Oxygen diffusion in perovskite: implications for electrical conductivity in the lower mantle

Experimental determination of oxygen self-diffusion in CaTiO(3) perovskite, a structural analog of (Mg,Fe)SiO(3) perovskite, confirms a theoretical relation between diffusion constants and anion porosity. Oxygen diffusion rates in (Mg,Fe)SiO(3) perovskite calculated with this relation increase by about eight orders of magnitude through the lower mantle. Electrical conductivity values calculated from these diffusion rates are consistent with inferred conductivity values for the lower mantle. This result suggests that the dominant conductivity mechanism in the deep mantle is ionic.     

Thermal equation of state of aluminum-enriched silicate perovskite

Inferences of the chemical homogeneity of Earth's mantle depend on comparing laboratory-derived equations of state of mantle phases with seismically determined properties of the material in situ. A uniform chemical composition of the entire mantle has been found to be consistent with measurements, to date, of these properties for the end-member MgSiO3 perovskite phase. New pressure-volume-temperature data for silicate perovskite containing 5 mole percent Al2O3 has yielded different values of the equation of state parameters, with the bulk modulus being significantly smaller at lower mantle conditions than for aluminum-free perovskite, thus requiring adjustments in other components to match seismic observations.     

The electrical conductivity of post-perovskite in Earth's D' layer

Recent discovery of a phase transition from perovskite to post-perovskite suggests that the physical properties of Earth's lowermost mantle, called the D' layer, may be different from those of the overlying mantle. We report that the electrical conductivity of (Mg0.9Fe0.1)SiO3 post-perovskite is >10(2) siemens per meter and does not vary greatly with temperature at the conditions of the D' layer. A post-perovskite layer above the core-mantle boundary would, by electromagnetic coupling, enhance the exchange of angular momentum between the fluid core and the solid mantle, which can explain the observed changes in the length of a day on decadal time scales. Heterogeneity in the conductivity of the lowermost mantle is likely to depend on changes in chemistry of the boundary region, not fluctuations in temperature.     

The effect of electrical coupling on the frequency of model neuronal oscillators

Neurons with oscillatory properties are a common feature of the nervous system, but little is known about how neural oscillators shape the behavior of neuronal networks or how network interactions influence the properties of neural oscillators. Mathematical models are used to examine the effect of electrically coupling an oscillatory neuron to a second neuron that is either silent or tonically firing. Models of oscillatory neurons with varying degrees of complexity show that this coupling can either increase or decrease the frequency of an oscillator, depending on its membrane potential wave form, the state of the neuron to which it is coupled, and the strength of the coupling. Thus, electrical coupling provides a flexible mechanism for modifying the behavior of an oscillatory neural network.     

生理电场对早期胚胎发育的影响

胚胎发育涉及一系列复杂的生理学、细胞生物学以及基因组学过程。已有研究表明,胚胎发育早期特别是原肠胚和神经胚时期存在着一定强度的内源生理电场,当存在类似内源生理电场强度的外源电场时,能引导细胞迁移、控制细胞极化、调节细胞增殖和分化,从而在一定程度上影响胚胎发育。本研究主要就内源生理及外源电场对胚胎发育的引导或干扰作用进行综述,以期为胚胎发育研究提供新思路。     

不同土地利用方式对土壤含水量、pH值及电导率的影响

以林芝地区八一镇5种植被类型下土壤为研究对象,研究其土壤剖面(0—50 cm)的含水量、pH值及电导率分布特征。结果表明,土地利用方式影响了土壤含水量、pH值和电导率在垂直剖面上的空间分布,尤其以表层(0—20 cm)土壤含水量和电导率受影响最为明显。草地土壤含水量表现出明显的“表聚”效应,即随着土层加深,含水量呈降低趋势。在区域空间上,土壤含水量和电导率具有较强的空间变异性,而土壤pH值的空间变异性较小。随着土层加深,各层土壤含水量和电导率之间的变异性逐渐减小。     

便携式土壤电导率测试系统的开发

介绍了一种自行设计的，基于电流-电压四端法的便携式土壤电导率(EC)在线测试仪的开发情况。该测试仪包括土壤电导率传感器、控制与数据采集器和计算机应用软件等。传感器有4个电极，2个用于向土壤中输入恒流，另外2个用于检测与土壤电导率密切相关的电压降；控制与数据采集器把传感器产生的电压信号转换为数字信号，计算并显示电导率；计算机应用软件把接收到的数据存入Microsoft Access数据库。在实验室土槽内对该测试仪传感器的性能进行了测试，并与电导率仪测量结果进行了比较分析。结果表明，传感器输出电压与电导率仪测量值变化趋势一致，采用多种非线性数学模型对各组数据进行了曲线拟合，结果均在幂函数模型上获得最佳回归，测定系数(R^2)大于0．99。     

Calculation of soil electrical conductivity using a genetic algorithm

The aim of this paper is to present an optimization methodology based on a genetic algorithm to obtain the soil electrical conductivity and its respective thicknesses. The method uses an experimental conductivity curve generated from the measurements made in the soil. This experimental curve is compared with a theoretical electrical conductivity curve produced by a genetic algorithm. The theoretical curve is based on Sunde’s algorithm and is exactly the inverse process of soil horizontal stratification into multi layers. The comparison between the two curves provides the error produced by the soil stratification process. Using the obtained values of electrical conductivity, the method intends to estimate characteristics such as water content, texture and salinity of the subsoil layers.     

