settings were identified in 13 122 cases, including 6768 household, 2733 health care, and 1174 nightlife cases. More than 6600 transmission settings were detected, and nightlife (72 of 380 [18.9%]; P P P Conclusions and RelevanceIn this case series study, COVID-19 cases identified in nightlife settings were associated with a higher likelihood of spreading COVID-19 than household and health care cases. Surveillance and interventions targeting nightlife settings should be prioritized to disrupt COVID-19 transmission, especially in the early stage of an epidemic.

Thyroid-hormone-disrupting chemicals are increasingly attracting attention because of their potential harmful effects on animal health, including on fishes. Here, we investigated the effects of exposure to the thyroid-hormone-disrupting chemicals 6-propyl-2-thiouracil (PTU) and tetrabromobisphenol A (TBBPA) on swim bladder inflation, eye development, growth, swimming performance, and the expression of thyroid-related genes in Japanese medaka (Oryzias latipes). PTU exposure resulted in reductions in eye size, growth, and swim bladder inflation, and these effects led to poorer swimming performance. These phenotypic effects were accompanied by increased expression of the thyroid-stimulating hormone subunit beta (tshβ) paralog tshβ-like, but there were no significant changes in expression for tshβ, deiodinase 1 (dio1), deiodinase 2 (dio2), and thyroid hormone receptor alpha (trα) and beta (trβ). For PTU exposure, we identified the key event (swim bladder inflation reduction) and an adverse outcome (swimming performance reduction). No significant effects from TBBPA exposure were seen on swim bladder inflation, eye development, growth, or swimming performance. However, expression of tshβ-like and tshβ (significantly enhanced) and trα and trβ (significantly reduced) were affected by TBBPA exposure albeit not in dose-dependent manners. There were no effects of TBBPA on the expression of dio1 and dio2. We thus show that the two thyroid-hormone-disrupting chemicals PTU and TBBPA differ in their effect profiles with comparable effects on the studied phenotypes and thyroid-related gene expression to those reported in zebrafish.

Paleotsunami studies along the Pacific coast of Tohoku, northern Japan, have been considerably developed recently, particuvclarly after the massive impact of the 2011 Tohoku-oki tsunami. Nevertheless, in the southernmost Shimokita Peninsula, studies pertaining to paleotsunami are underdeveloped, leading to vague understanding of the tsunamigenic sources northward of the Tohoku region, along with incomplete hazard evaluation. Paleotsunami deposits in Shimokita can be related not only to the Japan trench along the Sanriku coast, but also to the Kuril trench along the Pacific coast of Hokkaido. In this study, we unveiled the paleotsunami history of Hachinohe in northern Tohoku. Using a combination of sedimentological, geochemical, paleontological, and mineralogical proxies, we characterized seven sand layers that dated from ca. 2700 to ca. 5500 yr BP based on radiocarbon (14C) ages as event deposits of marine origin. Sedimentological and paleontological evidence coupled with ground penetrating radar imagery revealed a marsh environment comprising successive extinct ponds, controlling the depositional environment. Numerical modeling ruled out the possibility of storms as genetic sources, leading to the conclusion that the presence of event deposits with marine sediments in the study area would be associated with tsunami inundation episodes. Based on 14C dating, the average frequency of recurrence of tsunamis is estimated as 545–736 years with a 2σ error range. This interval is shorter than that estimated in Harashinai, northern Sanriku Coast, near our survey site, which suggests an average of 530 to 956 years (2σ) for the same time frame. The previously recorded limited paleotsunami evidence and absence of an estimated recurrence interval in the Shimokita Peninsula reaffirms the importance of Hachinohe as a tsunami record site for the activity of both trenches.

To help characterise the palaeogeographic and lacustrine environmental changes that resulted from the Holocene transgression and residual subsidence in the eastern Kanto Plain of central Japan, we analysed four drill cores and reviewed other core data from the southern part of the Lake Inba area. Fossil diatom assemblages yielded evidence of centennial-scale palaeogeographic and salinity responses to sea-level changes since the late Pleistocene. We determined that the seawater incursion into the Lake Inba area during the Holocene transgression occurred at approximately 9000 yr. We also recognised a late Holocene regression event corresponding to the Yayoi regression, considered to have occurred from ca. 3000 to ca. 2000 yr, and a subsequent transgression. Our data clarify some of the palaeogeographic changes that occurred in the Lake Inba area and document an overall trend toward lower salinity in the lake during the regression. In particular, the environment in Lake Inba changed from brackish to freshwater no later than 1000 yr. From the detailed palaeogeographic and palaeo-sea-level reconstruction, we recognised that residual subsidence occurred during the Holocene in this area. Thus, comparison of sea-level reconstructions based on modelling and fossil diatom assemblages is effective in interpreting Holocene long-term subsidence.

