High-pressure phase relations in the system TiO2–ZrO2 to 12?GPa: stability of αPbO2-type srilankite solid solutions of (Ti1?x , Zr x )O2 (0?≤?x?≤?0.6)

Phase relations in the system TiO₂–ZrO₂ were examined in the pressure range of 3.5–12?GPa at 1,800?°C, using multianvil apparatus. At 1,800?°C, TiO₂ rutile transforms to αPbO₂ structure at 10?GPa, and the αPbO₂-type solid solution is stable in compositional range between TiO₂ and about (Ti_0.6, Zr_0.4)O₂ at 3.5–12?GPa. Combination of the present results with the published data at 0–3?GPa demonstrates that continuous solid solution with the αPbO₂-type structure is stable between TiO₂ and (Ti_1?x , Zr _x )O₂ (x?≈?0.6) at 0–12?GPa. This indicates that both the αPbO₂-type TiO₂ and srilankite Ti₂ZrO₆ with the same structure belong to the continuous solid solution system though the two phases have been regarded as different minerals. With increasing ZrO₂ content, lattice parameters of a- and c-axes of the αPbO₂-type solid solution increase, but b-axis is almost constant or slightly decreases. At higher pressure, the αPbO₂-type solid solution dissociates into two phases, αPbO₂-type phase and tetragonal zirconia. Srilankite with more TiO₂-rich composition than Ti₂ZrO₆ might be found in natural rocks derived from the deep upper mantle.     

An Important Ornithischian Tracksite in the Early Jurassic of the Shenmu Region,Shaanxi, China

A large track site with multiple,well-preserved trackways of an Early Jurassic quadrupedal ornithischian dinosaur is the first report of Moyenisauripus-like trackways from Asia,herein named Shenmuichnu...     

Desorption kinetics of hydrophobic organic contaminants from marine plastic pellets

This study investigated the desorption behavior of polychlorinated biphenyls (PCBs) from marine plastic pellets. Long-term desorption experiments were conducted using field-collected polyethylene (PE) pellets. The results indicate that the desorption kinetics highly depends on the PE-water partition coefficients of PCB congeners. After 128 d of the experiment, the smallest congener considered (CB 8) had desorbed nearly completely (98%), whereas major fractions (90–99%) of highly chlorinated congeners remained in the pellets. An intraparticle diffusion model mostly failed to reproduce the desorption kinetics, whereas an aqueous boundary layer (ABL) diffusion model well approximated the data. The desorption half-lives are estimated to 14 d to 210 years for CB 8 to CB 209 in an actively stirred solution (ABL thickness: 30 μm). Addition of methanol to water enhanced the desorption to a large extent. A need for further work to explore roles of organic matter in facilitating solute transfer is suggested.     

The 11 March 2011 East Japan Earthquake and Tsunami: Tsunami Effects on Coastal Infrastructure and Buildings

The 11 March 2011 East Japan Earthquake and Tsunami caused unprecedented damage to well-engineered buildings and coastal structures. This report presents some notable field observations of structural damage based on our surveys conducted along the Sanriku coast in April and June 2011. Engineered reinforced concrete buildings failed by rotation due to the high-velocity and deep tsunami inundation: entrapped air in the buildings and soil liquefaction by ground shaking could have contributed to the failure. The spatial distribution pattern of destroyed and survived buildings indicates that the strength of tsunami was affected significantly by the locations of well-engineered sturdy buildings: weaker buildings in the shadow zone tended to survive while jet and wake formations behind the sturdy buildings enhanced the tsunami forces. We also found that buildings with breakaway walls or breakaway windows/doors remained standing even if the surrounding buildings were washed away or destroyed. Several failure patterns of coastal structures (seawalls) were observed. Flow-induced suction pressure near the seawall crown could have caused the failure of concrete panels that covered the infill. Remarkable destruction of upright solid-concrete type seawalls was closely related with the tsunami induced scour and soil instability. The rapid decrease in inundation depth during the return-flow phase caused soil fluidization down to a substantial depth. This mechanism explains severely undermined roads and foundations observed in the area of low flow velocities.     

