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Abstract Background As a blood-borne pathogen, hepatitis C virus (HCV) has long been a major threat associated with needle-stick injuries (NSIs) mainly because no vaccine is available for HCV. Following an NSI, we usually test the source patient for HCV antibody (HCV-Ab). Since HCV-Ab positivity does not necessarily indicate current infection, HCV RNA is further examined in patients positive for HCV-Ab. Direct-acting antivirals (DAAs) have enabled us to treat most HCV-infected patients; therefore, we speculate that the rate of HCV RNA positivity among HCV-Ab-positive patients decreased after the emergence of DAAs. This cross-sectional study was performed to investigate the change in the actual HCV RNA positivity rate in source patients before and after the interferon (IFN)-free DAA era. Methods This was a cross-sectional study of NSI source patients at a tertiary academic hospital in Japan from 2009 to 2019. IFN-free DAA regimens were first introduced in Japan in 2014. Accordingly, we compared HCV status of NSI source patients that occurred between 2009 and 2014 (the era before IFN-free DAAs) with those that occurred between 2015 and 2019 (the era of IFN-free DAAs) in a tertiary care hospital in Japan. Results In total, 1435 NSIs occurred, and 150 HCV-Ab-positive patients were analyzed. The proportion of HCV RNA-positive patients significantly changed from 2009 through 2019 (p = 0.005, Cochran–Armitage test). Between 2009 and 2014, 102 source patients were HCV-Ab-positive, 78 of whom were also positive for HCV RNA (76.5%; 95%CI, 67.4–83.6%). Between 2015 and 2019, 48 patients were HCV-Ab-positive, 23 of whom were also positive for HCV RNA (47.9%; 95%CI, 34.5–61.7%; p = 0.0007 compared with 2009–2014). In the era of IFN-free DAAs, 9 of 23 HCV RNA-negative patients (39.1%) and 2 of 22 HCV RNA-positive patients (9.1%) were treated with an IFN-free combination of DAAs (p = 0.0351). Regarding the departments where NSIs occurred, HCV RNA-negative patients were predominant in departments not related to liver diseases in the era of IFN-free DAAs (p = 0.0078, compared with 2009–2014). Conclusions Actual HCV RNA positivity in source patients of NSIs decreased after the emergence of IFN-free DAAs. IFN-free DAAs might have contributed to this reduction, and HCV RNA-negative patients were predominant in departments not related to liver diseases in the era of IFN-free DAAs.

The incidence of nonalcoholic steatohepatitis (NASH) is increasing worldwide, including in Asian countries. We reported that the hepatic expression of bile salt export pump (BSEP) was downregulated in patients with NASH, suggesting that BSEP is involved in the pathogenesis of NASH. To identify the underlying mechanism, we analyzed Bsep heterozygous knock-out (Bsep+/- mice) and wild-type (WT) C57BL/6J mice fed a high-fat diet (HFD) (32.0% animal fat) or normal diet. We examined histological changes, levels of hepatic lipids and hepatic bile acids, and expression of genes related to bile acid and cholesterol metabolism. HFD-fed Bsep+/- mice exhibited milder hepatic steatosis and less weight gain, compared to HFD-fed WT mice. The concentrations of total bile acid, triglycerides, and cholesterols were reduced in the liver of HFD-fed Bsep+/- mice. Regarding hepatic bile acid metabolism, the expression levels of Farnesoid X receptor (Fxr) and Multidrug resistance-associated protein 2 were significantly upregulated in HFD-fed Bsep+/- mice, compared to HFD-fed WT mice. Furthermore, several alterations were observed in upstream cholesterol metabolism in the liver. The expression levels of bile acid metabolism-related genes were also altered in the intestine of HFD-fed Bsep+/- mice. In conclusion, HFD-fed Bsep+/- mice exhibited significant alterations of the expression levels of genes related to bile acid and lipid metabolism in both the liver and ileum, resulting in alleviated steatosis and less weight gain. These results suggest the importance of BSEP for maintenance of bile acid and cholesterol metabolism. Further investigations of the involvement of BSEP in the pathogenesis of NASH will provide greater insight and facilitate the development of novel therapeutic modalities.

