Average Conductivity Research Articles

Internal loading of phosphorus in streams described by a Sediment-Water Exchange Model for Phosphorus (SWEMP): From lab to field scale

The reaction of phosphorus (P) between sediments and water in streams strongly affects the surface water P concentrations. A new reactive transport model (SWEMP: Sediment-Water Exchange Model for Phosphorus) was developed to describe redox dependent P sorption in the sediment and vertical diffusive transport of solutes to the overlying stream. The model parameters were independently obtained to first predict P release in ten different sediment-water batch systems and in two flumes. Input parameters are the degree of P saturation of the sediment, its organic matter content, dissolved oxygen (DO) concentration and temperature. The dissolved P concentrations in the overlying waters ranged from 0.02 to 1.2 mg P L−1 in these systems and were correctly predicted by the model within, on average, a factor 1.3 (batch) or 1.1 (flume). The P flux from the sediment towards the overlying water increased with increasing sediment P:Fe ratio and respiration rates, and with decreasing DO and water pH. After validation of the model with experimental data, it was used to predict monthly P concentrations in Flemish rivers using the total P emission data, total discharge, average sediment properties and the monthly averaged water temperatures, DO concentrations and electric conductivity. The monthly average P concentrations oscillate annually between 0.24 and 0.73 mg P L−1 and predictions matched the long-term monitoring data within 10 % using only one adjustable parameter for the entire water system (N > 250,000). The model predicts that summer peaks in P are related to internal loading from the sediment under anoxic conditions rather than to emission-dilution effects, i.e. external input of P and/or its concentration at lower flow rates. This suggests that, surface water P concentrations can be lowered by enhanced DO in the water, the addition of Fe and Al rich binding agents to the sediments and by reducing P emissions.

Acoustic and thermal performance of luffa fiber panels for sustainable building applications

Sound-absorbing and thermal-insulating materials have a noteworthy role in the performance of buildings. In recent years, there has been a significant focus on utilizing natural fibers as construction materials for thermal insulation and sound absorption purposes. In this study, luffa, an abundant and eco-friendly natural fiber, was explored as a sustainable material with potential high acoustic and thermal performance due to its intrinsic hollow and sponge-like structure. The experiments were designed using the response surface method based on central composite design (RSM-CCD) to find the best combination of input variables including thickness, density, and binder content for optimal performance. The sound absorption average (SAA) and effective thermal conductivity (Keff) values of the panels ranged from 0.16-0.68, and 0.033–0.054 W/(mK), respectively. It was found that both the SAA and Keff are significantly influenced by thickness and density, while binder content does not have a significant effect. The optimal condition for fabricating luffa panels was found to be a thickness of 40 mm, density of 225 kg/m3, and binder content of 7.5 %. Furthermore, the acoustic characteristics of the optimized panels were examined in a conference hall using the Odeon software. The acoustic absorption properties of panels were also predicted using the Johnson–Champoux–Allard and Attenborough models.

Design and investigation of cold storage material for large-scale application in supercritical compressed air energy storage system

The compressed air energy storage is widely studied as promising large-scale energy storage technology. This study focus on the design and investigation of cold storage material for large-scale application in supercritical compressed air energy storage system. Different kinds of cold storage materials for supercritical compressed air energy storage system are comparatively analyzed at first, and the sodium chloride is selected as the suitable cold storage material for supercritical compressed air energy storage system. Meanwhile, the thermal and mechanical properties of suitable sodium chloride particle are measured. The results show that the density of sodium chloride particle is 2.1589 g/cm3. The average specific heat and thermal conductivity of sodium chloride particle are 0.81 J/(g·K) and 5.8576 W/(m·K) in the test temperature range. In addition, the average values of Mohs hardness and Vickers hardness of processed sodium chloride particles are 3 Mohs and 11.7 HV, respectively. The maximum compressive strength of sodium chloride samples tested at −196 °C and 20 °C are 6.25 MPa and 24.45 MPa, respectively. Furthermore, the abradability of sodium chloride particles are tested, the mass loss rate of sodium chloride particles is 0.11 %. The cold storage performance of the designed and processed sodium chloride particle cold storage materials is numerically simulated. The average temperature of sodium chloride particles gradually decreases from 293.15 K to 119.26 K, which can storage 37,128.57 kJ cold energy in total. This work can provide basic data for the further cold storage material research of supercritical compressed air energy storage system.

