Stress Release Research Articles

Innovative assessment of lipid-induced oxidative stress and inflammation in harvested human endothelial cells.

Studying acute changes in vascular endothelial cells in humans is challenging. We studied ten African American women and used the J-wire technique to isolate vein endothelial cells before and after a four-hour lipid and heparin infusion. Dynamic changes in lipid-induced oxidative stress and inflammatory markers were measured with fluorescence-activated cell sorting. We used the surface markers CD31 and CD144 to identify human endothelial cells. Peripheral blood mononuclear cells isolated from blood were used as a negative control. The participants received galantamine (16 mg/day) for 3 months. We previously demonstrated that galantamine treatment effectively suppresses lipid-induced oxidative stress and inflammation. In this study, we infused lipids to evaluate its potential to increase the activation of endothelial cells, as assessed by the levels of CD54+ endothelial cells and expression of Growth arrest-specific 6 compared to the baseline sample. Further, we aimed to investigate whether lipid infusion led to increased expression of the oxidative stress markers IsoLGs and nitrotyrosine in endothelial cells. This approach will expedite the invivo identification of novel pathways linked with endothelial cell dysfunction induced by oxidative stress and inflammatory cytokines. This study describes an innovative method to harvest and study human endothelial cells and demonstrates the dynamic changes in oxidative stress and inflammatory markers release induced by lipid infusion.

Harnessing stimuli‐responsive biomaterials for advanced biomedical applications

AbstractCell behavior is intricately intertwined with the in vivo microenvironment and endogenous pathways. The ability to guide cellular behavior toward specific goals can be achieved by external stimuli, notably electricity, light, ultrasound, and magnetism, simultaneously harnessed through biomaterial‐mediated responses. These external triggers become focal points within the body due to interactions with biomaterials, facilitating a range of cellular pathways: electrical signal transmission, biochemical cues, drug release, cell loading, and modulation of mechanical stress. Stimulus‐responsive biomaterials hold immense potential in biomedical research, establishing themselves as a pivotal focal point in interdisciplinary pursuits. This comprehensive review systematically elucidates prevalent physical stimuli and their corresponding biomaterial response mechanisms. Moreover, it delves deeply into the application of biomaterials within the domain of biomedicine. A balanced assessment of distinct physical stimulation techniques is provided, along with a discussion of their merits and limitations. The review aims to shed light on the future trajectory of physical stimulus‐responsive biomaterials in disease treatment and outline their application prospects and potential for future development. This review is poised to spark novel concepts for advancing intelligent, stimulus‐responsive biomaterials.

#770 Urinary PTM3 Fetuin-A in CKD patients with and without diabetic kidney disease

Abstract Background and Aims Fetuin-A is a member of the cystatins superfamily, primarily synthesized in the liver, which is involved in multiple physiological processes including calcium homeostasis, cell signaling, calcification inhibition and the regulation of insulin sensitivity. Diabetes mellitus may impact upon Fetuin-A regulation and kidney tubular cells produce Fetuin-A as part of stress and inflammatory response and release it in urine in case of kidney damage. A novel post-translational modification (PTM) fragment derived from the cleavage of Fetuin-A (PTM3) has recently emerged as a very sensitive biomarker for early kidney damage, but its usefulness in the context of CKD has not been assessed yet. In this study, we aimed at evaluating the clinical significance of urinary PTM3 fetuin A in a pilot cohort of CKD patients with or without diabetic kidney disease (DKD). Method We enrolled 47 adult patients with CKD (mean CKD-Epi 40.10 ± 16.5 mL/min/1.73 m2) due to DKD (n = 34) or other causes (n = 13). PTM3 levels were measured in the urine (uPTM3) using a commercially available ELISA kit. 15 healthy individuals served as controls. Clinical, anthropometric and laboratory parameters were also recorded. Results Collectively, all CKD patients displayed higher levels of uPTM3 than the ones of control group (0.84 [0.10-1.15] vs 29.68 [2.50-55.16] ng/mL p = 0.0005). Moreover, uPTM3 values were higher in DKD patients than in non-DKD CKD patients (39.4 [4.20-28.2] vs. 4.15 [0.29-1.38] p < 0.01). uPTM3 had a remarkable diagnostic capacity at ROC analysis to discriminate CKD patients from controls (AUC 0.776; p < 0.001; Fig. 1) and, within CKD patients, to discriminate between DKD and non-DKD patients (AUC 0.673; p = 0.02; Fig. 2). At multivariate correlation analyses, only proteinuria (β = 0.442; p = 0.02) and BMI (β = 0.334; p = 0.04) values remained significantly associated with uPTM3 Fetuin-A in the whole cohort, thus indicating that renal damage following metabolic syndrome may play a significant impact on the overall balance of this protein. Conclusion uPTM3 could be a novel sensitive biomarker reflecting renal damage in CKD patients and could also represent an additional tool for assessing the renal involvement in diabetic patients. Further studies are needed to evaluate whether uPTM3 measurement may predict different disease evolution in these patients.

