Stress Changes Research Articles

Pore characteristics and microscopic damage mechanism of disintegrated carbonaceous mudstone exposed to dry-wet cycles

Disintegrated carbonaceous mudstone (DCM), derived from pre-disintegration treatments of waste carbonaceous mudstone, is utilized as filler for highway embankments with the aim of conserving resources. However, the mechanical behavior of DCM is greatly influenced by its microstructure, particularly pore characteristics. The aim of this study is to investigate the pore characteristics and microscopic damage mechanisms of DCM subjected to dry-wet cycles. Triaxial tests, along with microscopic observations using scanning electron microscopy and mercury intrusion porosimetry, were performed. Three-dimensional pore models were reconstructed from the microscopic test results via the Markov chain-Monte Carlo method. Subsequently, a finite element method that accounts for the anisotropy of porosity was proposed based on these pore models. Finally, numerical triaxial tests were performed to analyze stress changes in DCM under triaxial loading using the proposed method. The results show that the shear strength and cohesion of the DCM decrease with an increase in dry-wet cycles, stabilizing notably after four cycles. Meanwhile, the porosity and the number of slender pores in the specimen increase, leading to intricate alterations in pore shape and distribution. A comparison between numerical and laboratory triaxial tests demonstrates closely aligned results, with distinct stress concentration behavior related to porosity anisotropy. It is revealed that dry-wet cycles cause an increase in porosity and the occurrence of more irregular-shaped pores, subsequently leading to a decrease in the cohesion. This microscopic mechanism is responsible for the shear strength damage of DCM.

Involvement of oxidative stress-AMPK-Cx43-NLRP3 pathway in extracellular matrix remodeling of gastric smooth muscle cells in rats with diabetic gastroparesis.

This study aimed to investigate the changes in oxidative stress, adenosine monophosphate-activated protein kinase (AMPK), connexin43 (Cx43), nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) expression, and extracellular matrix (ECM) in the gastric smooth muscle tissues of rats with diabetic gastroparesis (DGP) and high glucose-cultured gastric smooth muscle cells, determine the existence of oxidative stress-AMPK-Cx43-NLRP3 pathway under high glucose condition, and the involvement of this pathway in ECM remodeling in DGP rats. The results showed that with increasing duration of diabetes, oxidation stress levels gradually increased, the AMPK activity decreased first and then increased, NLRP3, CX43 expression, and membrane/cytoplasmratio of Cx43 expression were increased in the gastric smooth muscle tissues of diabetic rats. Changes in ECM of gastric smooth muscle cells wereobserved in DGP rats. The DGP group showed higher collagen type I content, increased expression of Caspase-1, transforming growth factor-beta 3 (TGF-β3), and matrix metalloproteinase-2 (MMP-2), decreased tissue inhibitor of metalloproteinase-1 (TIMP-1) expression, and higher interleukin-1betacontent when compared with the control group. For gastric smooth muscle cells cultured under higher glucose, the MMP-2 and TGF-β3 expression wasdecreased, TGF-β1 and TIMP-1 expression was increased, the interleukin-1betacontent was decreased in cells after inhibition of NLRP3 expression; the NLRP3 and Caspase-1expression was decreased, and adenosine triphosphate content was lower after inhibition of Cx43; the expression of NLRP3, Caspase-1, P2X7, and the membrane/cytoplasm ratio of CX43 expression was decreased in cells after inhibition of AMPK and oxidative stress, the phospho-AMPK expression was also decreased after suppressing oxidative stress. Our findings suggest that high glucose induced the activation of the AMPK-Cx43-NLRP3 pathway through oxidative stress, and this pathway was involved in the ECM remodeling of gastric smooth muscles in DGP rats by regulating the biological functions of TGF-β3, TGF-β1, MMP-2, and TIMP-1.

