Reaction of forsterite with hydrogen molecules at high pressure and temperature

High pressure and temperature reactions of a mixture of forsterite and hydrogen molecules have been carried out using a laser heated diamond anvil cell at 9.8–13.2 GPa and ~1,000 K. In situ X-ray diffraction measurements showed no sign of decomposition or phase transitions of the forsterite under these experimental conditions, indicating that the olivine structure was maintained throughout all runs. However, a substantial expansion of the unit cell volume of the forsterite was observed for samples down to ~3 GPa upon quenching to ambient pressure at room temperature. The Raman spectroscopy measurements under pressure showed significant shifts of the Raman peaks of the Si–O vibration modes for forsterite and of the intramolecular vibration mode for H₂ molecules toward a lower frequency after heating. Additionally, no OH vibration modes were observed by Raman and FT-IR spectroscopic measurements. These lines of evidence show that the observed volume expansion in forsterite is not explained by the incorporation of hydrogen atoms as hydroxyl, but suggest the presence of hydrogen as molecules in the forsterite structure under these high pressure and temperature conditions.     

Movement of radiocaesium fallout released by the 2011 Fukushima nuclear accident

The moment magnitude (M _w) 9.0 Tohoku-Oki Earthquake occurred on March 11, 2011, generating an unusually large tsunami. The seismic shocks and tsunami inundation severely damaged the Fukushima Daiichi Nuclear Power Plant. Radionuclide emission due to reactor breakdown contaminated wide areas of Fukushima and its surroundings. Heavy rainfall causes runoff across surface soil, and fine soil particles are susceptible to uptake by the flowing water. The high radioactivity of grains suspended in floodwater indicates that radioactive fallout was streamed into rivers in particulate form and transported downstream under high-flow conditions. Here, we investigated the diachronic mode of ¹³⁴Cs and ¹³⁷Cs in central Fukushima, through which the contaminated air mass drifted and caused wet deposition of radionuclides. Stratigraphic measurements of radioactivity in sediment cores is the method employed in this study to determine the basin-wide movement of ¹³⁴Cs and ¹³⁷Cs, to evaluate the significance of the erosion–transportation–accumulation processes on natural decontamination in terrain characterized by steep slopes and high precipitation. Stratigraphic results illustrate the process of fluvial sediment discharge, and the massive deposition of radiocaesium suggests basin-wide movement of fallout during concentrated rainfall. Grain suspension in torrential currents is an important pathway for transportation of radionuclides from land to sea, and the appearance of hotspots on floodplains and the offshore sea floor is the consequence of erosion and transportation under seasonal heavy precipitation. Radioactive horizons occur in offshore sediment columns and thus radiocaesium discharged from the estuary will persist forever under the sea floor if no artificial disturbance occurs.     

Evaluation of ADEOS-II GLI ocean color atmospheric correction using SIMBADA handheld radiometer data

The performance of the “version 2” Global Imager (GLI) standard atmospheric correction algorithm, which includes empirical absorptive aerosol correction and sun glint correction, was evaluated using data collected with handheld above-water SIMBADA radiometers during 23 cruises of opportunity (research vessels, merchant ships), mostly in the North Atlantic and European seas. A number of 100 match-up data sets of GLI-derived and SIMBADA-measured normalized water-leaving radiance (nL _W ) and aerosol optical thickness (AOT) were sorted out, using objective selection criteria, and analyzed. The Root-Mean-Square (RMS) difference between GLI and SIMBADA nL _W was about 0.32 μW/cm²/nm/sr for the 412 nm band, showing improvement by 30% in RMS difference with respect to the conventional “version 1” GLI atmospheric correction algorithm, and the mean difference (or bias) was reduced significantly. For AOT, the RMS difference was 0.1 between GLI estimates and SIMBADA measurements and the bias was small (a few 0.01), but the ?ngstr?m exponent was systematically underestimated, by 0.4 on average, suggesting a potential GLI calibration offset in the near infrared. The nL _W differences were not correlated to AOT, although performance was best in very clear conditions (AOT less than 0.05 in the 865 nm band). Despite the relatively large scatter between estimated and measured nL _W , the derived chlorophyll-a concentration estimates, applying the same ratio algorithm (GLI OC4V4) to GLI and SIMBADA, were consistent and highly correlated in the range of 0.05–2 μg/l. The large variability in chlorophyll-a concentration estimate for clear clean water areas (e.g. with the concentration range lower than about 0.05 μg/l) turns out to be due to the nature of the “band ratio” based in-water algorithm.     

