Significance of stemflow in groundwater recharge. 2: A cylindrical infiltration model for evaluating the stemflow contribution to groundwater recharge

A primary model for evaluating the effect of stemflow on groundwater recharge has been developed. The model, a cylindrical infiltration model (CI model), is based on the infiltration area of stemflow-induced water instead of canopy projected area for determining the stemflow inputs to the soil surface. The estimated ratio of recharge rate by stemflow to the total recharge rate determined with this model agrees closely with values obtained from the mass balance of chloride in subsurface waters. This primary model is considered to be useful for estimating the effect of stemflow on groundwater recharge.     

Modern observations of solar prominences

We review observational studies of solar prominences with some reference to theoretical understandings. We lay emphasis on the following findings: (1) An important discovery was made by Leroy, Bommier, and Sahal-Bréchot concerning the direction of the magnetic field inside some high-altitude, high-latitude prominences, where the field vector points in the opposite direction from the one which would be expected from the potential field calculated from the observed photospheric magnetic field. (2) Landman suggests the possibility of a high total density of 10^–11 g cm ^–3 for the main body of quiescent prominences, 50 times higher than the value hitherto believed. (3) Flow patterns, nearly parallel to the magnetic neutral lines, were detected in the 10⁵ K plasma near and in prominences. (4) Coronal loop structures were found overlying prominences as viewed from X-ray photographs. We propose also an evolutionary scheme by taking the magnetic field topologies into account.The fundamental question why a prominence is present remains basically unanswered.     

Encystment and excystment of <Emphasis Type="Italic">Gyrodinium instriatum</Emphasis> Freudenthal et Lee

In the present study, we have investigated the conditions influencing encystment and excystment in the dinoflagellate Gyrodinium instriatum under laboratory conditions. We incubated G. instriatum in modified whole SWM-3 culture medium and in versions of modified SWM-3 from which NO₃ ⁻, PO₄ ³⁻, NO₃ ⁻ + PO₄ ³⁻, or Si had been omitted and observed encystment. Percentage encystment was high in the media without N and without P, while the percentage encystment in the medium lacking both N and P was highest. Moreover, to investigate N or P concentration which induced the encystment, Gyrodinium instriatum was also incubated in media with different concentrations of inorganic N and P; the concentrations of NO₂ ⁻ + NO₃ ⁻ and PO₄ ³⁻ were measured over time. The precursors of cysts appeared within 2 or 3 days of a decrease in NO₂ ⁻ + NO₃ ⁻ or PO₄ ³⁻ concentration to values lower than 1 μM or 0.2 μM, respectively. When cysts produced in the laboratory were incubated, we observed excystment after 8–37 days, without a mandatory period of darkness or low temperature. We incubated cysts collected from nature at different temperatures or in the dark or light and observed excystments. Natural cysts excysted at temperatures from 10 to 30°C, in both light and dark, but excystment was delayed at low temperatures. These studies indicate that G. instriatum encysts in low N or P concentration and excysts over a wide temperature range, regardless of light conditions, after short dormancy periods.     

The responses of hydrological processes and sediment yield to land‐use and climate change in the Be River Catchment,Vietnam

In this study, we investigated the responses of hydrology and sediment yield with impacts of land‐use and climate change scenarios in the Be River Catchment, using the Soil and Water Assessment Tool (SWAT) hydrological model. The calibration and validation results indicated that the SWAT model is a powerful tool for simulating the impact of environmental change on hydrology and sediment yield in this catchment. The hydrologic and sediment yield responses to land‐use and climate changes were simulated based on the calibrated model. The results indicated that a 16.3% decrease in forest land is likely to increase streamflow (0.2 to 0.4%), sediment load (1.8 to 3.0%), and surface runoff (SURQ) (4.8 to 10.7%) and to decrease groundwater discharge (GW_Q) (3.5 to 7.9%). Climate change in the catchment leads to decreases in streamflow (0.7 to 6.9%) and GW_Q (3.0 to 8.4%), increase in evapotranspiration (0.5 to 2.9%), and changes in SURQ (?5.3 to 2.3%) and sediment load (?5.3 to 4.4%). The combined impacts of land‐use and climate changes decrease streamflow (2.0 to 3.9%) and GW_Q (12.3 to 14.0%), increase evapotranspiration (0.7 to 2.8%), SURQ (8.2 to 12.4%), and sediment load (2.0 to 7.9%). In general, the separate impacts of climate and land‐use changes on streamflow, sediment load, and water balance components are offset each other. However, SURQ and some component of subsurface flow are more sensitive to land‐use change than to climate change. Furthermore, the results emphasized water scarcity during the dry season and increased soil erosion during the wet season. Copyright © 2012 John Wiley & Sons, Ltd.     

Gradient field of undersea sound speed structure extracted from the GNSS-A oceanography

Marine Geophysical Research - After the twenty-first century, the Global Navigation Satellite System-Acoustic ranging (GNSS-A) technique detected geodetic events such as co- and postseismic effects...     

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.     

Source distribution of acoustic emissions during an in-situ direct shear test: Implications for an analog model of seismogenic faulting in an inhomogeneous rock mass

We monitored acoustic emission (AE) events during an in-situ direct shear test on a specimen composed of a slate-dominant alternation of slate and sandstone, measuring 0.5 m long, 0.5 m wide and 0.2 m high. The test was conducted in a survey tunnel for an underground powerhouse in central Japan. The AE epicenters located on a fractured plane are compared with the locations of joints and a loosening seam, the height distribution of the fractured plane, and the horizontal movement of the test block prior to failure. We conclude that an initially intact region of rock bounded by the joints and the seam is fractured, generating the AE. Considering these results in connection with asperity models of seismogenic faulting for a subduction-zone earthquake, the significant contrast of stress conditions derived from the geological inhomogeneity and the uneven fractured plane is analogous to that due to subducted seamounts and horst-graben structures on a subducted oceanic plate. For an inland earthquake, the intact regions on an expected shear plane can be considered to be a portion of the fault asperity that causes strong ground motion, while the weakened portion can be considered to correspond to a region of aseismic creep. Consequently, large-scale inhomogeneous rock fracturing experiments such as the in-situ direct shear test may provide useful insights as analog models of seismogenic faulting. Furthermore, understanding of inhomogeneous rock-mass fracturing obtained from such experiments will not only contribute to a better understanding of the mechanism of earthquakes but also provide valuable knowledge for AE monitoring applications in rock engineering, such as the predictions of rockbursts in mines and the monitoring of fractures around large underground chambers.     

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.     

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.     

冻结法施工旁通道的冻土压力现场监测方法

冻结法广泛用于盾构隧道的旁通道施工,但设计上对于冻结引起的作用在隧道上的冻胀力还没有明确取值方法,其主要原因之一是缺乏现场测量数据。以上海长江隧道的旁通道施工为背景工程,采用新型土压力计监测。首先介绍了PAD式土压力计的基本特征和安装方法,然后介绍了自动数据采集和测点设置原则,接着通过实例重点说明电缆保护的重要性和保护措施。上述监测工作保证了全部5个土压力计的正常工作,并获得了有效的实测数据。数据显示,冻结工法造成的最大荷载增量远小于预期值,这主要是由于施工上设置了泄压孔,从而减少了作用在管片上的冻胀力