Sunflower and Watermelon Seeds and Their Hybrids with Pineapple Leaf Fibers as New Novel Thermal Insulation and Sound-Absorbing Materials.

Pineapple leaf fiber (PALF), striped sunflower seed fiber (SFSF), and watermelon seed (WMS) are considered natural waste polymer materials, which are biodegradable and sustainable. This study presents new novel thermal insulation and sound absorption materials using such waste as raw materials. PALF, SFSF, and WMS were used as loose, bound, and hybrid samples with different compositions to develop promising thermal insulation and sound-absorbing materials. Eleven sample boards were prepared: three were loose, three were bound, and five were hybrid between PALF with either SFSF or WMS. Wood adhesive was used as a binder for both the bound and hybrid sample boards. Laboratory scale sample boards of size 30 cm × 30 cm with variable thicknesses were prepared. The results show that the average thermal conductivity coefficient for the loose samples at the temperature range 20-80 °C is 0.04694 W/(m.K), 0.05611 W/(m.K), and 0.05976 W/m.K for PALF, SFSF, and WMS, respectively. Those for bound sample boards are 0.06344 W/(m.K), 0.07113 W/(m.K), and 0.08344 W/m.K for PALF, SFSF, and WMS, respectively. The hybrid ones between PALF and SFSF have 0.05921 W/m.K and 0.06845 W/(m.K) for two different compositions. The other hybrid between PALF and WMS has 0.06577 W/(m.K) and 0.07007 for two different compassions. The sound absorption coefficient for most of the bound and hybrid boards is above 0.5 and reaches higher values at some different frequencies. The thermogravimetric analysis for both SFSF and WMS shows that they are thermally stable up to 261 °C and 270 °C, respectively. The three-point bending moment test was also performed to test the mechanical properties of the bound and hybrid sample boards. It should be mentioned that using such waste materials as new sources of thermal insulation and sound absorption materials in buildings and other applications would lead the world to utilize the waste until zero agrowaste is reached, which will lower the environmental impact.

Ultrathin MXene film interaction with electromagnetic radiation in the microwave range

The quick progress in communication technologies demands superior electromagnetic interference (EMI) shielding materials. However, achieving a high shielding effectiveness (SE) with thin films, which is needed for microscale, flexible, and wearable devices, through absorption of EM radiation remains a challenge. 2D titanium carbide MXene, Ti3C2Tx, has been shown to efficiently reflect electromagnetic waves. In this paper, we investigated the electromagnetic shielding of ultrathin printed Ti3C2Tx films and recorded absorption up to 50% for 4 nm-thick films. This behavior is explained by impedance matching. Analysis of the sheet impedance in the X-band frequency range allows us to correlate the EMI shielding mechanism with the electrical conductivity measured within the same range. The average bulk in-plane conductivity for 4 to 40 nm-thick films reaches 106 S/m, while the average relaxation time is estimated at around 2.3 ps. Our figures of merit are similar to those reported for ultrathin metal films, such as gold, showing that an abundant MXene material can replace noble metals. We demonstrate that the MXene conductivity mechanism does not change from direct current to THz. The conventional method of reporting EMI SE is correlated with absolute values of transmitted, reflected, and absorbed power, which allows us to interpret previous results on MXene EMI shielding. Considering the easy deposition of thin MXenes films from solution onto a variety of surfaces, our findings offer an attractive alternative for shielding microscale devices and personal electronics.

Study on performance and mechanism of foamed ceramics based on lead fuming furnace slag

This paper proposes a new method for preparing lightweight and thermally insulated foamed ceramics via direct high-temperature foaming using lead fuming furnace slag as the major material, quartz sand as the texturizer, borax as the flux, and AlN as the foaming agent. The effects of the chemical composition and sintering process parameters on the crystalline phase transformation, pore structure, and properties of the foamed ceramics were investigated. The foaming mechanism during sintering was also examined using TG-DSC analysis and pore morphology analyses. These results indicate that the slag content strongly affects the formation of the pore structure. Different sintering parameters can modify the pore structure, and a single crystalline phase (CaSiO3) was generated during the sintering process. Under the optimum conditions, the foamed ceramics showed the best overall performance with the bulk density, apparent porosity, average pore size, thermal conductivity, and compressive strength of 0.221 g cm−3, 84.53 %, 1.10 mm, 0.1100 W/(m·K), and 2.52 MPa, respectively. Its excellent porous structure and low thermal conductivity make it suitable as a thermal insulation material in building partition walls.