Abstract This paper describes the instrumentation and the first results of an upper atmospheric observing project conducted in New Zealand. We operate an all-sky aurora camera and a 64-Hz sampling induction magnetometer at Middlemarch, as well as 1-Hz sampling fluxgate magnetometers which have been operative at three stations in New Zealand, Middlemarch, Eyrewell and Te Wharau. Green and red auroras corresponding to the 557.7 nm and 630.0 nm emissions, respectively, were observed on the night of 5 August 2019. Pc1 pulsations were observed in the frequency range of ~ 0.2–1 Hz before and after a small (minimum Dst = − 40 nT) geomagnetic storm during 4–6 October 2020. Before the geomagnetic storm, Pc1 pulsations with several center frequencies were observed regardless of local time. During the recovery phase, an IPDP (interval of pulsations of diminishing period) type of Pc1 and four subsequent intervals of Pc1s were detected. The Ionospheric Alfvén Resonator (IAR) was also identified with spectral resonance structures during this magnetic storm. Lower harmonic modes of the IAR were present throughout the local nighttime, but higher harmonic modes with frequency of 5–15 Hz seemed to disappear at the onset time of substorms. This is the first report of the IAR at such a high frequency range and this is the first IAR observation in the southern hemisphere. Examples of applying cross-phase analysis to observation data of fluxgate magnetometers are also given. Graphical Abstract

We have identified nearly 1,000 onsets using two pairs of hemispheric conjugate ground magnetometers where the onset is defined based on a sharp decline in the H component of the magnetic field at a ground magnetometer station. Specifically, we used the pair of stations at West Antarctica Ice Sheet Divide and Sanikiluaq, Canada; Syowa, Antarctica; and Tjörnes, Iceland. While the onset time in the southern hemisphere is identified by eye, the value of the differences in the onset time between the northern and southern hemispheres is determined using cross covariance. We observe differences in the onset time between the two hemispheres as large as several minutes, but 53% of the events show no difference in the onset time. Using statistics, we show that the largest differences in onset time are associated with the summer and winter seasons and when the IMF By value is limited between 0.5 and 2.5 nT, which is the IMF By range when the local time difference between the northern and southern hemisphere foot points is the smallest. The results indicate that ionospheric conductivity associated with solar illumination plays a role in the differences in onset time between the northern and southern hemisphere when only non-zero differences in onset time are considered. We validate these results with two other less robust methods. The median value of the differences in onset time indicates that the onsets occur ∼23 s earlier in the winter hemisphere than that in the summer hemisphere. It has been reported that the time difference between the start of the substorm in the magnetotail and the observed auroral break up (substorm auroral onset) in the ionosphere is 30 s to 2 min in the current disruption model and the near earth neutral line model, respectively. Our results may be of interest to those two models.

