Changes In Electrical Conductivity Research Articles

Honeycomb-like three-dimensional reduced graphene oxide supported NiCoO2/rGO composite anode material to boost lithium storage performance

NiCoO2 anode has some drawbacks such as unsatisfied electrical conductivity and severe volume change during cycling, leading to dissatisfactory rate capability and poor cycling stability. In order to address these issues, a NiCoO2 nanosheet/reduced graphene oxide composite (NiCoO2/rGO) is prepared via solvothermal process followed by heat treatment employing the honeycomb-like three-dimensional rGO as the support. This NiCoO2/rGO exhibits reversible charge specific capacities of 1124.0 and 414.5 mAh g−1 at 100 and 2000 mA g−1, respectively. After 300 cycles at 500 mA g−1, the charge specific capacity remains 114.8% of the initial value. The lithium storage performance is much superior to the bare NiCoO2, which is attributed to the support of the highly conductive and robust 3D rGO matrix that not only enhances the electrical conductivity and charge transfer, but also buffers the volume change, maintaining the structural integrity and electrical conduction of the electrode during cycling.

Fascinating Electrical Transport Behavior of Topological Insulator Bi2 Te3 Nanorods: Toward Electrically Responsive Smart Materials.

Electrical conductivity and dielectric parameters are general inherent features of materials. Controlling these characteristics through applied bias will add a new dimension to regulate the dynamic response of smart materials. Here, a fascinating electrical transport behavior is observed in topological insulator (TI) Bi2 Te3 nanorods, which will play a vital role in intelligent materials or devices as a unit for information reception, processing or feedback. The Bi2 Te3 nanorod aggregates exhibit a monotonic resistance response to voltage, with observed four-fold change of electrical conductivity in a small range electric field of 1Vmm-1 . The dielectric constant and dielectric loss of Bi2 Te3 nanorod composites also show strong dependences on bias voltage due to the unique electrical transport characteristics. The unique voltage-controlled electrical responses are attributed to the change of Fermi levels within the band structure of disordered TInanorods, which are non-parallel to the applied electric field. The excellent controllable inherent characteristics through electric field endows Bi2 Te3 nanomaterials bright prospects for applications in smart devices and resistive random access memories.

Salival biomarkers in inflamatory oro-cranio-cervical inflamatory alterations

During the COVID 19 pandemic, the general population suffered from high degrees of stress, the consequence of which was an increase in myofascial pain syndrome. This inflammatory ailment which affects soft tissues causes pain, muscular rigidity, and modifies posture due to hyperactivity. A state of muscular ischemia leads to structural and chemical changes, and to variations in saliva’s electrical conductivity. The objective of this research was to measure the changes in pH and electrical conductivity of saliva samples, and to use these as biomarkers during therapeutical Maxillary Functional Orthopedics (Planas’ Simple Indirect Tracks and Simões Network 20). All the subjects that took part in the study evidenced changes in the beforementioned biomarkers, as well as clinical improvement of their symptoms.

Facile synthesis of nano-Ag decorated Nb2O5 on the 3D graphene framework for high-performance lithium storage

Niobium-oxide based materials are well-known in electrochemical energy area because of their unique structural advantage, which can realize fast ion insertion/extraction and interfacial pseudo-capacitance effects. However, instinct poor electrical conductivity and terrible volume change of Nb2O5 under lithiation/delithiation have hindered its practical application. Here, a three-dimensional (3D) graphene network has been constructed by a simple hydrothermal reaction and utilized to buffer the severe structural variation of Nb2O5. Meanwhile, silver nanoparticles have been incorporated into this 3D structure through silver-mirror reaction, by which the charge-transfer ability of the composite (Ag-Nb2O5@rGO) can be significantly improved. The obtained Ag-Nb2O5@rGO can contribute a charge capacity of ∼ 208.0 mAh/g at 0.5C and ∼ 106.6 mAh/g up to 20C. Meanwhile, superior cyclic performance with ∼ 80 % capacity retention after 500 cycles at 2.5C can be achieved. This demonstrates that the Ag-Nb2O5@rGO composite can work as a high-performance anode for electrochemical energy devices.

