Electrical Conductivity Method Research Articles

Fundamental study on measurement of soil pH and electrical conductivity in batch tests for the determination of soil-soil solution distribution coefficient

Soil-soil solution distribution coefficient, Kd, is used to understand the mobility of radionuclides in the soil environment. Soil pH and electrical conductivity (EC) are the important factors affecting soil Kd, but existing methods for Kd employed different conditions, as well, standard soil pH and EC methods varied in the test conditions. It would be desirable to measure both pH and EC using the same soil solution for Kd with portable meters (non-glass electrode type) that need only a small liquid volume. In this study, at first, we utilized portable pH and EC meters to examine effects of different conditions on measurements, i.e., the water/soil ratios, contact time and standing time. The results showed that portable meter measurements of soil supernatant after 1 h shaking and 1 h standing could provide comparable pH and EC values with other standard soil tests. Then measurements of pH, and EC up to 168 h were carried out, considering the Kd methods for radiocesium (Cs); only slight differences in these values were observed compared to the standard test method. Considering these results, further analysis was carried out on the correlation between soil Kd-Cs and pH and found a clear decrease of Kd-Cs at pH<5.

Antimicrobial and aggregation properties of asymmetric gemini surfactants based on 1-(2-hydroxypropyl)-4-ethyl piperazine and alkyl bromides

Asymmetric gemini surfactants were synthesized by the quaternization reaction of 1-(2-hydroxypropyl)-4-ethyl piperazine with (C9, C10, C12, and C14) alkyl bromides. The surface tension of their aqueous solutions was determined by the Du Nouy ring method and the conductometric method of specific electrical conductivity. According to the concentration dependence graphs of surface tension and specific electrical conductivity, critical micelle concentration – CMC, degree of association of the counterion – β, surface area occupied by the head group of the surfactant – Amin, maximum surface excess concentration – Γmax, effectiveness or surface pressure –πCMC, adsorption efficiency – pC20 were calculated, and the change of these parameters depending on the length of the alkyl chain was determined. Simultaneously, variations in Gibbs free energies of micellization and adsorption processes were computed. The diameters of aggregates formed by asymmetric gemini surfactants in water were determined by the DLS method. Antimicrobial abilities of asymmetric gemini surfactants against gram positive and gram negative bacteria and fungi were defined by the disk diffusion method.

Association and clouding behaviour of surfactants in aqueous solution of propranolol hydrochloride drug: Understanding of the effects of potassium salts and temperatures

The investigation of the assembly of lithium dodecyl sulfate (LDS) and cloudy creation of triton X-100 (TX-100) in aqueous solution of amphiphilic drug propranolol hydrochloride (PLH) has been carried out by electrical conductivity and cloud point estimation method respectively. The influences of three potassium electrolytes (KCl, K2SO4, and K3PO4) on the micellization of LDS and clouding of TX-100 in presence of PLH drug have been examined. The conductivity experiments were conducted at temperatures between 288.15 and 323.15 K, with a 5 K interval.The introduction of PLH drug promotes the micelle formation of LDS up to 1 mmol kg−1 of drug. The critical micelle concentration (CMC) values of LDS in aqueous solution of PLH were shifted to lower values in aqueous electrolytes media. The cloud point (CP) of TX-100 + PLH system was observed to be increased with the rise in concentrations of PLH in aqueous medium. The reduction in the CP values of TX-100 and PLH mixed system has been attained with the enrichment of the concentrations of electrolytes and at a specific mole fraction of electrolytes, the CP values exhibited the order: CP (KCl (aq.)) > CP (K2SO4 (aq.)) > CP (K3PO4 (aq.)). The Gibbs free energy of assembly (ΔGm0) appeared as negative (spontaneous assembly) whereas ΔGc0 of clouding showed positive magnitudes indicating the nonspontaneous nature of the clouding process. The micellization of LDS demonstrate the endothermic and exothermic nature at lower and higher investigated temperature as revealed from the sign of ΔHm0values.. The positive values of entrpoyΔSm0 exhibit the micellization process to be entropically driven phenomena. The phase separation of TX-100 and PLH mixed system is entropy contributed in aqueous medium while the clouding in the presence of salts is enthalpy contributed evidenced from the negative enthalpy of clouding.