Future changes in tropical cyclone activity in the North Indian Ocean projected by high-resolution MRI-AGCMs

New and previous versions of the high-resolution 20- and 60-km-mesh Meteorological Research Institute atmospheric general circulation models are used to investigate potential future changes in tropical cyclone (TC) activity in the North Indian Ocean (NIO). Fifteen ensemble experiments are performed under the International Panel on Climate Change A1B scenario. Most of the ensemble future (2075–2099) experiments do not project significant future changes in the basin-scale TC genesis number; however, they commonly show a substantial increase (by 46 %) in TC frequency over the Arabian Sea and a decrease (by 31 %) in the Bay of Bengal. Projected future changes in TC genesis frequency show a marked seasonal variation in the NIO: a significant and robust reduction during the pre-monsoon season, an increase during the peak-monsoon season, and a westward shift during the post-monsoon season. Several large-scale thermodynamic and dynamical parameters are analysed to elucidate the physical mechanism responsible for the future changes in TC activity; this analysis reveals a seasonal dependence of the relative contribution of these parameters to the projected future changes in TC genesis frequency.     

Study of a Bistatic Radar System Using VLBI Technologies for Detecting Space Debris and the Experimental Verification of its Validity

Space debris are increasing around the Earth. The observation of space debris is a key issue for the investigation and monitoring of space environment. But the observation opportunities and the detection ability are limited in existing monostatic radar systems. This paper proposes a bistatic radar which is composed of a transmitting station and a receiving-only station. A carrier wave modulated by PN-PSK signals is used in combination with a VLBI (Very Long Baseline Interferometry) recorder for range measurement between space debris and stations. The receiving radio wave is processed on the basis of VLBI techniques. Accordingly, the system is shown to have significant advantages over a monostatic radar. We actually formed a bistatic radar system, and observed a satellite in order to experimentally verify the validity. The configuration of the system, data analysis and the experimental results are described.     

Change in habitat selection by Japanese macaques (Macaca fuscata) and habitat fragmentation analysis using temporal remotely sensed data in Niigata Prefecture,Japan

The aim of this study was to evaluate changes in macaque habitat selection during a 29-year period. We focused on the 1970s, when little crop damage was caused by Japanese macaques (Macaca fuscata), and the 2000s, when the damage became remarkable. Landsat/MSS from 1978 and ALOS/AVNIR-2 from 2007 were employed for land-cover mapping. For the 2007 land-cover classification, we applied an object-oriented image classification and a classification and regression tree. The Kappa coefficient of the 2007 land-cover map was 0.89. For the 1978 land-cover classification, change detection using principal component analysis and object-oriented image classification were applied to reduce resolution difference errors. The Kappa coefficient of the 1978 land-cover map was 0.84. We applied a Random Forest model for machine learning and data mining to predict the habitat selection of macaques. Several important environmental factors were identified for macaque habitat selection: the ratio of coniferous forest to farmland, distance to farmland, and maximum snow depth. The Random Forest model was extrapolated to the 1978 land-cover map. Over the 29-year period, coniferous forest changed to broad-leaved forest and/or mixed forest within the macaque habitat area. Coniferous forests were not selected as food resources by Japanese macaques. Furthermore, large-scale patches of farmland were used as food resources over the 29-year period. These changes indicated that habitat selection by Japanese macaques changed over the study period. The results show that the home range of macaques expanded, and macaques may now be distributed over a wider area as a result of changes in landscape configuration. Thus, forest planning, such as sustainable management of artificial conifer forests, is important for reducing crop damage.     

Heavy oil exposure induces high moralities in virus carrier Japanese flounder Paralichthys olivaceus

The relationship between chemical exposure and disease outbreak in fish has not been fully defined due to the limitations of experimental systems (model fish and pathogens). Therefore, we constructed a system using the Japanese flounder, Paralichthys olivaceus, and viral haemorrhagic septicemia virus (VHSV), and evaluated it by heavy oil (HO) exposure. The fish were exposed to HO at 0.3, 0.03, 0.003, and 0 g/L following VHSV infection at doses of 10(2.5) or 10(3.5) tissue culture infectious dose (TCID)50/fish. As a result, groups given the dual stressors showed more than 90% mortality. Although VHSV infection at 10(2.5) and 10(3.5) TCID50/fish without HO exposure also induced high mortality, at 68.8% and 81.3%, respectively, HO exposure induced faster and higher mortality in the virus carrier fish, indicating that chemical stressors raise the risk of disease outbreak in fish. The experimental system established in this study could be useful for chemical risk assessment.     