Infiltration and solute transport under a seasonal wetland: bromide tracer experiments in Saskatoon,Canada

In the northern glaciated plain of North America, the duration of surface water in seasonal wetlands is strongly influenced by the rate of infiltration and evaporation. Infiltration also plays important roles in nutrient exchange at the sediment–water interface and groundwater recharge under wetlands. A whole‐wetland bromide tracer experiment was conducted in Saskatchewan, Canada to evaluate infiltration and solute transport processes. Bromide concentrations of surface water, groundwater, sediment pore water and plant tissues were monitored as the pond water‐level gradually dropped until there was no surface water. Hydraulic head gradients showed strong lateral flow from under the wetland to the treed riparian zone during the growing season. The bromide mass balance analysis showed that in early spring, almost 50% of water loss from the wetland was by infiltration, and it increased to about 70% in summer as plants in and around the wetland started to transpire more actively. The infiltration contributed to recharging the shallow, local groundwater under the wetland, but much of it was taken up by trees without recharging the deeper groundwater system. Emergent plants growing in the wetlands incorporated some bromide, but overall uptake of bromide by vegetation was less than 10% of the amount initially released. After one summer, most of the subsurface bromide was found within 40–80 cm of the soil surface. However, some bromide penetrated as deep as 2–3 m, presumably owing to preferential flow pathways provided by root holes or fractures. Copyright © 2004 Crown in the Right of Canada. Published by John Wiley & Sons, Ltd.     

Geologically controlled bi-directional exchange of groundwater with a hypersaline lake in the Canadian prairies

Hypersaline lakes occur in hydrologically closed basins due to evaporitic enrichment of dissolved salts transported to the lakes by surface water and groundwater. At the hypersaline Lydden Lake in Saskatchewan, Canada, groundwater/lake-water interaction is strongly influenced by the geological heterogeneity of glacial deposits, whereby a highly permeable glaciofluvial sand/gravel deposit is underlain by glaciolacustrine deposits consisting of dense clay interspersed with silt/sand lenses. Pressure head distribution in a near shore area indicates a bi-directional flow system. It consists of topographically driven flow of fresh groundwater towards the lake in the sand/gravel aquifer and density-driven, landward flow of saline groundwater in the underlying glaciolacustrine deposits. Electrical resistivity tomography, and chemical and isotopic composition of groundwater clearly show the landward intrusion of saline water in the heterogeneous unit. The feasibility of bi-directional flow and transport is supported by numerical simulations of density-coupled groundwater flow and transport. The results suggest that the geologically controlled groundwater exchange processes have substantial influences on both inputs and outputs of dissolved minerals in hypersaline lakes in closed basins.     

Global scale evaluation of coastal fresh groundwater resources

This paper presents a simplified approach to assess the effects of global warming on global coastal groundwater resources over the next century based on the smallest but necessary number of elements such as rainfall, temperature, hydraulic conductivity of the aquifers, and population changes regarding the consumption of groundwater. The positive aspect in this approach is that there is availability of the above elements in the majority of the planet. Methodology includes a sharp interface concept model and simplified estimation of groundwater recharge using limited climate data. The evaluation shows that the future climate changes would decrease fresh groundwater resources in Central American, South American, South African and Australian regions whereas most of the areas in Asia, except South-East Asia. Combinations of fresh groundwater loss and global population are considered to state the vulnerability of future fresh groundwater supply. Vulnerability assessment shows that South Asia, Central America, North Africa and the Sahara, South Africa and the Middle East countries are highly vulnerable whereas, Northern Europe, Western part of South America, New Zealand and Japan are less vulnerable with respect to future fresh groundwater supply. Further, this paper highlights the necessity Integrated Coastal Management (ICM) practices in these vulnerable coastal regions to ensure the sustainable development in coastal regions.     