Background Outbreaks of enterovirus D68 (EV‐D68) respiratory infections in children were reported globally in 2014. In Japan, there was an EV‐D68 outbreak in the autumn of 2015 (September–October). The aim of this study was to compare EV‐D68‐specific polymerase chain reaction (PCR)‐positive and EV‐D68‐specific PCR‐negative patients. Methods Pediatric patients admitted for any respiratory symptoms between September and October 2015 were enrolled. Nasopharyngeal swabs were tested for multiplex respiratory virus PCR and EV‐D68‐specific reverse transcription‐PCR. EV‐D68‐specific PCR‐positive and ‐negative patients were compared regarding demographic data and clinical information. Results A nasopharyngeal swab was obtained from 76 of 165 patients admitted with respiratory symptoms during the study period. EV‐D68 was detected in 40 samples (52.6%). Median age in the EV‐D68‐specific PCR‐positive and ‐negative groups was 3.0 years (IQR, 5.5 years) and 3.0 years (IQR, 4.0 years), respectively. The rates of coinfection in the two groups were 32.5% and 47.2%, respectively. There was no significant difference in the history of asthma or recurrent wheezing, length of hospitalization, or pediatric intensive care unit admission rate between the groups. The median days between symptom onset and admission was significantly lower for the EV‐D68‐positive group (3.0 days vs 5.0 days, P = 0.001). EV‐D68 was identified as clade B on phylogenetic analysis. No cases of acute flaccid myelitis were encountered. Conclusions More than half of the samples from the children admitted with respiratory symptoms were positive for EV‐D68‐specific PCR during the outbreak. Asthma history was not associated with the risk of developing severe respiratory infection.

Recently, we experienced an outbreak of acute hepatitis A virus (HAV) infection between 2018 and 2020. Herein, we describe this male-dominant HAV infection outbreak observed among non-human immunodeficiency virus (HIV)-infected persons in the northern part of Tokyo, Japan. Clinical information was collected from patient interviews and from medical record descriptions. In the present study, 21 patients were retrospectively analyzed. A total of 90.4 and 33.3% of patients were males, and men who have sex with men (MSM), respectively. The total bilirubin levels and platelet counts tended to be lower in the MSM group than in the non-MSM group. C-reactive protein (CRP) levels tended to be higher in acute liver failure (ALF) patients than in non-ALF patients. Prolonged cholestasis was observed in one patient (4.8%). We also found that 18 HAV isolates belonged to HAV subgenotype IA/subgroup 13 (S13), which clustered with the HAV isolate (KX151459) that was derived from an outbreak of HAV infection among MSM in Taiwan in 2015. Our results suggest that the application of antivirals against HAV, as well as HAV vaccines, would be useful for the treatment and prevention of severe HAV infection.

Objective: Stroking calves during the postnatal period could effectively improve humancalf relationships. The objective of this study is to examine how daily calf stroking frequency during the postnatal period affects the establishment of human-calf relationships.Methods: Six calves were stroked by a trainer for 6 minutes once daily for 5 days after birth (D1). Six calves were stroked by a trainer for 3 minutes twice daily for 5 days after birth (D2). A further four calves were stared at but not stroked as the control group. The overall stroking or staring duration was the same for all groups, at 6 min/d and 30 min over 5 days. The tests for reactions to the stationary trainer in an unfamiliar environment and avoidance distance measurements for an approaching trainer were conducted at 1 month and 3 months after the treatment.Results: Calves in both stroking groups approached significantly closer to the stationary trainer, vocalized less, and looked at the trainer shorter than the control group at 1 month. However, at 3 months, there was no significant difference between the D1 and the control group, whereas the D2 approached significantly closer to the trainer and vocalized less, and looked at the trainer for a shorter time than the control group. For the avoidance distance, the trainer could approach closer to both stroking groups than the control at 1 month, however, there was no difference among groups at 3 months.Conclusion: Our results suggested that the difference in the calf stroking procedure affected the established human-calf relationships, even though the total stroking duration was the same for all stroked calves. It is likely to be more effective to stroke more frequently than intensively when the aim is to establish better human-calf relationships within limited labor time.

