Changes In Conductivity Research Articles

Competitive influence of interface effect, scale effect and mixed salt ratio on thermal conductivity of mesoporous complex nitrate

The rising prominence of energy security and climate change issues necessitates the advancement of sustainable energy development and energy storage technologies. Enhancing the capabilities of mesoporous composite phase change materials (CPCMs) has gained considerable research interest. CPCM’s heat storage and release performance is largely determined by its thermal conductivity. While the existing literature has documented the individual effects of the composition ratio of mixed molten salts, scale effects, and interfacial effects on thermal conductivity, no studies have been found that investigate the competitive interplay among these three factors with respect to their impact on thermal conductivity. This study aims to gain a deeper insight into the thermal conductivity changes of CPCM consisting of mixed molten salts as the phase change material (PCM) and mesoporous skeleton. A combination of molecular dynamics simulations and experimental investigations was employed to explore how interface effects, scale effects, and the proportion of mixed salts contribute to the thermal conductivity of CPCM. The findings indicate that augmented thermal conductivity, resulting from interface effects, supersedes the diminishing effects of interionic interactions. Compared to mixed salt ratios, interface effects primarily result in variations in the thermal conductivity of CPCM. The thermal conductivity of mixed nitrates escalates alongside scale increases. In the 3–4 nm range, the scale effect and mixed nitrate proportions do not notably compete in terms of influence on thermal conductivity, interface effects are more profound than scale effects. In the 4–9.5 nm range, the scale effect is more profound than mixed nitrate ratios. If the skeleton transitions from SiO2 to Al2O3, the impact of the interface effect on thermal conductivity is greater influential than the scale effect. While transitioning the interface from Al2O3 to ceramic, the effect of the interface is less than or equal to that of the scale effect on the thermal conductivity.

Enhancement of battery thermal management effect by a novel MOF based composite phase change material

The introduction of phase change materials (PCMs) into battery thermal management systems (BTMS) can effectively enhance the cooling performance, safety and practical thermal management applications of lithium-ion batteries (LIBs). However, further study is needed to address the low heat conductivity and rapid phase change leakage of PCMs. This study proposed a metal–organic framework based shape-stabilized composite PCM (MOF/expanded graphite (EG) /multi-walled carbon nanotube (MWCNT) /paraffin wax (PW)) to construe battery cooling system, and its effect of battery thermal management is experimentally tested under various conditions. The results show the CPCM reveals a superior thermal management effect under varying ambient temperatures and discharge multipliers and outperforms natural convection. Even in the harsh environment of 40 °C and 3 C, the maximum temperature (Tmax) and Tmax difference (ΔTmax) of the CPCM-cooled module are 61.38 and 2.67 °C, which are 22 and 9 °C below the natural air-cooled module. Remarkably, the ΔTmax of the CPCM-cooled battery module in discharge decreases with the temperature rise at the discharge rate of 3 C, which is the exact opposite to the case of the air-cooled module. Moreover, the ΔTmax of CPCM-cooled module is 1.69, 1.84, 2.67 °C, all below the safe 5 °C at high temperatures (40 °C) as the discharge rate increases. The designed MOF-CPCM cooling system can effectively improve the temperature uniformity and thermal safety of the battery in harsh environments. Therefore, this novel MOF-based CPCM shows great promise in BTM.

A Thermal Impedance Model for IGBT Modules Considering the Nonlinear Thermal Characteristics of Chips and Ceramic Materials

The traditional method of calculating junction temperature does not consider the dependence of a material’s thermal conductivity on temperature, in which the thermal conductivity changes with temperature. However, with an increase in junction temperature, the temperature sensitivity (TS) will have a more significant impact on the actual temperature of chips. This study established an improved IGBT equivalent thermal impedance model that considers the nonlinear characteristics of the TS of chips and ceramic materials. The Fourier series analysis method was used to obtain the heat flux density curve, and then the heat diffusion angles of each layer were solved. Moreover, iterations were performed until the thermal conductivity and temperature of the chip and ceramic layers matched the nonlinear characteristics of the TS. When the power loss was less than 200 W, the maximum error of the junction temperature calculated by the proposed method considering TS was 3%, while the maximum error of the method without considering TS was 9.5%. Compared with the finite element simulation, the proposed method has a faster solving speed and high accuracy. The proposed method only requires the input material parameters, size parameters, and boundary conditions to solve the junction temperature, which has strong practicality and high accuracy.