Optimizing the Heat Loss from an Insulation Material and Boundary Layer Thickness of Airflow through a Hot Plate Using Nonlinear Least-Squares Error and Linear Programming Algorithms.

Heat loss is a major challenge in heat transfer problems. Several researchers have minimized heat loss for different heat transfer cases, focusing on one optimization technique; however, not all optimization techniques are suitable for a given problem. A limited number of studies have compared different techniques for a given problem under boundary conditions and constraints. This review revisits basic heat transfer problems and identifies a promising technique for each problem to minimize heat loss. The paper considers three techniques: nonlinear least-squares error (LSE), interior point linear programming (IPLP), and genetic algorithm. Two cases are studied: 1. heat loss optimization from cylindrical insulating surfaces and 2. laminar airflow on a heated plate. The results are compared for each technique, and a suitable technique is recommended for each considered case. Nonlinear LSE is found to be most suitable for case 1. IPLP and GA are recommended for the Case 2 problem. The average thermal conductivity is found to be 0.081 W/mK. The average insulation thickness is found to be 213.25 mm. This research will act as a basis for future research to justify and implement suitable techniques for different heat transfer problems.

Interannual variability of soil thermal conductivity and moisture on the Abernethy Flats (James Ross Island) during thawing seasons 2015–2023

The knowledge of soil thermal properties is important for determining how a soil will behave under changing climate conditions, especially in the sensitive environment of permafrost affected soils. This paper represents the first complex study of the interplay between the different parameters affecting soil thermal conductivity of soils in Antarctica. Antarctic Peninsula is currently the most rapidly warming region of the whole Antarctica, with predictions of this warming to continue in the upcoming decades. This study focuses on James Ross Island, where the Abernethy Flats automatic weather station is located in a lowland area with semi-arid climate. Air and ground temperature, soil heat flux and soil moisture during the thawing season were monitored on this site from 2015 to 2023. Moreover, two approaches to determining soil thermal conductivity were compared – laboratory measurements and calculation from field data. During this period, mean annual temperatures have increased dramatically for both air (from −6.9 °C in 2015/2016 to −3.8 °C in 2022/2023) and ground (from −6.5 °C to −3.2 °C), same as active layer thickness (from 68 cm to 95 cm). Average soil thermal conductivity for the thawing period reached values between 0.49 and 0.74 W/m.K−1 based on field data. Statistically significant relationships were found between the seasonal means of volumetric water content and several other parameters – soil thermal conductivity (r = 0.91), thawing degree days (r = −0.87) and active layer thickness (r = −0.88). Although wetter soils generally have a higher conductivity, the increase in temperature exhibits a much stronger control over the active layer thickening, also contributing to the overall drying of the upper part of the soil profile.

Study on the pump schedule impact in hydraulic fracturing of unconventional reservoirs on proppant transport law

In unconventional reservoir hydraulic fracturing, using a pump schedule with proppant concentration constant (PCC) instead of the proppant concentration stepwise increasing (PCSI) is considered an innovative approach to reduce operation costs and risks. However, the large-scale application of PCC lacks sufficient theoretical support. This study investigates the impact of two pump schedules on proppant transport behavior through visualized proppant transport experiments and the model that couples fracture propagation with proppant transport. The experiments demonstrate that PCC facilitates proppant transport and reduces flow fluctuations in complex fractures, while PCSI enhances the filling of near-well fractures. The proppant concentration (the ratio of proppant volume to fracturing fluid volume) reaches 20 % or when a combination of 40/70-mesh and 20/40-mesh quartz sands is used for injection, the pump schedule influence becomes negligible. An increase in fracture complexity, proppant size, and proppant concentration all lead to a reduced influence of the pump schedule on the dune shape. Numerical simulation reveal that the fracture area and average fracture conductivity is similar for different pump schedules, but PCC yields a slightly larger propped fracture area (ranging from 1 % to 4 %) and results in a more uniform conductivity. PCC could achieve similar fracture filling when the proppant concentration is more than 15 % or there is no significant demand for near-well conductivity. Overall, both two pump schedules have a relatively insignificant impact on the transport process of proppants and the final sand dune shape. By comparing pressure curves during hydraulic fracturing, it was evident that PCC resulted in fewer fluctuations. Analyzing production data from 93 wells with PCSI and 59 wells with PCC, it was observed that PCC enhances production and reduces proppant flowback post-fracturing. This research provides a theoretical foundation for the application of PCC pump schedule in hydraulic fracturing.