Place perception and restorative experience of recreationists in the natural environment of rural tourism

IntroductionIn contemporary society, people spend long periods under high stress, and tourism activities have gradually been internalized as a new means of stress release and self-recovery. Studies have found that the high-quality natural environment of rural tourism destinations has a higher restorative effect than other places, and the rural natural environment can provide psychological recovery to visitors on top of offering visual beauty and other experiences.MethodsThis paper starts with the relationship between rural place perception and restorative experience evaluation. Based on theories such as the restorative environments theory, we investigates whether rural natural environmental factors have a restorative effect on recreationists through collecting 300 questionnaires and using SPSS 26.0 structural equation modeling for analysis.ResultsThe study found that there is a positive correlation between rural natural perception, place dependence, and restorative experience, forming a positive feedback loop dynamic system. The analysis suggests that enhancing the perception of the rural natural environment and place attachment can improve the restorative experience of recreationists in rural settings.DiscussionThis research establishes a systematic research framework for the relationship between rural natural perception, place attachment, and restorative experience, to deeply understand the dynamic interaction between them. It reveals the relationship between rural natural perception and restorative experience, suggesting that enriching the perceptual elements in rural natural spaces can meet the diverse needs of recreationists, enhance the sense of dependence and identification with rural spaces, and thus promote the psychological well-being and restorative experience of recreationists. The study also finds that place dependence plays a mediating role between rural natural perception and restorative experience. Place attachment and place identity, as mediating variables, act as bridges and catalysts in the process of rural natural perception affecting restorative experience.

In-plane compressive properties and failure mechanisms of gradient Cf/ZrB2–SiC composites in high-temperature environment

The gradient Cf/ZrB2–SiC composites can exert the dual advantages of low-density and excellent heat resistance, but which have the complex mechanical properties due to the inhomogeneous geometry characteristics. The in-plane compressive behavior and failure analysis can examine the material integrity and the effect of inhomogeneous characteristics. The in-plane compressive elastic modulus distribution is expressed mathematically by using the superficial elastic modulus, back elastic modulus, and the gradient pore distribution. The superficial elastic modulus and the gradient pore distribution of the gradient materials were characterized by nanoindentation test and Micro-CT statistics. The back of the gradient materials is the porosity needled C/C composites without introducing ZrB2–SiC matrix, whose elastic modulus can be referenced from our previous work. The in-plane compressive experiments of the gradient materials in the high-temperature environment were also conducted to study the failure mechanisms. The strength of the gradient materials is further revealed by the temperature-dependent properties of carbon fibers and thermal residual stress release. The results indicate the gradient structure can effectively eliminate the delamination damage, but the high temperature drastically weakens the ability of needled fibers suppressing delamination damage in the high-porosity region of the gradient materials. This study can be helpful to the material design and evaluation of mechanical properties for the gradient Cf/ZrB2–SiC composites.

