Flare activity in AM Canum Venaticorum

Flare activity on AM CVn was observed photometrically at 16^h20^m UT of 20 February, 1990. The amplitude of the flare is about 0.2 mag. The shape of the flare and the subsequent amplitude enhancement of the 1051 s period are quite similar to those previously observed by Mararet al. (1988).     

Natural groundwater of a gas field utilizable for a bioremediation of trichloroethylene-contamination

Groundwater from a shallow aquifer in Mobara, a city in a natural gas field in Chiba Prefecture, Japan, was found to contain a significant amount of dissolved methane (<3.1 mM) along with nitrate, phosphate and methane-oxidizing bacteria (methanotrophs, <9.9×10⁶ MPN ml^–1) which can degrade trichloroethylene (TCE). This water exhibited high methanotroph growth activity and rapid degradation of TCE. This water was introduced into a TCE-contaminated aquifer. The concentration of TCE at the monitoring well 2 m down-gradient of the injection pit decreased from 128 g L^–1 before the injection to less than the lower detection limit of 12.5 g L^–1 after the injection, while it decreased only slightly (to 86 g L^–1) when control water was injected. These results demonstrate the feasibility of utilizing a natural groundwater resource containing methane and methanotrophs without any additives for bioremediation of a TCE-contaminated site.     

Chaos in cosmic ray air showers

Unexpected chaotic features are found in time series of arrival time intervals of successive air showers with (E > 3 × 10¹⁴ eV). Over 99 % of air shower arrival time intervals obey the Poisson distribution law representing stochastic behaviors, but occasionally there are air showers showing real chaotic behaviors as distinguished from both random and colored noises. With two systems of the Kinki university installations, we found 13 cases showing chaotic time series in 3.36 yr with the system-1 and the 1.37 yr with the system-2. Five out of 10 chaotic air showers of the Kinki installation are detected during the same time zone also by the Osaka City university installation which is at 115 km distance from the Kinki one. In a remarkable example of September 19, 1991, the correlation dimension was observed to have dropped from about 4 to the minimum of 1.3 and recovered smoothly in about 38 h. The chaos structure in this case is detected in nearly the same time zone at the Ohya station of the Institute for Cosmic Ray Research, University of Tokyo, which is separated from the Kinki one by 460 km. Formation of chaos structure due to energetic cosmic ray dust particles is suggested. Progress of cosmic ray physics may be expected with the study of air showers marked with chaos.     

Glacial hazards in the Rolwaling valley of Nepal and numerical approach to predict potential outburst flood from glacial lake

In recent years, climate change and retreating glaciers constitute a major hazard in the Himalaya of South Asia. Glacial lakes are rapidly developing or increasing due to climate change. The rapid development of the lake may cause outburst of the lake. The outburst discharge from the glacial lake can cause catastrophic flooding and disaster in downstream area. Therefore, it is necessary to investigate the impact of climate change on glacial lakes and to understand the characteristics of the glacial lake outburst. In this study, the field assessment of Tsho Rolpa Glacial Lake in the Himalaya of Nepal has been presented and the impact of climate change on this glacial lake has been discussed. The Tsho Rolpa Glacial Lake is the largest and most potentially dangerous glacial lake in Nepal. In addition, a numerical model has been also developed for computing the characteristics of glacial lake outburst due to moraine dam failure by seepage and water overtopping. The numerical model is tested for the flume experimental cases. The simulated results of the outburst discharge, the dam surface erosion, and the temporal variation of the moisture movement in the dam are compared with those obtained from the hydraulic model experiments. The moisture profile calculated by numerical model was agreeable with the experimental moisture profile. The simulated failure surface of the dam due to seepage by considering the suction in slope stability analysis gave more agreeable results than the Janbu's simplified method. The results of the outburst discharge and dam surface erosion also agreed with the experimental results.     

On meteotsunamis around Tsushima Strait generated by the Baiu front

On July 15, 2009, a meteotsunami occurred over Tsushima Strait and flood damage was recorded on the west coast of Tsushima Island. This study investigated the meteorological systems related to that meteotsunami event using surface observation data, grid-point value data, and a mesoscale meteorological model. The mid-latitude trough in the mid-troposphere approached the moist air of the Baiu precipitation system, and a cold downdraft occurred over a wide area of western Japan. In the western Tsushima Strait, the warm, moist air of the lower atmosphere kept the front of the cold downdraft stationary. Around this area, an atmospheric gravity wave was generated continuously with the wave-conditional instability of the second kind mechanism and propagated toward Tsushima Island. The atmospheric gravity wave generated a pressure disturbance at sea level, which produced the meteotsunami. The frequency of the pressure disturbance using the numerical model had a peak in the 5- to 20-min period range, which corresponded with the peak frequency range of the observed tidal records.     