Preparing large-scale, uniform, and high-performance Cu–Cr–Zr strips by a novel continuous expanding extrusion process

A novel continuous expanding extrusion process for manufacturing Cu–Cr–Zr strips was proposed in the present study. The U-shaped strips with a cross-section of 420 mm × 19 mm were successfully prepared by taking the upward continuous casted Φ 28 mm rods as raw material. Electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) were employed to characterize the microstructure and precipitates, respectively, which revealed that the microstructure of the continuous extruded strip is very fine and uniform across the entire cross-section and the Cr precipitates are in a dispersed distribution in the matrix helping to improve the strength of the alloy. The average grain size is approximately 1 μm and much smaller than that of the as-cast state (in millimeters). The average micro-hardness, tensile strength, and electrical conductivity of the extruded strip are 120 HV, 328.8 MPa, and 82.6 % IACS, respectively, increasing approximately by 31.6 %, 29.3 %, and 125.5 % in comparison to these of the as-cast state. In addition, the fracture elongation can maintain a very high level (average value ∼28.9 %). The strengthening mechanisms were then quantitatively calculated, which showed that grain boundary strengthening, precipitation strengthening, and dislocation strengthening take comparable contributions. Thus, our investigations provide new insights into manufacturing high-performance Cu–Cr–Zr strips.

Conductive 3D nano-biohybrid systems based on densified carbon nanotube forests and living cells

Conductive biohybrid cell-material systems have applications in bioelectronics and biorobotics. To date, conductive scaffolds are limited to those with low electrical conductivity or 2D sheets. Here, 3D biohybrid conductive systems are developed using fibroblasts or cardiomyocytes integrated with carbon nanotube (CNT) forests that are densified due to interactions with a gelatin coating. CNT forest scaffolds with a height range of 120–240 µm and an average electrical conductivity of 0.6 S/cm are developed and shown to be cytocompatible as evidenced from greater than 89% viability measured by live-dead assay on both cells on day 1. The cells spread on top and along the height of the CNT forest scaffolds. Finally, the scaffolds have no adverse effects on the expression of genes related to cardiomyocyte maturation and functionality, or fibroblast migration, adhesion, and spreading. The results show that the scaffold could be used in applications ranging from organ-on-a-chip systems to muscle actuators.Graphical abstract

Determination of Bayındır Dam Lake (Ankara) Zooplankton Fauna

Zooplankton samples were collected from four stations in Bayındır Dam Lake between April 2022 and January 2023 using a 60 μm plankton net with horizontal and vertical hauls, and some water quality parameters (water temperature, pH, dissolved oxygen, and conductivity) were determined in-situ. The annual mean water temperature, dissolved oxygen, pH and conductivity were 17.64±7.64 °C, 7.92±0.18 mgL-1, 9.26±1.00 mgL-1, 368.52±24.69 µS cm-1 respectively. Water quality parameters were within normal limits for most aquatic organisms. A total of 87 species were recorded in the reservoir, including 66 rotifers (75.86%), 15 cladocerans (17.24%) and 6 copepods (6.90%). A total of 22 families from Rotifera, 5 families from Cladocera and 2 families from Copepoda were recorded. Brachionidae and Lecanidae (Rotifera) having most of the species were the richest families with 10 species each. With 8 Chydoridae species from Cladocera and 5 Cyclopoidae species from Copepoda, they were discovered to be the most numerous family. It was determined that the dam lake zooplankton consisted of widely distributed cosmopolitan and eutrophication indicator species.