Surface characteristics and material removal mechanisms during nanogrinding on C-face and Si-face of 4H-SiC crystals: Experimental and molecular dynamics insights

4H-SiC wafers hold significant promise for applications in power devices and radiofrequency devices. In order to develop a cost-effective and efficient grinding technology for 4H-SiC wafers, it is imperative to thoroughly investigate the mechanisms underlying damage evolution on different crystal faces of 4H-SiC. Our approach involved employing a range of experimental techniques including nanoindentation, scratching, and grinding, coupled with molecular dynamics (MD) simulation to systematically analyze the material removal mechanisms on both the C-face and Si-face. Through a comprehensive comparison of mechanical properties, surface morphology, and subsurface damage distribution between the C-face and Si-face, we uncovered the plastic deformation mechanisms operating on each face. Our research findings emphasize that, compared to the Si-face, the C-face exhibits higher elastic modulus and hardness, but lower fracture toughness. Additionally, due to the C-face’s greater propensity for high-density dislocation formation compared to the Si-plane, stress release occurs in the machining area, resulting in smaller normal forces and aiding in reducing surface roughness after grinding. This study provides important guidance for the grinding of the two critical basal planes of single-crystal 4H-SiC.

Experimental Verification of Geometric Changes Caused by the Release of Residual Stresses for Large-Scale Welded Frames.

This paper presents geometric analyses of welded frames after free relaxing and vibratory stress relief (VSR). The tested frames were components of a prototype packaging machine. Two types of relaxation were carried out to remove stresses introduced as a result of the welding process. One of the frames was subjected to free relaxation, while the other one was subjected to accelerated vibration relaxation. Detection of the frame geometry changes was performed using a photogrammetric system. In addition, an evaluation of the geometry change was conducted for fifteen variants of a steel frame support. A comparative analysis of the geometric deviations of the frames after free and vibratory stress relief confirmed the assumption that the frame post vibration stress relief better reproduces the nominal dimensions. Nevertheless, it should be emphasized that after vibratory stress relief, the frame is not subject to further deformation, which is a desirable effect. In the case of free relaxing, the frame undergoes dimensional changes in a random manner. In summary, carrying out accelerated vibratory stress relief allows for control of spontaneous dimensional changes in the designed frame of a packaging machine resulting from spontaneous relaxation of stresses arising from the welding process. The shortening of the relaxation process of the welded frame is also an unquestionable advantage.

Genomic identification and expression analysis of acid invertase (AINV) gene family in Dendrobium officinale Kimura et Migo

BackgroundDendrobium officinale Kimura et Migo, a renowned traditional Chinese orchid herb esteemed for its significant horticultural and medicinal value, thrives in adverse habitats and contends with various abiotic or biotic stresses. Acid invertases (AINV) are widely considered enzymes involved in regulating sucrose metabolism and have been revealed to participate in plant responses to environmental stress. Although members of AINV gene family have been identified and characterized in multiple plant genomes, detailed information regarding this gene family and its expression patterns remains unknown in D. officinale, despite their significance in polysaccharide biosynthesis.ResultsThis study systematically analyzed the D. officinale genome and identified four DoAINV genes, which were classified into two subfamilies based on subcellular prediction and phylogenetic analysis. Comparison of gene structures and conserved motifs in DoAINV genes indicated a high-level conservation during their evolution history. The conserved amino acids and domains of DoAINV proteins were identified as pivotal for their functional roles. Additionally, cis-elements associated with responses to abiotic and biotic stress were found to be the most prevalent motif in all DoAINV genes, indicating their responsiveness to stress. Furthermore, bioinformatics analysis of transcriptome data, validated by quantitative real-time reverse transcription PCR (qRT-PCR), revealed distinct organ-specific expression patterns of DoAINV genes across various tissues and in response to abiotic stress. Examination of soluble sugar content and interaction networks provided insights into stress release and sucrose metabolism.ConclusionsDoAINV genes are implicated in various activities including growth and development, stress response, and polysaccharide biosynthesis. These findings provide valuable insights into the AINV gene amily of D. officinale and will aid in further elucidating the functions of DoAINV genes.