Determination of the Change in Electrical Conductivity of Single, Bimetallic and Trimetallic Cylindrical Billets with Plastic Deformation Induced by Upsetting Process

Determination of the Change in Electrical Conductivity of Single, Bimetallic and Trimetallic Cylindrical Billets with Plastic Deformation Induced by Upsetting Process

Stochastic Generation of Electrolyzer Catalyst Layers

Developing clean energy technologies, such as polymer electrolyte membrane electrolysis (PEMWE), is essential to mitigate the negative impacts of climate change. However, one persistent barrier to PEMWE uptake is high catalyst costs, which can account for up to 47% of total stack costs [1]. This makes the catalyst a key target for cost savings via material optimization, as the mechanisms linking structure, mass transport, and charge transport remain relatively ambiguous in the literature [2], [3]. Previous studies have explored stochastic material generation and pore network modelling in the porous transport layer (PTL), but such analysis has yet to be performed for the bulk catalyst layer [4].In this study, we introduced a method for replicating the complex pore structure observed in commercially available catalyst materials using stochastic generation techniques. This method creates catalyst structures by using a desired pore size distribution (PSD) as an input, identifying and generating the macro- and microporous regions of the PSD, and then combining the two regions using a custom divider. Statistical analysis (two sample t-test and two sample K-S test) was used to determine the similarity of generated structures to previously imaged commercial catalyst materials. Moreover, pore network modelling techniques were applied to the generated structures to evaluate electrical and mass transport properties. Through these methods, we show that both transport properties and PSD characteristics of generated materials were within experimentally measured ranges, and altering elements of the PSD can result in order of magnitude changes in electrical conductivity, proton conductivity, and through plane permeability.The methodology presented in this work can be used to evaluate transport properties of various catalyst and catalyst-layer designs with novel pore size distributions. The local transport properties obtained can provide estimates for catalyst properties seldom reported in the literature, facilitating the design and informing the fabrication of next generation, ultra low loading catalyst materials.[1] A. Mayyas, M. Ruth, et al., Manufacturing Cost Analysis for Proton Exchange Membrane Water Electrolyzers, United States (2019).[2] Z. Taie, X. Peng, et al., ACS Appl. Mater. Interfaces, 12, 47, 52701–52712 (2020).[3] J. Lopata, Z. Kang, et al., J. Electrochem. Soc., 167. 064507 (2020).[4] J. K. Lee, C. H. Lee, and A. Bazylak, J. Power Sources, 437, 226910 (2019).

Wearable Conductive Polymer Matrix Composites for Breath Monitoring with Ammonia Detection

Conductive polymers, such as polyaniline (PANI), Polythiophene (PTh), polypyrrole (PPy), etc., are widely used for gas sensors due to their excellent electrical conductivity and low cost to manufacture [1]. In particular, PANI has attracted more attention due to its ease of synthesis, high environmental stability, and high reactivity with ammonia gas. In addition, the selection of acid-base dopant during the preparation process of polyaniline can adjust carrier concentrations for the change in electrical conduction or resistance to improve sensing properties. There have been many reports on the fabrication of flexible gas sensors using PANI [2-4]. Bandgar et al. [5] synthesized a low-temperature flexible polyaniline gas sensor by in-situ chemical oxidation polymerization of aniline on a polyethylene terephthalate (PET) substrate, showing 99% reproducibility, rapid response and recovery. Still, the response value was only 26% in 100 ppm ammonia atmosphere. Qi et al. [6] prepared a gas sensor by in-situ polymerization of aniline on non-woven fabric. The high air permeability of the fabric effectively improved the performance of the polyaniline-based gas sensor. Due to the outbreak of the COVID-19 pandemic, the use of face masks in public has become essential to reduce the spread of the virus. Some reports claim that the increased carbon dioxide in the mask over time may cause medical issues related to the respiratory system. Therefore, monitoring breathing air quality can help detect the wearer's vital conditions.In this study, we used a disposable mask as a flexible substrate to prepare polypropylene/carbon nanotube/polyaniline composite film through a layer-by-layer method. The polypropylene/carbon nanotube composite films were prepared by applying the carbon nanotube aqueous solution with surfactants evenly on the surface of a mask filter layer by a drop-coating method. Then, the in-situ polyaniline polymerization was performed on the surface of the polypropylene/carbon nanotube composite film through ammonium sulfate. The polypropylene/carbon nanotube /polyaniline composite film exhibits high sensitivity, fast sensing response/recovery time, room temperature operation, reliable flexibility, and cycle stability. The synthesized and wearable masks have demonstrated real-time detection respiratory rate and other breathing conditions such as CO2 and humidity. The ammonia gas sensing can also be used as a potential biomarker for health screening. The design and integration of multiple gas sensing materials in masks will help wearers better understand their own body conditions.