The present article aims at a consistent understanding of observation, theoretical model, and simulation with the geomagnetic sudden commencement (SC) observed in the morning and afternoon at high and middle latitudes in the northern and southern hemispheres and at the noontime equator on 12 May 2021. The SC in Bx- and By-components of the geomagnetic field, SCx,y, was composed of the positive/negative preliminary (PI) and main impulses (MI) as SCx (+ -) and SCy (- +) in the morning and SCx (- +) and SCy (+ -) in the afternoon at middle latitudes in the northern hemisphere. SCx in the southern hemisphere is in the same polarity as those in the northern hemisphere, except for SCx (+ +) in the morning. SCy in the southern hemisphere has reverse polarity to those in the northern hemisphere. The PIx in the northern hemisphere matches the well-established two-cell Hall current vortices with anti-clockwise and clockwise directions in the morning and afternoon, respectively, and the MIx matches reverse Hall current vortices. The PIx and MIx in the southern hemisphere meet the Hall currents that are mirror images of those in the northern hemisphere with respect to the equator except for the positive MI in the morning. The PIy in the northern hemisphere is shown to meet the northward and southward Pedersen currents in the morning and afternoon, respectively, and the MIy meets reverse Pedersen currents. The PIy and MIy in the southern hemisphere are found to meet the Pedersen currents that are mirror images of those in the northern hemisphere. At the equator, typical SCx (- +) is observed, meeting the Cowling currents that should be supplied by the Pedersen currents responsible for the observed midlatitude SCy in the northern and southern hemispheres. The electric fields of the PI and MI observed by the HF Doppler sounders at the middle latitudes in the northern hemisphere are westward and eastward, respectively, in both the morning and afternoon, meeting the conventional dusk-to-dawn PI and dawn-to-dusk MI electric fields. The onset of the PI is found to be simultaneous with the resolution of a few seconds from high latitude to the equator in both the northern and southern hemispheres, indicating instantaneous achievement of the Pedersen–Cowling currents from high latitude to the equator. The instantaneous achievement of the energy-consuming Pedersen–Cowling currents is explained by the TM0/TEM mode wave in the Earth-ionosphere waveguide/transmission line rather than the compressional waves in the magnetosphere and F-region ionosphere. REPPU (REProduce Plasma Universe) global simulation model equipped with a potential solver at the inner boundary of the model magnetosphere reproduces the PI and MI electric fields at middle latitudes and SCx (- +) at the dayside equator. The simulation results are found to be consistent with most features of observations, such as the time scale of PI and MI, direction of the midlatitude electric field and generation of the Cowling currents. The simulation proves that the electric fields and FACs are generated in the outer magnetosphere, transmitted to the polar ionosphere and then to the equator in the Pedersen–Cowling current circuit.

The Polar Environment Data Science Center (PEDSC) is one of the centers of the Joint Support-Center for Data Science Research (DS) of the Research Organization of Information and Systems (ROIS), which was established in 2017. The purpose of the PEDSC is to promote the opening and sharing of the scientific data obtained by research activities in the polar region led by the National Institute of Polar Research (NIPR). Activities of the PEDSC have been carried out along a five year plan with the following seven specific tasks since 2017: (1) construction of an integrated database; (2) upgrade and interoperable use of the three existing database systems (NIPR Science Database, Arctic Data archive System (ADS), and Inter-university Upper atmosphere Global Observation NETwork system (IUGONET)); (3) processing of the time-series digital data; (4) processing of the sample data; (5) data publication in the Polar Data Journal; (6) collaboration with external communities; and (7) promoting data science using the database and database system.

At Syowa Station, Antarctica, the baseline values, or the difference between the absolute and continuous measurements, vary relatively significantly in summer. They are possibly due to artificial disturbances from magnetized objects, and/or changes of the instrumental environment such as involving the tilt and temperature of the sensor for continuous observations. To evaluate the effect of the sensor tilt, we continuously monitored its behavior with electronic tiltmeters over two successive summer seasons (Jan.-Feb. 2013, Nov. 2013-Feb. 2014), while also intensifying the frequency of the absolute observation. The variability of the tilt was found such that, its angular changes in the East-West and North-South directions were 30 to 50 and 10 arcseconds, respectively. The observed variations of the baseline values can be attributed primarily to the sensor tilt changes, with its contribution estimated to be up to 60 to 100% for the D component and 30 to 40% for the H and Z components.

Electron precipitation plays major role in magnetospheric physics and space weather. Here the authors show nonlinear behavior of the wave–particle interaction in the magnetosphere as the evolution of chorus electromagnetic waves detected by the Arase satellite and PWING observatory.

