High Stress Conditions Research Articles

Variation in Physiological Traits of Blackgram (Vigna mungo L.) Genotypes under High Temperature Stress

Background: Blackgram is one of the important short duration pulse crop which is sensitive to high temperatures. The rising global temperatures are threatening the yield of blackgram by altering the physiological processes at cellular level. Keeping this in view, the present investigation was carried out for better understanding of genotypic variability and the physiological mechanisms governing heat stress tolerance which can help in identifying heat tolerant blackgram genotypes that can yield better under climate change scenarios. Methods: Thirty blackgram genotypes selected from temperature induction response technique were evaluated for physiological efficiency under natural high temperature conditions during summer, 2022 and 2023. Field experiment was conducted at Agricultural College Farm, Acharya N.G Ranga Agricultural University, Agricultural College, Bapatla. Physiological and yield parameters were recorded at flowering and the data were analyzed statistically and pooled. Result: Significant genetic variability was observed among the blackgram genotypes with respect to all the physiological traits under high temperature stress conditions. Among the 30 genotypes tested for thermotolerance, the genotypes TBG-129, PU-1804, LBG-1015, PU-31 and TBG-104 were found to withstand high temperature stress at reproductive stage by maintaining higher total chlorophyll, carotenoids, chlorophyll stability index, total biomass production, cooler canopies resulting into higher canopy temperature depression, less membrane injury index values and higher yield. Correlation analysis revealed a strong positive correlation for all the physiological traits with seed yield except membrane injury index under heat stress conditions. The PCA results revealed considerable variability among the traits accounting for 82.65% of total variability. The genotypes TBG-129, PU-1804, LBG-1015 and TBG-104 can be potentially used as donors in the breeding programmes for the development of heat tolerant genotypes.

Antioxidant capacity and lipid composition of Brachionus plicatilis and Artemia enriched with a mixture of different post-processing formats of Navicula salinicola and Isochrysis galbana and lipid emulsions

Live prey used by the aquaculture industry are usually poor in some essential nutrients including long chain polyunsaturated fatty acids (LC-PUFA) and must be enriched to improve their nutritional value prior to larval feeding. Standard enrichment protocols are commonly based on lipid emulsions, being associated to a high oxidative stress condition. The combination of microalgae and lipid emulsion can palliate this situation, where the oxidative stress can be partially compensated by the antioxidant compounds present in microalgae. The maintenance of living microalgae in culture facilities is laborious, and the produced biomass may present fluctuating properties, leading to a serious bottleneck in the cultivation of live prey. Hence, substitutes for live microalgae including pastes or dried formats are receiving increasing research attention due to its nutritional stability, longer shelf-life and easy handling. In this study four different microalgae formats combined with a lipid emulsion are tested as enrichment products for Brachionus plicatilis and Artemia. Thus, fresh, frozen and spray-dried Navicula salinicola (NFRE, NFRO and NSD, respectively), and spray-dried Isochrysis galbana (ISD) were mixed with a commercial oil concentrate (IncromegaTM) or a marine lecithin (LC 60®), and added for 5 h to the rotifer or Artemia culture media. The antioxidant capacity of the microalgae extracts and the live prey activity of antioxidant enzymes, peroxides index (PxI) and thiobarbituric acid reactive substances (TBARS) were evaluated. The lipid profile of microalgae formats and enriched live preys was also determined. Ethyl acetate extract was the most antioxidant active extract of all microalgae formats. In addition, overall, I. galbana seems to be better than any N. salinicola format for a more effective protection against oxidative stress and for live prey lipid enrichment. Both rotifer and Artemia cultured with the mixture of I. galbana and the lipid emulsion generally showed higher DHA/EPA and EPA/ARA ratios. Moreover, the combination of the microalgae with LC 60® lipid emulsion highly favored Artemia´s polar lipid and DHA incorporation. Among microalgae products, both spray-dried formats better enhanced live prey n-3 LC-PUFA content. Our results highlight the great potential of new microalgae-derived products to improve effectiveness of current live prey lipid enrichment protocols used in aquaculture.

Correlation analysis between occupational stress and metabolic syndrome in workers of a petrochemical enterprise: based on two assessment models of occupational stress.