A Study on the Time-Frequency Characteristics of Electromagnetic Radiation Signals during Concrete Cracking

At the moment of rupture, brittle materials such as concrete, coal, and rocks experience a sudden stress change that generates oscillating positive and negative charges on the crack surfaces, resulting in the emission of electromagnetic radiation (EMR) signals. While extensive investigations have focused on the EMR signals produced during the fracturing of coal and rocks, limited attention has been given to the signals arising from concrete cracking. Previous studies have predominantly concentrated on amplitude or frequency domain analysis, lacking a comprehensive exploration of the time-frequency domain characteristics of electromagnetic signals. In this study, various magnetic field sensors capable of collecting frequencies ranging from 50Hz to 50kHz are developed. A laboratory testing platform for concrete cracking is established with the utilization of data acquisition equipment and a rock point load tester. The EMR signals are subjected to time-frequency domain analysis using Short-Time Fourier Transform (STFT) methods. The study explores the relationship between the time-frequency domain characteristics of EMR signals and concrete dimensions, as well as the instantaneous stress drop at the moment of fracture. Experimental findings reveal that the dominant frequency of EMR signals generated during concrete cracking is in the low-frequency range. As the instantaneous stress drop at the moment of fracture increases, the frequency of the EMR signals shifts towards higher frequencies and the signals around 10kHz has a longer duration. When the frequency of EMR signals is lower than 20kHz, larger concrete dimensions result in greater stress drops at the moment of fracture, leading to higher intensity EMR signals. Utilizing the EMR characteristics of concrete cracking holds promise for monitoring the safety and stability of concrete structures.

Analysis of non-physiological shear stress-induced red blood cell trauma across different clinical support conditions of the blood pump.

Systematic research into device-induced red blood cell (RBC) damage beyond hemolysis, including correlations between hemolysis and RBC-derived extracellular vesicles, remains limited. This study investigated non-physiological shear stress-induced RBC damage and changes in related biochemical indicators under two blood pump clinical support conditions. Pressure heads of 100 and 350mmHg, numerical simulation methods, and two in vitro loops were utilized to analyze the shear stress and changes in RBC morphology, hemolysis, biochemistry, metabolism, and oxidative stress. The blood pump created higher shear stress in the 350-mmHg condition than in the 100-mmHg condition. With prolonged blood pump operation, plasma-free hemoglobin and cholesterol increased, whereas plasma glucose and nitric oxide decreased in both loops. Notably, plasma iron and triglyceride concentrations increased only in the 350-mmHg condition. The RBC count and morphology, plasma lactic dehydrogenase, and oxidative stress across loops did not differ significantly. Plasma extracellular vesicles, including RBC-derived microparticles, increased significantly at 600min in both loops. Hemolysis correlated with plasma triglyceride, cholesterol, glucose, and nitric oxide levels. Shear stress, but not oxidative stress, was the main cause of RBC damage. Hemolysis alone inadequately reflects overall blood pump-induced RBC damage, suggesting the need for additional biomarkers for comprehensive assessments.

Associations between Stress Mindset and Changes in Positive Affect during a Speech Task: A Preliminary Study

A stress mindset is an individual’s belief that stress has either enhancing (stress-is-enhancing mindset: SEM) or debilitating (stress-is-debilitating mindset: SDM) consequences. This study examined the associations between SEM and changes in positive affect during a speech task using a sample of 32 Japanese college students as participants. It was hypothesized that participants with SEM would show a greater increase in positive affect over time than those with SDM. The participants rested for three minutes, prepared for three minutes, delivered a speech about themselves in front of an evaluator and video camera (task period), and again rested for three minutes. Positive affect was measured immediately after the two resting periods and during the speech. The participants were divided into groups of 17 and 15 in the SEM and SDM groups, respectively, based on their stress mindset scores. Both groups were fairly matched concerning age and male/female ratio. Change patterns of positive affect did not differ between the two groups, which did not support the hypothesis. However, positive affect was significantly higher in the SEM group compared with the SDM group. The present results differed from previous findings reported in North America. Inconsistent results are discussed related to differences in the speech task and cross-cultural variations of happiness and coping with stressors between North America and Japan.

High Ammonia Nitrogen-Induced Reproductive Toxicity in Goldfish (Carassius auratus) Mature Ovary