Comparison of Water and DTPA Extractants for Testing of Greenhouse Soilless Substrates

ABSTRACT The main purpose of this study was to improve the accuracy and reliability of nutrient analysis on soilless substrates by comparing two different saturated medium extract (SME) methods, using either water (SMEW) or DTPA (diethylenetriamine-pentaacetic acid, SMED) as extractants. A series of analyses were performed to compare ion levels quantified from either SMEW or SMED. Substrate pH, electrical conductivity (EC) and nutrient data were analyzed from a survey of substrate components (coconut coir, peat, bark, perlite, vermiculite), and blended greenhouse propagation substrates using the SMEW and SMED methods. In addition, a series of SMEW and SMED extracted samples were sent to three commercial soil testing laboratories for nutrient analysis. The objectives of these analyses were to (1) validate that published relationships between SMEW and SMED methods were consistent with correlation curves for pH, EC and nutrient levels across a wide range of soilless substrates, (2) compare statistical variability of results from SMEW and SMED methods and (3) compare variability in results between different laboratories. The results validated that previously published standards for interpreting SMEW extractions can be used for SMED method for macronutrients and EC due to an approximately 1:1 relationship for test results between extraction methods. Up to 2 orders of magnitude higher levels of micronutrients were extracted for iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) using SMED compared with SMEW, with low correlation between extractants. Concentrations of ions from SMED extractions were less variable than SMEW for micronutrient analysis but were comparable for macronutrient analysis. Results from this study were combined with published research to provide suggested ranges using SMED for soilless substrates.

A comparative study assessing the validity of water absorption methods when applied to secondary fine aggregates

The valorization of secondary sands is crucial for fostering a circular economy within the construction sector. One significant obstacle in this endeavor stems from the high water absorption (WA) rates commonly reported for secondary sands. This high WA leads to increased water and cement demand in cementitious mixes and elevates costs. The only widely standardized method to measure the WA of fine aggregates is the cone method, which has proven ill-suited for fine aggregates with angular particles or a high content of fines. This study undertakes a comparative evaluation of the cone method and seven alternative methods: immersion, centrifugation, paper sheet, colorimetric, volumetric flask, continuous drying, and electrical conductivity. Tests were performed on natural river sand and three types of secondary sand. Findings reveal that the continuous drying and electrical conductivity methods demonstrates the greatest potential in terms of reliability and applicability. Also the volumetric flask and centrifugation methods show some potential, provided that critical refinements are made to the corresponding test protocols.

Characterization and applicability of the Naima–Tiaret–Algeria illite-montmorillonite clay for methylene blue dye removal: adsorption kinetic, isotherm and thermodynamic studies

ABSTRACT An illite-montmorillonite clay from Naima, IMN (Algeria) was treated via physical and chemical treatment (TIMN) and investigated for the removal of methylene blue. IMN and TIMN clays were characterized by XRD, XRF, SEM-EDS, DSC-TG, FTIR and DC electrical conductivity methods. To analyze the sorption behavior of MB on the clays, a mechanistic model for interpreting the sorption data was developed. IMN clay revealed high sorption capacity (1.925 × 10−2 kg kg−1) for MB in 60 min. The pseudo-second-order model had a very good agreement to describe the MB adsorption process. The adsorption capacities, qe,exp, of 4.327 × 10−2 and 4.914 × 10−2 kg kg−1 for IMN and TIMN, respectively, were obtained. The free energy from the D–R model from adsorbing MB using IMN and TIMN ranged from 1.581 to 0.745 × 10−3J mol−1, respectively, suggesting that the process is physisorption. Besides, the sorption process was more sensible to temperatures that increase was beyond 40 °C causing a decrease in adsorption capacity, indicating that the adsorption reaction of MB onto IMN was exothermic. The adsorption mechanism of I/M clay to remove MB was likely based on hydrogen bonding, electrostatic attraction, cation exchange and n–π interaction. These results proved that TIMN was a promising adsorbent for removing MB from simulated wastewater.