Metabolic Reprogramming: A Byproduct or a Driver of Cardiomyocyte Proliferation?

Defining mechanisms of cardiomyocyte proliferation should guide the understanding of endogenous cardiac regeneration and could lead to novel treatments for diseases such as myocardial infarction. In the neonatal heart, energy metabolic reprogramming (phenotypic alteration of glucose, fatty acid, and amino acid metabolism) parallels cell cycle arrest of cardiomyocytes. The metabolic reprogramming occurring shortly after birth is associated with alterations in blood oxygen levels, metabolic substrate availability, hemodynamic stress, and hormone release. In the adult heart, myocardial infarction causes metabolic reprogramming but these changes cannot stimulate sufficient cardiomyocyte proliferation to replace those lost by the ischemic injury. Some putative pro-proliferative interventions can induce the metabolic reprogramming. Recent data show that altering the metabolic enzymes PKM2 [pyruvate kinase 2], LDHA [lactate dehydrogenase A], PDK4 [pyruvate dehydrogenase kinase 4], SDH [succinate dehydrogenase], CPT1b [carnitine palmitoyl transferase 1b], or HMGCS2 [3-hydroxy-3-methylglutaryl-CoA synthase 2] is sufficient to partially reverse metabolic reprogramming and promotes adult cardiomyocyte proliferation. How metabolic reprogramming regulates cardiomyocyte proliferation is not clearly defined. The possible mechanisms involve biosynthetic pathways from the glycolysis shunts and the epigenetic regulation induced by metabolic intermediates. Metabolic manipulation could represent a new approach to stimulate cardiac regeneration; however, the efficacy of these manipulations requires optimization, and novel molecular targets need to be defined. In this review, we summarize the features, triggers, and molecular regulatory networks responsible for metabolic reprogramming and discuss the current understanding of metabolic reprogramming as a critical determinant of cardiomyocyte proliferation.

Rapid Fabrication of Large-Grain Opal Films and Photonic Crystal Hydrogel Sensors by a Filter Paper-Enhanced Evaporation Chip.

Developing a rapid fabrication method for crack-free opal films is a significant challenge with broad applications. We developed a microfluidic platform known as the "filter paper-enhanced evaporation microfluidic chip" (FPEE-chip) for the fabrication of photonic crystal and inverse opal hydrogel (IOPH) films. The chip featured a thin channel formed by bonding double-sided adhesive poly(ethylene terephthalate) with a polymethyl methacrylate cover and a glass substrate. This channel was then filled with nanosphere colloids. The water was guided to evaporate rapidly at the surface of the filter paper, allowing the nanospheres to self-assemble and accumulate within the channel under capillary forces. Experimental results confirmed that the self-assembly method based on the FPEE-chip was a rapid platform for producing high-quality opal, with centimeter-sized opal films achievable in less than an hour. Furthermore, the filter paper altered the stress release mechanism of the opal films during drying, resulting in fewer cracks. This platform was proven capable of producing large-grain, crack-free opal films of up to 30 mm2 in size. We also fabricated crack-free IOPH pH sensors that exhibited color and size responsiveness to pH changes. The coefficient of variation of the gray color distribution for crack-free IOPH ranged from 0.03 to 0.07, which was lower than that of cracked IOPH (ranging from 0.07 to 0.14). Additionally, the grayscale peak value in 1 mm2 of the crack-free IOPH was more than twice that of the cracked IOPH at the same pH. The FPEE-chip demonstrated potential as a candidate for developing vision sensors.