Solute distribution in porous rhyolite as evaluated by sequential centrifugation

Pore water in a porous rhyolite, having a porosity of 27% and pore radii ranging from >25 μm to 0.008 μm, was centrifugally extracted stepwise with increasing centrifugal speed to examine the potential variations of the compositions of pore water and their relationships to reaction and transport occurring in the rock. The rock was soaked for from 1 h to 7 days in an aqueous solution prior to centrifugation. To evaluate the effect of adsorption under minimum effect of dissolution, Li⁺ and Br⁻ were added to the solution as tracer ions. As centrifugal speed increased, water was extracted in order of large to small pores and the thickness of residual water film became thinner. The concentrations of ions dissolving from the rock (Na⁺, K⁺, Ca²⁺, etc.) after 7 days of immersion were relatively constant in pores of 1-10 μm radii and exponentially increased by 3-100 fold with decreasing pore radius to 0.1 μm. These ions are dissolved from the rock and transported toward the exterior of the rock by diffusion. The calculation using a reactive-transport equation showed that the observed concentration changes reflect the change in solute distribution profile with pore size. The concentration of Si after 7 days of immersion was approximately constant or slightly decreased with increasing centrifugal speed, which appears to be controlled by the solubility. The concentration of Li⁺ decreased with increasing centrifugal speed after 1 h of immersion but the trend changed after 7 days of reaction. Initial behavior of Li⁺ is explained by adsorption on pore walls, and the change of trend is explained by desorption of that previously adsorbed, slight amounts of dissolution, and inflow from the outside of the rock. The change in concentration of Br⁻ with increasing centrifugal speed was small, probably because Br⁻ was not adsorbed on the surfaces. The sequential centrifugation thus provides information on the solute distribution associated with reaction and transport occurring in rock pores.     

Sound velocities of Na0.4Mg0.6Al1.6Si0.4O4 NAL and CF phases to 73 GPa determined by Brillouin scattering method

The sound velocities of two aluminum-rich phases in the lower mantle, hexagonal new Al-rich phase (NAL) and its corresponding high-pressure polymorph orthorhombic Ca-ferrite-type phase (CF), were determined with the Brillouin scattering method in a pressure range from 9 to 73 GPa at room temperature. Both NAL and CF samples have identical chemical composition of Na_0.4Mg_0.6Al_1.6Si_0.4O₄ (40 % NaAlSiO₄–60 % MgAl₂O₄). Infrared laser annealing in the diamond anvil cell was performed to minimize the stress state of the sample and obtain the high-quality Brillouin spectra. The results show shear modulus at zero pressure G ₀ = 121.960 ± 0.087 GPa and its pressure derivative G’ = 1.961 ± 0.009 for the NAL phase, and G ₀ = 129.653 ± 0.059 GPa and G’ = 2.340 ± 0.004 for the CF phase. The zero-pressure shear velocities of the NAL and CF phases are obtained to be 5.601 ± 0.005 km/sec and 5.741 ± 0.001 km/sec, respectively. We also found that shear velocity increases by 2.5 % upon phase transition from NAL to CF at around 40 GPa.     

Linear Stability of Thermal Convection in Rotating Systems with Fixed Heat Flux Boundaries

Linear stability of rotating thermal convection in a horizontal layer of Boussinesq fluid under the fixed heat flux boundary condition is examined by the use of a vertically truncated system up to wavenumber one. When the rotation axis is in the vertical direction, the asymptotic behavior of the critical convection for large rotation rates is almost the same as that under the fixed temperature boundary condition. However, when the rotation axis is horizontal and the lateral boundaries are inclined, the mode with zero horizontal wavenumber remains as the critical mode regardless of the rotation rate. The neutral curve has another local minimum at a nonzero horizontal wavenumber, whose asymptotic behavior coincides with the critical mode under the fixed temperature condition. The difference of the critical horizontal wavenumber between those two geometries is qualitatively understood by the difference of wave characteristics; inertial waves and Rossby waves, respectively.