Оценка требований к точности сенсоров океанографических зондов при косвенном определении солености морской воды

The issues of measuring the mass of dissolved substances or absolute salinity under environmental conditions in situ using automated instruments still remain open. How these issues are likely to be resolved depends on the development of new oceanographic measurement technologies. Salinity is one of the seawater parameters that cannot yet be directly measured in situ. Until now, all known, existing or promising, methods for determining salinity are indirect. The purpose of this work is to find the maximum sensitivity coefficients in order to assess the uncertainty of sensors of input quantities and compare various methods for indirect determination of salinity. To solve this problem, the work uses methods of direct and inverse metrology problems. In this work, these problems were solved for four fundamentally different methods of indirect (calculated) determining of the salinity of sea water: 1) the relative electrical conductivity method (RCM), 2) the speed of sound method (SSM), 3) the density method (DM) and 4) the refractive index method (RIM). Depending on environmental conditions, the maximum values of sensitivity coefficients (13 coefficients in total) for the output value (salinity) were found for all input parameters of each method. By solving inverse problems for the accepted conditional base level of salinity uncertainty and at maximum sensitivity coefficients, estimates of the uncertainty of sensors of input parameters for each of the four methods were calculated. The results obtained make it possible to estimate the required accuracy of sensors of input quantities at any given level of uncertainty of the output quantity or the actual accuracy of the output quantity at any given level of uncertainty of sensors of input quantities. From the three promising methods for indirect salinity determination, MPP is the best candidate to replace MOE in the near future.

Synthesis of polyaniline-coated composite anion exchange membranes based on polyacrylonitrile for the separation of tartaric acid via electrodialysis.

The increasing need to tackle major societal challenges such as environmental sustainability and resource scarcity has heightened global interest in green and efficient separation technologies. The separation of organic acids, particularly tartaric acid, holds significant industrial importance in the food and pharmaceutical sectors. Purifying tartaric acid is crucial due to its roles as a chiral catalyst, antioxidant, and stabilizer, which are vital for ensuring product quality and efficiency. In this study, we synthesized heterogeneous anion exchange membranes by casting a solution of polyacrylonitrile (PAN) homogeneously dispersed with micronized anion exchange resin [polystyrene-divinylbenzene-trimethyl ammonium chloride (PS-DVB-TAC)]. These membranes were further coated with polyaniline (PANI) through in situ polymerization at different time intervals such as 2, 12, and 24 h. Cation exchange membranes were also prepared by solution casting of PAN dispersed with micronized cation exchange resin, sulfonated poly-styrene-co-divinylbenzene, and SPS-DVB. These synthesized anion exchange membranes with and without a PANI coating were examined for their separation performance of tartaric acid, along with the cation exchange membranes in a four-compartment electrodialyser at a constant voltage. The newly fabricated membranes were characterized by different techniques, including attenuated total reflectance-Fourier transform infrared spectroscopy for functional group analysis, scanning electron microscopy for their surface morphology, and the four-probe method for electrical conductivity. In addition, ion exchange capacity and water uptake have been measured. The electrodialysis experiments showed that 14.82 wt% of tartrate ions moved into the product compartment through the uncoated anion exchange membrane within 30 min at a voltage of 30 V. Under the same conditions, membranes coated with PANI at 2, 12, and 24 h raised the separation efficiency to 21.19%, 34.13%, and 37.21%, respectively. Findings indicate that membranes coated with PANI for extended periods demonstrate superior separation efficiency for tartaric acid. Consequently, this energy-efficient method shows significant potential for application in the food and pharmaceutical industries for separating tartaric acid and other organic and amino acids. This research can advance practical and sustainable separation technologies, addressing critical societal issues like resource efficiency and environmental sustainability.