Sympathetic transduction to blood pressure in patients with chronic kidney disease.

Patients with chronic kidney disease (CKD) are more than twice as likely to die from a cardiovascular event than those with normal kidney function. Although CKD may increase resting sympathetic activity, quantification of resting sympathetic outflow alone does not account for the ensuing vasoconstriction, and blood pressure (BP) change (i.e., sympathetic transduction). Patients with CKD have been reported to exhibit elevated α-adrenergic receptor sensitivity, which may predispose this population to greater sympathetic transduction. We tested the hypothesis that patients with CKD have augmented sympathetic transduction to BP. In 16 patients with CKD, 17 bodyweight-matched (BWM) controls, and 11 lean controls of a similar age muscle sympathetic nerve activity (MSNA) and beat-to-beat BP were continuously recorded during quiet supine rest. Signal averaging was used to quantify changes in mean arterial pressure (MAP) and total vascular conductance (TVC) following spontaneous bursts of MSNA. Peak increases in MAP following MSNA bursts were not different among patients with CKD and the control groups (CKD: 2.3 ± 1.1mmHg; BWM controls: 2.1 ± 1.0mmHg; lean controls: 1.7 ± 0.9mmHg; P = 0.28). Likewise, nadir reductions in TVC following all bursts of MSNA were not different among patients with CKD and either control group (P = 0.69). Both patients with CKD and controls had graded increases in MAP and decreases in TVC with increasing burst size, which were not different among groups (all P > 0.05). In summary, these data indicate that patients with CKD do not have augmented sympathetic transduction to BP.

Corrugated veneer panel thermophysical properties

The article substantiates the need to develop new mechanisms for the hardwood use in modern conditions of Republic of Karelia timber industry. One of the potential uses of birch wood in wooden house construction is building materials production from veneer and slab materials based on it. A large amount of associated waste from processing birch wood into veneer stands out as one of the key problems. A new slab joinery and construction material made of corrugated birch veneer is considered. The purpose of this study is to evaluate the thermophysical properties of a corrugated board made of birch wood. To achieve this goal, the tasks and methods of research are defined. An experimental device has been developed to conduct an experiment to determine the values of thermophysical characteristics. DS18B20 temperature sensors were used to measure the surface temperature, as well as to monitor device operation and the room air temperature. The sensors are connected to the Arduino microcontroller platform, which was used to record and transmit sensor readings. Additionally, the course of the experiment was monitored using a thermal imager Testo 875-1i. During the experiment, more than 1000 measurements were carried out. As a result of data processing, a diagram of the dependence of the density of the heat flux passing through the sample on time, as well as diagrams of the dependence of thermal conductivity and thermal resistance on the temperature difference on the sample surfaces, was obtained. The diagrams show the regression dependences of changes in heat flux density, thermal conductivity and thermal resistance during measurements. The values of the heat flux density, thermal conductivity coefficient and thermal resistance calculated on the basis of regression equations and the values obtained experimentally are determined. The directions of further research of the material under consideration are determined.

Unraveling the origin of conductivity change in Co-doped FeRh phase transition

Unraveling the origin of conductivity change in Co-doped FeRh phase transition

Temperature and state-dependent electrical conductivity of soft biological tissue at hyperthermic temperatures