In the present study, we assessed the negative effects of triphenyltin (TPT) on zebrafish (Danio rerio) by exposing embryos and early-stage larvae to various concentrations of TPT from 2 h after fertilization (haf) until 30 days after hatching (dah). Whether test groups were fed or fasted during ecotoxicity studies using fish models has varied historically, and whether this experimental condition influences test results is unknown. Here, we confirmed that the lethal concentration of TPT to embryo and early-stage larvae (i.e., 3 dah or younger) showed in fed (lowest observed effect concentration (LOEC); 6.34 μg/L) and fasted (LOEC; 6.84 μg/L) groups. In addition, 84% and 100% of the larvae in the 2.95 and 6.64 μg/L exposure groups, respectively, had uninflated swim bladders; all affected larvae died within 9 dah. This finding suggests that morphologic abnormalities in early larval zebrafish are useful as endpoints for predicting the lethality of chemical substances after hatching. We then assessed the expression of several genes in the thyroid hormone pathway, which regulates swim bladder development in many fish species, including zebrafish. Larvae exposed to 6.64 μg/L TPT showed significant increases in the mRNA expression levels of thyroid hormone receptor α (trα) and trβ but not of thyroid stimulating hormone β subunit. These findings suggest that TPT disrupts the thyroid system in zebrafish.

Sterigmatocystin is a genotoxic and hepatocarcinogenic mycotoxin that contaminates foods and environments worldwide. Sterigmatocystin is produced as a precursor to aflatoxin B1 or as an end product by certain Aspergilli. Aspergillus section Versicolores is one of the major sections including sterigmatocystin-producing species and is thus a potential health and environmental hazard. Recently, the taxonomy of this section was revised and classified into 14 species on the basis of molecular phylogenetic analysis. However, investigation of the distribution and sterigmatocystin production of each species has been limited; in particular, its distribution in foods has been scarcely reported. In this study, we collected isolates of Aspergillus section Versicolores from various foods and environments in Japan and investigated their distribution and sterigmatocystin production. The isolates were classified into nine species or species groups, which revealed that A. creber, A. puulaauensis/tennesseensis and A. sydowii are the main species/species groups in Japan. In addition, A. versicolor sensu stricto was detected with some frequency, specifically in foods. Furthermore, the two species A. creber and A. versicolor sensu stricto frequently produced sterigmatocystin. It is therefore important for food safety to intensively monitor these two species and distinguish them from other species, especially A. sydowii, which is not considered to produce sterigmatocystin.

This work reports a combined theoretical and experimental study on large phenol-acetylene clusters, Ph(Ac)n, 8 ​≤ ​n ​≤ ​12, extending our earlier work on the smaller clusters [Singh, G.; Nandi, A.; Gadre, S. R.; Chiba, T.; Fujii, A. J. Chem. Phys. 2017, 146, 154303]. Several trial cluster geometries are generated using the molecular electrostatic potential (MESP) for placing additional acetylene moieties, followed by geometry optimization at B97D/aug-cc-pVDZ level theory. The infrared spectra of energetically low-lying (within 0.5 ​mH window) isomers of the clusters are calculated and averaged. The O–H stretching band shows two peaks due to the presence of energetically close isomers differing in the arrangement of acetylenes around the O–H group. The acetylenic C–H stretching band appears around 3260 ​cm−1. The C–H band shows a red shift of about 3 ​cm−1 on going from n ​= ​8 to 12. Moderately size-selected IR spectra of Ph(Ac)n (n ​= ​~10 and ~13) prepared by a supersonic jet expansion are measured for the acetylenic C–H region by infrared-ultraviolet double resonance spectroscopy combined with time-of-flight mass spectrometry. The observed spectral features are in agreement with the trends of the frequency shift and asymmetric line shape of the C–H stretch band predicted by the theoretical calculations.

Objective Decremental responses in the repetitive nerve stimulation (RNS) test in amyotrophic lateral sclerosis (ALS) patients have been reported, although their possible diagnostic role has received little investigation. We investigated their diagnostic role in differentiation between ALS and cervical spondylotic amyotrophy (CSA), an important ALS mimic especially in Japan. Methods Patients were prospectively enrolled and the diagnosis was confirmed by follow-up. RNS was performed on the abductor pollicis brevis (APB), upper trapezius (trapezius) and deltoid muscles. Results Enrolled subjects consisted of 53 ALS and 37 CSA patients. Abnormal decremental responses (>5%) were observed in 32%, 51% and 75% of ALS patients and 3%, 0% and 20% of CSA patients for the APB, trapezius and deltoid muscles, respectively. The sensitivity for 23 ALS patients with upper-limb onset was 78% for the trapezius and 100% for the deltoid muscles. Conclusions An abnormal decremental response in the trapezius muscle was 100% specific to ALS in comparison with CSA: abnormal decrement in this muscle would strongly suggest ALS. No decrement in the deltoid muscle might exclude ALS in patients having symptoms with upper-limb onset. Significance RNS is useful in differentiation between ALS and CSA.

The aim of this study is to actualize an in-situ measurement system of greenhouse gases using a UAV. This paper presents vertical profiles of CO 2 concentration as a measurement result with operation and long-term maintenance for a periodic flight tests. For this study, a new joint part with a single structure for improving strength of the sensor mount is developed. Moreover, routine maintenance to replace a router and periodic regulation of the analyzer is provided. After updating flight altitude permission over 150 m, we conducted flight tests up to 500 m. We compare individual linear correction and liner regression applied for vertical profiles of CO 2 concentration. We address that correction using linear regression has advantage to reduce burden for in-situ measurement.