Contribution of dissolved organic matter to seawater salinity measured by optic refractometer: a case study of DOM extracted from Aoshan Bay

Dissolved organic matter (DOM) in seawater, consisted of a complex mixture of compounds and accounted for about 90% of marine organic carbon, is an important part of the global carbon cycle and also a part of absolute salinity of seawater. As the components of DOM are non-ionized in seawater, electric conductivity measurement cannot observe its contribution to salinity, which could lead to measurement error in salinity. Salinity measurement based on optic refractive index could reveal contribution of all dissolved matters in seawater including both non-ionized and ionized components. In this paper, a comparative study of DOM contribution to the salinity measurement by optic refractive index method and electric conductivity method was carried out for the first time. Adding DOM, extracted from Aoshan Bay, Qingdao, China, into Chinese Standard Seawater, our experimental results showed an increase of optic refractive index at 1.19×10-4 ± 4×10-6 per 1g/kg of DOM, which corresponds to a practical salinity increase of 0.697 ± 0.036 PSU per 1 g/kg of DOM. While, the conductivity of seawater measured by a conductivity-temperature sensor showed a decrease of 0.00065 ± 0.00008 mS/cm per 1 g/kg of DOM, which corresponded to a decrease of salinity at 0.00052 ± 0.00007 PSU per 1 g/kg of DOM. By comparing the optic and electric measurement results, the contribution of non-conductive components in the dissolved organic matters to salinity could be distinguished, which has great significance for the measurement of absolute salinity, global carbon cycle etc.

The Electrical Conductivity and Drying Method Changed the Secondary Metabolite Content and Photoprotective Effects of Hydroponically Cultivated Agastache rugosa Kuntze

Many studies have examined how various cultivation methods and elicitors elevate target crop values. Post-harvest treatments, such as the drying method, may alter the final product’s characteristics. We investigated the effect of nutrient solution concentration during the hydroponic cultivation and drying method (cold air drying and freeze drying) after harvesting Agastache rugosa Kuntze, an herb used for folk medicine and as a deodorant, spice, and tea in East Asia. To explore the properties of A. rugosa, we determined its growth parameters, secondary metabolites, and photoprotective effects. We observed the highest growth and yields in A. rugosa grown under 4.0 dS·m−1 electrical conductivity (EC) conditions. However, the EC 2.0 group showed higher antioxidative properties than those grown in EC 1.5 and 4.0 conditions. Drying conditions varied the content and ratios of major active compounds (rosmarinic acid, tilianin, and acacetin) in A. rugosa. Cold air drying caused rosmarinic acid transmutation to tilianin and acacetin, and tilianin showed a stronger positive correlation with antioxidative and photoprotective activities than rosmarinic acid. The increased tilianin content in cold-air-dried A. rugosa accompanied the improved photoprotective effects in dermal cell lines. This study reveals the effects of cultivation and drying methods in A. rugosa production, and proposes alternate industrial production techniques.

Self-aggregation of cationic gemini surfactants with amide groups in the spacer and variable alkyl chain length

AbstractSynthesis, aggregation parameters and antimicrobial activity of novel cationic gemini surfactants with two amide groups in gemini spacer structure and a variable number of carbon atoms in alkyl tails ranging from 12 to 15 are reported. The critical micelle concentration of gemini surfactants was determined using surface tension and electrical conductivity methods. The cmc values were found in the range 0.83 to 0.06 mM. The interfacial area, micelle ionisation degree and the Gibbs free energy per molecule and alkyl chain were calculated from the surface tension and conductivity curves. Particle size analysis using the dynamic light scattering method confirmed the formation of small spherical micelles 6–7 nm large in size for gemini surfactants with 12 and 13 carbon atoms in the alkyl chain. A large size above 50 nm was found for the aggregates composed of long-chain gemini molecules with 14 and 15 carbon atoms. The zeta potential of gemini surfactants shows a continuous increase with the increasing alkyl chain length. Micelle aggregation number of gemini surfactants correlates well with the hydrodynamic size data. Small aggregation number values were found for short-chain gemini molecules with 12 and 13 carbon atoms in the alkyl chain. Long-chain gemini molecules with 14 and 15 carbon atoms exhibit aggregate growth represented by an increase in the aggregation number values while maintaining the spherical or spheroidal shape of micelles. The investigations of antimicrobial activity against Gram-positive bacteria, Gram-negative bacteria and yeast indicate the increasing antimicrobial efficiency towards the short-chain surfactant with 12 carbon atoms in the alkyl chain. A possible cut-off effect presence is proposed to explain the dependence of antimicrobial activity on the surfactant alkyl tail length.