Objective: We present a physics-based, temperature and state-dependent electrical conductivity model for soft biological tissue under thermal therapies with a quantified damage parameter that represents the state of soft biological tissue (degree of denaturation). Most existing models consider electrical conductivity to be only temperature-dependent and evaluate tissue damage during post-processing after temperature calculation. Our model allows tissue damage to be coupled into the thermal model for a more accurate description of both RF ablation and electrosurgery. Methods: We model the denaturation process with an Arrhenius-type differential equation for chemical kinetics and a modified Stogryn equation for electrical conductivity under state transition. We present experimental data from two types of heating procedures at 128 kHz to validate and showcase the capability of our model. Results: Our model is able to capture the change in electrical conductivity during heating, cooling, and reheating procedures, which distinguishes different states and shows the irreversibility of denaturation. The model also accurately captures tissue change during slow cooking at a constant temperature, highlighting a state dependence. Conclusion: By incorporating state dependence into the model for electrical properties, we are able to capture the denaturation process more accurately and distinguish different degrees of damage. Our model allows the modeling of procedures involving repeated heating or cooling, which is impossible for models without a state dependence. While being able to adapt to patient-specific needs, the model can be used to improve planning and control in future robot-assisted surgeries to reduce unnecessary damage.

Gadolinium-Sensitive Artificial Nanochannel Membrane for Information Encryption.

Inspired from ion channels in the myelinated axon of Xenopus laevis found to be affected by gadolinium on axonal currents, we present a solid nanochannel membrane sensitive to gadolinium (Gd3+), which can be achieved via the use of the macrocyclic triacetic acid derivative in the host-guest chemistry approach. The macrocyclic nanochannel has good responsiveness toward Gd3+, even at the nanomolar concentration level, evidenced by discernible changes in rectification, ionic conductance, and XPS analyses. Notably, the Gd3+-sensitive nanochannel membrane can be switched by the addition of a diethylenetriaminepentaacetic acid (DTPA) derivative. Further studies have indicated that the gated behavior of Gd3+ in the nanochannel can be attributed to the strong binding strength between DO3A and Gd3+, which induces a surface charge reversal within the nanochannel. The mechanism has been confirmed through several experimental techniques, including isothermal titration calorimetry (ITC) experiments, fluorescence titration experiments, and finite element analysis. Based on its Gd3+ responsiveness of the constructed ion channel, we successfully developed an advanced multilevel information encryption application of the artificial solid nanochannel membrane. Furthermore, it is anticipated that a more effective encryption system will be built by utilizing the bionic ion channel system's ease of use and straightforward functionalization.

McArdle sign and neck flexion-induced change in central motor conduction in multiple sclerosis.

Rapidly reversible weakness with neck flexion (McArdle sign) is common in patients with multiple sclerosis (MS). The pathophysiology is unknown. To evaluate changes in central motor conduction time (CMCT) in patients with and without McArdle sign. We measured McArdle sign with a torque cell and CMCT with neck flexed and extended in patients with MS, other causes of myelopathy, and healthy controls. CMCT was prolonged with neck flexion disproportionately in those with MS-associated myelopathy (MSAM) with prominent McArdle sign compared to MS patients with lesser degrees of McArdle sign, and to controls. McArdle sign may result from stretch-induced slowing of conduction due to demyelination.

Core‐Shell Amorphous FePO4 as Cathode Material for Lithium‐Ion and Sodium‐Ion Batteries

AbstractAmorphous FePO4 (AFP) is a promising cathode material for lithium‐ion and sodium‐ion batteries (LIBs & SIBs) due to its stability, high theoretical capacity, and cost‐effective processing. However, challenges such as low electronic conductivity and volumetric changes seriously hinder its practical application. To overcome these hurdles, core‐shell structure synthesis emerges as a useful solution. In this work, we for the first time made this comprehensive review on the progresses of core‐shell amorphous FePO4 (CS‐AFP). This review summarizes 1) various synthesis methods such as template method, microemulsion method, and other methods, 2) characterization techniques, and 3) their involvement in improving electrochemical performance in LIBs and SIBs. In terms of further understanding the underlying mechanisms of advancing electrochemical performance of CS‐AFP, the future perspective on two main aspects were insighted: (i) in situ characterization and (ii) novel designs of materials and structure for CS‐AFP.

