Search Results (438)

Bi₆Fe₂Ti₃O₁₈ (BFTO) ceramics were synthesized via a solid-state reaction route using stoichiometric amounts of Bi₂O₃, TiO₂, and Fe₂O₃ powders. A thermal analysis of the powder mixture was conducted to optimize the heat treatment parameters. Energy-dispersive X-ray spectroscopy (EDS) confirmed the conservation of the chemical composition following calcination. Final densification was achieved through hot pressing. The crystal structure of the sintered samples, examined via X-ray diffraction at room temperature, revealed a tetragonal symmetry for BFTO ceramics sintered at 850 °C. Electron backscatter diffraction (EBSD) provided detailed insight into the crystallographic orientation and microstructure. Broadband dielectric spectroscopy (BBDS) was employed to investigate the dielectric response of BFTO ceramics over a frequency range of 10 mHz to 10 MHz and a temperature range of −30 °C to +200 °C. The temperature dependence of the relative permittivity (ε_r) and dielectric loss tangent (tan δ) were measured within a frequency range of 100 kHz to 900 kHz and a temperature range of 25 °C to 570 °C. The impedance data obtained from the BBDS measurements were validated using the Kramers–Kronig test and modeled using the Kohlrausch–Williams–Watts (KWW) function. The stretching parameter (β) ranged from ~0.72 to 0.82 in the impedance formalism within the temperature range from 200 °C to 20 °C. Full article

Novel high-entropy perovskite oxide powders were synthesized using a sol-gel process. The B-site contained five cations: chromium, cobalt, iron, manganese, and nickel. The B-site cations were present on an equiatomic basis. The A-site cation was lanthanum, with calcium doping. The amount of A-site doping varied from 0 to 30 at%, yielding a composition of La_1−xCa_x(Co_0.2Cr_0.2Fe_0.2Mn_0.2Ni_0.2)O_3−δ. The resulting perovskite powders were pressurelessly sintered in air at 1400 °C for 2 h. Sintered densities were measured, and the grain structure was imaged via scanning electron microscopy to investigate the effect of doping. Samples were cut and polished, and their resistance was measured at varying temperatures in air to obtain the electrical conductivity and the mechanism that governs it. Plots of electrical conductivity as a function of composition and temperature indicate that the increased configurational entropy of the perovskite materials has a demonstrable effect. Full article

Cassava is the sixth most important food crop and is cultivated in more than 100 countries. The crop tolerates low soil fertility and drought, enabling it to play a role in climate adaptation strategies. Cassava generally requires careful preparation to remove toxic hydrogen cyanide (HCN) before its consumption, but HCN concentrations can vary considerably between varieties. Climate change and low inputs, particularly carbon and nutrients, affect agriculture in Pacific Island countries where cassava is commonly grown alongside traditional crops (e.g., taro). Despite increasing popularity in this region, there is limited experimental data about cassava crop management for different local varieties, their relative toxicity and nutritional value for human consumption, and their interaction with changing climate conditions. To help address this knowledge gap, three field experiments were conducted at the Koronivia Research Station of the Fiji Ministry of Agriculture. Two varieties of cassava with contrasting HCN content were planted at three different times coinciding with the start of the wet (September-October) or dry (April) seasons. A time series of measurements was conducted during the full 18-month or differing 6-month durations of each crop, based on destructive harvests and phenological observations. The former included determination of total biomass, HCN potential, carbon isotopes (δ¹³C), and elemental composition. Yield and nutritional value were significantly affected by variety and time of planting, and there were interactions between the two factors. Findings from this work will improve cassava management locally and will provide a valuable dataset for agronomic and biophysical model testing. Full article

Inselbergs are rocky outcrops with specialized vegetation, including woody species growing in poorly developed soils. We investigated whether populations of the lithophytic tree Pseudobombax petropolitanum A. Robyns (Malvaceae), a key species endemic to Atlantic Forest inselbergs, have convergent or divergent patterns of functional traits related to leaf chemistry. This study was carried out on three inselbergs located in southeastern Brazil. Green and senescent leaves from nine healthy trees and soil samples were collected in each inselberg. The carbon, nitrogen, phosphorus, potassium, calcium, and magnesium concentrations, and the natural abundances of δ¹³C and δ¹⁵N, were measured in leaves and soil, and the C/N, C/P, and N/P ratios were calculated. The specific leaf area (SLA) was measured, and the nutrient retranslocation rate between green and senescent leaves was estimated. Divergences between populations were observed in the concentrations of potassium and magnesium in the green and senescent leaves, as well as in the C/P and N/P ratios in senescent leaves. Our results suggest that nutrient and water dynamics may differ in some inselbergs due to specific nutrients or their relationships, even though there were convergences in most functional traits related to leaf chemistry among the Pseudobombax populations. The divergences among the populations could have important implications for species selection in the ecological restoration context. Full article

