Hiroshi Machida −respected tephrochronologist, teacher, leader

Professor Emeritus Hiroshi Machida (Hiroshi hereafter) is the leading tephrochronologist of his generation in Japan. Perhaps more than any other geoscientist from Japan, Hiroshi carried the insights and advances of tephra studies and their application in palaeoenvironmental and archaeological applications, landscape processes, and volcanology and hazard analysis, to the outside world through a succession of papers and books written in English and through conference presentations. He has been the ‘international face’ of tephra studies in Japa

A simple device to measure and record wet bulb globe temperature for prevention of heat disorders

熱中症予防対策に使用する目的で,湿球黒球温度を自動的に連続して測定･記録できる簡便な装置を試作した｡この装置を本学グラウンドに設置し,2008年夏季の暑熱環境の測定を行った結果に若干の考察を加えて報告した

Sakurajima-Satsuma (Sz-S) and Noike-Yumugi (N-Ym) tephras: new tephrochronological marker beds for the last deglaciation, southern Kyushu, Japan

Two prominent tephras, Sakurajima-Satsuma (Sz-S) erupted from Sakurajima volcano and Noike-Yumugi (N-Ym) erupted from Kuchierabujima Island, provide new key marker beds for dating and synchronizing palaeoenvironmental and archaeological records in the last deglaciation in southern Japan. These tephras were identified on the basis of glass major-element compositions in two distal areas, a marine core (IMAGES MD98-2195) in the northern part of the East China Sea and on the central part of Tanegashima Island, and related their stratigraphic positions to the marine oxygen isotope-based chronology. In MD98-2195, Sz-S, 0.8 cm in thickness at 9.12 m depth and N-Ym, 3 cm in thickness at 9.30 m depth, are both white, vitric, ash-grade tephras. On Tanegashima Island, Sz-S, 10 cm in thickness and N-Ym, 3 cm in thickness, are stratigraphically constrained by well-characterised marker tephras Kikai-Akahoya (7,300 cal BP) and Aira-Tn (29,000 cal BP). Sz-S is rhyolitic and homogeneous on the basis of glass major-element compositions assayed by electron microprobe. Pumiceous glass shards predominant in distal Sz-S tephra indicate that it derived from pumice fall units that correspond to pumiceous and phreatomagmatic fine ash units constituting proximal Sz-S tephra. N-Ym is rhyolitic and glass major-element analyses reveal compositional diversity between units, suggesting that the lower and middle tephra units dispersed to the east, whereas the upper unit was dispersed north to north-west from the vent. Stratigraphically, Sz-S occurs at around the start of the late-glacial reversal (cooling) in oxygen isotope records of MD98-2195, corresponding to the end of GI-1 and the start of GS-1 in the ice-core events of NGRIP (GICC05), consistent with a terrestrial age of ˜12,800 cal BP. Based on the oxygen isotope stratigraphy, the tephra identified in the core as N-Ym at 9.30 m depth is close to the end of Greenland GI-1 and hence has an age of ˜13,000 cal BP, but on Kuchierabujima Island it has an age based on ¹⁴C assay of charcoal of c. 14,900 cal BP. Although this age discrepancy (14.9 vs 13.0 cal ka) needs resolution, the occurrence in core MD98-2195 of N-Ym shows that it is more widespread than hitherto demonstrated. The widespread distributions and key stratigraphic positions for the two marker tephras indicate that they are thus critical isochrons for precise correlation of palaeoenvironmental changes and prehistoric cultural events during the last deglaciation in southern Kyushu, and for relating such changes and events to the ice-core chronology via the marine oxygen isotope chronostratigraphy

Re-examination of previous correlation of distal Ks5 Tephra and proximal Oda pyroclastic flow deposits in South Kyushu, SW Japan

Two pyroclastic flow deposits named Nabekura (Nb) and Oda (Oda) Pyroclastic Flow Deposits in ascending order, in the southern Kyushu Island, SW Japan, are intercalated in the Kokubu Group distributed around the northern coastal area of the Kagoshima Bay. The purpose of this study is to reveal their differences in petrographic properties such as glass chemistry and refractive indices of volcanic glass shards, hornblende, and orthopyroxene. Nb and Oda are evidently distinguished by refractive indices of orthopyroxene and variation in the chemical composition of glass shards. We re-examined the proposed correlation of Oda with Ks5 (Boso Peninsula, Central Japan) by previous studies, comparing other two distal tephras petrographically similar to Ks5. It is concluded that Oda is not correlated to Ks5, OgA, and Hg-7