Evaluation of geophysical parameters for groundwater productivity in the Commune of Jesse, Delta State Nigeria


 Aquifer geohydraulic properties in Jesse were studied by the application of vertical electrical sounding (VES) and pumping test. The VES data was collected using ABEM SAS 1000 Terrameter and results processed using manual matching of curves and computer iteration, and interpreted in the forms of geologic models and geoelectric layers. The aquiferous unit was found at a depth of 5.30 m to 30.30 m with a range of resistivity from 87.30 Ω-m to 1945.40 Ω-m. Dar-Zarrouk parameters estimation and results of borehole pumping test produced the aquifer hydraulic parameters. The hydraulic conductivity values range from8.171 - 8.279 m/day, transmissivity from 43.8770 - 517.7480 m2/day, and formation factor from 0.369 - 8.501. These results are indications of a prolific and high yielding aquifer capable of withstanding long duration of pumping. Results of groundwater electrical conductivity and total dissolved solids ranged from 11.65 - 198.80 μs/cm, and 29.40 - 35.40 mg/dm3 respectively, signifying very moderate mineralization of the groundwater. The average electrical conductivity of 68.04 μS /cm and total dissolved solids of 32.58 mg/L were lesser than the acceptable limits of the Nigerian Standard for Drinking Water Quality (NSDWQ) of 1000 μS/cm and 500 mg/L respectively. This study affirmed that the aquifer in Jesse is suitable for groundwater exploitation for local and regional purposes.

Optimization of Irrigation of Wine Grapes with Brackish Water for Managing Soil Salinization

Water scarcity and quality are critical impediments to sustainable crop production. In this study, HYDRUS-2D was calibrated using field measurements of water contents and salinities in the soil under wine grapes irrigated with river water (Rw, 0.32 dS/m). The calibrated model was then used to evaluate the impact of (a) four different water qualities ranging from 0.32 (Rw) to 3.2 dS/m (brackish water, Gw) including blended (Mix) and monthly alternating (Alt) irrigation modes; (b) two rainfall conditions (normal and 20% below normal); and (c) two leaching options (with and without 30 mm spring leaching irrigation) during the 2017–2022 growing seasons. Irrigation water quality greatly impacted root water uptake (RWU) by wine grapes and other water balance components. Irrigation with brackish water reduced average RWU by 18.7% compared to river water. Irrigation with blended water or from alternating water sources reduced RWU by 8.8 and 7%, respectively. Relatively small (2.8–8.2%) average annual drainage (Dr) in different scenarios produced a very low (0.05–0.16) leaching fraction. Modeling scenarios showed a tremendous impact of water quality on the salts build-up in the soil. The average electrical conductivity of the saturated soil extract (ECe) increased three times with Gw irrigation compared to Rw (current practices). Blended and alternate irrigation scenarios showed a 21 and 28% reduction in ECe, respectively, compared to Gw. Irrigation water quality substantially impacted site-specific actual basal (Kcb act) and single (Kc act) crop coefficients of grapevine. Threshold leaching efficiency estimated in terms of the salt mass leached vs. added (LEs; kg/kg) for salinity control (LEs > 1) was achieved with LFs of 0.07, 0.12, 0.12, and 0.15 for the Rw, Mix, Alt, and Gw irrigations, respectively. Applying annual leaching irrigation (30 mm) before bud burst (spring) in the Mix and Alt with Rw and Gw scenarios was found to be the best strategy for managing irrigation-induced salinity in the root zone, lowering the ECe to levels comparable to irrigation with Rw. Modeling scenarios suggested that judicious use of water resources and continuous root zone monitoring could be key for salinity management under adverse climate and low water allocation conditions.

Evaluation of Two Chilean Native Macroalgae: “Pelillo” (Gracilaria chilensis) and “Lamilla” (Ulva sp.) for Thermal Insulation Application

Energy consumption in the residential sector and air pollution are relevant topics for the global population. One of the causes, especially in cold climate cities, is that buildings maintain a high energy consumption for heating and cooling, primarily using low-efficiency biomass combustion for heating, which releases a significant amount of particulate matter into the environment. In this context, thermal insulation materials play a crucial role in reducing the energy demand of buildings, requiring advancements in the sustainable development of such materials within the context of climate change. This study carried out an evaluation of two algae species found along the Chilean coasts, with the aim of characterizing them and creating a prototype of a sustainable material. Their physicochemical properties were analyzed, and the results demonstrate that the algae exhibit excellent thermal insulation properties, with an average thermal conductivity of 0.036 [W/mK]. This result is comparable to expanded polystyrene (EPS), a widely used material in the Chilean and global markets, which has an average thermal conductivity value of 0.038 [W/mK]. Additionally, the algae show a good thermal stability, and their morphology contributes to the development of a bulk material, as they possess a porous structure with air chambers between the fibers.