Comparison between the electrical conductivity method and radicle emergence test as a rapid test of sorghum seed vigor

Sorghum (Sorghum bicolor L. Moench) belongs to multipurpose crops. All parts of sorghum can be used both as main products and derivative products; some derivative products produced from the sorghum plant consist of sugar, bioethanol, biomass, handicraft raw materials and starch. This study aims to determine the time required for testing the vigor and viability of sorghum seeds using the electrical conductivity and radicle emergence methods. The study was conducted in two experimental stages using a completely randomized design. The first experiment consisted of two factors: the number of sorghum seeds (40, 70 and 100 grains) and the volume of soaking water (75, 100, 125, and 150 ml). The second experiment consisted of two factors: research method (germination/control method, electrical conduction method, and radicle emergence method) and varieties (consisted of Numbu, Kawali, Suri 3, and Suri 4). The first experiment's results showed that the best electrical conductivity method on Suri 4 varieties were 40 seeds and 150 ml water volume. The electrical conductivity value is negatively correlated with Germination capacity, vigor index, growth of speed, maximum growth potential, and sprout growth rate. Time needed for Electrical Conductivity method in this study was three days. The germination period of 96 hours gives the best results on the radicle emergence of sorghum seed varieties. Vigor index, growth of speed, germination capacity, and maximum growth potential are positively correlated with the value of radicula emergence.Keywords: Electrical Conductivity, Radicle emergence, Vigor, Viability, Germination

Thermophysical Properties of Acetaminophen in Aqueous Solutions of Protic Ionic Liquids Based on Ethanolamine at T = 288.15–318.15 K

Protic ionic liquids (PILs), a novel category of inexpensive and sustainable solvents, have been employed to solve industrial and medicine solubility problems. Using a combination of ultrasonic, volumetric, and electrical conductivity methods at 288.15–318.15 K and a pressure of ≈87.1 kPa, researchers investigated the thermophysical properties of acetaminophen (ACP) in water and aqueous solutions of three protic ionic liquids (PILs), which are composed of the cations 2-hydroxyethylammonium, bis(2-hydroxyethyl)ammonium, and tris(2-hydroxyethyl)ammonium as well as the anion lactate. Study of intermolecular interactions using the thermophysical properties is very important because it provides a deep insight into the forces that are functional in the liquid mixtures. For the medication acetaminophen in water and aqueous PIL solutions, thermophysical parameters including apparent molar volume and apparent molar isentropic compressibility are examined in the current work. The findings showed that interactions between acetaminophen and PILs predominated in the systems under study and that these interactions increased as the PIL concentrations rose. The positive transfer results have been interpreted using the cosphere overlap model.

The physicochemical and thermophysical properties of sodium dodecyl sulfate: The influence of p-toluene sulfonyl chloride and temperature

In the present study, we report on the interaction between a hydrotrope, p-toluene sulfonyl chloride (p-TSC), and an anionic surfactant, sodium dodecyl sulfate (SDS) which has been performed using electrical conductivity, Fourier transform infrared (FTIR), 1H NMR, density, dynamic viscosity, and kinematic viscosity measurements. The effect of p-TSC on the micellization of SDS in non-aqueous (ethanol) medium at various temperatures (viz., 298.15, 303.15, 308.15, 313.15, 318.15, and 323.15 K) was investigated using the electrical conductivity method. The results show that the CMC value increases as the concentration of the hydrotrope is increased. It is noteworthy that at higher concentrations of hydrotrope, the trend of micelle formation is reversed (i.e., reverse micelles are formed). The thermodynamic parameters in micellization have also been evaluated. The FTIR and 1H NMR data reveal the physicochemical properties of the pure and mixed systems and confirm no covalent bond formation takes place. Density, dynamic viscosity, and kinematic viscosity of the pure as well as mixed systems at various temperatures were also reported.