Ammonia nitrogen is one of the major pollutants in aquaculture. However, the mechanism of ammonia stress on ovarian development and follicular atresia is unknown. In this study, goldfish (Carassius auratus) were exposed to different ammonia concentrations, including 0 (control, C) and 50 mg/L (high, H) for 48 hr at 21 ± 0.5°C. Histology of the ovarian tissue sections revealed that the high ammonia concentrations inhibited the maturation of oocytes, and induced broken and wrinkled radiation bands, follicular membranes, and the accumulation of rod-shaped yolk particles. From the transcriptome data, a total of 1,405 differentially expressed genes (DEGs) were detected between H and C groups. Most DEGs were highly enriched in low-density lipoprotein particle-mediated signaling, oxidative stress-induced premature senescence, and ovarian steroidogenesis pathway. Furthermore, a total of 19 genes were selected and determined by quantitative real-time polymerase chain reaction (qRT-PCR). The changes in oxidative stress and antioxidant activity indicated the excessive accumulation of reactive oxygen species (ROS) in ovarian tissue. The ovarian apoptosis was induced in the H group. The downregulation of genes involved in the ovarian steroidogenesis pathway indicated that ammonia nitrogen stress prevented the synthesis of sexual hormones. These results suggest that high-concentration ammonia stress induces ovarian damage in goldfish, affecting its antioxidant function, leading to excessive ROS accumulation, ovarian apoptosis, and hindered steroid synthesis, adversely affecting reproductive performance.

Inflammaging and prognostic markers of endometriosis

Inflammaging, an age-associated inflammation, is a cellular stress response caused by DNA damage, activation of oncogenes or inactivation of tumor suppressors, oxidative stress, chemotherapy, mitochondrial dysfunction, or epigenetic changes. Damage to macromolecules leads to the cessation of proliferation due to the activation of pathways such as p53/p21CIP1 and p16INK4a/RB. These form the senescence-associated secretory phenotype (SASP), the molecular/cellular manifestations of which in endometrial cells have features similar to those observed in endometriosis. Presently, there are no uniform diagnostic criteria or established molecular markers that can predict the development and course of endometriosis. In this regard, it is relevant to develop new minimally invasive examination methods, statistically based criteria and molecular markers for early diagnosis and prognosis of endometriosis. This review article is devoted to identifying molecular markers that characterize the pathogenesis of endometriosis during inflaming. The aim of the study was to consider modern ideas about the mechanisms of inflaming and its role in the development of endometriosis to determine possible molecular markers for predicting the course of the pathology. We used the PubMed, Scopus and Google Scholar databases to analyze and systematize the literature over the past ten years. Our review reflects the main molecular mechanisms and prognostic criteria that characterize the development of endometriosis during inflaming.

InSAR- and PCA-Based Inversion Reveals the Surface Deformation and Earthquake Sequence in the Weiyuan-Rongxian Shale Gas Field

In recent years, the rapid expansion and development of the shale gas industry in the Sichuan Basin has coincided with a series of unexpected moderate-sized earthquakes. Given that the Sichuan Basin is situated within a stable interior block, the focal mechanism of the 2019 earthquake sequence (ML4.7, ML5.4, and ML5.2) in the Weiyuan-Rongxian area remains a subject of debate. In this study, we propose a joint InSAR- and PCA- based inversion method utilizing the distributed Mogi model to investigate the spatial-temporal characteristics of a gas reservoir and evaluate the induced Coulomb stress change. The surface deformation derived from Sentinel-1 data between 2015 and 2021 was consistent with the spatial distribution of production wells, and it correlated with the temporal changes in reservoir volume associated with the shale gas operating process. The Coulomb stress loading on the regional faults suggests that human activities associated with shale gas operation likely triggered the three moderate earthquakes. Furthermore, our results indicate Coulomb stress loadings of 10 kPa, 15 kPa, 5 kPa, 3 kPa, and 87 kPa on the Dongxingchang fault, Gaoqiao fault, Dayaokou fault, Niujingao fault, and Lijiachang fold, respectively. Consequently, fluid injection and extraction during shale gas development could be contributing to the elevated seismic activity in the Weiyuan-Rongxian area.

Numerical simulation of fault activity in the Qilian tectonic belt and dynamic background of Menyuan earthquake series

Some faults in the Qilian tectonic belt are seismogenic areas for strong earthquakes, including the western section of the Lenglongling fault, which frequently occures moderate-strong Menyuan earthquakes. In this study, using GPS velocity data of 1991–2015 as the boundary constraints, a three-dimensional viscoelastic finite element dynamic model is constructed by comprehensively considering the regional dynamic environment, crust-mantle transverse-longitudinal inhomogeneity, and spatial spreading of a complex fault system. The objective is to investigate the long-period characteristics of fault movement and stress change in the Qilian tectonic belt caused by tectonic loading, and to discuss the seismogenic conditions of the Menyuan earthquakes. The results show that the annual change of long-period movement and stress of the major faults in the Qilian Mountain tectonic zone are characterized by significant segmentation. Due to its unique geometric bend morphology, the western section of Lenglongling fault has a low movement rate, significant slip deficit and high shear stress accumulation, which are conducive to the gestation and occurrence of earthquakes. Furthermore, the seismogenic area of the Menyuan earthquake series is jointly subjected to NE-SW compressive and NW-SE tensile stress fields, and the maximum shear stress and elastic strain energy accumulate faster than in the surrounding areas. Overall, the western section of the Lenglongling fault has a strong dynamic background and favorable conditions for the frequent occurrence of the Menyuan earthquake series.