Field demonstration of in-situ microemulsion flushing for enhanced remediation of multiple chlorinated solvents contaminated aquifer

The remediation of in-situ microemulsion flushing for multiple chlorinated solvents contaminated groundwater is challenging, because different chlorinated solvent has major influence on microemulsion formation and solubilization behaviors. This work was conducted to evaluate the remediation effectiveness for various chlorinated solvents contaminated site and monitor the disturbance of groundwater during in-situ microemulsion flushing process. Groundwater at this site was contaminated with chlorobenzene (MCB), chloroaniline and nitrochlorobenzene. The medium layer was mainly composed of fine and silty sand, with average hydraulic conductivity of 4.97 m/d. Results of this field-scale test indicated in-situ microemulsion flushing successfully enhanced the apparent solubility of various chlorinated solvents. Post-flushing concentration of various chlorinated solvents were 1.33–71.6-fold the concentration of pre-flushing values at 10 sampling locations within the test zone. This field was flushed with 16.8 m3 microemulsion, removing approximately 18.49 kg chlorinated solvents. Besides, a trend in the desorption order of various chlorinated solvents was observed. The least hydrophobic pollutant was flushed first, followed by contaminants of increasing hydrophobicity. In addition, during remediation process, the indexes of groundwater fluctuated insignificantly, indicating the reagent had little disturbance to aquifer. This field work demonstrated the feasibility of in-situ microemulsion enhanced remediation via increasing apparent solubility of multiple chlorinated solvents.

Disentangling carcass size and climate effects on soil biogeochemistry during decomposition

When an animal dies the decomposition of its carcass releases multiple compounds that become available to soil microbiota altering soil biogeochemistry. This zone of affected substrate is characterized by significant changes to numerous soil biogeochemical parameters including pH, conductivity, microbial respiration rates, dissolved organic carbon (DOC), C/N ratios, carbon and nitrogen stable isotopes (δ13C and δ15N), and major/trace elemental concentrations. Although the effects of animal decomposition on these parameters have been recorded for various organisms and in a variety of ecosystems several knowledge gaps remain, including: the effect of carcass size; and decomposition effects in prairie ecosystems (i.e., semi-arid climates). the effect of carcass size; and decomposition effects in prairie ecosystems (i.e., semi-arid climates). Here, we investigate how soil biogeochemical parameters are affected by the decomposition of a horse carcass (~660 kg) in a prairie ecosystem in comparison to beavers (~18 kg) in a temperate forest. Three parameters were identified as significantly influenced by carcass size: conductivity, DOC, and microbial respiration rate. Average soil conductivity underneath the horse carcass was three to fifteen times higher than control soils and reached a maximum at 1114 ADD, while maximum soil conductivity values were observed after 160 ADD in beaver-associated soils. Maximum DOC concentrations were observed after 160 ADD in beaver-associated soil (67 ± 40 mg C gdw-1) and after 1114 ADD in horse-associated soil (326 ± 115 mg C gdw-1). Microbial respirations rates were both greater in horse-associated soil and longer-lasting compared to beaver-associated soil. Respiration rates were greatest in two of the three horse-associated soils after 1114 ADD (~733 µg CO2-C gdw-1 day-1), which significantly differs compared to beaver-associated soils (300 ± 90 µg CO2-C gdw-1 day-1 at 160 ADD). Taken together, these results demonstrate that larger carcasses result in a greater release of decomposition products, including C, and greater stimulation of soil heterotrophic communities. Other measured biogeochemical indicators of decay suggest a mixed influence due to carcass size and climate, notably δ15N values of the soil, and major element concentrations. Climate was revealed to be more important in controlling changes to pH and gravimetric moisture than carcass size, with baseline soil conditions and type playing critical roles. Additionally, in semi-arid regions such as western South Dakota, the role of wet-dry cycles on carcasses undergoing decomposition may help to explain the pulses observed with C concentrations and C cycling. This study provides the first direct comparison of soil biogeochemistry associated with the decomposition of two different sized taxa decayed in two different climates. Attempting to normalize climate data using ADD was found to be an imperfect system that does not account for all climate variables affecting decomposition. Unravelling patterns in decomposition can better help to constrain nutrient cycling in modern and ancient ecosystems.

