Numerical investigation for pressure mitigation effects of dike on blast wave

The three-dimensional and two-dimensional axisymmetric fluid dynamics simulations were carried out to clarify the blast pressure mitigating effects of dike’s configuration in hemispherical explosion. The simulated peak overpressure on the ground under the hemispherical explosion was compared with the empirical formula by Kingery, and the simulated data were validated. In the analysis, the simplification techniques for the numerical simulation were employed under the following two assumptions. The pressure distribution behind the wide dike was estimated using the axisymmetric flowfield, and the back step model was applied under the small condition for θ, the angle formed by the ground and the line between the explosion core and the dike front corner. From the simulated results, it is clarified that the large θ provided the great reduction of the blast wave pressure at faraway position. In the small θ condition, the conditions of the dike end position and the dike height were significant parameters determining the magnitude of pressure reduction and mitigated area. The pressure reduction at the dike end and mitigated area were predicted numerically, and related to the dike conditions.     

Roadside nanoparticles corresponding to vehicle emissions during one signal cycle

The behavior of nanoparticles (NPs) in the roadside atmosphere has not been clarified because it involves unstable volatile components. It was thought that the number concentration (NC) and NP size distribution change due to variations in traffic conditions (e.g., traffic volume [TV], velocity, acceleration, etc.) near the intersection, but the SMPS (Scanning Mobility Particle Sizer) lacks the temporal resolution required for rapid, transient measurements. Using a fast-response aerosol spectrometer capable of providing near-instantaneous particle NC measurements in real time, the behavior of NPs during one signal cycle became clear, and it was understood that the effect of condensation/evaporation processes is important, in addition to coagulation. As for the relation of the NC in proportion to the TV, this did not show a constant line but rather a hysteresis curve during the signal cycle, because the gas-particle equilibrium state at the roadside atmosphere was variable. Using two points of simultaneous measurement and on-board measurement, the behavior of NPs could be confirmed in response to the characteristics of automotive exhaust, which varied due to the on-road driving state, engine conditions, vehicle position, or traffic light timing, at the intersection. The on-board measurement of NP size distribution in the exhaust plume from a diesel vehicle was carried out as a reference for direct particle emissions, compared with the roadside NPs. The coagulation/deposition model simulation using the direct particle emissions underestimated the NCs compared with the observed values. The gas-particle equilibrium model could explain the underestimated portion caused by the condensation of ambient VOC (Volatile Organic Compounds) onto the particles. If this hypothesis is correct, the condensable VOC amount in the roadside atmosphere is suggested to be very large.     

Scenario study for a regional low-carbon society

Japan should undertake drastic greenhouse gas (GHG) emission reductions by the middle of this century in order to mitigate climate change problems. Municipalities should design and execute scenarios toward a low-carbon society suited to their respective regions. This study describes long-term future visions developed for Shiga Prefecture targeting CO₂ emission reductions of 30–50% by 2030, and presents scenarios to attain these targets, which are achievable with mild economic growth. For targets over a 30% reduction, region-specific measures including land-use reform and citizen behavioral changes are necessary. Compared with other regions in Japan, Shiga should give priority to a modal shift in transport, efficiency improvements in industry, and photovoltaic energy generation.     

Gasification and smelting system using oxygen blowing for plastic waste including polyvinyl chloride

A new type of waste gasification and smelting system using oxygen blowing based on high-temperature metallurgy, was developed by Sumitomo Metals, Japan. This system can steadily gasify and melt not only municipal waste, but also plastic waste and polyvinyl chloride (PVC) waste by using a top-blow oxygen lance together with sideways-blow oxygen lances. As a result of gasification in the high-temperature reducing atmosphere and rapid gas cooling, dioxin-free, high-calorie purified gas was produced. Ash components in the wastes were smelted in a high-temperature reducing atmosphere, and high-quality slag free of heavy metals was produced. Most of the chlorine in the wastes was converted into hydrogen chloride in the off gas. The hydrogen chloride can be recovered as hydrochloric acid or chlorine, which are recyclable to PVC manufacturing.     

Oxygen-radical-mediated toxic effects of the red tide flagellate Chattonella marina on Vibrio alginolyticus

Toxic mechanisms of the red tide flagellate, Chattonella marina, collected in 1985 from Kagoshima Bay, Japan, were studied at the subcellular level. C. marina was found to reduce ferricytochrome c at a rate related to the concentration of plankton cells. Ca. 50% of the cytochrome c reduction was inhibited by the addition of 100 U superoxide dismutase ml^-1. These results suggest that a part of the cytochrome c reduction was caused by a superoxide anion which was extracellulary released from C. marina. Moreover, a small amount of hydrogen peroxide was detected in the C. marina suspension using the fluorescence spectrophotometric assay method. The identity of the hydrogen peroxide was confirmed by its reaction with 500 U catalase ml^-1. It is thus proposed that C. marina produces harmful active oxygen radicals and therefore exhibits a toxic effect on surrounding living organisms. In agreement with these results, C. marina strongly inhibited the proliferation of marine bacteria, Vibrio alginolyticus, in a plankton/bacteria co-culture system. The growth inhibition of bacteria caused by C. marina was related to the density and the metabolic potential of C. marina. Ruptured plankton showed no toxic effect on the bacteria. Furthermore, the toxic effect of C. marina on V. alginolyticus was completely suppressed by the addition of catalase and superoxide dismutase. In addition to these radical-scavenging enzymes, a chemical scavenger, sodium benzoate, also had a protective effect. These results suggest that oxygen radicals are important in the toxic action of C. marina.     