Abstract Transient mesospheric echo in the VHF range was detected at an altitude of 65–70 km during the auroral breakup that occurred from 2220 to 2226 UT on June 30, 2017. During this event, the footprint of the Arase satellite was located within the field of view of the all-sky imagers at Syowa Station in the Antarctic. Auroral observations at Syowa Station revealed the dominant precipitation of relatively soft electrons during the auroral breakup. A corresponding spike in cosmic noise absorption was also observed at Syowa Station, while the Arase satellite observed a flux enhancement of > 100 keV electrons and a broadband noise without detecting chorus waves or electromagnetic ion cyclotron waves. A general-purpose Monte Carlo particle transport simulation code was used to quantitatively evaluate the ionization in the middle atmosphere. Results of this study indicate that the precipitation of energetic electrons of > 100 keV, rather than X-rays from the auroral electrons, played a dominant role in the transient and deep (65–70 km) mesospheric ionization during the observed auroral breakup.

Abstract The plasmas (electrons and ions) in the inner magnetosphere have wide energy ranges from electron volts to mega-electron volts (MeV). These plasmas rotate around the Earth longitudinally due to the gradient and curvature of the geomagnetic field and by the co-rotation motion with timescales from several tens of hours to less than 10 min. They interact with plasma waves at frequencies of mHz to kHz mainly in the equatorial plane of the magnetosphere, obtain energies up to MeV, and are lost into the ionosphere. In order to provide the global distribution and quantitative evaluation of the dynamical variation of these plasmas and waves in the inner magnetosphere, the PWING project (study of dynamical variation of particles and waves in the inner magnetosphere using ground-based network observations, http://www.isee.nagoya-u.ac.jp/dimr/PWING/ ) has been carried out since April 2016. This paper describes the stations and instrumentation of the PWING project. We operate all-sky airglow/aurora imagers, 64-Hz sampling induction magnetometers, 40-kHz sampling loop antennas, and 64-Hz sampling riometers at eight stations at subauroral latitudes (~ 60° geomagnetic latitude) in the northern hemisphere, as well as 100-Hz sampling EMCCD cameras at three stations. These stations are distributed longitudinally in Canada, Iceland, Finland, Russia, and Alaska to obtain the longitudinal distribution of plasmas and waves in the inner magnetosphere. This PWING longitudinal network has been developed as a part of the ERG (Arase)-ground coordinated observation network. The ERG (Arase) satellite was launched on December 20, 2016, and has been in full operation since March 2017. We will combine these ground network observations with the ERG (Arase) satellite and global modeling studies. These comprehensive datasets will contribute to the investigation of dynamical variation of particles and waves in the inner magnetosphere, which is one of the most important research topics in recent space physics, and the outcome of our research will improve safe and secure use of geospace around the Earth.

This paper reports simultaneous observations of visible noctilucent clouds (NLC) and polar mesosphere summer echoes (PMSE) at Syowa Station (69°01′S, 38°61′E) in Antarctica. During a 1.5 h interval from 2000 to 2130 UT (2300 to 0030 LT) on Feb. 11, 2009, visible NLC were observed south of Syowa Station. The oblique sounding HF radar of SuperDARN at Syowa Station simultaneously observed peculiar echoes in the closest two range gates. The echoes had a small Doppler velocity and a narrow spectral width, which are consistent with the characteristics of PMSE in the SuperDARN data. The simultaneous appearance of the visible NLC and peculiar near-range echoes observed by the HF radar suggests that the echoes were actually a signature of PMSE in the HF band. In addition, the data from the simultaneous measurements show that the spatial distributions of NLC and PMSE in the HF band were collocated with each other, which implies that oblique sounding HF radar is a useful tool for estimating the two-dimensional horizontal distribution of PMSE.

During 2010 and 2011, some large facilities (e.g. a mechanical workshop, an atmospheric radar and a container yard) were constructed near the geomagnetic observation site at Syowa Station, Antarctica. Iron materials used in these facilities could potentially affect the geomagnetic field at the observation site. To evaluate the amount of artificial magnetic noise caused by the iron materials, we carried out magnetic surveys around Syowa Station before and after construction of the facilities. The results show that the iron materials generate a maximum of 1.0 nT of artificial noise at the geomagnetic observation site.