Feedback Control of Flow Separation Using Plasma Actuator and FBG Sensor

A feedback control system for mitigating flow separation was developed by using a string-type dielectric-barrier-discharge (DBD) plasma actuator and a fiber Bragg grating (FBG) sensor. Tangential jets were induced from the string-type DBD plasma actuator, which was located at 5% chord from the leading edge of an NACA0024 airfoil. The FBG sensor was attached to the interior surface near the root of the cantilever beam modeled on the pressure surface of the airfoil. The strain at the cantilever root was reflected in the form of Bragg wavelengths (λB) detected by the FBG sensor when the cantilever tip was vibrated by the flow near the trailing edge of the airfoil. It was found that calculating running standard deviations in the Bragg wavelength (λB′) detected by the sensor was valuable for judging flow separation in real time. The feedback control of flow separation on the NACA0024 airfoil was successfully demonstrated by setting λB′=0.0028 with periodic flow separations generated in a wind tunnel by oscillating a side wall of the test section with frequency fw=0.42 Hz. It was confirmed that the appearance probability of flow separation tends to decrease with a decrease in the duration for calculating λB′ and with an increase in the duration of jet injection

Global tephra studies: role and importance of the international tephra research group “Commission on Tephrochronology” in its first 60 years

Tephrochronology is a correlational and age-equivalent dating method whereby practitioners characterize, map, and date tephra (or volcanic ash) layers and use them stratigraphically as connecting and dating tools in the geosciences (including volcanology) and in studies of past environments and archaeology. Modern tephra studies per se began around 100 years ago (in the 1920s), but the first collective of tephrochronologists with a common purpose and nascent global outlook was not formed until 7 September 1961 in Warsaw, Poland. On that date, the inaugural “Commission on Tephrochronology” (COT) was ratified under the aegis of the International Union for Quaternary Research (INQUA). The formation of COT is attributable largely to the leadership of Kunio Kobayashi of Japan, the commission's president for its first 12 years. We were motivated to record and evaluate the function and importance of COT because tephrochronology continues to grow globally and its heritage needs to be understood, appreciated, and preserved. In addition, studies on cryptotephras, which are fine-grained glass-shard and/or crystal concentrations preserved in sediments or soils but insufficiently numerous to be visible as a layer to the naked eye, have also expanded dramatically in recent times. Therefore, in this article, we review the role and impacts of COT under the umbrella of INQUA for 53 of the last 60 years or under IAVCEI (International Association of Volcanology and Chemistry of the Earth's Interior) for 7 of the last 60 years, including since 2019. The commission also functioned under other names (abbreviated as COTS, CEV, ICCT, COTAV, SCOTAV, and INTAV; see Table 2 for definitions). As well as identifying key persons of influence, we describe the development of the commission, its leaders, and its activities, which include organizing nine specialist tephra field meetings in seven different countries. Members of the commission have participated in numerous other conferences (including specialist tephra sessions) or workshops of regional to international scale, and they have played leading roles in international projects such as INTIMATE (INTegrating Ice-core, MArine and TErrestrial records) and SMART (Synchronising Marine And ice-core Records using Tephrochronology). As well as strongly supporting early-career researchers including graduate students, the commission has generated 10 tephra-themed journal volumes and two books. It has published numerous other articles including field guidebooks, reports, and specialist internet documents/sites. Although its fortunes have ebbed as well as flowed, the commission began to prosper after 1987 when key changes in leadership occurred. COT has blossomed further, especially in the past decade or so, as an entire new cohort of specialists, including many engaged in cryptotephra studies, has emerged alongside new geoanalytical and dating techniques or protocols to become a vibrant global group today. We name 29 elected officers who have been involved with COT since 1961 as well as 15 honorary life members. After reviewing the aims of the commission, we conclude by evaluating its legacies and by documenting current and future work

Molecular-beam epitaxial growth of a far-infrared transparent electrode for extrinsic Germanium photoconductors

We have evaluated the optical and electrical properties of a far-infrared (IR) transparent electrode for extrinsic germanium (Ge) photoconductors at 4 K, which was fabricated by molecular beam epitaxy (MBE). As a far-IR transparent electrode, an aluminum (Al)-doped Ge layer is formed at well-optimized doping concentration and layer thickness in terms of the three requirements: high far-IR transmittance, low resistivity, and excellent ohmic contact. The Al-doped Ge layer has the far-IR transmittance of >95 % within the wavelength range of 40--200 microns, while low resistivity (~5 ohm-cm) and ohmic contact are ensured at 4 K. We demonstrate the applicability of the MBE technology in fabricating the far-IR transparent electrode satisfying the above requirements.Comment: 18 pages, 7 figures, accepted for publication in the PAS

A crowdsourcing approach to collecting photo-based insect and plant observation records

Scientific field observation by members of the public is known as citizen science and has become popular all across the world. Citizen science is advantageous for collecting large amounts of scientific data and can be seen as a crowdsourcing approach to data collection. Information and communications technology is enhancing the availability of citizen science. Mobile devices, such as mobile phones, that have a digital camera with a global positioning system (GPS) are necessities for contemporary life and can be utilised as powerful observation tools in citizen science. A web-based system has been developed as a data collection tool for citizen science. Participants submit an e-mail with a photo taken by their mobile phones. The photos contain location information, which can be easily and automatically embedded if the mobile phone is equipped with GPS. Collaboration has been undertaken with regional event managers, such as museum curators and held citizen science events in each region and for various target taxonomic groups. All photos were stored in the data server and the organisms were taxonomically identified by citizen scientists, regional managers and the authors. In total, 154 species and 843 data records were collected in this project conducted from 2011 to 2016