Occupational stress is becoming a common phenomenon around the world. Being in a high occupational stress state for a long time may destroy the metabolic balance of the body, thereby increasing the risk of metabolic diseases. There is limited evidence regarding the correlation between occupational stress and metabolic syndrome (MetS), particularly in the petrochemical workers. A total of 1683 workers of a petrochemical enterprise in China were included in the survey by cluster sampling method. The occupational stress assessment was carried out by the Job Content Questionnaire and the Effort-Reward Imbalance Questionnaire, and the general demographic characteristics, work characteristics, occupational hazards, lifestyle and health examination data of the participants were collected. Logistic regression and multiple linear regression were used to analyze the correlations and influencing factors between occupational stress and its dimensions with MetS and its components. A total of 1683 questionnaires were sent out, and 1608 were effectively collected, with an effective recovery rate of 95.54%. The detection rates of occupational stress in Job Demand-Control (JDC) and Effort-Reward Imbalance (ERI) models were 28.4% and 27.2%, respectively. In this study, 257 participants (16.0%) were diagnosed with MetS. Compared with the non-MetS group, body mass index (BMI), waist circumference (WC), systolic blood pressure (SBP), diastolic blood pressure (DBP), triglycerides (TG) and fasting blood-glucose (FBG) levels were significantly higher in the MetS group, and high density lipoprotein-cholesterol (HDL-C) levels were significantly lower (P < 0.001). The results of multiple linear regression showed that after adjusting for nation, marital status, education, work system, smoking and drinking, and further adjusting for occupational hazards, the D/C ratio was significantly negatively correlated with SBP in the JDC model. Social support was negatively correlated with WC. In the ERI model, there was a significant positive correlation between over-commitment and FBG. The detection rates of occupational stress and MetS were high in workers of a petrochemical enterprise. In the JDC model, occupational stress was negatively correlated with SBP, and social support was negatively correlated with WC. In the ERI model, there was a significantly positive correlation between over-commitment and FBG.

Stress affects navigation strategies in immersive virtual reality

There are known individual differences in both the ability to learn the layout of novel environments and the flexibility of strategies for navigating known environments. However, it is unclear how navigational abilities are impacted by high-stress scenarios. Here we used immersive virtual reality (VR) to develop a novel behavioral paradigm to examine navigation under dynamically changing situations. We recruited 48 participants (24 female; ages 17–32) to navigate a virtual maze (7.5 m × 7.5 m). Participants learned the maze by moving along a fixed path past the maze’s landmarks (paintings). Subsequently, participants experienced either a non-stress condition, or a high-stress condition tasking them with navigating the maze. In the high-stress condition, their initial path was blocked, the environment was darkened, threatening music was played, fog obstructed more distal views of the environment, and participants were given a time limit of 20 s with a countdown timer displayed at the top of their screen. On trials where the path was blocked, we found self-reported stress levels and distance traveled increased while trial completion rate decreased (as compared to non-stressed control trials). On unblocked stress trials, participants were less likely to take a shortcut and consequently navigated less efficiently compared to control trials. Participants with more trait spatial anxiety reported more stress and navigated less efficiently. Overall, our results suggest that navigational abilities change considerably under high-stress conditions.

Study on the hot corrosion-creep failure mechanism of Ni-based single crystal superalloy considering the stress dependence

The accelerated creep failure of Ni-based single crystal superalloy by hot corrosion is confirmed by creep tests at 900 °C/550 MPa–400MPa in air and salt environments. The analysis of creep curve, microstructure and fracture type shows that there are obvious differences in hot corrosion-creep behavior under high, middle and low creep stress conditions, indicating that there is the stress dependence between the influence of hot corrosion on the creep properties of the alloy. Hot corrosion accelerates creep failure of Ni-based single crystal superalloy by decreasing the deformation resistance, reducing the effective stress area, and affecting the creep fracture mode.

