The effect of water on the electrical conductivity of olivine

It is well known that water (as a source of hydrogen) affects the physical and chemical properties of minerals--for example, plastic deformation and melting temperature--and accordingly plays an important role in the dynamics and geochemical evolution of the Earth. Estimating the water content of the Earth's mantle by direct sampling provides only a limited data set from shallow regions (<200 km depth). Geophysical observations such as electrical conductivity are considered to be sensitive to water content, but there has been no experimental study to determine the effect of water on the electrical conductivity of olivine, the most abundant mineral in the Earth's mantle. Here we report a laboratory study of the dependence of the electrical conductivity of olivine aggregates on water content at high temperature and pressure. The electrical conductivity of synthetic polycrystalline olivine was determined from a.c. impedance measurements at a pressure of 4 GPa for a temperature range of 873-1,273 K for water contents of 0.01-0.08 wt%. The results show that the electrical conductivity is strongly dependent on water content but depends only modestly on temperature. The water content dependence of conductivity is best explained by a model in which electrical conduction is due to the motion of free protons. A comparison of the laboratory data with geophysical observations suggests that the typical oceanic asthenosphere contains approximately 10(-2) wt% water, whereas the water content in the continental upper mantle is less than approximately 10(-3) wt%.     

Experimental measurement of the electrical conductivity of single crystal olivine at high temperature and high pressure under different oxygen fugacities

At 1.0?4.0 GPa and 1123?1473 K and under oxygen fugacity-controlled conditions (Ni+NiO, Fe+Fe₃O₄, Fe+FeO and Mo+MoO₂ buffers), a YJ-3000t Model six-anvil solid high-pressure apparatus and a Sarltron-1260 Impedance/Gain-Phase analyzer were employed to conduct an in situ measurement of the electrical conductivity of single crystal olivine. Experimental results showed that: (1) within the range of experimentally selected frequencies (10³?10⁶ Hz), the electrical conductivity of the sample is of great dependence on the frequency; (2) with the rise of temperature (T), the electrical conductivity (σ) will increase, and the Arrenhius linear relationship is established between lgσ and 1/T; (3) under the control of oxygen buffer Fe+Fe₃O₄, with the rise of pressure, the electrical conductivity tends to decrease whereas the activation enthalpy and independent-of-temperature preexponential factor tend to increase, with the activation energy and activation volume of the sample estimated at (1.25±0.08) eV and (0.105±0.025) cm³/mol, respectively; (4) under given pressure and temperature conditions, the electrical conductivity tends to increase whereas the activation energy tends to decrease with increasing oxygen fugacity; and (5) the mechanism of electrical conduction of small polarons can provide insight into the behavior of electrical conduction of olivine under high pressure and high temperature.     

一种基于客户端行为的邮件帐户异常检测方法

在对邮件用户WebMail登录、ESMTP验证发送邮件、POP3接收邮件的三种邮件客户端行为统计特征分析研究的基础上,提取ESMTP验证次数、POP3验证次数两种特征建立客户端行为模型,提出一种基于邮件用户客户端行为的邮件帐户异常检测方法,并应用到华中科技大学校园网邮件系统中.实验证明,该方法能有效、快速地检测出异常的...     

MTM与MTC模型中PGB对qq→tt过程的单圈修正

本文分别在多标度ＴＣ模型（ＭＴＭ）与带有一个标量子的ＴＣ模型（ＭＴＣ）中研究了赝标哥尔斯通粒子（ＰＧＢ）对Ｔｅｖａｔｒｏｎ上ｔｏｐ夸克对产生截面的单圈贡献．我们发现在ＭＴＭ中该贡献是显著的，当ｔｏｐ夸克的质量取１７６ＧｅＶ，色八重态ＰＧＢ的质量可以取到６００ＧｅＶ时，该修正值达到２９％，这是很有实验意义的，然而在ＭＴＣ中，该修正较小，不可观测     

对流边界层顶部夹卷层厚度特征及其参数化分析

运用大涡模拟结果分析并讨论了对流边界层顶部夹卷层厚度特征及其参数化．常见的参数化方案是建立归一化夹卷层厚度与对流理查森数（Ri＊）之间的指数对应关系,但不同研究结果得到的幂指数有很大差异．分析表明：“Ri＊方案”本身是造成这种不确定性的原因;另一种理查森数（RiN）,即浮力理查森数,可以较好地表征夹卷层厚度．大涡模拟结果表明：“RiN方案”能够有效地减小夹卷层厚度参数化的不确定性．为消除湍流随机性对参数化的影响,我们对大涡模拟结果进行了时间平均处理,并用所得数据讨论了夹卷层厚度与浮力理查森数之间的关系．结果表明：两者之间有很好的指数对应关系,平均幂指数为-2／5;计算结果同时显示,幂指数仍然存在一定的变化范围（-1／3～-1／2）．夹卷层厚度的这种特性反映出夹卷过程的复杂性,即兼有热泡和界面振荡的特征．     