Carbon isotopes in magmatic systems serve as powerful tracers for understanding magma evolution, mantle processes, the deep carbon cycle, and the origin of Earth’s carbon. This review provides a comprehensive overview of carbon isotope measurements and behavior in magmatic systems, highlighting recent technological advancements and scientific insights. We begin by examining methods for measuring δ¹³C in volcanic gases, vesicles, glasses, melt, and fluid inclusions. We then explore the behavior of carbon isotopes in magmatic systems, especially during magmatic degassing. Finally, we evaluate what recent advances mean for our understanding of the carbon isotope signature of the Earth’s upper mantle. Full article

Research on dolomite has long been central in geoscience, yet understanding the origin of Middle Ordovician dolomite in the northeast of the North China Platform remains limited. Based on this, this study focuses on dolomite of Majiagou Formation in Liujiang Basin, and analyzes its genetic process. The research is based on the measured geological section and conducts high-precision analysis and testing, encompassing major and trace elements, rare earth elements, stable carbon and oxygen isotopes, strontium isotopes, crystal structure parameters, and micro-area elements of dolomite. Analysis of V/(V + Ni), Th/U, Sr/Ba, Mn/Sr, (Eu/Eu*) _N, (Ce/Ce*) _N, and the dolomite crystal parameters indicates that the formation of dolomite is related to evaporation. Furthermore, REE and micro-area characteristics of dolomite, as well as the significant negative deviation of δ¹³C and δ¹⁸O, in conjunction with ⁸⁷Sr/⁸⁶Sr deviating from the standard values of Ordovician seawater, suggest an origin of the dolomite in this formation with mixed-water dolomitization and burial dolomitization. A comprehensive assessment of dolomite formation suggests three distinct stages: early-stage evaporation dolomitization, subsequent mixed-water dolomitization, and later-stage burial dolomitization. The research further corroborated that dolomite formation is a complex outcome resulting from the interplay of various geological processes over space and time. Full article

The structural and electrical properties of double perovskite compounds SrLaFe_1−xMn_xTiO_6−δ (x = 0, 0.33, 0.67, and 1.0) were studied using X-ray diffraction (XRD) and dielectric impedance measurements. The reparation of perovskite compounds was successfully achieved through the precursor solid-state reaction in air at 1250 °C. The purity phase and crystal structures of perovskite compounds were determined by means of the standard Rietveld refinement method using the FullProf suite. The best fitting results showed that SrLaFeTiO_6−δ was orthorhombic with space group Pnma, and both SrLaFe_0.67Mn_0.33TiO_6−δ and SrLaFe_0.33Mn_0.67TiO_6−δ were cubic structures with space group Fm3m, while SrLaMnTiO_6−δ was tetragonal with a I/4m space group. The charge density maps obtained for these structures indicated that the compounds show an ionic and mixed ionic–electronic conduction. The dielectric impedance measurements were carried out in the range of 20 Hz to 1 MHz, and the analysis showed that there is more than one relaxation mechanism of Debye type. Doping with Mn was found to reduce the dielectric impedance of the samples, and the major contribution to the dielectric impedance was established to change from a capacitive for SrLaFeTiO_6−δ to a resistive for SrLaMnTiO_6−δ. The fall in values of electrical resistance may be related to the possible occurrence of the double exchange (DEX) mechanism among the Mn ions, provided there is oxygen deficiency in the samples. DC-resistivity measurements revealed that SrLaFeTiO_6−δ was an insulator while SrLaMnTiO_6−δ was showing a semiconductor–metallic transition at ~250 K, which is in support of the DEX interaction. The dielectric impedance of SrLaFe_0.67Mn_0.33TiO_6−δ was found to be similar to that of (La,Sr)(Co,Fe)O_3-δ, the mixed ionic–electronic conductor (MIEC) model. The occurrence of a mixed ionic–electronic state in these compounds may qualify them to be used in free lead solar cells and energy storage technology. Full article