VOC Detection with Zinc Oxide Gas Sensors: A Review of Fabrication, Performance, and Emerging Applications

Energy‐efficient, high‐specificity gas sensors provide practical suitability for stability and response factors. The recognition of ignitable gases (methane (CH <sub>4</sub>), propane (C <sub>3</sub>H <sub>8</sub>), and hydrogen (H <sub>2</sub>) and harmful gases (carbon oxide (CO) and hydrogen sulfide (H <sub>2</sub>S)) in an enclosed and out‐of‐door space are essential to safeguard the human lives and infrastructural spaces. One of the crucial conductive‐type metal oxide semiconductor (MOS) gas sensors yielding wide applications is zinc oxide (ZnO). This study highlights the various types of ZnO gas sensors, their fabrication techniques, and specific vital characterizations. The devices based on MOS are utilized to sense various target gases through redox reactions. The variation in oxide surface with target gas interactions is transduced to a change of sensor conductance. This review also provides insight into integrating ZnO gas sensors with technologies such as materials engineering, the Internet of things and big data. Moreover, this review addresses ZnO gas sensors' challenges and future directions.

Tailoring the Optical and Color Properties of Gamma Irradiated Polycarbonate/Cerium Oxide Nanocomposite Films for Their Application in Optoelectronic Devices

Nanocomposites (NC) of amorphous polycarbonate (PC) and cerium oxide (CeO2) nanoparticles (NPs) were prepared. The synthesized CeO2 had a nanonature of average particle size 22 nm, as indicated from their high resolution transmission electron microscopy images (HTEM). Samples of the PC/CeO2 NC films were irradiated with several γ ray doses (10-80 kGy). The resultant outcome of the γ irradiation on the optical properties of the NC films was studied using ultraviolet spectroscopy (UV-vis). Upon raising the γ ray dose up to 80 kGy, the maximum dose used, the direct bandgap decreased from 4.92 to 3.91 eV. The Urbach energy showed an opposite trend; it increased from 0.46 to 0.92 eV. This could be attributed to the domination of chain crosslinks. Also, the optical dielectric loss (ε”) assisted in identifying the nature of the microelectronic transitions. It was found that the PC/CeO2 NC films had direct allowed transitions. Additionally, the γ induced changes in the optical conductivity were studied. Moreover, the optical color changes between the pristine and the irradiated films were evaluated. The pristine NC film was uncolored. It showed significant color changes when irradiated with γ radiation up to 80 kGy. The induced modifications in the optical properties suggest that the γ radiation is an effective means for modifying the properties that allows the use of PC/CeO2 NC in optoelectronic devices.

Pressure-regulated rotational guests in nano-confined spaces suppress heat transport in methane hydrates

Materials with low lattice thermal conductivity are essential for various heat-related applications like thermoelectrics, and usual approaches for achieving this rely on specific crystalline structures. Here, we report a strategy for thermal conductivity reduction and regulation via guest rotational dynamics and their couplings with lattice vibrations. By applying pressure to manipulate rotational states, we find the intensified rotor-lattice couplings of compressed methane hydrate MH-III can trigger strong phonon scatterings and phonon localizations, enabling an almost three-fold suppression of thermal conductivity. Besides, the disorder in methane rotational dynamics results in anharmonic interactions and nonlinear pressure-dependent heat transport. The overall guest rotational dynamics and heat conduction changes can be flexibly regulated by the rotor-lattice coupling strength. We further underscore that this reduction mechanism can be extended to a wide range of systems with different structures. The results demonstrate a potentially universal method for reducing or controlling heat transport by developing a hybrid system with tailored molecular rotors.

Transcriptomic Profile of Tef (Eragrostis tef) in Response to Drought.

The threat to world food security posed by drought is ever increasing. Tef [Eragrostis tef (Zucc.) Trotter] is an allotetraploid cereal crop that is a staple food for a large population in the Horn of Africa. While the grain of tef provides quality food for humans, its straw is the most palatable and nutritious feed for livestock. In addition, the tef plant is resilient to several biotic and abiotic stresses, especially to drought, making it an ideal candidate to study the molecular mechanisms conferring these properties. The transcriptome expression of tef leaf collected from plants grown under drought conditions was profiled using RNA-Seq and key genes were verified using RT-qPCR. This study revealed that tef exhibits a complex molecular network involving membrane receptors and transcription factors that regulate drought responses. We identified target genes related to hormones like ABA, auxin, and brassinosteroids and genes involved in antioxidant activity. The findings were compared to physiological measurements such as changes in stomatal conductance and contents of proline, chlorophyll and carotenoid. The insights gained from this work could play vital role in enhancing drought tolerance in other economically important cereals such as maize and rice.

