Microbiological characteristics of bentonite deposits were investigated as a natural analogue of microbial behavior in the buffer material for geological disposal of radioactive waste. Distributions of microorganisms in bentonite were examined at four sites in two different bentonite deposits in Japan. The sites included pond bottom, wetland, and wet mine gallery environments where bentonite layers have been left undisturbed for 2 to 30 years. Excavation was performed without using drilling water and the center parts of the cores were used for microbial examination. Plate counts with R2A medium of aerobic and anaerobic bacteria at the drilling mouth ranged from 10 5 to 10 7 /g DW (dry weight) and from 10 3 to 10 6 /g DW, respectively. The CFDA-AM (Carboxyfluorescein diacetate acetoxymethyl ester) cell counts ranged from 10 6 to 10 9 /g DW. Bacterial numbers in the bentonite layers declined with distance from the drilling mouth; both aerobes and anaerobes were less than 10 2 /g DW and CFDA-AM cell counts less than 10 6 /g DW for core samples taken from approximately 1 m depth, except at the pond bottom. These results suggest that microbial activity in natural bentonite is lower than in typical soils and aquatic sediments and does not spread easily.
Aim To report on the effects of a smartphone application, among the medical staff and medical students, for learning English as a foreign language. Methods We conducted an exploratory quasi-experimental study among eight medical staff and 10 medical students in Japan. The participants used an application called ABC Talking (created by ABC Talking Laboratories Inc, currently unavailable due to application renewal), loaded onto their smartphones, to talk with native English speakers from overseas. The participants used the application for five minutes twice a day over five consecutive days as per their convenience. The study collected quantitative and qualitative data using assessments on the participants’ listening and speaking skills and questionnaire. The assessment scores of the first five sessions were compared to those of the last five. Average self-assessment scores and teacher assessment scores were compared using a t -test. A paired t -test was performed on quantitative data of the questionnaire, and content analysis was performed on qualitative data. Results More than 80% of the calls were made from home and 70% occurred between 9PM and 1AM. The participants’ self-assessment scores on their listening and speaking skills increased significantly from the first five sessions to the last five sessions (14.8–26.1%). However, there was no significant change in the assessments by the teachers (−4.5–2.1%). The self-assessment scores of those with low English proficiency were lower than the teachers’ assessment scores. Improvement of communicative self-confidence and communicative competence, two factors that affect willingness to communicate, were seen from the questionnaire. Conclusion Using smartphone applications allows on-demand English training, which may be especially useful to medical staff and students who have unpredictable work schedules. Teachers should be aware that learners tend to assess themselves lower than their actual ability so that they can give appropriate feedback to the learners.
Full-scale tests were performed to evaluate the technical feasibility of a transport system with air-bearings at the underground HLW disposal tunnel for pre-assembled heavy disposal packages, which consist of a waste package and buffer material. Transport conditions in the disposal tunnel, such as roughness and unevenness of the curved surface, make it difficult to achieve smooth movement using the commercial airbearing transport system. In order to evaluate the applicability of the air-bearing transport system to such conditions, tests using a full-scale test device (modified package) and simulated tunnel surface were conducted. Based on the tests, the applicability of this transport system to a disposal tunnel was confirmed.
Fabricated stainless steel structures are susceptible to stress corrosion cracking (SCC), despite being placed in chloride-containing natural water or humid atmospheres. The present paper describes a model that can define the conditions under which SCC is initiated and propagated, based on analyses of actual SCC incidents induced at welded flanges of cylindrical stainless steel structures.Whenever the vitrified radioactive waste canister storage conditions deviate from normal and appropriate conditions due to earthquakes or tsunamis, the exposed canisters are expected to suffer SCC within 400 hours to 7 years, according to the analytical results obtained such as degree of sensitization, residual stress distribution, chloride ion concentration, and temperature.
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