Background/Objectives: Major adverse cardiovascular events (MACE)—including heart attacks and strokes—are the leading cause of death in patients with peripheral artery disease (PAD), yet biomarker research for MACE prediction in PAD patients remains limited. Inflammatory proteins play a key role in the progression of atherosclerosis and may serve as useful prognostic indicators for systemic cardiovascular risk in PAD. The objective of this study was to evaluate a broad panel of circulating inflammatory proteins to identify those independently associated with 2-year MACE in patients with PAD. Methods: We conducted a prospective cohort study involving 465 patients with PAD. Plasma concentrations of 15 inflammatory proteins were measured at baseline using validated immunoassays. Patients were followed over a two-year period for the development of MACE, defined as a composite endpoint of myocardial infarction, stroke, or mortality. Protein levels were compared between patients with and without MACE using the Mann–Whitney U test. Cox proportional hazards regression was used to determine the independent association of each protein with MACE after adjusting for baseline demographic and clinical variables, including existing coronary and cerebrovascular disease. To validate the findings, a random forest machine learning model was developed to assess the relative importance of each protein for predicting 2-year MACE. Results: The mean age of the cohort was 71 years (SD 10), and 145 participants (31.1%) were female. Over the two-year follow-up, 84 patients (18.1%) experienced MACE. Six proteins were significantly elevated in PAD patients who developed MACE: interferon gamma (IFN-γ; 42.55 [SD 15.11] vs. 33.85 [SD 12.46] pg/mL, p < 0.001), tumor necrosis factor alpha (TNF-α; 9.00 [SD 5.00] vs. 4.65 [SD 4.29] pg/mL, p < 0.001), chemokine (C-X-C motif) ligand 9 (CXCL9; 75.99 [SD 65.14] vs. 5.38 [SD 64.18] pg/mL, p = 0.002), macrophage inflammatory protein-1 beta (MIP-1β; 20.88 [SD 18.10] vs. 15.67 [SD 16.93] pg/mL, p = 0.009), MIP-1δ (25.29 [SD 4.22] vs. 17.98 [SD 4.01] pg/mL, p = 0.026), and interleukin-6 (IL-6; 12.50 [SD 40.00] vs. 6.72 [SD 38.98] pg/mL, p = 0.035). After adjusting for all baseline covariates, only two proteins—TNF-α (adjusted HR 1.66, 95% CI 1.28–2.33, p = 0.001) and IFN-γ (adjusted HR 1.25, 95% CI 1.12–2.29, p = 0.033)—remained significantly and independently associated with 2-year MACE. These findings were corroborated by the random forest model, where TNF-α and IFN-γ received the highest importance scores for predicting 2-year MACE: (TNF-α: 0.15 [95% CI 0.13–0.18], p = 0.002; IFN-γ: 0.19 [95% CI 0.17–0.21], p = 0.001). Conclusions: From a panel of 15 proteins, TNF-α and IFN-γ emerged as inflammatory biomarkers associated with 2-year MACE in PAD patients. Their measurement may aid in cardiovascular risk stratification, helping to identify high-risk individuals who could benefit from early multidisciplinary referrals to cardiology, neurology, and/or vascular medicine specialists to provide intensified medical therapy. Incorporating these biomarkers into PAD management may improve systemic cardiovascular outcomes through more personalized and targeted treatment approaches. Full article

The goal of this study is to evaluate how the inclusion of synthetic wax, added in 0.5% increments from 1.5% to 3.5%, affects the characteristics of PMB 45/80-65 (polymer-modified bitumen) during both short-term (RTFOT) and long-term (PAV) aging processes. Tests were carried out to assess the fundamental properties of the binder, leading to the determination of the penetration index (PI) and the plasticity range (PR). The binder’s properties were examined at below-freezing operating temperatures, with creep stiffness measured using a bent beam rheometer (BBR) at −10 °C, −16° C, −22 °C, and −28 °C. The rheological properties of the asphaltenes were evaluated based on both linear and nonlinear viscoelasticity. The experimental study explored temperature effects on the rheological properties of composite materials using a DSR dynamic shear rheometer at 40 °C, 60 °C, and 80 °C over a frequency range of 0.005 to 10 Hz. The main parameters of interest were composite viscosity (η*) and zero shear viscosity (η₀). Viscoelastic parameters, including the dynamic modulus (G*) and phase shift angle (δ), were determined, and Black’s curves were used to illustrate the relationship between these parameters, where G*/sinδ was determined. The MSCR test was employed to investigate the impact of bitumen on the asphalt mixture’s resistance to permanent deformation and to assess the degree and efficacy of asphalt modification. The test measured two parameters, irreversible creep compliance (J_nr) and recovery (R), under stress levels of 0.1 kPa (LVE) and 3.2 kPa (N-LVE). The Christensen–Anderson–Marasteanu model was used to describe the bitumen behavior during binder aging, as reflected in the rheological study results. Ultimately, this study revealed that synthetic wax influences the rheological properties of PMB 45/80-65 polymer bitumen. Specifically, it mitigated the stiffness reduction in modified bitumen caused by polymer degradation during aging at an amount less than 2.5% of synthetic wax. Full article