The Force–Frequency Characteristics of Quartz Wafers under a Cantilever Beam Structure

This study investigated the force–frequency characteristics of quartz wafers inside a cantilever beam frame. Firstly, the force–frequency coefficient formula of quartz wafers with fixed ends under axial force was analyzed. Firstly, the formula for the force–frequency coefficient of quartz wafers with fixed ends under axial force was analyzed. A force–frequency coefficient formula suitable for cantilever beam structures was derived by considering the changes in surface stress and stiffness of quartz wafers with fixed ends and one end under force on the other. Subsequently, the formula’s accuracy was verified by experiments, and the accuracy was more than 92%. In addition, strain simulation analysis was performed on three different shapes of quartz wafers, and experimental verification was carried out on two of them. The results revealed that trapezoidal quartz wafers and cantilever beam structures exhibited superior stress distribution to rectangular chips. Furthermore, by positioning electrodes at various locations on the surface of the quartz chip, it was observed that, as the electrodes moved closer to the fixed end, the force–frequency coefficient of the rectangular quartz chip increased, along with an increase in chip strain under the cantilever structure. In summary, this study provides a new approach for designing cantilever quartz resonator sensors in the future.

Assessment of Refracturing Potential of Low Permeability Reservoirs Based on Different Development Approaches

The technique of refracturing is an effective method to solve the rapid decline in oil well production caused by factors such as severe reservoir energy loss and fracture failure after the initial hydraulic fracturing of low-permeability reservoirs. The key to designing refracturing lies in establishing a model for evaluating the potential fracturing layers. Based on the geological characteristics of the low-permeability conglomerate reservoir in the Lower Wuerhe area of the Eig District of the Xinjiang Oilfield, this paper studies the influence of different development approaches on the distribution pattern of remaining oil in the reservoir. A coupled model of remaining oil distribution and the in situ stress field is established and discusses the characteristics of the four-dimensional in situ stress field under different development modes. This paper analyzes the influence of geological factors and well network factors on the distribution of residual oil, and analyzes the influence of various factors, such as reservoir properties and injection and extraction parameters, on ground stress. Based on the residual oil distribution and ground stress changes, an evaluation method for screening potential fractured layers in reservoirs with different development modes (water injection development and depletion development) is developed.

Normal fault reactivation induced by hydraulic fracturing: Poroelastic effects

Numerous surface-felt earthquakes have been spatiotemporally correlated with hydraulic-fracturing operations. Because large deformations occur close to hydraulic fractures (HFs), any associated fault reactivation and resulting seismicity must be evaluated within the length scale of the fracture stages and based on the precise fault location relative to the simulated rock volumes. To evaluate the changes in Coulomb failure stress (CFS) with injection, we conduct fully coupled poroelastic finite-element simulations using a pore-pressure cohesive zone model for the fracture and fault core in combination with a fault-fracture intersection model. The simulations quantify the dependence of CFS and the fault reactivation potential on the host rock and fault properties, spacing between the fault and the HF, and the fracturing sequence. We find that fracturing in an anisotropic in-situ stress state does not lead to fault tensile opening but rather dominant shear reactivation through a poroelastic stress disturbance over the fault core ahead of the compressed central stabilized zone. In our simulations, poroelastic stress changes significantly affect fault reactivation in all the simulated scenarios of fracturing 50–200 m away from an optimally oriented normal fault. Asymmetric HF growth due to the stress shadowing effect of the adjacent HFs leads to (1) a larger reactivated fault zone following the simultaneous and sequential fracturing of multiple clusters compared with single-cluster fracturing and (2) a larger unstable area ([Formula: see text].1) over the fault core or a higher potential of the fault slip following sequential fracturing compared with simultaneous fracturing. The fault reactivation area is further increased for a fault with lower conductivity and a higher opening-mode fracture toughness of the overlying layer. To reduce the risk of fault reactivation by hydraulic fracturing under the reservoir characteristics of the Barnett Shale, Fort Worth Basin, it is recommended to (1) conduct simultaneous fracturing instead of sequential and (2) maintain a minimum distance of approximately 200 m for HF operations from known faults.