Fine Recycled Concrete Aggregates Treated by Means of Wastewater and Carbonation Pretreatment

Fine recycled concrete aggregate (FRCA) possesses substantial limitations for its use due to its significant porosity. Extensive research on the effect of carbonation on the accessible porosity of coarse recycled concrete aggregate is available in the literature, but FRCA information is scarce. The present paper presents results of the effect of carbonation on different fractions of FRCA from &lt;0.125 mm to 4 mm previously sprayed with wastewater from mortar production as an additional source of portlandite. The results of water absorption via the electrical conductivity method, TGA, XRD+Rietveld+PONKCS analysis, EDS mapping, and Life Cycle Assessment (LCA) demonstrate that the efficiency of the treatment depends on the particle size range of the FRCA. It was most effective for the extreme size fractions &lt;0.25 mm and &gt;1 mm of FRCA as a result of the relationship between the amount of precipitated calcium carbonate and the initially accessible porosity in each fraction. As a consequence, mortar produced with 30% replacement of natural sand with carbonated FRCA showed no impact on compressive strength.

Experimental Study on the Dynamic Characteristics of Gas-Centered Swirl Coaxial Injector under Varying Ambient Pressure

To determine the dynamic characteristics of a gas-centered swirl coaxial injector under backpressure, an experimental system of dynamic injection in a backpressure chamber was constructed. Filtered water and nitrogen were used as simulant media for rocket propellants, which are typically used with this kind of injector. An inertial flow pulsator was manufactured to generate the pulsation of the flows that feed to the liquid injector. The electric conductance method was adopted to measure liquid film thickness. After the pulsation of incoming flow in the feedline was tested, and the operating conditions for the injector to start pulsating were validated, the effects of the chamber backpressure and the recess length of the injector on the dynamic characteristics of spray, such as liquid film thickness, breakup length, and amplitude of pulsation, have been investigated in detail. Experimental results demonstrated that the increase in chamber backpressure prompts the liquid sheet to rupture earlier with a shorter breakup length, which results from the increased density of the ambient gas. Chamber backpressure suppresses the pulsation of the outlet flow, especially for a longer recess length. Moreover, a decrease in the recess length results in a reduction in breakup length due to an intense gas–liquid shearing in a narrower recess section. For a lower backpressure, the amplitude of outlet flow generally increases when the recess length increases. However, this phenomenon is not obvious for the conditions of higher backpressure and lower pulsation frequency.

The Influence of Dissolved Organic Matter to the Seawater Refractive Index Using Optical Refractometer

Optic refractive index is a good proxy for in situ salinity measurement of seawater according to TEOS-10. Currently, salinity of seawater is estimated by practical salinity (SP), which is calculated by measuring electric conductivity, temperature and pressure using Conductivity-Temperature-Depth (CTD) sensors. However, the electric conductivity method only takes into account the conductive compositions to seawater salinity and ignores the contribution of non-ionic components. However, non-ionic components in seawater affect seawater salinity according to the definition of salinity of seawater, but they could not be measured by conductivity sensor. Optical refractive index is sensitive to all dissolved matters of seawater including ionic and non-ionic components. Here, we take the dissolved organic matter (DOM) extracted from Aoshan Bay seawater as the representative sample to experimentally study the contribution of the non-ionic component to the refractive index of the standard seawater. Seawater refractive indices with different DOM concentrations were measured by a home-made V-shaped groove refractometer. The experimental results show that refractive index of seawater increases linearly with increasing DOM concentration at rate of 1.19 × 10-4/1(g/kg) DOM.