Phase stability at low radio frequencies is severely impacted by ionospheric propagation delays. Radio interferometers such as the giant metrewave radio telescope (GMRT) are capable of detecting changes in the ionosphere’s total electron content (TEC) over larger spatial scales and with greater sensitivity compared to conventional tools like the global navigation satellite system (GNSS). Thanks to its unique design, featuring both a dense central array and long outer arms, and its strategic location, the GMRT is particularly well-suited for studying the sensitive ionospheric region located between the northern peak of the equatorial ionization anomaly (EIA) and the magnetic equator. In this study, we observe the bright flux calibrator 3C48 for ten hours to characterize and study the low-latitude ionosphere with the upgraded GMRT (uGMRT). We outline the methods used for wideband data reduction and processing to accurately measure differential TEC ($\delta \mathrm{TEC}$) between antenna pairs, achieving a precision of< mTECU (1 mTECU = ${10}^{-3}$ TECU) for central square antennas and approximately mTECU for arm antennas. The measured $\delta \mathrm{TEC}$ values are used to estimate the TEC gradient across GMRT arm antennas. We measure the ionospheric phase structure function and find a power-law slope of $\beta =1.72\pm 0.07$, indicating deviations from pure Kolmogorov turbulence. The inferred diffractive scale, the spatial separation over which the phase variance reaches $1{\mathrm{rad}}^2$, is ∼6.66 km. The small diffractive scale implies high phase variability across the field of view and reduced temporal coherence, which poses challenges for calibration and imaging. Full article

Thin, dense and nanocrystal bismuth oxide films were prepared by the in situ plasma-assisted reactive evaporation (ARE) method using lead doping. Thin films were deposited at room temperature and at 500 °C temperature on glass and silicon substrates. X-ray diffraction, SEM, EDS, and optical measurements were applied to characterize these bismuth oxide films. The results showed that it is possible to synthesize the δ-Bi₂O₃ phase thin films at a temperature lower than 729 °C using an plasma-assisted reactive evaporation (ARE) method and stabilize it (to room temperature) using the additives of lead oxide. The influence of lead oxide concentration on phase formation was investigated. The optimal amount of lead oxide dopant was determined. An excess of lead oxide concentration forms PbO and δ-Bi₂O₃ mixture phases and nanorods appear in films. The synthesized δ-Bi₂O₃ phase was metastable; it transformed into the β-Bi₂O₃ phase after thermal impact during impedance measurements. The cross section of thin film sample shows the dense and monolithic structure. Optical measurements show that the optical band gap increases with increasing lead concentration. It was found that the highest total ionic conductivity of (Bi_1−xPb_0.26)₂O₃ is 0.165 S/cm at 1073 K temperature and activation energy is ΔE_tot = 0.5 eV. Full article

We recently classified baryonic matter in the ground and first excited states thanks to the discrete group of braids inherent to $SU{\left(2\right)}_2$ Ising anyons. Remarkably, the braids of $SU{\left(2\right)}_4$ anyons allow the neutrino mixing matrix to be generated with an accuracy close to measurements. This is an improvement over the model based on tribimaximal neutrino mixing, which predicts a vanishing solar neutrino angle ${\theta }_{13}$, which has now been ruled out. The discrete group of braids for $SU{\left(2\right)}_4$ anyons is isomorphic to the small group $(162,14)$, generated by a diagonal matrix ${\sigma }_1=R$ and a symmetric complex matrix ${\sigma }_2=FR{F}^{-1}$, where the $(3\times 3)$ matrices F and R correspond to the fusion and exchange of anyons, respectively. We make use of the Takagi decomposition ${\sigma }_2=U^{T}DU$ of ${\sigma }_2$, where U is the expected PMNS unitary matrix and D is real and diagonal. We obtain agreement with the experimental results in about the $3\sigma$ range for the complex entries of the PMNS matrix with the angles ${\theta }_{13}\sim 10°$, ${\theta }_{12}\sim 30°$, ${\theta }_{23}\sim 38°$, and ${\delta }_{CP}\sim 240°$. Potential physical consequences of our model are discussed. Full article

