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The effects of an AC electric field on ice nucleation temperature and nucleation rate were investigated by freezing distilled water while exposing it to varied AC electric field strengths and frequencies. To eliminate the influence of ion injections and electric field concentrations at a metal electrode surface on ice nucleation, distilled water filled in resin cuvettes are used as samples. The samples are exposed to AC electric field induced by parallel plate electrodes placed outside of the cuvettes. The cuvettes and parallel plate electrodes placed in a freezer with an inside temperature fixed at −15°C. The electric field strength in the sample is 2 or 7.5 kV/m and frequency varies from 50 Hz to 10 kHz. The ice nucleation temperature and the nucleation rate of distilled water increase with increasing the electric field strength and the frequency. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Contributions of abiotic and biotic processes on travertine deposition are still not well‐understood due to technical difficulties, despite that the travertines draw attention as analogues for ancient microbial carbonates and oil reservoirs. To evaluate their contributions, this study examined eight hot springs in Japan. Water chemistry analyses showed common downstream trends: a decrease in CO2 concentration and increases in CO32− concentration and pH. Mineralogical analysis showed that the constituent minerals of travertines at six hot springs were both calcite and aragonite, while one was just calcite and another only aragonite. Microscopic observations of travertine surfaces indicated the dominance of cyanobacteria secreting extracellular polymeric substances without a detectable amount of carboxyl groups. Small particles were sometimes entangled/covered by these cyanobacteria. Microelectrode measurements showed the occurrence of abiotic CaCO3 precipitation and photosynthetic induction/inhibition of CaCO3 precipitation, the extent of which was different at each site. By integrating these results, the contributions of abiotic and biotic processes were evaluated. Cyanobacteria inhabiting travertine surfaces were generally not calcified regardless of an ambient high CaCO3 saturation state; instead, they contributed to creating pore spaces and trap/bind suspended particles. Downstream CO2 degassing increased the CaCO3 saturation state by shifting carbonate chemical equilibrium and caused abiotic CaCO3 precipitation. Suspended particles trapped by cyanobacteria increased the surface area for crystal growth to further accelerate precipitation. The contribution of photosynthesis‐induced CaCO3 precipitation was low because of several factors, including variable cyanobacteria populations and photosynthetic inhibition of CaCO3 precipitation. The average contributions of photosynthesis‐induced CaCO3 precipitation, Ca2+ adsorption and abiotic precipitation in the eight hot springs were 16%, 3% and 81%, respectively, indicating predominance of the abiotic process for travertine deposition. Mineralogical composition of travertines significantly correlated with concentrations of SO42− and Mg2+, much more than with Mg/Ca ratio and water temperature, suggesting their importance for controlling CaCO3 polymorphs in travertines. [ABSTRACT FROM AUTHOR]

Mineral dust affects the microphysical and radiative properties of mixed‐phase clouds and hence the radiative balance of the Earth by acting as ice nucleating particles (INPs). However, the importance of Asian dust as INPs is not well understood. In this study, we examined the contribution of Asian dust to global dust INPs and its effect on cloud radiative forcing (CRF) using a global aerosol‐climate model with an ice nucleation parameterization that links INP number concentrations to ambient temperature and dust number concentrations. Our model well reproduces INP number concentrations measured over the Tokyo Metropolitan area in Japan during May 2017, when Asian dust was transported to Japan. Our simulation for the years 2013–2017 shows that Asian dust extends from its source regions (e.g., the Gobi and Taklimakan Deserts) to the North Pacific, North America, and the Arctic. Notably, Asian dust is transported to higher altitudes (i.e., to temperature regimes relevant for the formation of mixed‐phase clouds) more efficiently than dust from other regions. The annual‐mean simulated contribution of Asian dust to global dust INPs is 15%, which is 4.4 times higher than its contribution to global atmospheric dust loading (3.4%). These characteristics of Asian dust show its high potential to act as INPs in mixed‐phase clouds. Sensitivity simulations show that Asian dust INPs have a positive net CRF of 0.054–0.19 W m−2 in East Asia and the North Pacific during 2013–2017 (cf. 0.092–1.0 W m−2 for dust from other regions). Key Points: Asian dust can be transported to temperature regimes relevant for mixed‐phase clouds more efficiently than dust from other sourcesAsian dust contributes 15% of the global dust ice nucleating particles (INPs), while its contribution to the global dust loading is only 3.4%INPs from Asian dust have a net cloud radiative forcing of 0.054–0.19 W m−2 in East Asia and the North Pacific [ABSTRACT FROM AUTHOR]

