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51.
C. Uyeda T. Takeuchi A. Yamagishi A. Tsuchiyama T. Yamanaka M. Date 《Physics and Chemistry of Minerals》1993,20(6):369-374
The diamagnetic properties of sheetsilicates are studied by measuring the magnetic orientation of micron-sized crystals. In the case of synthetic phlogopite with the average diameter of 0.65 μm and the thickness of 0.2 μm, the alignment of the grains is achieved in the magnetic field below 35 kOe. The planes of the platy single-crystal grains were alignned parallel to the field when the alignment was achieved. The alignment of the grains is realized because the field-induced anisotropic energy, caused by the diamagnetic anisotropy in the mineral's crystal structure, exceeds thermal agitation energy in the applied field. By analyzing the field dependence of grain alignment, the diamagnetic anisotropy per formula unit, Δχ, of sheetsilicate mineral is estimated even if a large single crystal is not provided. The field-induced anisotropic energy is proportional to NΔχ where N is the number of molecules in the grain. A linear correlation has been found between the Δχ value and the F/OH mole ratio among the measured sheetsilicates. This correlation supports the assumption that the hexagonally packed oxygen-layer in the crystal lattice induces the anisotropies of the sheetsilicates. 相似文献
52.
Hiroyuki Hashiguchi Manabu D. Yamanaka Toshitaka Tsuda Mamoru Yamamoto Takuji Nakamura Tatsuhiro Adachi Shoichiro Fukao Toru Sato Daniel L. Tobing 《Boundary-Layer Meteorology》1995,74(4):419-424
Based on continuous observations of the planetary boundary layer (PBL) with anL-band (1357.5 MHz) boundary-layer radar (BLR) at a hilly location in Japan, we have discovered that on clear days, a thin enhanced echo layer corresponding to the top of the PBL (or mixed layer) appeared at about 500 m height in the morning and ascended to about 1500 m in the afternoon. Strong upward velocities were observed below the echo layer (or inside the PBL), reaching 1500 m in the afternoon. 相似文献
53.
54.
Asten Michael W. Yong Alan Foti Sebastiano Hayashi Koichi Martin Antony J. Stephenson William J. Cassidy John F. Coleman Jacie Nigbor Robert Castellaro Silvia Chimoto Kosuke Cornou Cécile Cho Ikuo Hayashida Takumi Hobiger Manuel Kuo Chun-Hsiang Macau Albert Mercerat E. Diego Molnar Sheri Pananont Passakorn Pilz Marco Poovarodom Nakhorn Sáez Esteban Wathelet Marc Yamanaka Hiroaki Yokoi Toshiaki Zhao Don 《Journal of Seismology》2022,26(4):757-780
Journal of Seismology - Site response is a critical consideration when assessing earthquake hazards. Site characterization is key to understanding site effects as influenced by seismic site... 相似文献
55.
Journal of Seismology - In the Kanto Basin, Japan, it has been reported that the dominant periods of long-period ground motions vary depending on the areas where earthquakes occurred. This suggests... 相似文献
56.
To obtain the basic information required before using Populus alba L. to phytoremediate degraded saline environments, we investigated the effects of saline irrigation on the growth, survival, Na partitioning, and Na dynamics of 1-year-old rooted cuttings. The plants were grown in a greenhouse in lysimeters containing sandy soil and were watered with field water (control) or solutions containing either 2000 or 5000 mg L?1 of a mixture of NaCl and CaCl2 (low- and high-salt treatments, respectively). All plants in the control and the low-salt treatment survived after 1 year of treatment, but the high-salt treatment significantly decreased growth and caused 20% mortality. Strong Na partitioning was observed in the roots in all three treatments, suggesting that this is an important salt tolerance mechanism in P. alba. Total Na uptake was similar in the low-salt and high-salt treatments, and was about 3 times the value in the control. However, the compartmentalization of Na in fallen leaves, dead leaves and dead branches in the high-salt treatment was about twice the level in the low-salt treatment. The plants accumulate Na under moderate levels of salinity, suggesting that P. alba is a good candidate for phytoremediating salinized soil. 相似文献
57.
To understand the processes transporting nitrate to the surface layer of the western and central equatorial Pacific, we measured
the nitrogen isotopic ratio of nitrate (δ
15NO
3
−
), which is a very useful tracer of the source of nitrate, above 200 m depth in this region in December 1999. δ
15NO
3
−
is higher (about 13.0‰) in the surface water than in the subsurface water (where it is about 6.5‰) due to isotopic fractionation
during nitrate uptake by phytoplankton. The δ
15NO
3
−
value has a roughly linear relationship with the natural logarithm of nitrate concentration (ln[NO
3
−
]). However, for values above 150 m depth, the intercept of this linear relationship varies with position from east to west.