竹炭导电性能及应用研究进展

分析了竹炭导电机制主要由离子引起或π电子移动以及与形成石墨化程度有关的研究,从竹林立地条件、竹材部位、炭化工艺、竹炭微观结构、竹炭粒径大小及竹炭的基本理化性能指标等方面分析其对竹炭导电的影响,再综述了竹炭及其复合材料的电磁屏蔽效能、竹炭电容器电极等领域应用研究进展,最后从竹炭生产技术、导电理论及应用领域存在的不足,提出了今后重点研究的4个方向。     

不同降雨强度下剖面土壤电导率的空间变异研究

应用传统统计学和地统计学方法,分析了重庆市中梁山坡耕地土壤电导率在无雨尧小雨、中雨和大雨4种降雨强度下的空间分布特征,并分析了不同降雨强度下土壤电导率与相关参数的相关性。结果表明：在一定条件下袁土壤孔隙水电导率和土壤含水率是影响土壤电导率的主要因素;土壤电导率具有明显空间变异性,不同降雨强度下同一土层电导率差异显著,不同土层间土壤电导率差异显著;对不同降雨强度下土壤电导率的变异函数理论模型拟合精度较高,无雨条件下,土壤电导率空间具有中等或强烈空间相关性,自相关域最大,不同降雨强度下0~10cm土层土壤电导率结构比为0,10~30、30~50 cm土层结构比均有不同程度下降。     

一种多点土壤电导率实时监测系统的研制

为获取建立溶质运移模型所需的土壤溶质浓度参数,根据土壤溶液电导率与溶液浓度c的线性关系,应用电流电压四端法,研制出一种多点土壤电导率实时监测系统。该系统硬件部分自行设计的四针微型探头可减小对溶质运移的扰动,且可高密度分布在土壤中;连接8路电导率探头和1路温度探头的高精度数据采集器DAB能够实现8通道土壤电导率测量及温度辅助测量,并可通过485总线接口实现系统规模的扩展。采用VC开发的监测显示平台能够完成采集器参数设置,数据采集、显示与存储功能。通过对采集器通道和探头的标定,有效解决了多点土壤电导率实时监测的一致性问题。标定试验结果表明,数据采集器8通道电导测量值与标准电导的相关系数为0.999 5,表明通道标定后有效提高了其测量准确度,减小了各通道测量差异;通道标定后采集器各通道测量的标准溶液电导G与其电导率σ具有良好的线性关系,但不同电导率条件下探头的测量结果存在较为明显的偏差,说明探头制作过程引起的结构差异不可忽略,进而采用分段标定方法对每一个探头的结构常数进行标定。     

钾细菌对江西酸性土壤养分活性作用的研究

采用液体培养法研究了供试钾细菌对江西 4种酸性土壤和陕南黄褐土中 K、P、Si、Fe、Mn、Zn等 6种元素的活化作用。结果表明 :1接种钾细菌后 ,4种酸性土壤和陕南黄褐土中的速效 K、P、Si、Fe、Mn的平均生物释放量分别为 2 0 .4,6 9.8,10 0 .4,42 .6 ,15 .9和 40 .7,40 .5 ,5 2 5 .9,199.4,81.9m g/ kg,较不接菌对照增加 10 .6 %,80 .8%,37.4%,372 .0 %,10 9.2 %和 2 2 .7%,5 2 1.6 %,172 .8%,12 0 4.0 %,131.7%,中性黄褐土中各元素的释放量及增率均高于酸性土壤 ;2钾细菌能使 40 %酸性土样中的 Zn元素发生轻度活化 ,其余酸性及中性土样中的 Zn元素固定 ;3钾细菌在液体培养过程中产酸 ,接菌后 4种酸性土壤培养液的 p H值平均降低 1.0单位 ,较对照降低14.8%,产酸可能是钾细菌活化养分的途径之一。     

电导法研究热处理对包衣棉种发芽率和活力的影响

对新收获的有休眠包衣棉种中棉所46进行热处理,研究热处理前后棉种发芽率和电导率等的变化.结果表明,热处理使棉种发芽率升高,初次芽率下降,电导率值上升,电导率增加速率在浸泡8～10 h时出现转折,电导率的增速更能代表包衣棉种的活力水平,热处理前后种子的活力水平相当,热处理后略高于未处理.     