Plastic behavior of a film type of epoxy adhesive under a wide range of stress multiaxiality conditions

The yield stress of rubber-modified epoxy adhesives is affected by hydrostatic stress in the adhesive layer. It is necessary to clarify whether hydrostatic stress modeling is essential for highly toughened epoxy adhesives and how hydrostatic stress should be considered under high multiaxial stress conditions. The elastic–plastic stress–strain behavior of a film-type epoxy adhesive AF163-2U was examined using a bulk adhesive tension test and a thick adherend shear test (TAST). The exponent Drucker–Prager model with an appropriate hydrostatic-stress sensitivity parameter (λ-parameter = 1.639) fully described the stress–strain curves both for the bulk adhesive tension test and TAST. The Hill’48 model of hydrostatic-stress-independent plasticity also simulated the bulk adhesive tension test and TAST as a response by determining the appropriate anisotropic parameters. To examine the effect of extremely high hydrostatic stress, a butt-joint tensile test and a finite element (FE) simulation were conducted using the exponent Drucker–Prager and Hill’48 models. The Hill’48 model completely failed in the butt-joint tensile test simulation. The exponent Drucker–Prager model, where a higher λ-parameter (=2.1) was required; consequently, it was concluded that the hydrostatic-stress effect should be considered for the adhesive model and the λ-parameter is not a fixed value but increases with increasing hydrostatic stress.

Oxidative Stress and Cerebral Vascular Tone: The Role of Reactive Oxygen and Nitrogen Species.

The brain's unique characteristics make it exceptionally susceptible to oxidative stress, which arises from an imbalance between reactive oxygen species (ROS) production, reactive nitrogen species (RNS) production, and antioxidant defense mechanisms. This review explores the factors contributing to the brain's vascular tone's vulnerability in the presence of oxidative damage, which can be of clinical interest in critically ill patients or those presenting acute brain injuries. The brain's high metabolic rate and inefficient electron transport chain in mitochondria lead to significant ROS generation. Moreover, non-replicating neuronal cells and low repair capacity increase susceptibility to oxidative insult. ROS can influence cerebral vascular tone and permeability, potentially impacting cerebral autoregulation. Different ROS species, including superoxide and hydrogen peroxide, exhibit vasodilatory or vasoconstrictive effects on cerebral blood vessels. RNS, particularly NO and peroxynitrite, also exert vasoactive effects. This review further investigates the neuroprotective effects of antioxidants, including superoxide dismutase (SOD), vitamin C, vitamin E, and the glutathione redox system. Various studies suggest that these antioxidants could be used as adjunct therapies to protect the cerebral vascular tone under conditions of high oxidative stress. Nevertheless, more extensive research is required to comprehensively grasp the relationship between oxidative stress and cerebrovascular tone, and explore the potential benefits of antioxidants as adjunctive therapies in critical illnesses and acute brain injuries.

Fatigue load spectrum generation of Indonesian high-speed trains

The high-speed trains designed and constructed in Indonesia will use Aluminum alloy Al 6061-T6 as a structural material. Aluminum alloys are prone to fatigue failure due to the absence of endurance limit of the material, hence fatigue life prediction has to be carried out. Fatigue cracks could initiate at the defects of welded joints. Analyzing the fatigue load spectrum of critical locations in the train structures is crucial to predicting fatigue life. These critical locations are selected from areas with high static stress and stress concentration. The loads are analyzed using the multibody dynamic with rigid body assumptions and track roughness following UIC Standard Code 518. The finite element method is used to calculate the stresses from the loads generated by the multibody dynamic. The load sequence is further analyzed with rainflow counting method, and the load exceedance curve can be constructed. Finally, the Miner Linear Cumulative Damage Model is used to predict fatigue life.

Enhancing chimeric antigen receptor T cell therapy by modulating the p53 signaling network with Δ133p53α

Chimeric antigen receptor (CAR) T cell dysfunction is a major barrier to achieving lasting remission in hematologic cancers, especially in chronic lymphocytic leukemia (CLL). We have shown previously that Δ133p53α, an endogenous isoform of the human TP53 gene, decreases in expression with age in human T cells, and that reconstitution of Δ133p53α in poorly functional T cells can rescue proliferation [A. M. Mondal et al., J. Clin. Invest. 123, 5247-5257 (2013)]. Although Δ133p53α lacks a transactivation domain, it can form heterooligomers with full-length p53 and modulate the p53-mediated stress response [I. Horikawa et al., Cell Death Differ. 24, 1017-1028 (2017)]. Here, we show that constitutive expression of Δ133p53α potentiates the anti-tumor activity of CD19-directed CAR T cells and limits dysfunction under conditions of high tumor burden and metabolic stress. We demonstrate that Δ133p53α-expressing CAR T cells exhibit a robust metabolic phenotype, maintaining the ability to execute effector functions and continue proliferating under nutrient-limiting conditions, in part due to upregulation of critical biosynthetic processes and improved mitochondrial function. Importantly, we show that our strategy to constitutively express Δ133p53α improves the anti-tumor efficacy of CAR T cells generated from CLL patients that previously failed CAR T cell therapy. More broadly, our results point to the potential role of the p53-mediated stress response in limiting the prolonged antitumor functions required for complete tumor clearance in patients with high disease burden, suggesting that modulation of the p53 signaling network with Δ133p53α may represent a translationally viable strategy for improving CAR T cell therapy.