Thermoelectric properties of Rashba compounds KSnX (X = Sb, Bi)

Here, we have presented the results of the detailed theoretical study of thermoelectric properties of two Rashba compounds KSnSb and KSnBi using first principles calculations based on density functional theory and Boltzmann transport theory taking spin–orbit coupling (SOC) into account. As these compounds have layered-type crystal structures, their transport parameters are found to be highly anisotropic. For KSnBi (KSnSb), the calculated lattice thermal conductivity κl along its crystallographic c axis is found to have ultralow value of 0.49 W m−1 K−1 (0.78 W m−1 K−1) even at room temperature, whereas almost twofold larger value of κl is estimated along its crystallographic a axis. However, large values of other transport parameters like electrical conductivity σ and thermopower S desirable for a high power factor (S2σ) are found along the a axis of these compounds. For KSnSb, the optimum a axis ZT=2.6 can be reachable for an electron concentration of 3.3 × 1019 cm−3 and at a temperature of 800 K. Comparable value of optimum a axis ZT=2.5 is also noted for KSnBi despite its strong susceptibility to bipolar conduction. Both these non-centrosymmetric compounds exhibit SOC-driven Rashba spin splitting of electronic bands, which affects both thermopower and electrical conductivity of these compounds. However, such Rashba spin splitting induced change in thermopower is almost negated by the concomitant change in electrical conductivity, resulting in no appreciable impact on power factor and hence ZT of the studied compounds.

Expression of connexin 43 protein in cardiomyocytes of heart failure mouse model.

Heart failure (HF) is the end stage of various cardiovascular diseases, with high morbidity and mortality, and is associated with a poor prognosis. One of the primary causes of HF is aortic valve disease, manifested by progressive aortic valve stenosis (AVS), resulting in increased left ventricular load, ventricular hypertrophy, ultimately ventricular dysfunction, and HF. Early assessment of the degree of cardiomyopathy and timely intervention is expected to improve patients’ cardiac function and delay or even avoid the occurrence of HF. The Wnt signaling pathway is mainly involved in regulating myocardial insufficiency after valve stenosis. Connexin 43 protein (Cx43) is an essential target of Wnt signaling pathway that forms gap junction (GJ) structures and is widely distributed in various organs and tissues, especially in the heart. The distribution and transformation of Cx43 among cardiac cells are crucial for the development of HF. To specifically label Cx43 in vivo, we established a new Cx43-BFP-GFP mouse model with two loxp sites on both sides of the tag BFP-polyA box, which can be removed by Cre recombination. This double-reporter line endowed us with a powerful genetic tool for determining the area, spatial distribution, and functional status of Cx43. It also indicated changes in electrical conduction between cells in a steady or diseased state.