#2834 Analysis of cyst hetero- and homogeneity to unravel common pathways in autosomal dominant polycystic kidney disease

Abstract Background and Aims Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease, with a prevalence of 1 in ca. 1000 individuals and accounting for 10% of the European dialysis population. It is most frequently (75-80%) caused by mutations in the PKD1 gene encoding Polycystin-1. Besides systemic manifestations such as liver cysts, hypertension and cardiac abnormalities, the most prominent phenotype is the gradual development of kidney cysts, leading to kidney enlargement and a decline in kidney function leading to end-stage kidney disease at an average age of ca. 50 years. The cysts arise from tubular epithelial cells in the nephron that start to dedifferentiate, proliferate and eventually secrete fluid into the cyst lumen promoting its swelling. This process is molecularly regulated by changes in Ca2+, cAMP, PKA and PI3K-Akt-mTOR signaling, among others. The renal cysts are further characterized by ciliary dysfunction, altered signal transduction, loss of polarity, apoptosis, mitochondrial abnormalities, metabolic reprogramming, inflammation, oxidative stress and epigenetic changes. However, the exact sequence of events and their relative importance in the process of cyst formation remains unclear. Therefore, we analyzed the transcriptomic cyst hetero- and homogeneity to identify the pathways that were different, but also shared among individual cysts. Method We performed RNA-Seq analysis on 40 individual cystic membranes of nephrectomized kidneys of 4 PKD1 patients. We included 4 samples of macroscopically healthy tissue from 2 ADPKD kidneys (histologically confirmed to have microcysts) and 4 samples from 4 healthy kidneys. Principal component, cluster and trajectory analysis was performed to explore cyst heterogeneity. Adjacent pieces of cystic membrane were analyzed for histology (H&E, Sirius Red) or stained with FITC-tagged Lotus Tetragonolobus Lectin (LTL) or Dolichos Biflorus Agglutinin (DBA), a proximal and distal tubular marker, respectively. Results Although the cysts clearly separated from the healthy tissues in the analyses, there was also a distinct heterogeneity observed among the cysts that was independent of patient, gender, cyst size, location or fluid color. Pathway analysis revealed that these changes were characterized by a gradual increase of interstitial (remodeling) and inflammation markers, and a gradual decrease in differentiation markers (e.g. development, intercellular junctions, basement membrane) along the trajectory pseudotime. We could identify 6 clusters of cystic samples, with 2 clusters deviating from the main trajectory. With respect to tubular/epithelial dedifferentiation, the decrease in proximal tubular markers already occurred in microcystic tissue and was stronger compared to the other tubular segments. Consequently, none of the analyzed cystic membranes stained positive for LTL, while others showed clear staining for DBA. Microcysts on the other hand stained positive for LTL or DBA. Several cysts showed RNA marker expression of multiple tubular segments. Indeed, smaller macrocysts (diameter in the mm range) were lined by both LTL- and DBA-positive regions. Conclusion By analyzing transcriptomic hetero- and homogeneity among individual cysts, the molecular alterations in ADPKD progression can be tracked down and determined whether they occur similarly in all cysts or at different levels. Our data also suggest that loss of proximal tubular markers in macrocysts is more prominent compared to the decrease in distal markers. Finally, inner cyst walls can consist of cyst-lining cells of multiple origins.

Experimental study on the thermal response of rocks to stress change and its significance