The properties of electric double layer at activated carbon surface and their effect on gold and silver adsorption from cyanide solutions

This paper looks at the properties of electric double layer (EDL) found at the surface of activated carbons. The study relied on the electrical conductivity method, which is based on simultaneous use of polarization dependences at direct current and conductometric measurements at alternating current. It was found that the adsorption of gold and silver intensifies in the anode region of carbon surface polarization. Two regions with peak adsorption were identified in the following ranges of potentials: +0.2&divide;+0.25 and +0.6&divide;+0.8 V. EDL diffusion helps improve the environment for the adsorption of cyanide complexes of gold and silver by active centres of the adsorbent surface. The authors believe that an increased mass transfer in the first range of potentials can be attributed to a decreased diffusion resistance caused by changed zero charge polarity, while in the second range of potentials it can be attributed to the cyan-ion oxidation reaction and an easier access of the negatively charged cyanide complexes of gold and silver to the positively charged surface of the carbon adsorbent. The polarization dependences by direct current in the anode region tend to monotonously rise, which is indicative of a lower EDL density, an increased conductivity at the adsorbent surface/solution boundary and improved adsorption conditions. Graphs showing a relationship between alternating current and carbon adsorbent potential helped determine maximum conducti vity values, which almost match the peak values of gold and silver adsorption. The authors established that the adsorbent&rsquo;s potential has a significant effect on the activated carbon adsorption of cyanide complexes of gold and silver. The use of the electrical conductivity method for examining the EDL helps explain certain features typical of the activated carbon adsorption of gold and silver from cyanide solutions.

Synergistic effects of CuI doping on enhancing thermoelectric performance for n-type Bi2O2Se fabricated by mechanical alloying

The extremely low electrical conductivity and time-consuming preparation methods limit potential practical applications for Bi2O2Se-based thermoelectric materials. To solve these problems, a fast preparation method of combining mechanical alloying (MA) with spark plasma sintering (SPS) has been successfully adopted to synthesize CuI-doped Bi2O2Se in this work. The electrical conductivity was largely improved from 3 S cm−1 to 296 S cm−1 at 823 K attributed to the optimized carrier concentration. Meanwhile, an extremely low lattice thermal conductivity value of 0.39 W m−1 K−1 at 823 K was achieved by intensive phonon scatterings from point defects and dense grain boundaries. Consequently, an enhanced ZT value reached 0.45 at 823 K, which resulted in ∼380% improvement over that of the pristine Bi2O2Se prepared by solid-state reaction (SSR). This work opens a new gate for synergistically optimizing electron and phonon transport properties for Bi2O2Se-based thermoelectric materials.

Estimation method for the anisotropic electrical conductivity of in vivo human muscles and fat between 10 kHz and 1 MHz

Objective. In low frequency dosimetry the variability in the electrical conductivity values assigned to body model tissues represents a major source of uncertainty. The aim of this study is to propose a method for estimating the conductivity of human anisotropic skeletal muscle and fat in vivo in the frequency range from 10 kHz to 1 MHz. Approach. A method based on bounded electrical impedance tomography was used. Bioimpedance measurements were performed on the legs of ten subjects. Anatomically realistic models of the legs were then created using magnetic resonance images. The inverse problem of the tissue conductivities was solved using the finite element method. The results were validated using resampling techniques. These findings were also used to study the effects of muscle anisotropy on magnetic field exposure. Main results. The estimated conductivities for anisotropic muscle were found to be in good agreement with values found in existing literature and the anisotropy was shown to decrease with increasing frequency, with the ratio of lateral to longitudinal conductivity increasing from 37% to 64%. The conductivity of fat was found to be almost a constant 0.07 S m−1 in the frequency range considered. Significance. The proposed method was shown to be a viable option when estimating in vivo conductivity of human tissue. The results can be used in numerical dosimetry calculations or as limits in future investigations studying conductivity with bioimpedance measurements.