Body composition in adolescents: estimation by total body electrical conductivity

This comparative study, conducted on 28 boys and girls of widely varying fatness, was designed to validate a new whole-body composition method [total body electrical conductivity (TOBEC)], based on bioelectrical properties of the human body. A significant correlation [r = 0.911; standard error of the estimate (SEE) = 5.3 kg] was demonstrated between the transformed TOBEC scores (TOBEC0.5 X Ht) and lean body mass (LBM) determined by hydrodensitometry and corrected for individual variations in hydration (LBMd + W). TOBEC determinations also correlated well with 1) total body water determined by deuterium oxide dilution (r = 0.877; SEE = 4.5 liters), 2) total body potassium determined by means of a 4 pi whole-body counter (r = 0.860; SEE = 430.7 meq), 3) LBM derived from skinfold thicknesses (r = 0.850; SEE = 5.8 kg). The residuals of the regression between LBMd + W and TOBEC scores did not show any significant correlation with either the potassium or the water content of the LBM. The results indicate that TOBEC is a simple, rapid, reliable, and noninvasive technique for delineating changes in body composition that occur in children during growth.     

A nondestructive method for measuring electrical conductivity of intracellular matter of tissue in situ

Summary A nondestructive method has been developed for measuring electrical conductivity of intracellular matter. The method is based on easily measurable electric parameters of cells in suspension. Experiments were made using suspensions of erythrocytes in a physiological salt solution. Results confirmed suitability of the method for determining conductance of the cytoplasm and were in close agreement with those reported by other authors. The method allows the determination of intracellular conductivity in tissue as well.     

基于分数阶微分优化光谱指数的土壤电导率高光谱估算

土壤电导率与含盐量具有高度相关性,精准的土壤电导率监测有助于了解区域土壤的盐渍化程度,对区域盐渍化防治与调控,农业可持续发展以及生态文明建设具有重要意义。为寻求预测土壤电导率的最佳高光谱参数,实现土壤盐分信息的高效监测,本研究对土壤样品进行室内高光谱和电导率测定,利用两波段优化算法对简化光谱指数(nitrogen planar domain index, NPDI)进行波段优化,筛选不同高光谱数据(原始高光谱反射率及其对应的5种数学变换)运算下的最敏感高光谱参数,从而建立土壤电导率高光谱估算模型。结果表明:1)NPDIs与土壤电导率之间的相关性显著,在原数据及其平方根、倒数、对数倒数、1.6阶微分变换形式下,优化光谱指数对土壤电导率的敏感程度更强,相关系数绝对值均超过0.80,且基于1.6阶微分变换的(R_(2020nm)+R_(1893 nm))/R_(1893 nm)波段组合相关系数绝对值最高,达到0.888。2)基于1.6阶微分波段优化的预测模型效果最佳,预测精度为R■=0.84,RMSE_(Pre)=2.07mS/cm,RPD=2.94,AIC=158.11。因此,对高光谱数据的适当数学变换有利于优化光谱指数更好地估算土壤电导率,进一步实现土壤盐渍化高精度动态监测。     

A new method for temperature compensation of electrical conductivity using temperature-fold dependency of fresh water

A new method for temperature compensation of electrical conductivity (EC) is proposed. A relationship between temperature and EC was investigated in detail by a simple experiment using natural and artificial fresh water. Results showed that the temperature dependency of EC varied from 0.03 to 0.02, with temperature increasing from 3°C to 35°C. This means that a traditional method for compensating for EC using a constant coefficient is invalid, so that a temperature-fold dependency must be taken into consideration to standardize EC to a common temperature.     

Bacteria detection utilizing electrical conductivity

Real-time and specific detection of single bacterium remains a fundamental challenge and draws very much attention. Using test patterns composed of interdigitated Au-electrode arrays modified with antibody, the specific and quantitative detection of the electrical conductivity of a single Escherichia coli (E. coli, JM109) has been carried out in this work. The key is to ensure low background current of the antibody-modified test patterns before bacteria detection (<0.7pA in this case) and minimize the residual moisture or hydration after E. coli immobilization, such as via the use of 1-min bake at 50 degrees C prior to electrical measurement. This method holds great potential for future application in the real-time, specific, and quantitative bacterium detection down to a single bacterium cell.     

On the electrical conductivity of rhodopsin solutions

Measurements were made on the conductivity of digitonin extracts of frog rhodopsin with and without previous light exposure. The light-dark difference in conductivity is observed at low concentrations of rhodopsin and detergent.     

Evaluation of a non-destructive method for determining egg composition using total body electrical conductivity (TOBEC) measurements

It is widely assumed that there is a positive relationship between egg quality (or egg size) and offspring fitness. However, obtaining unequivocal data in support of this hypothesis has been hampered by the lack of any method for non-destructive determination of egg composition, preventing a direct analysis of egg quality and subsequent chick growth and survival in the same egg(s). In this paper, we describe the application of a rapid, non-destructive technique using measurement of total body electrical conductivity (TOBEC) for determination of egg composition in intact eggs. The TOBEC index was positively and highly correlated with egg lean mass and with the mass of some egg components (albumen and water content). Values for predicted lean mass, based on the regression equation for lean mass against TOBEC index, were within ±6% of actual lean mass. Egg lipid mass was most accurately predicted (±15%) using a multiple regression model, with fresh egg mass and TOBEC index included as independent variables. Egg temperature, and the position of the egg in the sampling chamber, markedly affected the TOBEC index obtained.     