Theoretical analyses and experimental study on the factors influencing the pressure resistance of the magnetorheological grease seal with pinch mode pole piece

This paper mainly focuses on experimental research and theoretical analysis on the pressure resistance capability of magnetorheological grease rotary shaft sealing with pinch mode pole piece structure. Combining magnetorheological grease and pinch mode pole piece structure, the using of permanent magnet as magnetic source is aiming to reduce the lag of yield stress establishment and release. Herein, the micro-nano composite magnetorheological grease was prepared. Right after the synthesis process, its magnetization properties and rheological properties were scientifically and systematically characterized. The influence of different gaps and tooth widths on the magnetic induction intensity is analyzed by finite element method. Based on the theoretical method, the pressure resistance capacity induced by magnetic force is calculated. By comparing the theoretical calculation and experimental results of the pressure resistance, the cause of error and failure is analyzed.

Mechanical Behavior of a Double-Layer Supported Large-Span Tunnel Excavated in Squeezing Rocks Employing Stress Release Technology

When excavating a large-span tunnel in squeezing rock, the tunnel support is subjected to significant loads. Therefore, the support structure must have enough stiffness and strength to withstand the pressure exerted by the ground. Various stress relief techniques can be used to reduce the ground pressure acting on the support and utilize the bearing capacity of the surrounding rock. One such technique is Deformation Reserved (DR). It involves reserving space outside the excavation boundary or between the two support layers. The proposed solution for the interaction between the double-layer tunnel support and the surrounding rock takes into account the excavation process and stress relief. The expressions for stress and deformation of the tunnel support and surrounding rock are provided in an elastoplastic solution. Parametric studies were conducted to investigate the effectiveness of a double-layer support structure with stress relief techniques. The monitoring data from the Lianchengshan Tunnel were compared with the proposed analytical solution. The results indicate that a larger reserved deformation behind the outer layer support is much more beneficial to tunnel stability when the total reserved deformation is constant. The ground pressure will be significantly reduced, thereby decreasing the force on the inner layer support.

Ginsenoside Rh2 Reduced Neurogenesis Dysfunction to Alleviate Depression-like Behaviour in CSDS-induced Mice

Background: Depression is a mental health disorder with high morbidity and disability rates that has harmful effects on public health worldwide. Despite many hypotheses about its mechanism have been put forward, its deeper mechanism is still unclear. Nowadays, there are many antidepressants developed by pharmaceutical companies, such as fluoxetine, ketamine, and paroxetine used in clinical practice, but the therapeutic effects are not satisfactory, with serious adverse reactions and drug addiction. Objective: Ginsenoside Rh2 (G-Rh2) is one of the major bioactive ginsenosides extracted from Panax ginseng that has been conducted for the treatment of many inflammatory diseases. However, the possible mechanisms of G-Rh2 involved in these neuroprotective effects on neuroinflammation are currently unclear. Methods: We established a CSDS depression model in normal mice, and then the depressive symptoms of mice were evaluated by a series of behavioral testing. Finally, molecular biology experiments were conducted to demonstrate that G-Rh2 had anti-inflammatory and antidepressant effects. Results: We showed that G-Rh2 (30 mg/kg) significantly relieved depressive behavior in mice via attenuating oxidative stress injury and release of proinflammatory cytokines. Moreover, G-Rh2 reduced impaired neurogenesis in the hippocampus of CSDS-induced mice. Conclusion: We demonstrated the anti-inflammatory and antioxidative effects of G-Rh2 to alleviate depression through improved neurogenesis in depressive mice for the first time. What's more, we aimed to verify the protective effects of G-Rh2 on neuroinflammation and provide novel insights for understanding the roles of G-Rh2 in the treatment of depression

Residual stress relief strategy in thick steel weldments via local induction heat treatment: Simulation and neutron diffraction experiment

This study investigated the effect of local induction post-weld heat treatment (PWHT) on residual stress relief in thick submerged arc welded steel plates. A combination of numerical and neutron diffraction methods was used to examine the effect of various PWHT parameters, such as annealing temperature and holding time, on the relief of residual stress in welded plates with various thicknesses. A sequentially coupled thermal–mechanical finite element model was used to calculate the residual stress distribution in welded AH36 steel plates before and after PWHT. The model was validated by comparing its predictions with the experimental measurements, and the results showed good agreement. The residual stress of the thick welded plates was effectively reduced via PWHT with local induction. The primary mechanism for this stress release was identified as stress relaxation caused by creep strain. Furthermore, a process map was established considering the PWHT conditions and plate geometry. This map provides a means of determining the optimal PWHT conditions to achieve desired stress reduction levels.