Trunk extensor muscle endurance and its relationship to action potential conduction velocity and spectral parameters estimated using high-density electromyography

Trunk extensor muscle fatigue typically manifests as a decline in spectral content of surface electromyography. However, previous research on the relationship of this decline with trunk extensor muscle endurance have shown inconsistent results. The decline of spectral content mainly reflects the decrease in average motor unit action potential conduction velocity (CV). We evaluated whether the rate of change in CV, as well as two approaches employing the change in spectral content, are related to trunk extensor muscle endurance. Fourteen healthy male participants without a low-back pain history performed a non-strictly controlled static forward trunk bending trial until exhaustion while standing. For 13 participants, physiologically plausible CV estimates were obtained from high-density surface electromyography bilaterally from T6 to L5. Laterally between L1 and L2, the linear rate of CV change was strongly correlated to endurance time (R2 = 0.79), whereas analyses involving the linear rate of change in spectral measures showed a lower (R2 = 0.38) or no correlation. For medial electrode locations, estimating CV and its relationship with endurance time was less successful, while the linear rate of change in spectral measures correlated moderately to endurance time (R2 = 0.44; R2 = 0.56). This study provides guidance on monitoring trunk extensor muscle fatigue development using electromyography.

Gamma irradiation-induced changes in structural, linear/nonlinear optical, and optoelectrical properties of PVB/BiVO4 nanocomposite for organic electronic devices

Herein, nanocomposite films based on polyvinyl butyral (PVB) and BiVO4 plates were synthesized through solution casting. The present study aims to investigate the impact of varying doses of gamma irradiation (0, 15, 30, 60, and 90 kGy) on the structural, dispersion, linear/nonlinear optical, and optoelectrical properties of PVB/BiVO4 nanocomposite films. The effects of gamma irradiation on various optical characteristics, such as refractive index (n), extinction coefficient (k), and other related parameters, have been observed. The study of dielectric behavior and the derivation of optoelectrical parameters, including high-frequency dielectric constant (ε∞), plasma frequency (ωP), relaxation time (τ), and optical mobility (µopt.), were conducted using the real and imaginary parts of the dielectric constants εr and εi. In addition, the linear optical susceptibility (χ(1)), the third-order nonlinear optical susceptibility (χ(3)), and the nonlinear refractive index (n2) were studied as a function of gamma irradiation doses. Furthermore, the results demonstrate that the average oscillator wavelength (λ0) values, oscillator strength (S0), and optical conductivity (σopt) vary significantly after gamma radiation treatment. Overall, the strong correlations between the linear/nonlinear optical and optoelectrical parameters of the irradiated PVB/BiVO4 nanocomposite films make them suitable for application in flexible organic electronic devices.

Preparation of cellular SiBOC foams by thermo‐foaming of polymethylvinylborosiloxane–wheat flour dough

AbstractA novel method for the preparation of SiBOC foams from a polymethylvinylborosiloxane (MVBS) solution in ethanol using wheat flour as a foam stabilizer and pore template has been reported. A dough prepared by mixing the MVBS solution and wheat flour undergoes foaming at 180°C due to the stabilization of bubbles created by ethanol vapor by the adsorption of wheat flour particles on their surface. The ceramization of the foamed body at 1500°C followed by burnout of carbon produced from the wheat flour results in SiBOC foams of hierarchical pore structure. The foam density (.68–.44 g cm−3), average cell size (1.81–.58 mm), compressive strength (3.9–1.7 MPa), and thermal conductivity (.33–.21 W m−1 K−1) decrease with an increase in wheat flour to MVBS weight ratio from .25 to 1. The population of smaller pores (∼5–50 μm) created by wheat flour particles on cell walls and struts increases with an increase in wheat flour to MVBS weight ratio. The presence of β‐SiC and turbostratic graphite nanodomains in amorphous SiBOC is evidenced by X‐ray diffraction and transmission electron microscopy analysis.