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To maximize the piezoelectric performance of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) single crystals, a pulse poling (PP) method is proposed in this study. This study investigates the effects of pulse poling on the piezoelectric and dielectric properties of these PMN–PT single crystals and explores the polarization rotation mechanisms. Our findings indicate a significant improvement in the piezoelectric properties postpulse poling. The optimal PP conditions are identified as 30 pulse numbers at a pulsed electric field of 5 kV/cm. The dielectric constant ɛT33/ɛ0 and piezoelectric coefficient d33 of PMN–0.28PT post PP are 7000–7700 and 2200–2530 pC/N, respectively, representing increases of 49% and 66% compared with those of postdirect current poling (DCP). Additionally, the domain structures of the PMN–0.28PT single crystals after various DCP and PP treatments are examined and compared using piezoelectric force microscopy. The enhanced piezoelectric properties are attributed to the finer domain structures, as well as increased domain wall density achieved through PP. This research introduces a novel domain engineering approach to improve the electromechanical properties of relaxor ferroelectric single crystals. [ABSTRACT FROM AUTHOR]

The Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) ferroelectric single crystals have been commercially available as important components in medical ultrasound transducers due to their excellent piezoelectric and electromechanical coupling performance. The variation in piezoelectric and dielectric properties of PMN-PT single crystals with ambient temperature is an important application indicator. In this work, the PMN-PT single crystals after direct current poling (DCP) and alternating current poling (ACP) were subjected to the cyclic thermal treatment process. The thermal cycling stability and microstructural changes in PMN-PT single crystals were investigated. The ACP single crystals exhibit a higher dielectric constant ε 33 T / ε 0 (6500–7600) and piezoelectric coefficient d33 (2100–2500 pC N−1) compared to the DCP single crystals (ε 33 T / ε 0 of 4100–5000, d33 of 1200–1300 pC N−1). Under thermal cycling at 60 °C, the DCP and ACP single crystals exhibit good thermal cycling stability after 150 cycles. Microstructural observations show that the domain structure of the DCP single crystals exhibits "staggered domain walls, inhomogeneous domain size, variety of domain structure," while the relatively homogeneous stripe-like domains were observed in the ACP single crystals. After thermal cycling, new fine striped domains appear in both the DCP and ACP single crystals due to the instability of rotated polarization, but the piezoelectric and dielectric properties are not greatly affected. This work provides an intensive understanding of the effects of thermal cycling on the domain structure, which is useful for applications. [ABSTRACT FROM AUTHOR]

Seasonal dynamics in the vertical distribution of leaf area index (LAI) may impact the seasonality of forest productivity in Amazonian forests. However, until recently, fine-scale observations critical to revealing ecological mechanisms underlying these changes have been lacking. To investigate fine-scale variation in leaf area with seasonality and drought we conducted monthly ground-based LiDAR surveys over 4 yr at an Amazon forest site. We analysed temporal changes in vertically structured LAI along axes of both canopy height and light environments. Upper canopy LAI increased during the dry season, whereas lower canopy LAI decreased. The low canopy decrease was driven by highly illuminated leaves of smaller trees in gaps. By contrast, understory LAI increased concurrently with the upper canopy. Hence, tree phenological strategies were stratified by height and light environments. Trends were amplified during a 2015-2016 severe El Niño drought. Leaf area low in the canopy exhibited behaviour consistent with water limitation. Leaf loss from short trees in high light during drought may be associated with strategies to tolerate limited access to deep soil water and stressful leaf environments. Vertically and environmentally structured phenological processes suggest a critical role of canopy structural heterogeneity in seasonal changes in Amazon ecosystem function.

The paper considers an inverse problem of simultaneously identifying the piecewise smooth conductivity and initial value of a heat conduction equation defined over a domain $ \Omega $ from the measurement at a fixed time and the Cauchy data on a part of the boundary of $ \Omega $. First, we analyze the regularity of the solution for the forward problem, especially the regularity of the solution near the interface where the conductivity is discontinuous. Then, based on this regularity, we prove the conditional stability by combining the logarithmic convexity theory and the conditional stability of identifying the conductivity. Upon having the uniqueness and conditional stability, we study the inverse problem numerically, which is to transform it into a minimization problem. The existence and stability results of the minimizer are rigorously analyzed. By decomposing the minimization problem into a solve-mark-refine-looping scheme, we propose an iterative algorithm with an adaptively matching regularization to preserve the smoothness and discontinuity of the conductivity, respectively. This algorithm is efficient and easy to implement numerically. Finally, we present two-dimensional and three-dimensional numerical examples to show the performance of the proposed algorithm. [ABSTRACT FROM AUTHOR]