We have developed a simple measuring system prototype that uses an unmanned aerial vehicle (UAV) and a non-dispersive infrared (NDIR) analyzer to detect regional carbon dioxide (CO2) concentrations and obtain vertical CO2 distributions. Here, we report CO2 measurement results for the lower troposphere above Ogata Village, Akita Prefecture, Japan (about 40&deg, N, 140&deg, E, approximately &minus, 1 m amsl), obtained with this UAV system. The actual flight observations were conducted at 500, 400, 300, 200, 100, and 10 m above the ground, at least once a month during the daytime from February 2018 to February 2019. The raw CO2 values from the NDIR were calibrated by two different CO2 standard gases and high-purity nitrogen (N2) gas (as a CO2 zero gas, 0 ppm). During the observation period, the maximum CO2 concentration was measured in February 2019 and the minimum in August 2018. In all seasons, CO2 concentrations became higher as the flight altitude was increased. The monthly pattern of observed CO2 changes is similar to that generally observed in the Northern Hemisphere as well as to surface CO2 changes simulated by an atmospheric transport model of the Japan Meteorological Agency. It is highly probable that these changes reflect the vegetation distribution around the study area.

To clarify whether Oryzias congeners, including freshwater, brackish water, and marine medaka, would be useful models for evaluating environmental chemical effects in various aquatic ecosystems, we examined the influence of salinity on their embryo development. We also compared the toxicity values of the organotin compounds triphenyltin and tributyltin, which remain pollutants of marine and freshwater ecosystems, between Oryzias latipes (freshwater), Oryzias melastigma (brackish water), and Oryzias javanicus (saltwater). Hatching and survival rates of O. latipes were significantly decreased at a salinity of 34, whereas O. melastigma and O. javanicus were adaptable to various salinities from freshwater to seawater. The lowest observed effect concentrations of organotin compounds for survival and embryo development were the similar in the three species. The similarity of the species’ responses to organotin compounds indicated that Oryzias congeners are useful for ecological risk assessment of chemicals in a range of aquatic ecosystems, from freshwater to marine.

We studied onshore sediment cores obtained from a coastal marsh on the south coast of Beppu Bay, northern Kyushu Island, Japan, to ascertain whether prehistoric intraplate earthquakes in the bay had generated tsunamis, and to establish a chronology and recurrence intervals for these earthquakes. The latter had been inferred from investigations on shallow offshore faults, but the timing of the fault movements has large uncertainties. We identified five sand layers in the up to 8.8 m long sedimentary sequence, which is mainly composed of non-marine organic-rich mud and marine organic-poor mud. Most sand layers, 1–20 cm thick, exhibit sharp upper and lower contacts with the surrounding muds, implying that they were deposited by sudden events. The sand layers are geochemically distinct, with peaks in Si, K, Ca, Ti, Mn, Fe, and Sr, and diatom assemblages dominated by brackish–marine and marine species. This suggests that the sand came from the sea bottom and/or shore rather than from the freshwater marsh. Based on radiocarbon age modeling, the depositional ages of these sand layers are: 3270–3450 cal yr BP, 4250–4510 cal yr BP, 4970–5280 cal yr BP, 5750–6750 cal yr BP, and 6430–7070 cal yr BP. The oldest deposit is inferred to record a tsunami associated with the 7.3 ka caldera-forming eruption of the Kikai volcano, southern Japan. Thus, we exclude it from the calculation of the recurrence interval of tsunamigenic intraplate earthquakes in the bay. Recurrence is approximately 460–1850 years, including the 1596 CE Keicho Bungo earthquake and a fault rupture 1700–2200 years ago, which have been reported in studies on ruptures of shallow offshore strike-slip and normal faults. Brackish–marine and marine species dominate the fossil diatom assemblages in the upper muddy sand layer (younger than 2750–2870 cal yr BP) above the non-marine organic-rich mud, implying that the muddy sand was deposited in an inner bay or tidal flat environment. The facies change from non-marine to marine sediments after 2750–2870 cal yr BP cannot be explained by a change in the regional sea level because the latter has fallen in the last 6000 years. Therefore, the most likely interpretation for this environmental change is a local coseismic subsidence of the marsh, probably attributed to a rupture of the active fault located south of the marsh. This study is the first to report on recurrent tsunamigenic intraplate earthquakes based on research of onshore tsunami deposits, and suggests that investigating tsunami deposits can contribute to an assessment of tsunami risks for intraplate earthquakes elsewhere.