Thermal conductivity effect of carrier gases on flame-ionization detector sensitivity

Data for six carrier gases of different thermal conductivities show a linear correlation between the logarithm of thermal conductivity and detector response. Carbon dioxide with a lower thermal conductivity than helium gives a ninefold increase in detector response.     

Comparing apparent electrical conductivity measurements on a paddy field under flooded and drained conditions

Every growing season, paddy fields are kept both flooded and drained for a significant period of time. As a consequence, these soils develop distinct physico-chemical characteristics. For practical reasons, these soils are mostly sampled under dry conditions, but the question arises how representative the results are for the wet growing conditions. Therefore, the apparent electrical conductivity (EC_a) of a 1.4 ha alluvial paddy field located in the Brahmaputra floodplain of Bangladesh was measured in both dry and wet conditions by a sensing system using the electromagnetic induction sensor EM38, which does not require physical contact with the soil, and compared both surveys. Due to the smooth water surface under wet conditions which ensured increased stability of the sensing platform, the results of the survey showed considerably reduced micro-scale variability of EC_a. Furthermore, the wet survey results more reliably furnished soil-related information mainly due to the absence of soil moisture dynamics. The differences between EC_a under wet and dry conditions were attributed to differences in soil texture, mainly the sand content variation having considerable effect on soil moisture differences when flooded following drainage. Accordingly, the largest differences between EC_a under wet and dry conditions were found in those parts of the field with a large sand content. Hence, the conclusion was that an EC_a survey on flooded fields has an added value to precision soil management.     

Mobile TDR for geo-referenced measurement of soil water content and electrical conductivity

The development of site-specific crop management is constrained by the availability of sensors for monitoring important soil and crop related conditions. A mobile time-domain reflectometry (TDR) unit for geo-referenced soil measurements has been developed and used for detailed mapping of soil water content and electrical conductivity within two research fields. Measurements made during the early or late season, when soil moisture levels are close to field capacity, are related to the amount of plant available water and soil texture. Combined measurements of water content and electrical conductivity are closely related to the clay and silt fractions of a variable field. The application to early season field mapping of water content, electrical conductivity and clay content is presented. The water and clay content maps are to be used for automated delineation of field management units. Based on a spatial analysis of the soil water measurements, recommendations are made with respect to sampling strategies. Depending on the variability of a given area, between 15 and 30 ha can be mapped with respect to soil moisture and electrical conductivity with sufficient detail within 8 h.     

New low-dimensional molecular metals: single-crystal electrical conductivity of nickel phthalocyanine iodide

Single crystals of NiPcI(1.0) (Pc = phthalocyanine), which are composed of one-dimensional stacks of (NiPc)(+0.33) molecules and chains of I(3)(-) molecules, exhibit metallic electrical conductivity in the stacking direction. At room temperature the mean free path of the carrier is 3.3 to 8.2 angstroms.     

电导法配合Logistic方程鉴定茶树抗寒性的探讨

研究了茶树品种迎霜在不同低温及处理时间下电解质外渗率的变化,探讨了电导法配合Logistic方程在鉴定茶树抗寒性上的应用。结果表明,电导法鉴定茶树抗寒性的低温处理时间2 h以上即可,梯度中心温度在-2 - -5℃。以此为基础,鉴定了10个供试茶树品种（系）的抗寒性。     

滨海盐土水溶性盐分电导率线性回归模型探析

根据4批次盐分含量与电导率（EC25）数据，拟建4个线性回归方程，通过对方程的显著性检验，区别不同地域高低盐分的实际情况，对方程进行检验，归并与探析，获得3个通用的线性回归模型；y12=-1.6929 0.004926x,y3矫=-18.2850 0.007999x,y4矫=-11.7302 0.007999x。供莆田滨海盐土在EC254400us/cm以下以及16000us/cm以下（即：盐分20g/kg以下以及116g/kg以下）范围内的盐分测试分析实践中参考运用，修正与完善。     

基于分数阶微分的博斯腾湖湖滨绿洲土壤电导率高光谱估算

[目的]探讨分数阶微分在高光谱估算湖滨带绿洲土壤电导率的可行性,实现土壤盐分的高精度监测.[方法]以博斯腾湖湖滨绿洲为研究区,引入分数阶微分对土壤高光谱反射率进行0～2阶微分处理,利用相关性检验和连续投影算法优选特征波段,构建土壤电导率的全波段和特征波段,以及利用连续投影算法优选的全波段和特征波段的4种偏最小二乘回归模...