A case study of Kelvin-Helmholtz vortices on both flanks of the Earth's magnetotail

Kelvin-Helmholtz instability (KHI) is a fundamental fluid dynamical process that develops in a velocity shear layer. It is excited on the tail-flanks of the Earth's magnetosphere where the flowing magnetosheath plasma and the stagnant magnetospheric plasma sit adjacent to each other. This instability is thought to induce vortical structures and play an important role in plasma transport there. While KHI vortices have been detected, the earlier observations were performed only on one flank at a time and questions related to dawn-dusk asymmetry were not addressed. Here, we report a case where KHI vortices grow more or less simultaneously and symmetrically on both flanks, despite all the factors that may have broken the symmetry. Yet, energy distributions of ions in and around the vortices show a remarkable dawn-dusk asymmetry. Our results thus suggest that although the initiation and development of the KHI depend primarily on the macroscopic properties of the flow, the observed enhancement of ion energy transport around the dawn side vortices may be linked to microphysical processes including wave-particle interactions. Possible coupling between macro- and micro-scales, if it is at work, suggests a role for KHI not only within the Earth's magnetosphere (e.g., magnetopause and geomagnetic tail) but also in other regions where shear flows of magnetized plasma play important roles.     

Formation Mechanism of Soft X-Ray Transient Trans-Equatorial Loop System

The Soft X-ray Telescope (SXT) onboard Yohkoh often observed large-scale coronal loops connecting two active regions situated in opposite hemispheres. These are the trans-equatorial loop systems (TLSs). The formation mechanism of TLSs is not yet known. We analyzed a TLS observed simultaneously with Yohkoh/SXT and a coronagraph (SOHO/LASCO-C1). SOHO/LASCO-C1 observed loop expansion and eruption at the west solar limb. Yohkoh/SXT observed a rising motion (chromospheric evaporation) of hot and dense plasmas from the active regions located at the footpoints of the loop. Important results of our analyses are that (1) the loop eruption and the rising motion of the plasmas were simultaneous, (2) the TLS had a cusp-like appearance, and (3) the highest temperature region of the TLS was located above the bright loop seen in soft X rays. These observational results (loop expansion, eruption, and chromospheric evaporation) suggest that this bright (high-density) TLS was created by the same mechanism by which a solar flare occurs, namely, magnetic reconnection. In this paper, we propose a formation mechanism of the TLS that forms between two independent active regions.     

A steady model of typical non-large-meander paths of the Kuroshio Current

Conditions south of Cape Shiono-misaki for the nearshore and offshore non-large-meander (NLM) paths of the Kuroshio Current are studied using a two-layer reduced gravity model. A steady and non-diffusive state is assumed, and the conservation laws of Bernoulli's function and potential vorticity along the current axis are used. Spatial changes of velocity and depth of the current are imposed as boundary conditions south of Cape Shiono-misaki. These conditions are based on the facts that are ohserved south of the cape: abrupt acceleration of the Kuroshio and the spatial change of sea levels. The current paths east of the cape are computed.This model reproduces well the actual nearshore NLM paths. It also produces offshore NLM paths west of and over the Izu Ridge, but not east of the Izu Ridge. Diffusion of vorticity may be important for the eastern part of the offshore NLM path.An increase of velocity south of the cape is necessary for producing realistic NLM paths. The velocity increase accompanies a decrease of current depth owing to Bernoulli's conservation, and the depth decrease in turn diminishes the absolute vorticity owing to the potential vorticity conservation. The velocity increase, on the other hand, strengthens the negative velocity shear and diminishes the relative vorticity. If the decreases of the relative and absolute vorticities compensate each other, the path goes excessively southward owing to the negative curvature south of the cape. Dominance of the relative vorticity change over the absolute vorticity change prevents, the path from shifting southward and causes the realistic NLM paths.The NLM paths need different amplitudes of the changes south of the cape depending on the velocity and transport of the current, but in any case, the nearshore NLM path needs larger changes than the offshore NLM path. This property and the amplitude of the changes are consistent with observations.