Activity of hydrogel-vitamin D3 /bacterioruberin nanoparticles on imiquimod-induced fibroblasts-keratinocytes spheroids

Topical administration of vitamin D3 (VD3) analogs and corticosteroids is the mainstay treatment for mild localized psoriasis. VD3 however is an unstable class II drug (insoluble and permeable), classically formulated as unattractive viscous and oil-based ointments or creams. In this work, nanostructured archaeolipid carriers (NAC) with a core loaded with VD3 and the C50 dipolar carotenoid from halophilic archaea bacterioruberin (BR): NAC-VD3, were formulated into a carbopol hydrogel: gNAC-VD3. After its rheological characterization, its anti-inflammatory and antioxidant activity was assessed on bi-cellular spheroids, consisting of a core of fibroblasts surrounded by a ring of keratinocytes activated with imiquimod (IMQ) as a psoriasis model. gNAC-VD3 (0.8 mg VD3/135 μg BR/gram gel) conserved the antioxidant activity, showed pseudoplastic non-Newtonian behaviour, stability over time, good occlusion capacity and spreadability, all suitable properties for topical application in patients with psoriasis. gNAC-VD3 did not decrease the viability of spheroids but significantly reduced the release of proinflammatory cytokines (IL-8, IL-6, TNF-α), oxidative stress (ROS), and matrix metalloproteinases from IMQ-induced spheroids to levels similar to the uninduced spheroids. Results suggest that gNAC-VD3 may constitute a potential anti-inflammatory agent for the topical treatment of mild psoriasis and deserves further in vivo exploration.

Geostress-associated settlements of a raft-foundation building due to shield tunnelling in soft ground

The stress state of soil may affect the building settlements induced by tunnelling, which, however, has not been well understood. In this study, 3D numerical analyses combined with in-situ measurements were performed to investigate the geostress-associated settlements of a raft-foundation building due to tunnelling in soft ground. Basically, two types of geostress fields were investigated: the first type considered the effect of additional stress generated in the foundation soil (FAS) due to building weight; while in the second type, a sequential twin tunnelling was presumed, and the effect of additional soil stress induced by the first tunnel (TAS) on the building response to the second tunnel was considered. The results indicated that FAS may aggravate the stress release of the foundation soil, and thus gave rise to a larger building settlement or inclination. In the sequential tunnelling process, the effect of TAS can be more complex: when the first tunnel lowered the stress of foundation soil, TAS effect of the first tunnel may help reduce the building settlements induced by the second tunnel; otherwise, it may aggravate building settlements. In addition to TAS effect, the sheltering effect was also found to play an important part in twin tunnelling.

Discharge and ignition mechanism of high-entropy alloy induced by crack propagation under quasi-static compressive load

In order to reveal the discharge and ignition mechanism of high-entropy alloy under quasi-static compression load, the stress, potential and ignition evolution process of high-entropy alloy with prefabricated cracks were tested. The atomic structure and dislocation evolution of high-entropy alloy during crack propagation and compression were determined by molecular dynamics simulation, and the discharge mechanism of crack tip was analyzed at the micro level. Based on the calculation of Gibbs free energy, the products in the ignition reaction process were predicted. The results of mechanical/thermal/electrical characteristics induced by compressive load show that the discharge usually occurs near the ignition moment of specimen fracture, and the maximum potential signal can reach 34.2 V. The formation of crack group, crack propagation, local stress concentration, charge accumulation and release at the crack tip jointly induce the generation of discharge signals. With the propagation of cracks, a large number of stacking faults appear and a diamond-shaped failure zone is formed. The increase of disordered atoms leads to fracture. During the compression process, a large number of dislocations induce the separation of charges, which aggravates the discharge at the crack tip. In the Hf-Zr-Ti-Ta-Nb-Cu high-entropy alloy system, the reaction product Ta2O5 is preferentially generated, while in the Ti–Zr-Hf-Cu system, Ti2O3 is preferentially generated. The tip discharge and chemical bond fracture during crack propagation induce ignition, and the chemical bond recombines with energy release.