Determination of intracellular conductivity from electrical breakdown measurements

The intracellular resistivity (conductivity) of cells can be easily calculated with high accuracy from electrical membrane breakdown measurements. The method is based on the determination of the size distribution of a cell suspension as a function of the electrical field strength in the orifice of a particle volume analyser (Coulter counter). The underestimation of the size distribution observed beyond the critical external field strength leading to membrane breakdown represents a direct access to the intracellular resistivity as shown by the theoretical analysis of the data. The potential and the accuracy of the method is demonstrated for red blood cells and for ghost cells prepared by electrical haemolysis. The average value of 180 Ω - cm for the intracellular resistivity of intact red blood cells is consistent with the literature.     

应用电导率法及Logistic方程测试椰子幼苗耐寒性研究

以一年生椰子的叶片为材料,在不同低温条件下处理12h后,对椰子5个品种叶片浸出液的电导率进行测定,应用Logistic方程建立回归模型求出半致死温度。结果表明,在低温胁迫过程中,5个椰子品种的相对电导率均随温度的下降而持续上升,耐寒性大小顺序依次为:海南高种椰子>黄矮椰子>红矮椰子>杂交种椰子>香水椰子,其半致死温度在7.34～12.44℃之间。研究结果为椰子的耐寒选育提供理论依据。     

Determination of intracellular conductivity from electrical breakdown measurements

The intracellular resistivity (conductivity) of cells can be easily calculated with high accuracy from electrical membrane breakdown measurements. The method is based on the determination of the size distribution of a cell suspension as a function of the electrical field strength in the orifice of a particle volume analyser (Coulter counter). The underestimation of the size distribution observed beyond the critical external field strength leading to membrane breakdown represents a direct access to the intracellular resistivity as shown by the theoretical analysis of the data. The potential and the accuracy of the method is demonstrated for red blood cells and for ghost cells prepared by electrical haemolysis. The average value of 180 omega X cm for the intracellular resistivity of intact red blood cells is consistent with the literature.     

Re-examination of the poisoned-partner effect with the two-bottle testing method

Revusky, Coombes and Pohl (Animal Learning and Behavior 10 (1982) 83–90) suggested that poisoned conspecifics function as aversive unconditional stimuli (USs) for rats (the poisoned-partner effect). The present study re-examines this effect with the two-bottle testing method. Rats were first given saccharin and later exposed to a poisoned conspecific. They exhibited an aversion to saccharin in the subsequent tests involving a choice between saccharin solution and water. Furthermore, the subjects that were only exposed to the poisoned conspecific later avoided saccharin. The poisoned-partner effect, therefore, can also be explained by sensitization. This finding suggests that poisoned conspecifics are simply salient stimuli that attract the rat’s attention, rather than aversive USs of food aversion learning for rats.     

In vivo measurements of electrical conductivity of porcine organs at low frequency: New method of measurement

Calculations of the induced currents created in the human body by external electromagnetic fields would be more accurate provided that more realistic experimental values of the electrical properties of the body were available. The purpose of this work is to experimentally obtain values for the conductivity of living organs in conditions close to the real situation. Two‐electrode in vivo measurements of the bioimpedance of some porcine organs have been performed. From these measurements and taking into account geometrical considerations, the electrical conductivity for the kidney, liver, heart, and spinal cord has been obtained and were found to be higher than the values reported in the literature. Furthermore, a new experimental procedure is proposed where the conductivity is determined from the values of the electrical potential and currents that are induced by an external electromagnetic field created by a coil placed close to the organ under study. Bioelectromagnetics 33:612–619, 2012. © 2012 Wiley Periodicals, Inc.     

A theory of electrical conductivity of non-equivalent molten salts

The electrical conductivity of non-equivalent molten salts has been theoretically investigated based on the linear response theory, which is an extension from the expression for equivalent molten salts as we have developed in the previous papers. The velocity correlation functions are expressed in terms of pair potentials and pair distribution functions. Using these functions and Langevin equations for ions, the relations among the conductivity coefficients are obtained. It is shown that the ratio of partial conductivities σ⁺/σ^?  is equal to |z ⁺|m ^? /|z ^? |m ⁺, which is an extensive expression from the inverse mass ratio in the case of equivalent molten salts. Numerical results for molten CaCl₂ and AlF₃ are presented, which agree well with the results of experiments and molecular dynamics simulations.     

干旱胁迫下沙棘叶片细胞膜透性与渗透调节物质研究

研究了在干旱胁迫下沙棘幼林苗木渗透调节能力与沙棘耐旱性的关系。结果表明：长期轻度及中度干旱胁迫下渗透调节物质中可溶性糖、游离氨基酸、Pro在干旱中、后期累积显著增加而降低渗透势,使沙棘具备较强的渗透调节能力而表现为低水势耐旱特性;K^ 在干旱下无显著累积。渗透调节物质（可溶性糖、游离氨基酸、Pro）的共同作用,使长期轻度、中度干旱下沙棘叶片可溶性蛋白降解少,细胞膜透性和MDA含量增加缓慢,重度二进下也能在一定时间内保持稳定,这些物质是构成沙棘强耐旱性的内在基础。