Summary Bedrock temperature contains effective information about changes in the crustal stress. A new method of Detecting crustal Stress Change by bedrock Temperature (DSCT) had been proposed. Understanding the stress-induced temperature response characteristics of loaded rocks is fundamental for applying DSCT. In this study, temperature observation experiments of different rocks and water-saturated sandstones subjected to tiered cyclic loading were conducted to investigate the temperature-stress relationship throughout the whole rock deformation and failure process. Through experiments, some valuable results are obtained: (a) temperature changes synchronously with stress and has a very strong linear correlation with it; (b) the magnitude of Temperature Response to Stress (TRS) is approximately 1 mK/MPa, ranging from strong to weak are sandstone, marble, diorite and basalt, respectively. The differences in TRS of various rocks are determined by their major rock-forming minerals, textures and structures; (c) the evolution of TRS experiences three stages: the TRS rises rapidly in the compression stage, slowly in the acoustic emission quiet period and a significant increase in TRS before rock failure is observed on marble, sandstone, and basalt, consistent with the abnormal bedrock temperature rise preceding earthquakes; (d) the TRS of water-saturated sandstones is higher compared to the dry ones, and the abnormal sharp increase in TRS before rock failure is also more significant in the former. These findings mentioned above promote the understanding of thermal anomalies preceding earthquakes.

Computational investigation of plasma arc welding process for aluminium alloys

Thermal stress is a very common phenomenon that occurs at the welded joint. Determination of the same at the joint is however difficult due to inhomogeneity of the weld joint metals and spreading of heat to the surroundings from the Heat Affected Zone (HAZ). Thermal stress induced at the welded joint changes the microstructure of grains which affects the mechanical properties of the welded material. Due to this, cracks may appear in the joint leading to failure of the weld. In the present study, three-dimensional model of two types of welded joint, i.e., Tee Joint and lap joint of two plates having dimensions 100 mm × 75 mm × 5 mm are prepared using ANSYS Workbench 2020 R2. Hex dominant meshing is chosen in order to have clear picture of the spread of temperature over the entire region. The change of Residual stress with variation of welding current and keeping welding voltage constant is also observed for weld joint made of Aluminium Alloy. In this study, conduct steady-state thermal analysis and structural analysis on an aluminium alloy 6063 to assess von Mises stress, von Mises strain, and deformation distribution induced by heating. Evaluate various welding joints to identify the most effective technique.

From the COVID-19 lockdown to the new normal: Two-year changes in daily stress and positive event processes.

The emergence of the novel COVID-19 disease and the social distancing measures implemented to curb its spread affected most aspects of daily life. Past work suggests that during times of more severe stress, people respond to daily stressors with relatively higher negative affect. However, little is known about how people responded to daily stressors and positive events at different moments in time during the COVID-19 pandemic. Thus, we examined longitudinal changes in daily event-related affect (covariation of daily stressors or positive events with same-day affect) from Spring 2020 (wave 1) to 2022 (wave 2). The sample consisted of 324 adults aged 18-80 (mean=52years; 89% women) from the US and Canada who completed weeklong daily diaries at both waves. The results revealed improvements in affective well-being, stressor-related affect (i.e., smaller fluctuations in affect on stressor days vs. nonstressor days), and positive event-related affect (i.e., lower negative affect on days with vs. without positive events). Furthermore, as people gradually resumed their social activities from 2020 to 2022, people reported being exposed to an increased frequency of both stressors and positive events. This study highlights the potential influence of socio-historical phenomena, such as an ongoing pandemic, on the events that people encounter and how they emotionally respond to them.

Endoplasmic Reticulum Stress Induced Senescence in Human Lung Fibroblasts.

Loss of proteostasis and cellular senescence have been previously established as characteristics of aging, however their interaction in the context of lung aging and potential contributions to aging-associated lung remodeling remains understudied. In this study we aimed to characterize endoplasmic reticulum (ER) stress response, cellular senescence, and their interaction in relation to extracellular matrix (ECM) production in lung fibroblasts from young (25-45 years) and old (>60 years) humans. Fibroblasts from young and old patients without significant preexisting lung disease were exposed to vehicle, MG132, etoposide or salubrinal. Afterwards, cells and cell lysates or supernatants were analyzed for ER stress, cellular senescence and ECM changes using protein analysis, proliferation assay and senescence-associated beta galactosidase (SA-β-Gal) staining. At baseline, fibroblasts from aging individuals showed increased levels of ER stress (ATF6 and PERK), senescence (p21 and McL-1) and ECM marker (COL1A1) compared to those from young individuals. Upon ER stress induction and etoposide exposure, fibroblasts showed an increase in senescence (SA-β-Gal, p21, Cav-1), ER stress (PERK) and ECM markers (COL1A1 and LUM) compared to vehicle. Additionally, CXCL8 and IL-6 levels were increase in the supernatants of MG132 and etoposide-treated fibroblasts, respectively. Finally, the ER stress inhibitor salubrinal decreased the expression of p21 compared to vehicle and MG132 treatments, however salubrinal inhibited COL1A1 but not p21 expression in MG132-treated fibroblasts. Our study suggests that ER stress response plays an important role in establishment and maintenance of a senescence phenotype in lung fibroblasts and therefore contributes to altered remodeling in the aging lung.