The 2011 magnitude (M) 9.0 Tohoku-oki earthquake was followed by seismicity activation in inland areas throughout Japan. An outstanding case is the M6.2 Northern Nagano earthquake, central Japan, occurred 13-h after the megathrust event, approximately 400 km away from its epicenter. The physical processes relating the occurrence of megathrust earthquakes and subsequent activation of relatively large inland earthquakes are not well understood. Here we use waveform data of a dense local seismic network to reveal with an unprecedented resolution the complex mechanisms leading to the occurrence of the M6.2 earthquake. We show that previously undetected small earthquakes initiated along the Nagano earthquake source fault at relatively short times after the Tohoku-oki megathrust earthquake, and the local seismicity continued intermittently until the occurrence of the M6.2 event, being likely 'modulated' by the arrival of surface waves from large, remote aftershocks off-shore Tohoku. About 1-h before the Nagano earthquake, there was an acceleration of micro-seismicity migrating towards its hypocenter. Migration speeds indicate potential localized slow-slip, culminating with the occurrence of the large inland earthquake, with fluids playing a seismicity-activation role at a regional scale. [ABSTRACT FROM AUTHOR]

The 2016 Kumamoto earthquakes, including an Mw-7 right-lateral earthquake on April 15 (UTC), occurred along faults within the Beppu−Shimabara graben in central Kyushu, Japan. Previous studies showed that the graben area was under heterogeneous stress conditions with north-south T-axes and spreading in a north-south direction. Here, we construct a detailed crustal deformation model using three-component Global Navigation Satellite System data in 2000-2010 and considering the distribution of geological fault traces in this area. Our inversion analysis suggests that the strain accumulation rate for the right-lateral seismic slip segment (corresponding to the Futagawa fault), where the largest of the 2016 Kumamoto earthquakes ruptured, was several times smaller than the other segments in the Beppu−Shimabara graben. Furthermore, we observe distinct subsidence along the Beppu−Shimabara graben. Our base model attributes the subsidence to deflation of magma reservoirs beneath volcanoes, but the observed vertical velocities are poorly fit. In order to improve the fitting results for the vertical deformation, we need more sophisticated volcano-deformation model (such as a sill-like deformation source for Mt. Aso) or graben model. [ABSTRACT FROM AUTHOR]

• Observation of synchronicity between shallow and deep seismic activities in a slab. • Evidence of rapid long-range seismic bursts propagating rapidly in a subduction. • Rapid water ascent in slab observed before a megathrust earthquake. • Observation of the propagation of pressure pulses in fluid channels. • Link between a subduction earthquake and the dehydration of slab minerals. Earthquake precursory phenomena like foreshocks are common but the physical processes which produce them and lead to rupture are poorly understood. Looking for clues about these processes, we explore here the long-term evolution of seismicity in a broad section of the Japan Trench slab around the 2011 Tohoku earthquake location and report the existence of long-range seismic bursts moving rapidly (∼1-2 days or less) between the deep and the shallow slab. Their presence is evidenced by synchronizations of deep and shallow seismic activities in the slab. Probabilities that these synchronizations could be due to chance are infinitesimal (<10−5). We show that a significant part of the activity in this subduction occurs during these bursts and that they are responsible for the foreshock sequence which preceded the earthquake. These observations support the existence of fluid channels connecting the deep slab, where water is released during dehydration, to the shallow seismogenic zone. [ABSTRACT FROM AUTHOR]

Abstract: Time-resolved data for size distribution, number concentration and chemical composition of atmospheric aerosols were taken from March 9 to 16, 2012 during Fukue Site Atmospheric Aerosol Observation Campaign (128.7°E, 32.8°N) organized by ASEPH (Impacts of Aerosols in East Asia on Plants and Human Health) project. A scanning mobility particle sizer was employed to continuously measure the particle size distribution from 14 nm to 670 nm and the total number concentration of particles (>3 nm) was measured by a condensation particle counter. Very large amount of polluted air mass transportation (PM2.5 > 65 μg m−3) was observed on March 11, associated with a sudden increase in particle number concentration having a mobility diameter from 100 to 300 nm. The transported air mass contained anthropogenic pollutants such as sulfate (>20 μg m−3), nitrate (>15 μg m−3) and black carbon (>3 μg m−3). Typical new particle formation and growth events were also observed on March 12–13. The onset of particle formation and nucleation bursts was identified at around noon and it is considered that these were nucleated species near the island area. It was found that some new particle formation events were associated with the long range transportation of polluted air mass from East Asian region. [Copyright &y& Elsevier]