Study on electric pulse effect on steel DP780 during roll forming

The electrophysical impact on metals introduces a novel optimization avenue for roll forming. This study explores the influence of different electric pulse parameters (peak current and frequency) on the roll forming behavior of DP780 high-strength steel. Through electric pulse-assisted tensile, bending, and roll forming experiments, coupled with microstructure and fracture morphology analyses, the study comprehensively assesses the impact of electric pulses on the mechanical properties and springback mechanism of DP780 sheets. Results indicate that electric pulses reduce deformation resistance and enhance the plasticity of DP780 sheets by repairing defects, promoting dislocation slip, and changing the fracture form of the material. Moreover, electric pulses effectively inhibit springback in roll forming, particularly at larger bending angles and under specific E-pulsing parameters. This is attributed to the promotion of residual stress release by electric pulses, leading to a reduction in springback. In conclusion, electric pulse assistance optimizes the roll forming process of DP780 high-strength steel, evidenced by decreased deformation resistance, improved material plasticity, and effective suppression of springback. These findings open up a new optimization pathway for sheet metal forming.

Middle to lower crustal earthquakes in the western East Sea (Sea of Japan) and their implications for neotectonic evolution

The western East Sea (Sea of Japan) is a seismically active region. A major earthquake in the western East Sea may cause damage in the eastern Korean Peninsula. The nature of seismicity in the western East Sea is important information for mitigation of seismic hazards. The seismicity in the western East Sea occur around the paleo-rifting structures where seismic and geophysical properties apparently change. Both reverse faulting and strike slip earthquakes occur in the region. Earthquake locations and focal depths are refined. The maximum focal depth generally increases from ∼10 km in the coast to ∼32 km in the continental slope of the western East Sea that is located in distance of ∼60 km from the coast. Mid to lower crust earthquakes continue around the paleo-rifting structures that may extend to the lower crust and Moho. Offshore earthquakes rarely occur in oceanic basins of bathymetry with >2 km. Clustered episodic earthquakes occur in four local offshore areas including the stress-induced areas by the 12 September 2016 ML5.8MW5.4 Gyeongju and 15 November 2017 ML5.4MW5.5 Pohang earthquakes. The spatiotemporal clustering of earthquakes suggests stress accumulation at localized paleo-rifting structures and episodic stress release. The mid to lower crustal earthquakes are confirmed from phase arrival time analyses with collocated vertically-separated sensors. The laterally progressive focal depth changes suggest neotectonic evolution of thrust across the crust in the paleo-rifting structure.

Controlled exfoliation of wafer-scale single-crystalline AlN film on MOCVD-grown layered h-BN

In this work, we present a stress-free AlN film with improved crystal quality assisted by h-BN and demonstrate the mechanical exfoliation of wafer-scale single-crystal AlN freestanding membrane and reveal the controllable exfoliation mechanism of AlN. Uniform and continuous wafer-scale h-BN is directly grown on c-plane sapphire using a flow modulation epitaxy mode by metal-organic chemical vapor deposition. The nucleation and evolution processes of quasi-van der Waals epitaxy (QvdWE) of AlN on h-BN are revealed. It is found that O2-plasma-treated h-BN can effectively promote the nucleation islands of AlN and contribute to the release of biaxial stress and the reduction of dislocation density in the epilayers. Eventually, the QvdWE growth of a stress-free AlN film (0.08 GPa) is achieved, and wafer-scale mechanical exfoliation of the AlN membrane has been realized. This work provides an effective strategy for the quality improvement of III-nitride films and paves the way for the vertical structure and flexible deep-ultraviolet optoelectronic devices.