A new window on subcutaneous ICD system performance: Z-lead impedance change over time in devices with and without extracellular matrix envelope use

Abstract Background Device impedance for subcutaneous ICDs (S-ICDs) may rise over time reflecting changes in tissue electrical conduction due to fibrosis from the natural foreign body response, increasing the risk of defibrillation failure. A biologic envelope optimized for S-ICDs may mitigate fibrosis and encourages angiogenesis around the device possibly decreasing impedance rise over time. The S-ICD system performs routine low-voltage Z-lead (LVZ) impedance testing (impedance between shocking coil and can) that may provide insight into the impedance changes on device functionality and efficacy over time. Purpose Explore early and late impedance changes over time in S-ICDs implanted with and without envelopes using periodic LVZ measurements. Methods 30 patients received S-ICDs (15 with envelope) between 1/2017 and 3/2021, after excluding those with device complications, uncontrolled comorbidities, or recent cardiac surgery. Impedance data was recorded at initial implantation. LVZ impedance data was extracted from the wireless remote monitoring system, trended over 0–4 years post implant, and analyzed blinded to patient information. Results 24 patients (12 envelope) had evaluable implant and chronic data sets. Baseline clinical characteristics were similar between groups. Impedance in general was higher in the envelope group at initial implantation (LVZ mean 89 Ω vs 74 Ω) and throughout the first year. Comparing envelope to no envelope, the initial average shock impedance was 87.3±30.50 vs 66.7±10.40, followed by an average low-V impedance drop of 29 Ω vs 17 Ω during the first month, with a recovery to 109 Ω vs 91 Ω at 30 months post implant. After 30 months, impedance trends demonstrated a modest linear increase up to 48 months in the no envelope group in comparison with a modest decrease in the envelope group (sample sizes too small to determine significance) (Figure 1). Conclusion The results demonstrate periodic LVZ testing in the S-ICD monitoring system can reliably trend changes in system impedance over time. Impedance measurements within the first 6–7 months (and most markedly within the first 3 months) appear to be transiently lower than the values seen after this timepoint suggesting that early impedance measurements may not predict steady-state impedance. Further studies are needed to explore the impact of envelope use and the S-ICD impedance changes beyond 30 months. Funding Acknowledgement Type of funding sources: None.

Nitrogen, Phosphorus, and Potassium Availability in Three Compost Derivatives from the Wine Industry and Two Fertilizers

Organic production worldwide shows ongoing advances in agronomic management. Compost is mainly used for nutritional management and its benefits in biological activity and soil construction are well known; however, there are questions regarding nutrient supply. The present experiment was conducted under controlled laboratory conditions to evaluate the dynamics of nitrogen (N), phosphorus (P), and potassium (K) delivery along with the real N supply of three composts made from residues of the wine industry and two fertilizers (organic fertilizer and conventional liquid fertilizer) in two soils with contrasting characteristics (clay loam and sandy loam). There were five incubation times (0, 7, 28, 56, and 112 d), five treatments for each soil with rate of 100 mg kg−1 of total N, including a control, three composts, and one fertilizer with three replicates and a split-plot experimental design. Results indicated that the composts generated P and K contributions, whose amounts were different in both soils; however, there was no net N contribution as available N. Both the organic and conventional fertilizers provided important N contributions, which differed in magnitude depending on the characteristics of each fertilizer and each soil. In addition, the three composts generated slight changes in pH and electrical conductivity (EC). The organic and liquid fertilizers produced moderate (36.1%) and high (65.2%) net N availability values for clay loam soil and sandy loam soil, respectively. For agronomic management decisions involving the use of these composts as a nutritional source, it is suggested that the present study be complemented with field experiments.

Constructing three-dimensional N-doped carbon coating silicon/iron silicide nanoparticles cross-linked by carbon nanotubes as advanced anode materials for lithium-ion batteries