竹材模型结构底部滚球与顶部TLD联合减震公式推导

结合第五届全国大学生结构设计竞赛赛题,对竹材模型结构提出了底部滚球与顶部水箱TLD联合减震的方案,并对运动微分方程、滚球球心加速度及滚球等效支承模型进行了公式推导,得到的有关公式对实际结构减震有一定的意义。     

Zircon SHRIMP U-Pb dating for olivine gabbro at Wangmuguan in the Beihuaiyang zone and its geological significance

In the Neoproterozoic, a large-scale magmatic activ- ity took place in the northern margin of the South China Block, with ages in a range of 700―800 Ma[1―4]). A systematic zircon U-Pb dating for bimodal metaigneous rocks in the Dabie-Sulu orogen yields ages of 758 ± 15 Ma[5], typifying rift magmatism along the northern margin of the South China Block during the middle Neoproterozoic. In addition, there is a widespread oc- currence of volcanic tuff interlayers around 635 Ma with the se…     

智能科技:推动虚拟仪器技术高速发展的强大动力

本文首先从IVI(IntelligentVirtualInstruments智能虚拟仪器 )驱动器对VXI总线pnp(plug&play ,即插即用 )标准仪器驱动器结构与功能上的全面改进 ,分析了智能化对虚拟仪器快速发展的强大推进作用。然后 ,剖析了当今时代智能科技分支林立 ,蓬勃发展的大好形势 ,指出了以智能化大力推动我国仪器工业飞速赶超世界先进水平的重要性与可能性。最后展望了IVI的未来的发展前景。     

中性top介子在NLC实验中的可能物理迹象

ＴＣ２模型预言的物理ｔｏｐ介子通过反常可以与规范玻色子（γ，Ｚ）发生耦合，因此在高能ｅ＋ｅ－碰撞中可以产生这种粒子．本文估计了中性ｔｏｐ介子πｔ°在ＮＬＣ实验中的产生几率，并讨论了其可能的物理迹象．     

边界界面导热系数插值格式的改进

分析表明现有文献中采用的边界界面导热系数插值格式与内部界面并不一致,仅适用于常系数和弱非线性导热问题,而对于强非线性问题则会产生较大误差。本文根据调和平均法推导出了新的边界界面导热系数插值公式,确保了边界与内部界面导热系数插值格式的一致性。通过几个具有精确解的非线性导热问题对本文插值格式进行了考核并与文献中的格式进行了对比。结果表明,采用本文改进格式可以明显提高非线性导热问题数值计算的精度,尤其对于边界零扩导问题采用改进格式可以得出物理上更为合理的解。     

Metastable garnet in oceanic crust at the top of the lower mantle

As oceanic tectonic plates descend into the Earth's lower mantle, garnet (in the basaltic crust) and silicate spinel (in the underlying peridotite layer) each decompose to form silicate perovskite-the 'post-garnet' and 'post-spinel' transformations, respectively. Recent phase equilibrium studies have shown that the post-garnet transformation occurs in the shallow lower mantle in a cold slab, rather than at approximately 800 km depth as earlier studies indicated, with the implication that the subducted basaltic crust is unlikely to become buoyant enough to delaminate as it enters the lower mantle. But here we report results of a kinetic study of the post-garnet transformation, obtained from in situ X-ray observations using sintered diamond anvils, which show that the kinetics of the post-garnet transformation are significantly slower than for the post-spinel transformation. Although metastable spinel quickly breaks down at a temperature of 1,000 K, we estimate that metastable garnet should survive of the order of 10 Myr even at 1,600 K. Accordingly, the expectation of where the subducted oceanic crust would be buoyant spans a much wider depth range at the top of the lower mantle, when transformation kinetics are taken into account.     

中药洁口净含漱液治疗牙龈炎、牙周炎疗效分析

目的:探讨中药局部用药对牙龈炎、牙周炎的治疗方法及治疗效果。方法:将牙龈炎、牙周炎患者60例随机双盲法分为洁口净组30例并以呋喃西林含漱液组30例为对照,探讨临床疗效。结果:中药洁口净组与对照组的有效率有显著性差异(P<0.01),治疗组优于对照组。结论:中药局部用药治疗牙龈炎、牙周炎是有效且安全的治疗途径。