Formative conditions and sedimentary structures of sandy 3D antidunes: an application of the gravel step‐pool model to fine‐grained sand in an experimental flume

Antidunes and their sedimentary structures can be useful in reconstructing paleo‐hydraulic conditions, especially for large discharge events. However, three‐dimensional (3D) antidunes in sand‐sized sediments have not yet been studied extensively, as compared to either two‐dimensional (2D) antidunes or antidunes in gravel‐sized sediments. In this study, we estimated formative conditions of gravel step‐pool morphologies and applied them to the formation of 3D antidunes over a sand bed. Formative conditions are expressed in terms of a relationship between the water discharge per unit width and the bed slope. Flume experiments demonstrated that 3D mound‐like antidune configurations and their associated internal sedimentary structures could be preserved. Internal sedimentary structures were characterized by shallow lens‐like structures whose bases were erosional. Although gently‐dipping concave‐upward lamination was dominant, convex‐upward lamination was occasionally observed. The dimensions of lenticular lamina‐sets can be used to estimate antidune geometry. Thus if 3D antidunes can be interpreted in the stratigraphic record, it is possible to estimate the paleo‐hydraulic parameters such as water discharge and bed slope more precisely than previously. Copyright © 2010 John Wiley & Sons, Ltd.     

High mercury levels in hair samples from residents of Taiji, a Japanese whaling town

We investigated the mercury concentrations in red meat from pilot whales consumed by some residents of the Japanese whaling town, Taiji, and in hair samples from 50 residents for their maker of mercury burden. The methyl mercury (M-Hg) level in the red meat was 5.9 μg/wet g, markedly higher than the US FDA action level and Cordex Alimentarius guideline level for predatory fish (1.0 μg/wet g). The average level of total mercury (T-Hg) in the hair from residents who ate whale meat more than once a month was 24.6 μg/g, whereas the average from the residents who did not consume any whale meat was 4.3 μg/g. The T-Hg concentrations in the hair from three donors exceeded 50 μg/g, the level for NOAEL set by WHO. The T-Hg level found in the Taiji whale meat consumers was markedly higher than that observed in the Japanese population overall (about 2 μg/g).     

导电薄层下三维岩脉的CSAMT响应分析

为了研究探测3D导电岩脉状目标体的可控源音频电磁法（CSAMT）的最佳观测装置,我们用压缩积分方程法数值模拟了赋存于导电薄层下的3D导电岩脉的电磁场响应.计算结果表明,最有效的源的位置是把发射源沿岩脉的走向放置.相对于其他几种装置,这种观测装置得到的异常场与主场的比值最大.利用这种最佳的观测装置,通过将异常场E_ya 和 H_xa与噪音作对比,研究了当岩脉的埋深和高度发生变化时岩脉的可探测性问题.当岩脉的顶部埋深增加时,导电岩脉的可探测性降低.岩脉高度的变化对异常场幅值的影响要小于岩脉顶部埋深所产生的影响.所以通常情况下,即便应用了最有效的CSAMT装置,也很难探测到岩脉的高度,应用钻孔中的探测可能会解决这个问题.     

Uniformity of Longitudinal Distribution of Coronal Mass Ejections

It was found that the heliographic longitudinal distribution of the occurrence of coronal mass ejections (CMEs) was not uniform around the solar minimum of cycle 21. This is confirmed by using the ² test for goodness of fit. Sunspot groups and flares show similar non-uniform distributions during the same period. This suggests that there was a longitudinal range where both large-scale and small-scale solar magnetic activities were very low around the solar minimum of cycle 21. The longitudinal range with low activity was more than 150 degrees and continued for approximately four rotations. As solar activity increased, CMEs occurred almost uniformly in heliographic longitude.     

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.     

耦合融雪的分布式流域"降雨-径流"数值模型

针对中国对耦合融雪的"降雨-径流"过程数值计算模型方面的研究较少,本文联合应用能量平衡方程及运动波理论的基础方程式,结合GIS技术构建分布式流域耦合融雪的"降雨-径流"数值计算模型,并应用流域实测资料进行了有效性验证。研究结果表明:在不考虑融雪条件下,实测流量与计算结果之间存在着较大的误差;在考虑融雪条件下,实测流量与计算结果之间的误差在基准允许范围之内(小于3%);在积雪与融雪区,对流域"降雨-径流"过程的数值计算须考虑融雪。该研究为积雪融雪区提供了一种耦合融雪的"降雨-径流"过程数值计算的新方法。     

Seismic assessment of two multi-tiered pagodas damaged by the 2015 Nepal earthquake

A seismic assessment of two multi-tier pagodas by numerical analysis is presented herein.The Changu Narayan temple and the Kumbeshwar temple in Nepal are used as the case studies.Both pagodas are built of brick masonry in earthen mortar,with timber columns and crossbeams.The Changu Narayan temple is a two-tier pagoda,and was seriously damaged during the 2015 Gorkha earthquake.The Kumbeshwar temple is a five-tier pagoda,and its top-tier collapsed due to the Gorkha earthquake.A seismic assessment was carried out using finite element(FE)analysis.The FE models were prepared,and dynamic identification tests and penetrometer tests were conducted.Pushover analysis and nonlinear dynamic analysis were performed as part of the seismic assessment.The main shock of the 2015 Gorkha earthquake was considered as the input accelerograms.The behavior between the two pagodas was compared with the collapse mechanisms and damage patterns observed in the actual structures.The comparison suggested common structural features of multi-tier pagodas.This study is dedicated to providing a better understanding of the seismic behavior of multi-tier pagoda-type structures and provides suggestions for their effective analysis.