Silicon (Si), have been considered as promising anode material for lithium-ion batteries (LIBs), due to its high theoretical specific capacity of 4200 mAh g−1. However, the poor electrical conductivity and large volume change during lithiation/delithiation process, resulting in poor cycling stability, and seriously hindered the practical application in LIBs. Herein, a multiple Si/FexSiy@NC/CNTs composite is synthesized and investigated as advanced anode materials for LIBs via a simple one-step method. Such multiple Si/FexSiy@NC/CNTs composite has several merits including the FexSiy can not only accommodate the huge volume change of Si nanoparticles, but also enhance the conductivity upon discharge/charge process. Furthermore, the in-situ growth CNTs may help establish a long-range conductivity, and the Nitrogen-doped carbon (NC) layer can further improve the conductivity of Si, as well as inhibit the direct contract between electrolyte and Si during cycling process. Accordingly, the Si/FexSiy@NC/CNTs-1 exhibits excellent cycling stability (a high capacity of 994.4 mAh g−1 is maintained at 1.0 A g−1 after 600cycles) and outstanding rate capability (a suitable capacity of 441.7 mAh g−1 was obtained even at 5.0 A g−1). Moreover, the assembled full cell can achieve a capacity of 141.4 mAh g−1 after 65 cycles at 1.0C, exhibiting outstanding cycling stability. This work provides a prospective way for the commercial production of high-performance Si-based anode materials for LIBs.

Investigation of the Influence of Technological Operating Conditions of Electric Discharge Installations on the Pre-Breakdown Characteristics of an Electric Discharge

This work deals with the influence of the parameters of the working fluid (hydrostatic pressure, temperature, electrical conductivity) and the geometry of the electrode system (the length of the interelectrode gap and the uninsulated part of the anode) on the pre-breakdown characteristics of an electric discharge in a liquid aqueous electrolyte (breakdown voltage and breakdown delay time) and the minimum charging voltage, which provides a stable high-voltage breakdown of the interelectrode gap. Studies have shown that an increase in the hydrostatic pressure leads to an increase in most of the studied characteristics. At the same time, an increase in the specific electrical conductivity and temperature was observed to lead to their decrease. At the same time, it was suggested that the effect of temperature on the pre-breakdown characteristics is associated with a change in the specific electrical conductivity of the working fluid during its heating. The data obtained showed no effect of the length of the interelectrode gap on the breakdown voltage and its breakdown delay time, as well as the minimum charging voltage. The results of the experimental studies made it possible to develop a criterion for determining the charging voltage, which provides a stable high-voltage breakdown of the water interelectrode gap. Its experimental verification has shown that it can be applied to the design of electric discharge equipment and to the choice of technological modes of operation in the specified range of parameters.

Electromechanical impedance-based embeddable smart composite for condition-state monitoring

In the present study, an alternating current (AC) based electro-mechanical impedance (EMI) technique was employed to evaluate the performance of smart cementitious composite-based impedance sensor (SCC- i S) over a frequency range, and then was employed as embeddable sensor for monitoring and assessing the health of concrete structure. For this purpose, a method for developing SCC-iS by reinforcing the carboxylic group (COOH-) multi-walled carbon nanotube (COOH-MWCNT) in the cementitious composite matrix is described. The optimal CNT concentration in SCC- i S was obtained based on the AC impedance measurement technique over a specified frequency range. After finding the optimal CNT concentration in SCC- i S, their piezoresistive behaviour (in terms of change in electrical impedance or electrical conductance) was examined using an electro-mechanical impedance measurement approach under uniaxial compressive loading. Finally, the developed sensor is employed as an embedded sensor for damage monitoring of structures under flexural loading. The acquired electrical impedance- and conductance- responses from the SCC- i S were utilized to evaluate the occurrence and progression of damage in real-time. The damage metric and the shift in frequency band were used to quantify the level of damage in the structures. From the experimental study, 0.50 wt% CNT concentration is found to be optimum for developing the efficient SCC- i S. Under the uniaxial compressive loading, the electrical variation in impedance (EVZ) and electrical variation in conductance (EVC) in SCC- i S exhibit excellent correlation with compressive strain and are capable of detecting the damage. The acquired signals from embedded SCC- i S show the effectiveness and sensitivity (in both qualitative and quantitative terms) for damage monitoring of structures; even they are capable of tracing the early-stage damage initiation in concrete structures. The electrical conductance spectra within a specified frequency range show a leftward shift, indicating the degradation in stiffness of concrete structure. Overall, the developed SCC- i S is the first of its kind and is found to be very effective and durable for real-time monitoring of structures, especially in the aggressive environment. • Development of smart nanoengineered composite using functionalized CNT. • Embedded sensors for capturing the electro-mechanical impedance (EMI) signature. • Sensor characterization and evaluation of piezoresistive behavior in frequency bands. • Demonstration for damage monitoring of structures under flexural loading. • Damage metric and shift in frequency band for accurate damage quantification.