With the rapid development of renewable energy in China, thermal power units are facing decommissioning issues, while the power system is confronted with severe challenges such as reduced grid strength and insufficient voltage support. For power systems with multiple renewable energy stations, the short-circuit ratio at the connection points of renewable energy stations is an important indicator for measuring grid strength. Engineering requirements specify that the short-circuit ratio at these connection points should not be lower than 2.0. This study focuses on transforming retired thermal power units into synchronous condensers to improve the short-circuit ratio at renewable energy station connection points. This paper first studies the impact of thermal power unit operation, shutdown, and synchronous phasor operation on the short-circuit ratio, deriving the short-circuit ratio expressions for renewable energy stations under different states of thermal power units. It further analyzes the impact of different main transformer capacities and unit transformation capacities on the short-circuit ratio. Next, a multi-dimensional evaluation system is constructed, incorporating the change in short-circuit ratio at grid-connection points of multiple renewable energy stations ($\Delta MRSC{R}_{\mathrm{S}}$), the main transformer capacity within short-circuit ratio enhancement range ($S_{\mathrm{T}}$), the pre-retrofit short-circuit ratio level at grid-connection points of multiple renewable energy stations ($S_{\mathrm{G}}$), and the retrofitted unit capacity ($MRSC{R}_{\mathrm{S}}$) to comprehensively assess the transformed thermal power units. Finally, a case analysis conducted on the modified IEEE-39 bus system using the PSASP platform verifies that operating thermal power units as synchronous condensers can significantly enhance the short-circuit ratios of multiple renewable energy sites. Given that small-capacity thermal units are approaching retirement, there is a stronger preference for retrofitting these smaller units as synchronous condensers. The multi-dimensional evaluation method proposed in this study specifically identifies small-capacity thermal units as the most suitable candidates for such retrofitting. This approach provides theoretical support for implementing synchronous condenser operation in retired thermal power units and promotes the coordinated optimization of grid security and renewable energy integration. Full article

Conventional WC-Co hard metals have proven to be difficult to manufacture by means of laser powder bed fusion (PBF-LB), resulting in residual pores, crack formation, foreign phase formation, and the inhomogeneous growth of the carbide phase. Alternative compositions such as the W-C-Ti system presented in this study need to be investigated. Through the employment of a high-throughput screening approach, 11 alloy compositions were investigated to determine the influence of the carbon content and tungsten–titanium ratios on microstructure formation and basic mechanical properties. Two screenings were conducted, with one varying the carbon content (10–35 at.%) and the other adjusting the W/Ti ratios (10:90 to 60:40 at.%). Microstructural analyses using scanning electron microscopy (SEM), X-ray diffraction (XRD), and hardness measurements provided insights into phase formation, grain distribution, and mechanical properties. The results showed that increasing the carbon content significantly enhanced the hardness (from 681 HV (10 at.% C) to 1898 HV (35 at.% C)) due to higher δ-(Ti,W)C_1−x carbide phase fractions. Alloys with a higher tungsten content exhibited finer microstructures and an improved crack resistance while maintaining a high hardness (1900–2100 HV). This study identified an alloy with 32.5 at.% W, 32.5 at.% Ti, and 35 at.% C as a promising candidate for further investigation, with properties similar to those of a conventional WC-Co hard metal. Full article

This paper investigates the impact of sintering temperature on oxygen vacancy concentration and its subsequent effect on the microstructure and electrical properties of $B{i}_{4}T{i}_3{O}_{12}$ (BIT) ceramics. To further clarify these effects, VASP software was employed to simulate BIT ceramics with varying oxygen vacancy concentrations.The experimental results demonstrate that sintering temperature significantly influences the oxygen vacancy concentration. At the optimal sintering temperature of 1080 °C, the BIT ceramics exhibit a balanced microstructure with a grain size of 4.16 μm, the lowest measured oxygen vacancy concentration of 18.44%, and a piezoelectric coefficient ($d_{33}$) of 9.8 pC/N. Additionally, the dielectric loss ($tan\delta$) remains below 0.2 at 500 °C, indicating excellent thermal stability. VASP-based simulations reveal that increasing the oxygen vacancy concentration from 18.56% to 44.55% results in a significant collapse of the band gap (from 2.8 eV → 1.0 eV) and a transition in conductivity type from p-type to n-type. This shift induces a leakage current-dominated threshold effect, leading to a decrease in piezoelectric properties ($d_{33}$ reduced from 9.8 to 6.9 pC/N). Atomic-scale density of states (DOS) analyses indicate that the delocalization of $T{i}^{3+}$ and the weakening of Bi–O hybridization collectively induce lattice distortion and ferroelectric inconsistency. These changes are correlated with an increase in dielectric loss and a slight reduction in Curie temperature (from 620 °C → 618 °C). In conclusion, this study comprehensively elucidates the influence of oxygen vacancy concentration on the microstructure and electrical properties of BIT ceramics. The findings provide a theoretical foundation and practical insights for designing high-performance piezoelectric ceramics. Full article