The 50th Japanese Antarctic Research Expedition (JARE-50) wintering party, consisting of 28 members, has conducted the third year program of the 7th four-year plan of JARE. JARE-50 took over the management of Syowa Station from JARE-49 on January 29, 2009 and handed over it to JARE-51 on February 1, 2010. Scientific observations carried out by JARE-50 were divided into the following five categories: 1. Steady Continuous Observations; 2. Long-term Monitoring; 3. Interdisciplinary Focused Projects; 4. Specific-Purpose Project on medical research; and 5. Preparatory Research for the future planned large atmospheric radar. There were many blizzards during the wintering, which required great efforts to clear snow. Sea ice conditions were stable, and almost all the planned outdoor operations were successfully performed. Various trainings and activities for safety management were carried out throughout the wintering, along with public outreach activities using the satellite communication network. Other items of note include photographing the Polar Mesospheric Cloud, voting in the Lower House election, the early arrival of five members of JARE-51 in November, and a visit by the Australian inspection team in January.

Circum-Antarctic balloons were launched from Syowa Station by the 44th Japanese Antarctic Research Experiment team in January 2003. Two balloons equipped with identical instruments were flown in formation around the Antarctic continent, in an attempt to separate temporal and spatial variations of the auroral phenomena. In this paper, we report instrument design, operation and some initial results of the ELF/VLF wave experiment by PPB No. 8 and 10 balloons.

Fiber Bragg grating (FBG) is an optical fiber sensor and is suitable for acoustic emission (AE) measurements of structures such as chemical plants that require water resistance, explosion proofing, and so forth, However, directionality has been a problem in conventional usage which glues the grating range of an FBG to the inspection surface. This study proposes a cylinder-FBG (C-FBG) sensor with the FBG glued to a cylindrical sensor holder. Effectiveness of the sensor was evaluated by characterizing directionality and frequency sensitivity of the sensor and by comparing the detected AE signals in a 3-point bending test of a carbon fiber reinforced plastic (CFRP) laminate against a conventional wide-band piezoelectric AE sensor. The features of the detected signals were similar to the signals detected by the wide-band AE sensor. These results show that it is possible to produce a wide-band cylindrical sensor without the directionality limitations of the conventional usage of FBG.

The 30th Japanese Antarctic Research Expedition (JARE-30) performed a Polar Patrol Balloon (PPB) experiment in January 1990. The launching date was January 5th. We could obtain position data until February 2nd and house keeping data until February 7th through ARGOS system. The trajectory of the PPB was about seven-eighth of a perfect circumpolar one. Auto-ballast system was normally operated to keep the flight level above 27km until 15 days after launch when all the ballast had been consumed, and then the balloon height became lower and lower. Before the ballast was completely consumed, the balloon drifted westward with a constant speed of about 18.7°per day by an easterly wind. After that the drifting speed gradually slowed down, eventually became zero on January 25th. On January 29th the balloon started drifting eastward. We calculated solar zenith angle and sunset angle at balloon height and found that the increase of ballast consumption began at the time when the maximum solar zenith angle became greater than a critical angle, in our case 92.4°. In order to understand the balloon drifting motion we referred to height profile data of zonal wind at Syowa Station during our flight. It was shown that when the balloon changed its drifting direction, the zonal wind direction was westerly at the balloon height.

Since 1984 the National Institute of Polar Research, the Institute of Space and Astronautical Science and collaborative scientists have conducted the long-term circumpolar balloon program that is called Polar Patrol Balloon (PPB) project, and they also have developed ballooning technologies for this program. This project aims at establishing a station network in the stratosphere over the Antarctic region for geophysical and astrophysical observations. Two test flight experiments that were performed by the 28th Japanese Antarctic Research Expedition (JARE) in 1987 have convinced us that PPB would come back to the launching area with a good possibility. During 1991 and 1993 (JARE-32-34) at Syowa Station. The PPB experiments will consequently be done for scientific researches. This brief paper reports unique advantages of PPB, specifications and expected trajectories of PPB, and planned scientific researches with PPB.