Encapsulating ultrafine Fe3O4 nanoparticles into interconnected 3D multiporous carbon for superior Li-ion energy storage

Although Fe3O4 has low cost and high theoretical capacity, its low electrical conductivity and significant volume changes during the reaction process result in poor electrochemical performance, particularly cycling performance, which limit its application as anode materials. To overcome these limitations, this study created Fe3O4@3D cellular carbon composites (Fe3O4@3D cellular carbon: Fe3O4@3D-CC) by homogeneously embedding ultrafine Fe3O4 nanoparticles of size around 10 nm in a three-dimensional cellular carbon skeleton using a template-assisted method. The porous structure enables for large volumes of electrolyte to be stored and features a dual continuous transport channel for ions and electrons, which can considerably improve the conductivity of the Fe3O4. Furthermore, 3D cellular carbon locks Fe3O4 nanoparticles, allowing them to adapt to volume changes during charge-discharge process and preventing structural degradation. Due to the aforementioned structural properties, this material has a first discharge-specific capacity of 2534 mA h g−1 at a rate of 0.1 C and can still reach 1011 mA h g−1 after 400 cycles at a high rate of 2 C. This keeps the theoretical capacity at 109 % and distinctly enhances the electrochemical performance of Fe3O4, particularly the cycling performance.

Anomalous electrical conductivity change in MoS2 during the transition from the amorphous to crystalline phase

Transition metal dichalcogenides exhibit unique properties, which make them interesting for fundamental studies and for applications in many devices. Here, we report on the anomalous electrical behavior during the amorphous-to-crystal phase transition of MoS2. While crystallization typically results in an increase in conductivity, the situation in MoS2 is opposite. Amorphous MoS2 shows a sheet resistance of 3.2 × 103Ω□ with the value remaining nearly constant until 200 °C, MoS2 samples annealed above 200 °C exhibit an unexpected two-step increase in sheet resistance. The first abrupt increase takes place after annealing at temperatures between 300 and 400 °C while the second increase occurs after heating to 700 °C with typical sheet resistance values of 1.2 × 105 and 8 × 106Ω□ after heating to 500 °C and 900 °C, respectively. Using a combination of X-ray photoelectron spectroscopy and X-ray diffraction studies and ab-initio modeling, we argue that the large electrical conductivity observed in amorphous MoS2 is associated with the existence of a large quantity of Mo–Mo homopolar bonds that exceed the percolation threshold. The dramatic increase in the sheet resistivity in the first step is accompanied by the formation of the Mo–S bonds upon the disassociation of homopolar Mo–Mo bonds for a further increase in the sheet resistance upon annealing temperatures of 700 °C that can be attributed to the grain boundary formation during crystallization of MoS2 into the 2H layered structure.

Resistive Switching in Ag2Te Semiconductor Modulated by Ag+‐Ion Diffusion and Phase Transition

AbstractMemristors are considered to be the fourth circuit element and have great potential in areas like logic operations, information storage, and neuromorphic computing. The functional material in a memristor, which has a nonlinear resistance, is the key component to be developed. Herein, resistive switching is demonstrated and the structural evolutions in Ag2Te are examined under an external electric field. It is shown that the electroresistance effect is originating from an electronically triggered phase transition together with directional Ag+‐ion diffusion. Using in situ transmission electron microscopy, the phase transition from the monoclinic α‐Ag2Te into the face‐centered cubic b‐Ag2Te, accompanied by a change in resistance, is directly observed. Diffusion of Ag+‐ions modulates the localized density of Ag+‐ion vacancies, leading to a change in electrical conductivity and influences the threshold voltage to trigger the phase transition. During the electric field‐driven phase transition, the spontaneous and localized multiple polarizations from the low‐symmetry α‐Ag2Te (referring to an antiferroelectric structure) are vanishing in the cubic b‐Ag2Te (referring to a paraelectric structure). The abrupt resistance change of thin Ag2Te caused by the phase transition and modulated by the applied electric field demonstrates its great potential as functional material in volatile memory and memristors with a low‐energy consumption.