This study was performed to measure the activity size distribution of aerosol particles associated with short-lived radon decay products in indoor air at Nagoya University, Nagoya, Japan. The measurements were performed using a low pressure Andersen cascade impactor under variable meteorological conditions. The results showed that the greatest activity fraction was associated with aerosol particles in the accumulation size range (100–1000 nm) with a small fraction of nucleation mode (10–100 nm). Regarding the influence of the weather conditions, the decrease in the number of accumulation particles was observed clearly after rainfall without significant change in nucleation particles, which may be due to a washout process for the large particles. [ABSTRACT FROM PUBLISHER]

Abstract: Volcanoes with silica-rich and highly viscous magma tend to produce violent explosive eruptions that result in disasters in local communities and that strongly affect the global environment. We examined the timing of 11 eruptive events that produced silica-rich magma from four volcanoes in Japan (Mt. Fuji, Mt. Usu, Myojin-sho, and Satsuma-Iwo-jima) over the past 306years (from AD 1700 to AD 2005). Nine of the 11 events occurred during inactive phases of solar magnetic activity (solar minimum), which is well indexed by the group sunspot number. This strong association between eruption timing and the solar minimum is statistically significant to a confidence level of 96.7%. This relationship is not observed for eruptions from volcanoes with relatively silica-poor magma, such as Izu-Ohshima. It is well known that the cosmic-ray flux is negatively correlated with solar magnetic activity, as the strong magnetic field in the solar wind repels charged particles such as galactic cosmic rays that originate from outside of the solar system. The strong negative correlation observed between the timing of silica-rich eruptions and solar activity can be explained by variations in cosmic-ray flux arising from solar modulation. Because silica-rich magma has relatively high surface tension (~0.1Nm−1), the homogeneous nucleation rate is so low that such magma exists in a highly supersaturated state without considerable exsolution, even when located relatively close to the surface, within the penetration range of cosmic-ray muons (1–10GeV). These muons can contribute to nucleation in supersaturated magma, as documented by many authors studying a bubble chamber, via ionization loss. This radiation-induced nucleation can lead to the pre-eruptive exsolution of H2O in the silica-rich magma. We note the possibility that the 1991 Mt. Pinatubo eruption was triggered by the same mechanism: an increase in cosmic-ray flux triggered by Typhoon Yunya, as a decrease in atmospheric pressure results in an increase in cosmic-ray flux. We also speculate that the snowball Earth event was triggered by successive large-scale volcanic eruptions triggered by increased cosmic-ray flux due to nearby supernova explosions. [Copyright &y& Elsevier]

Anthophyllite or another species of Mg-amphibole commonly occurs in an intervening zone between the higher grade orthopyroxene zone and lower grade talc zone in progressively metamorphosed peridotites. However, the anthophyllite zone is absent in some of the thermally metamorphosed peridotite complexes in SW Japan despite the existence of the other zones. A comparative study presented here reveals similarities in rock composition and metamorphic pressure-temperature conditions at high-grade zones between the metaperidotite complexes, and differences in the following respects. The metaperidotite complex that contains an anthophyllite zone has less abundant magnetite and olivine that is more homogeneous than the complex where the anthophyllite zone is absent. It is likely that the degree of cation diffusion in olivine crystals depends on duration of heat retention in metaperidotites during thermal metamorphism, which is supported by the variation in mineralogy of intrusive rocks and pelitic hornfelses surrounding the metaperidotites, and by calculations based on a simplified model of thermal conduction. The long duration of heat retention looks to be a necessary condition for the formation of anthophyllite crystals, which have a sluggish nucleation rate. In addition, the circulation of reducing fluids during prolonged metamorphism likely promoted the decomposition of magnetite and the growth of anthophyllite, into which iron is preferentially distributed. This study cautions about kinetic controls and redox conditions for anthophyllite formation in metaperidotites. [ABSTRACT FROM AUTHOR]

This paper presents a modal aerosol model (MAM) developed to be used in three dimensional air quality models. MAM, which represents the aerosol distribution with four modes, has the advantage of simplicity and speed efficiency associated to modal models, while mass transfer is modeled with a dynamic approach. To assess the ability of MAM to represent mass transfer, MAM is compared to a size-resolved model based on the dynamic approach and to a version of MAM based on an equilibrium approach. Comparisons are done using measurements of inorganic species made in Japan as initial conditions. Furthermore, it is shown that MAM combined with a well chosen mode splitting scheme is able to deal accurately with the simultaneous occurrence of strong nucleation/condensation and coagulation, as may be observed in high nucleation episodes. [ABSTRACT FROM AUTHOR]