Bacterial growth rate and the relative abundance of bacteria to heterotrophic nanoflagellates in the euphotic and disphotic layers in temperate coastal waters of Sagami Bay,Japan

This study aimed to clarify the vertical differences in bacterial growth and grazing pressure on bacteria by heterotrophic nanoflagellates (HNF) and to identify the controlling factors of bacterial growth in temperate coastal waters of Sagami Bay, Japan. In addition to environmental factors, the annual monthly variations in bacterial growth rate (BGR) and the relative abundance of bacteria to HNF (BA/HNFA) were investigated in the euphotic and disphotic layers between May 2012 and May 2013. Significant vertical differences in BGR and BA/HNFA were evident between the two layers during the thermal stratification times of May to October 2012 and April to May 2013. BGR indicated significantly stronger limitation of bacterial growth in the euphotic layer compared to the disphotic layer. In contrast, significantly lower BA/HNFA was observed in the euphotic layer, suggesting significantly higher grazing pressure on bacteria by HNF. However, significant differences in BGR and BA/HNFA were not observed between the two layers from November 2012 to Match 2013, when the water column was well-mixed vertically due to the cooling and wind-induced mixing of surface water. This study indicates that bacteria in the euphotic layer grow less actively and are more vulnerable to predatory grazing by HNF relative to the disphotic layer during the stratification period. Further, multiple regression analyses indicate that bacterial growth was most controlled by the concentrations of chlorophyll a and dissolved organic carbon in the euphotic and disphotic layers, respectively.     

Small-scale landfills: impacts on groundwater and soil

In Brazil, the large quantities of solid waste produced are out of step with public policies, technological developments, and government budgets for the division. In small municipalities, the common lack of technological knowledge and financial conditions for suitable waste disposal has resulted in a large number of illegal dumps. Therefore, small sanitary landfill facilities are working with simplified operations focusing on cost reduction and meeting the economic and technological standards of the city without endangering the environment or public health. Currently, this activity is regulated at a federal level although there is some uncertainty regarding the risk of soil and aquifer contamination as theses facilities do not employ liners. Thus, this work evaluates a small landfill to identify changes in soil and groundwater using geotechnical parameters, monitoring wells, and geophysical tests performed by electrical profiling. It is verified that based on current conditions, no contaminants have migrated via underground water aquifers, and overall no significant changes have occurred in the soil. It is concluded that, despite its simplicity, the method investigated is a viable alternative for the final disposal of municipal solid waste from small cities, especially in developing countries.     

Distribution and dispersal of the early larval stages of the Japanese spiny lobster Panulirus japonicus in the East China Sea

The annual distribution and dispersal of early‐stage phyllosoma of the Japanese spiny lobster Panulirus japonicus were examined in the East China Sea and the Sea of Japan off western Japan. Early‐stage larvae were sampled mainly in summer and relatively near the coast off western Kyusyu Island. Few larvae were found in the other three seasons in the East China Sea and the Sea of Japan. This finding suggests that P. japonicus larvae are retained in coastal areas for a few months after hatching until stage V and are transported offshore until autumn, before they grow to stage VI. Examination of archival drifter data off western Kyusyu Island during the spawning season of P. japonicus supported the relatively rapid dispersal of the larvae from the East China Sea near Japan to the Pacific Ocean or the Sea of Japan. Larval transport from the East China Sea to the Pacific Ocean, which is considered to be a main distribution area of middle‐ and late‐stage larvae, would occur in the south at approximately 32–33°N in the East China Sea near western Kyusyu Island.     

Eoarchean–Paleoproterozoic zircon inheritance in Japanese Permo-Triassic granites (Unazuki area,Hida Metamorphic Complex): Unearthing more old crust and identifying source terrranes

U–Pb zircon geochronology of two Permo-Triassic granites (samples OT-52 and OT-272 with ages of 229 ± 8 Ma and 256 ± 2 Ma, respectively) in the Unazuki area, Hida Metamorphic Belt, southwest Japan, revealed the presence of Eoarchean to Paleoproterozoic inheritance. Inheritance is consistent with both samples showing low zircon saturation temperatures for their bulk compositions. In OT-52, dark in CL, low Th/U zircon domains have a mean ²⁰⁷Pb/²⁰⁶Pb age of 1940 ± 17 Ma, which is consistent with an age of 1937 ± 6 Ma for anatexis in the Precambrian Busan gneiss complex in Korea. Eoarchaean inherited zircons with ²⁰⁷Pb/²⁰⁶Pb ages from ca. 3750 to 3550 Ma are common in OT-272 but are few in OT-52, suggesting a source from rocks with affinities to those in the Anshan area in the northeast China part of the North China Craton. On the other hand, a Hida Metamorphic Belt metasedimentary gneiss into which the granites were intruded contains ca. 1840, 1130, 580, 360, 285 and 250 Ma zircons (Sano et al., 2000). These ages suggest that the Unazuki Mesozoic granites did not originate from proximal Hida Metamorphic Complex rocks, but instead from unrelated rocks obscured at depth. The predominance of Eoarchean to Paleoproterozoic age components, and the marked lack of 900–700 Ma components suggest that the source was the (extended?) fringe of the North China Craton, rather than from Yangtze Craton crust. The Mesozoic evolution of Japan and its linkages to northeast Asia are discussed in the context of these results.