Sensing of Acetaminophen Drug Using Silicon-Doped Graphdiyne: a DFT Inspection.

Using first-principles calculations, we studied the electronic properties of graphdiyne (GDY) nanosheet and its Si-doped counterpart, SiGDY. Both GDY and SiGDY sheet surfaces were examined for acetaminophen (AP) drug adsorption using adsorption energy, charge transfer, and change in electrical conductivity (as indicators). As shown in this study, pure GDY has little affinity for AP. In specific, only 7.83 percent of the GDY surface's bandwidth energy changed after AP adsorption. On SiGDY, AP has a gaseous energy value of - 18.75kcal/mol, as well as an aqueous energy value of - 49.39kcal/mol. The water-phase solubility of the prescribed medications is determined using their solvation energy value. These charges are transferred between AP and the SiGDY sheet, which is extremely positively charged, giving AP the necessary binding energy. After AP adsorption, the electrical conductivity of SiGDY was increased by approximately 19.01 percent.

A new portable electrical impedance tomography system for measuring two-dimensional stem water content distribution

Stem water content (StWC) is an important parameter for characterizing plant–water relations. Most sensors and methods can measure only one-dimensional StWC, and those measuring two-dimensional (2D) StWC distributions are expensive. In this study, we developed a low-cost and portable electrical impedance tomography (EIT) system to measure 2D StWC distributions in vivo. The performance of the EIT system was tested in a laboratory setting. An analog stem made of gypsum and two true stems cut from apple trees were used to calibrate the relationship between the average StWC (θv¯) and average change in electrical conductivity (Δσ¯) determined by the EIT system during the stepwise drying procedure. Evaporation experiments were conducted in the laboratory with hollow analog and cut stems to detect variations in StWC (Δθv) and its 2D distribution. Finally, the EIT system was installed in an apple tree for the in vivo monitoring of the diurnal variation of the 2D StWC distribution. The results indicated that the optimal measurement frequency of the EIT system was 47 kHz. After correcting for the effect of temperature, the average relative error of the measurement was reduced (approximately 80.21%). The effective height of the volume sensitivity of the EIT system was approximately 6 cm. The relationship between θv¯ and Δσ¯ showed a strong positive correlation, with all R2 values higher than 0.9808 for the analog stem and two cut stems. Moreover, the actual and EIT-estimatedθv¯ of the analog and cut stems during the evaporation experiments agreed well (R2 = 0.9367 and 0.9610, respectively), which validated the feasibility of the EIT system for StWC measurements. Furthermore, the in vivo EIT-estimated Δθv distribution of the apple tree was highly consistent with the regulation of diurnal variation in StWC in a greenhouse under irrigation and drought stress conditions. The new portable EIT system was able to measure the 2D StWC distribution and has great potential for application in drought monitoring of plant in the near future.

Assessment of physicochemical characteristics of biofertilizers and their role in the rooting capacity of plants

The concentration of supplied mineral nutrients is one of the most important and limiting factors for enhancing the efficiency of plant nutrition. Optimal concentration of nutrient solutions (NS) provide plants with the necessary amount of nutrients. From this point of view, research on several physicochemical parameters that characterize concentrations of NS and uptake of nutrients by the plants remains an actual problem. The changes of electrical conductivity (EC) and total dissolved solids (TDS) depending on the concentration of biofertilizer as well as the role of biofertilizer solutions on the rooting capacity of cuttings (lateral sprouts) of Callisia fragrans are presented here. The EC and TDS of the biofertilizer-water mixture changed gradually according to the biofertilizer concentration. The biofertilizer solution was a good medium for the rooting of C. fragrans cuttings. The results could help to provide the crops with the necessary amount of mineral nutrients and regulate the suitability of irrigation during the entire vegetation period.