12‐hydroxyeicosatetraenoic acid (12‐HETE), a major metabolite of arachidonic acid, is converted by 12/15‐lipoxygenase and implicated in diabetic retinopathy (DR). Our previous study demonstrated a positive correlation between 12‐HETE and the prevalence of DR. However, reasons for the increased production of 12‐HETE are unclear, and the underlying mechanisms through which 12‐HETE promotes DR are unknown. This study aimed to elucidate the correlation between 12‐HETE and DR onset, investigate potential mechanisms through which 12‐HETE promotes DR, and seek explanations for the increased production of 12‐HETE in diabetes. We conducted a prospective cohort study, which revealed that higher serum 12‐HETE levels could induce DR. Additionally, G protein‐coupled receptor 31 (GPR31), a high‐affinity receptor for 12‐HETE, was expressed in human retinal microvascular endothelial cells (HRMECs). 12‐HETE/GPR31‐mediated HRMEC inflammation occurred via the p38 MAPK pathway. 12‐HETE levels were significantly higher in the retina of mice with high‐fat diet (HFD)‐ and streptozotocin (STZ)‐induced diabetes than in those with only STZ‐induced diabetes and healthy controls. They were positively correlated with the levels of inflammatory cytokines in the retina, indicating that HFD could induce increased 12‐HETE synthesis in patients with diabetes in addition to hyperglycemia. Conclusively, 12‐HETE is a potential risk factor for DR. The 12‐HETE/GPR31 axis plays a crucial role in HRMEC dysfunction and could be a novel target for DR prevention and control. Nevertheless, further research is warranted to provide comprehensive insights into the complex underlying mechanisms of 12‐HETE in DR. [ABSTRACT FROM AUTHOR]

Culvert is an important part of railway, and it is also the most neglected railway equipment in daily maintenance. The deterioration and mechanical performance of culvert structure directly affect the safety and stability of the line. Aiming at the problems of insufficient bearing capacity, excessive settlement, dislocation and durability reduction of heavy haul railway culverts under the condition of speed-up reconstruction, this paper conducts the mechanism analysis of culvert reinforcement with assembled corrugated plate, the performance analysis and sensitivity analysis of culvert reinforcement with key parameters of corrugated plate and the practical engineering application technology of culvert reinforcement with corrugated plate based on the methods of finite element analysis, test detection and engineering application. The results show that the overall stiffness of the culvert structure is significantly improved, the stress and deformation of the culvert roof are significantly reduced, and the reinforcement effect is better after using corrugated plate reinforcement technology. Under the same size condition and compared with the rectangular and triangular corrugated plate structures, the maximum vertical displacement and maximum stress value of the roof span can be reduced by 20% or more after the culvert is reinforced by the circular arc corrugated plate, and the circular arc corrugated plate has better reinforcement effect. Under the combined load of the main force, with the increase of the wave height and wave distance of the corrugated plate, the Mises stress of the corrugated plate decreases gradually, and the Mises stress is inversely proportional to the span of the culvert. The field test results of 16 culverts show that the stress and deformation of culverts with different spans and frame culverts are significantly reduced after corrugated plate reinforcement, and the mid-span deflection and dynamic strain are reduced by more than 40% compared with those before reinforcement. Corrugated plate technology has a good reinforcement effect in the culverts of heavy haul railway. [ABSTRACT FROM AUTHOR]

Pyrite exhibits considerable potential as an adsorbent in wastewater treatment. However, few pyrite adsorbents are directly obtained from natural pyrite, as most are composite materials that require a complex preparation process. To develop a pyrite-based adsorbent with a simple preparation process, pyrite was processed by calcination at 400, 600, and 800 °C for 4 h and ball-milled into a fine powder. The adsorption properties of the pyrite powder were systematically explored. The calcined pyrite powder was characterized by SEM-EDS and XRD. The results revealed that the pyrite calcined at 600 °C exhibited excellent adsorption properties and was primarily composed of Fe7S8. The optimum conditions for Cr(VI) removal were a temperature of 45 °C, an adsorbent dosage of 1 g, an equilibration time of 60 min, and an initial pH of 3. Moreover, the calcined pyrite powder exhibited excellent reusability, and the Cr(VI) removal rate exceeded 65% after three cycles. The Cr(VI) adsorption on pyrite can be well described by the Freundlich model and pseudo-second-order kinetic equation. The calcination temperature is the main factor affecting the adsorption performance of pyrite. Therefore, the calcined pyrite powder is expected to be an excellent adsorbent for Cr(VI) in the wastewater treatment industry. Pyrite has shown promising development prospects in the field of wastewater purification. However, the preparation of most pyrite-based adsorbents is complicated. Upon high-temperature calcination, pyrite is used in traditional Chinese medicine clinics to promote the healing of fractures. The efficiency and underlying mechanism of Cr(VI) adsorption from water using calcined pyrite was investigated. The adsorbent was prepared using a simple method and exhibited excellent adsorption performance, thus allowing its application in preparing ore-based adsorbents for water pollution treatment. [ABSTRACT FROM AUTHOR]