A novel use of TiO2 fiber for photocatalytic ozonation of 2,4-dichlorophenoxyacetic acid in aqueous solution

More efficient oxidation methods are needed to degrade especially newly emerging recalcitrant organic contaminants at low concentrations in the water environment. Reduced photonic efficiency of immobilized TiO2 is a major challenge in TiO2-assisted advanced oxidation processes (AOP). Mineralization of 2,4-dichllorophenoxyacetic acid (2,4-D) in low aqueous solution by O3/UV/TiO2 using the world's first high-strength TiO2 fiber was investigated and compared with O3, UV/TiO2, and O3/TiO2 in laboratory batch ex...     

Bioelectrochemical conversion of urea to nitrogen using aminated carbon electrode

Urea decomposes to ammonia and carbon dioxide via carbamic acid, and amine groups can be introduced to the glassy carbon electrode surface during the electrode oxidation of carbamic acid. This modified carbon electrode has excellent catalytic activity of the oxidation of carbamic acid, and can be used to electrooxidize urea by combining urease reaction and electrode oxidation. We found that nitrogen gas is finally produced by the carbamic acid produced from urea. The production of nitrogen was confirmed by gas chromatography-mass spectrometry, and fragment pattern of hydrazine was also detected in the electrolyzed solution of urea. We intend to describe new electrochemical conversion system of urea to harmless nitrogen gas. The electrode oxidation current of urea was decreased by addition of radical trapping agent such as DMPO (5,5-dimethyl-1-pyrroline N-oxide), and this fact suggests that carbamic acid radical couples to form nitrogen-nitrogen bond, and this dimer is oxidized to nitrogen. The electrode oxidation current of urea became larger when oxygen was removed. This fact indicates that the intermediate species (probably hydrazine) produced by the electrolysis is oxidized by not only electrode reaction but also oxygen.     

Efficacy of forming biofilms by naphthalene degrading Pseudomonas stutzeri T102 toward bioremediation technology and its molecular mechanisms

In natural environments, bacteria often exist in close association with surfaces and interfaces. There they form "biofilms", multicellular aggregates held together by an extracellular matrix. The biofilms confer on the constituent cells high resistance to environmental stresses and diverse microenvironments that help generate cellular heterogeneity. Here we report on the ability of Pseudomonas stutzeri T102 biofilm-associated cells, as compared with that of planktonic cells, to degrade naphthalene and survive in petroleum-contaminated soils. In liquid culture system, T102 biofilm-associated cells did not degrade naphthalene during initial hours of incubation but then degraded it faster than planktonic cells, which degraded naphthalene at a nearly constant rate. This delayed but high degradation activity of the biofilms could be attributed to super-activated cells that were detached from the biofilms. When the fitness of T102 biofilm-associated cells was tested in natural petroleum-contaminated soils, they were capable of surviving for 10 wk; by then T102 planktonic cells were mostly extinct. Naphthalene degradation activity in the soils that had been inoculated with T102 biofilms was indeed higher than that observed in soils inoculated with T102 planktonic cells. These results suggest that inoculation of contaminated soils with P. stutzeri T102 biofilms should enable bioaugmentation to be a more durable and effective bioremediation technology than inoculation with planktonic cells.     

Comprehensive Study on Enteric Viruses and Indicators in Surface Water in Kyoto,Japan, During 2014–2015 Season

Certain enteric viruses that are present in the water environment are potential risk factors of waterborne infections. To better understand the impact of viruses in water, both enteric viruses and their potential indicators should be comparatively investigated. In this study, occurrences of GI- and GII-noroviruses (NoVs), sapovirus (SaV), rotavirus (RoV), Aichi virus 1 (AiV-1), enterovirus (EV), and pepper mild mottle virus (PMMoV) were quantitatively determined in surface water samples in Japan. Additionally, the genotype distribution of GI- and GII-NoVs was determined using a next-generation amplicon sequencing. PMMoV was the most abundant virus regardless of season and location, indicating its usefulness as an indicator for the viral contamination of water. Other potential indicators, AiV and EV, were less abundant than GII-NoV. Viruses other than PMMoV showed seasonality, i.e., EV and other viruses (NoVs, SaV, RoV, and AiV-1) became prevalent during summer and winter, respectively. SaV showed a relatively high abundance at a location that was affected by untreated wastewater. Regarding NoV genotypes, GI.1, GI.2, GI.4, GI.5, GI.6, GII.3, GII.4, GII.6, and GII.17 were found from the surface water samples. GII.4 and GII.17 seemed to have contributed to the high abundance of GII-NoV in the samples. Interestingly, GII.17 strains became prevalent in the water samples before becoming prevalent among gastroenteritis patients in Japan. These findings provide further insights into the properties of viruses as contaminants in the water environment.