Capacitance-Based Structural Self-Sensing of Stress: Effect of Water/Cement

Abstract The compressive stress self-sensing properties of mortars with different water-cement ratios are investigated without the need for any conductive additives. Mortar specimens are cyclically loaded and the corresponding capacitance and resistance are measured. The aluminum foil that is used as the electrode is wrapped around the prismatic sample. A coplanar configuration of electrodes is used. Capacitance and resistance increase with increasing water/ cement (W/C) ratio. Stress causes decrease in capacitance and increase in resistance. The relationship between stress and fractional capacitance-resistance (except for the sample with 0.30 W/C ratio) change is reasonably consistent. The effectiveness of stress sensing (the fractional change in capacitance-resistance per unit of stress) decreases monotonically as the maximum stress increases, regardless of the W/C ratio. It is found that the dependence of the effectiveness of the stress sensing on the W/C ratio decreases with an increase in the maximum stress.

Fatigue behavior of 4D printed materials: a review

Abstract4D printing presents a new direction in additive manufacturing through the incorporation of the time dimension into objects, thereby empowering them to modify their shape, properties, or functioning in stimulus to external influences. It is critical to investigate the fatigue behavior of these materials to comprehend their durability and reliability in the context of repeated stress or environmental changes. However, there has been limited effort to study this phenomenon. The purpose of this literature review is to consolidate the current understanding of the fatigue properties of 4D printed materials and identify areas where research is lacking. The impact of this work is to establish a foundation through a literature review for advancements in material science and manufacturing research that can improve the understanding of the fatigue behavior of 4D printed materials.

The Stress State before the MS 6.8 Luding Earthquake on 5 September 2022 in Sichuan, China: A Retrospective View Based on the b-Value

On 5 September 2022 (BJT), Luding, located in southwestern Sichuan Province, China, experienced an MS 6.8 earthquake. This earthquake occurred within the historical rupture zone of the 1786 MS 7.75 event, part of the southern section of the Xianshui He Fault belt. Given the average 155-year recurrence interval for strong earthquakes in this area, the 236 years since the last event made this earthquake somewhat expected. However, prior to this event, we did not detect any anomalies indicating low surface b-values, which are often indicative of a high-stress state in the source area before strong earthquakes, as highlighted by numerous studies. Our research focused on the northern section of the eastern boundary of the Sichuan–Yunnan sub-block, encompassing the Xianshui He, Anning He, Zemu He, and Daliang Shan fault belts. We meticulously located earthquakes of ML ≥ 1.5 from 2009 to May 2022. The catalog was divided into two periods: 2009–2014 and 2015–May 2022. Using an AIC-constraint method, we analyzed the changes in b-values (Δb) in the latter period compared to the former. Our findings revealed a significant abnormal Δb zone (Δb < −0.3), with a radius of approximately 50 km, when ΔAIC ≥ 2 was selected. Intriguingly, the epicenter of the recent Luding MS 6.8 earthquake fell within this abnormal zone. Furthermore, we calculated the b-value cross-section for the southern section of the Xianshui He fault belt using a directory of precisely located small earthquakes. This revealed that the location, scale, and shape of the abnormally low-b-value area corresponded with the large displacement co-seismic area of the main earthquake, affirming the b-value’s effectiveness in identifying asperities. The b-value’s temporal evolution prior to the mainshock exhibited a nearly decade-long continuous decrease, signifying a long-term stress-loading process akin to that observed before many strong earthquakes. The b-value anomalies observed from different profiles before the Luding earthquake underline the necessity of a comprehensive, multi-dimensional analysis of such anomalies. Finally, our analysis indicates that nine earthquakes with MS ≥ 6.5, including the Luding MS 6.8 event, have contributed to increased Coulomb Failure Stress change (ΔCFS) in the Daofu (DF)–Kangding (KD) section of the Xianshui He fault belt and the northern section of the Anning He fault belt south of Shimian (SM), with amplitudes surpassing the 0.01 MPa threshold. This suggests the potential for strong earthquakes in these zones.