The National Space Development Agency of Japan (NASDA) developed a practical protocol to optimize protein crystallization conditions for microgravity experiments. This protocol focuses on the vapor diffusion method using high density protein crystal growth (HDPCG)—hardware developed by the University of Alabama, Birmingham—that flew on the STS-107 mission. The objective of this development was to increase the success rate of microgravity experiments by setting crystallization conditions based on knowledge of crystal growth and fluid dynamics. The protocol consists of four steps: (1) phase diagram preparation, (2) estimation of condensation rate in the vapor diffusion method, (3) fluid dynamic property measurement, and (4) fluid dynamic simulation. First, a phase diagram was constructed. Crystallization characteristics were investigated by a microbatch method. The data were recalculated based on classical nucleation theory and the crystallization boundary was determined as a function of time. The second step was to develop a practical model to estimate the condensation rate of the crystallizing solution, including protein and precipitant, as a function of the precipitant concentration and solution volume. By considering the crystallization map and the vapor diffusion condensation model we were able to optimize the crystallization conditions that generate crystals in the desired time. This was particularly important in a shuttle mission whose mission duration is limited. The third step was fluid dynamic property measurement necessary for fluid dynamics simulation and crystal growth study. The last step was to estimate the mass transport in space on the basis of the fluid dynamics simulation transport model. It turned out that neither the vapor phase nor the solution phase was seriously affected by gravity until nucleation provided the hardware was set in a normal direction. Therefore, we concluded that the optimized crystallization conditions could be directly applied to microgravity experiments. By completing the approach, we were able to control the time for nucleation in the vapor diffusion method. [ABSTRACT FROM AUTHOR]

We analyze high sampling waveforms of the initial part of P-wave recorded at the 1800-m-deep borehole seismographs at the Nojima fault from December 1999 to May 2000 to clarify the initial rupture process of microearthquakes. We select 12 events with high S/N, whose magnitudes range from −0.3 to 2.2 and hypocentral distances from 1 to 11 km. We adopt the two different source models by and by . The former (model by Sato and Hirasawa (SH model)) generates only a ramp-like onset of velocity pulse. The later (model by Sato and Kanamori (SK model)) is able to generate a weak initial phase that is controlled by a trigger factor and the length of pre-existing crack. We perform the waveform inversion to estimate the optimum source parameters of each model. Waveforms of 5 of the 12 events are clearly reproduced by both SH model and SK model with a large trigger factor and a small length of pre-existing crack. The others are explained by not SH model but only SK model with a small trigger factor and a large length of the pre-existing crack, indicating that the weak initial phase is a nucleation phase and reflects the source process. These seven events satisfy roughly a relation that a large event has a large length of the pre-existing crack; the final crack length is proportional to the length of the pre-existing crack. [Copyright &y& Elsevier]

In the last decade, the real time ground–based geomagnetic observations realized in correlation with the Vrancea seismicity in Romania, together with supplementary studies related to some earthquakes (Mw9.0 Tohoku, Japan on 11 March 2011 and Mw8.3 Coquimbo, Chile on 16 September 2015), enlarged our knowledge about the relationship between the pre-seismic anomalous phenomena and the final stage of the earthquake nucleation. To identify possible ultra-low-frequency (ULF) geomagnetic signals prior to the onset of an Mw8.1 earthquake, we retroactively analyzed the data collected on the interval 1 August–16 September 2017 at the Geomagnetic Observatories in Teoloyucan (TEO), Mexico and Tucson (TUC) USA, with the last taken as a reference. Daily mean distributions of the polarization parameter BPOL (geomagnetic polarization parameter) and standard deviation are obtained for both observatories using a fast Fourier transform (FFT) band-pass filtering in the ULF range (0.001–0.083 Hz). Further on, we investigated the singularity of the pre-seismic signal associated with an Mw8.1 earthquake and applied a statistical analysis based on a standardized random variable equation; results are presented as BPOL* time series on the interval 1–26 September. Finally, the hourly mean distribution, obtained as difference BPOL (TUC-TEO) on the interval 7–9 September emphasizes an anomalous signal with five hours before the onset of the Mw8.1 earthquake. [ABSTRACT FROM AUTHOR]