On the other hand, the data at 200 m depth at all observation stations are concentrated around a single point (ln[NO
3
−
] = 2.5 and δ
15NO
3
−
= 6.5‰) and do not fit the linear relationships for the shallower values. To examine the meaning of the observed distributions
of δ
15NO
3
−
and nitrate concentration we developed a box model including nitrogen and nitrogen isotopic cycles. By reproducing the observed
relationship between δ
15NO
3
−
and nitrate concentration using this model we found that most nitrate is transported horizontally from the eastern equatorial
Pacific. We also conducted case studies and investigated the effects of differences in pathways of nitrate transport on the
distributions of δ
15NO
3
−
and nitrate concentration. From these studies we concluded that the observed linear relationships between δ
15NO
3
−
and ln[NO
3
−
], having a common slope around 6‰ but different intercepts at each station, are evidence of the significant horizontal transport
of nitrate to the surface water in this area. 相似文献
58.
A simplified physical model is proposed in this article to describe differences among basins in substance distributions which were not well described by previous simplified models. In the proposed model, the global ocean is divided into the Pacific/Indian Ocean (PI), the Atlantic Ocean (AT), the Southern Ocean and the Greenland/Iceland/Norwegian Sea. The model is consisted of five physical parameters, namely the air-sea gas exchange, the thermohaline circulation, the horizontal and vertical diffusions, and the deep convection in the high-latitude regions. Individual values of these parameters are chosen by optimizing model distribution of natural 14C as a physical tracer. The optimal value for a coefficient of vertical diffusion in the low-latitude region is 7.5 × 10–5 [m2s–1]. Vertical transports by the Antarctic Bottom Water and the North Atlantic Deep Water are estimated at 1.0 Sv and 9.0 Sv. Global-mean air-sea gas exchange time is calculated at 9.0 years. Using these optimal values, vertical profiles of dissolved inorganic carbon without biological production in PI and AT are estimated. Oceanic responses to anthropogenic fluctuations in substance concentrations in the atmosphere induced by the industrialization and nuclear bomb are also discribed, i.e., the effects appear significantly in AT while a signal is extremely weak in PI. A time-delay term is effective to make the PI water older near the bottom boundary. 相似文献
59.
In order to investigate compression mechanism and the pressure-induced amorphization of portlandite, Ca(OH)2, the crystal structure has been refined up to 9.7?GPa using Rietveld analysis. Angular-dispersive synchrotron X-ray powder diffraction experiments were performed using a diamond anvil cell and an imaging plate at BL-18C in the Photon Factory at KEK, Japan. Compression behavior is highly anisotropic and the c axis is approximately 2.5 times as compressible as the a axis (βa=0.004, βc=0.011?GPa?1). Because the refined fractional coordinate, z, of the O atom increases linearly with pressure, compression along the c axis is due to the shortening of the interlayer spacing. The compression mechanism shows no change up to the amorphization pressure and is basically the same as that of brucite, Mg(OH)2, observed below 10 GPa. The octahedral regularity of CaO6 approaches a regular configuration with pressure. The interlayer O…O distance is expected to be about 2.75 Å at the amorphization pressure and should affect hydrogen bonding. 相似文献
60.
The responses of atmospheric pCO2 and sediment calcite content to changes in the export rain ratio of calcium carbonate to organic carbon are examined using
a diffusion-advection ocean biogeochemical model coupled to a one-dimensional sediment geochemistry model. Our model shows
that a 25% reduction in rain ratio decreases atmospheric pCO2 by 59 ppm. This is caused by alkalinity redistribution by a weakened carbonate pump and an alkalinity increase in the whole
ocean via carbonate compensation with decreasing calcite burial. The steady state responses of sedimentary calcite content
and calcite preservation efficiency are rather insensitive to the deepening of the saturation horizon of 1.9 km. This insensitivity
is a result of the reduced deposition flux that decreases calcite burial, counteracting the saturation horizon deepening that
increases calcite burial. However, in the first 10,000 years the effect of reduced calcite deposition on the burial change
is more prominent; while after 10,000 years, the effect of saturation horizon deepening is more dominant. The lowering of
sediment calcite content for the first 10,000 years is effectively decoupled from the 1.9 km downward shift of the saturation
horizon. Our results are in part a consequence of the more dominant role that respiration CO2 plays in sediment calcite dissolution over bottom water chemistry in our control run and support the decoupling of calcite
lysocline depth and saturation horizon shifts, as suggested originally by Archer and Maier-Reimer (1994) and Archer et al. (2000). 相似文献