Evaluate the potential adsorption of graphynes (perfect and doped) for nitrogen mustard gas: A first principles study

Density functional theory (DFT) calculations are used to thoroughly examine the reactivity and electronic sensitivity of pristine and BN-doped graphyne (BNG) toward nitrogen mustard (NM). Graphyne’s electrical conductivity is unaffected by the weak adsorption of NM, which occurs via the Cl atom on the material with an adsorption energy of roughly −3.1 kcal.mol−1. In addition to decreasing graphyne’s reactivity and work function, substituting isoelectronic BN linkages for CC linkages enhances the HOMO-LUMO energy gap (Eg). BNG’s electrical conductivity increases when Eg drops from 2.99 to 1.82 eV due to the adsorption of NM. Additionally, a significant change in BNG’s work function results in a variation in the field electron emission current. Lastly, it is anticipated that the desorption of NM from the BNG surface will take a brief recovery time of roughly 0.05 s at room temperature. It has also been demonstrated that NM concentration affects changes in electrical conductivity. The findings also suggest that BNG could be a promising NM sensor.

NiS2/FeS2 binary nanoparticles confined in interconnected carbon framework with regulated pore structure enabled by citric acid for enhanced sodium storage properties

Recently, pyrite iron disulfide (FeS2) has emerged as a promising anode candidate for sodium-ion batteries (SIBs) due to its high theoretical capacity, affordability, non-toxicity and abundant resource in nature. However, the utilization of FeS2 still confronts the challenges of inferior rate capability and cycling instability for sodium storage, stemming from its low electronic conductivity and substantial volume changes during cycling. Herein, to address these obstacles, NiS2/FeS2 binary nanoparticles encapsulated within a network of interconnected N-doped porous carbon framework (NiS2/FeS2@NPC) are prepared by a successive solid-state ball milling, carbonization and sulfurization strategy with coordination complex of nickel iron Prussian blue analogue (NiFe-PBA) as precursor. The introduction of citric acid plays a critical role for the formation of interconnected carbon framework with regulated internal porous structure, thereby achieving heterostructured NiS2/FeS2@NPC with modulated specific surface area and pore volume. The rational design of interconnected N-doped porous carbon framework and heterogeneous structure guarantees rapid ion/electron transport kinetics, alleviated mechanical stress, and enhanced structural integrity. Benefitting from these advantages, the optimal NiS2/FeS2@NPC-1 electrode exhibits a high reversible capacity (545 mAh/g at 1 A/g), superior rate capability (267 mAh/g at 5 A/g) and ultrastable long-term cycling performance (98.5 % retention over 1000 cycles at 5 A/g). This study presents a novel and efficient design approach for creating durable and high-rate anode materials based on metal sulfides for SIBs.

High-performance flexible CoFe2O4/N-doped carbon nanofiber composite anode materials for sodium-ion batteries

Graphite is traditionally used as an anode material but is unsuitable for use in sodium-ion batteries because it has a low specific capacity and poor safety characteristics, it is therefore necessary to develop alternative anode materials. Flexible CoFe2O4 nanoparticle/N-doped carbon nanofiber films were prepared by electrospinning and calcination. The advantages of this process included inexpensive starting materials, easy preparation, and suitability for commercialization. The inherent shortcomings of CoFe2O4, such as poor electronic conductivity and large changes in volume, were mitigated via elemental doping and the formation of composites with high-quality carbon materials. Nitrogen-doped carbon nanofibers with large specific surface areas and superior mechanical properties were used as the supporting skeleton of the material. These nanofibers limited the volume expansion of CoFe2O4 throughout the cycling process and increased the ion diffusion velocity in the material. The optimal integration of nanoscale CoFe2O4 particles, which possess a higher theoretical specific capacity, with a nitrogen-doped carbon nanofiber conductive framework featuring a crosslinked three-dimensional structure facilitated the infiltration of the electrolyte into the electrode. This integration reduced the diffusion distance of sodium ions and effectively reduced the volume expansion of the material, as well as damage to the material during the electrochemical reaction. After 200 cycles at a current density of 0.1 A g−1, it provided a high sodium storage capacity of 365.7 mA h g−1. The capacity was maintained at 176.3 mA h g−1 even at a high current density of 2 A g−1. Exhibits good cycle stability.

The Effect of Eco-Friendly Deicing Agents Containing Humic Acid on Plant Growth

Objectives:In this experiment, we used an environmentally friendly snow removal agent containing calcium chloride (CaCl2) and humic acid (HA) to alleviate salt stress on chili pepper seedlings, and analyzed its effect on plant growth. As an alternative to minimize the negative effects of existing chloride-based snow removal agents on plants and soil, we investigated whether humic acids contribute to improving plant physiological responses and soil electrical conductivity (EC). Evaluated.Methods:For 21 days, we set up a control group (Count.), a calcium chloride treatment group (CaCl2), a humic acid treatment group (HA), and a mixed treatment group (HUA2, HUA5, HUA10) in which humic acid and calcium chloride were mixed. The growth of stems and roots was measured. In addition, the high mortality rate of leaves and changes in soil electrical conductivity (EC) were measured to evaluate the effect of alleviating salt stress.Results and Discussion:As a result of the experiment, stem length increased in the control group, humic acid treatment group (HA), and humic acid and calcium chloride mixed treatment groups (HUA2, HUA5, HUA10), and the greatest growth was observed in HUA5 among the mixed treatment groups. On the other hand, in the calcium chloride treatment group (CaCl2), stem growth did not occur and the high leaf mortality rate was 66.7%, which had a negative effect on growth. The soil EC value was lowest at 0.21mS/cm in the humic acid only treatment group (HA) and highest at 1.25mS/cm in the calcium chloride treatment group (CaCl2). In the mixed treatment group, the EC value tended to decrease as the humic acid concentration increased. This indicates that humic acid can play a role in reducing salt stress and promoting plant growth.

Boosting the Photoresponse of Azobenzene Single-Molecule Junctions via Mechanical Interlock and Dynamic Anchor.

As the most classic photoisomerization system, azobenzene has been widely utilized as a building unit in various photoswitching applications. However, attempts to build azobenzene-based single-molecule photoswitches have met with limited success, giving low on/off ratios. Herein, we demonstrate two designs of azobenzene-based photoresponsive single-molecule junctions, based on mechanically interlocked diazocine and azobenzene-based dynamic anchors, respectively. Molecular conductance measurements using the scanning tunneling microscope breaking junction (STMBJ) technique revealed dramatic conductance changes upon photoillumination, achieving a high on/off ratio of ∼3.7. Using density functional theory (DFT), we revealed peculiar quantum interference (QI) effects in the diazocine molecular switch, indicating that diazocine is an excellent candidate for molecular photoswitches. The asymmetric azobenzene devices with a dynamic anchor exhibit switching behavior between a fully off state and a highly conductive state associated with the trans/cis conformation transition. The findings of this work not only present the design and development of functional molecular devices based on azobenzene units but also provide insight into the fundamental properties of light-induced quantum interference in azobenzene-based molecular devices.

Adsorption Properties of Metal Atom (Co, V, W, Zr)-Modified MoTe2 for CO, CH3CHO, and C6H6 Gases: A DFT Study.

This study investigates the adsorption characteristics of the pristine MoTe2 monolayer and the metal atom (Co, V, W, Zr)-modified MoTe2 monolayer on the hazardous gases CO, CH3CHO, and C6H6 based on the density functional theory. The adsorption mechanism was studied from the perspectives of molecular density differences, band structures, molecular orbitals, and the density of states. Research analysis showed that the changes in conductivity caused by the adsorption of different gases on the substrate were significantly different, which can be used to prepare gas sensing materials with selective sensitivity for CO, CH3CHO, and C6H6. This study lays a reliable theoretical foundation for the gas sensing analysis of toxic and hazardous gases using metal atom-modified MoTe2 materials.