Individual Differences in Risk and Protective Factors: The Role of Self-Compassion Components among Emergency Responders.

This study investigates individual differences in protective and risk factors among rescue workers (RWs), particularly Red Cross members, to optimize well-being and job performance under high-stress conditions. Employing a person-centered approach, two psychological profiles were identified: an adaptively resilient profile and a maladaptively vulnerable profile, characterized by distinct personality traits, coping methods, life events, and social support networks. A notable external criterion, self-compassion, discerned the profiles with maladaptively vulnerable individuals who exhibited higher self-judgment, social isolation, and emotional over-identification. The study also examined the impact of job roles on these profiles, discovering a prevalence of adaptive resilience among drivers, contrasting with team members who displayed maladaptive resilience and lower self-compassion scores. These insights suggest a nuanced method for identifying RWs who require specialized support, proposing tailored interventions, especially those enhancing self-compassion. The study, through an extensive psychological metric analysis, provides a deeper comprehension of resilience and vulnerability among RWs. This research highlights the importance of recognizing individual differences in protective and risk factors, thereby contributing to the enhancement of mental health and resilience in high-stress professions.

Research on the Method of Absolute Stress Measurement for Steel Structures via Laser Ultrasonic

Accurate measurement of the stress in steel structures is crucial for structural health monitoring. To achieve this goal, a novel technique, the laser ultrasonic technique, was used in absolute stress measurement in this study. The feasibility of this technique has been verified through theoretical analysis and finite element (FE) analysis. A stress measurement experiment in steel specimens was conducted and the relationship between ultrasonic relative wave velocity and stress was explored. The results revealed that there is a similar linear correlation between the ultrasonic relative wave velocity and absolute stress. The stress can be obtained based on ultrasonic relative wave velocity. According to the stress measurement results, it was found that the absolute error between the measured stress and theoretical stress was largest when the stress level was low, and that the measured error of stress gradually decreased with increases in the applied stress. The relative error between the measured stress and the theoretical stress was within 10% when the stress was higher than 100 MPa. This further verifies the reliability of the laser ultrasonic technique under high-stress conditions. Additionally, the impact of temperature and surface roughness on stress measurement was analyzed. The stress error in stress measurement increased similarly linearly with the increase in temperature and increased non-linearly with the increase in roughness. The corresponding compensation methods were proposed to effectively improve the accuracy of measurement.

Deformations and damages of tunnels subjected to strike-slip faulting: Effects of tectonic stress and cross-sectional shape

Deep-buried tunnels are vulnerable to strike-slip faulting, the responses of which are complicated. However, the effects of tectonic stress and cross-sectional shape on behaviors of tunnels in strike-slip faults have not been detailly investigated. This study performs numerical modeling to study the deformations and damages of tunnels subjected to strike-slip faulting, focusing on the effects of tectonic stress and cross-sectional shape. A three-dimensional numerical model is applied, which is validated by the test from the previous study. Different lateral stress coefficients (from 0.5 to 3.0) and cross-sectional shapes of tunnels (circular shape, horseshoe shape, and egg shape) are modeled. The results show that tectonic stress and cross-sectional shape have a great influence on tunnel responses during strike-slip faulting. The failure mode of the tunnel is highly dependent on the tectonic stress. The tensile damage controls in low tectonic stress conditions, while compressive damage domains in high tectonic stress conditions. The tensile damage initials at the arch waist in the vicinities of fault planes, while the compressive damage mainly occurs at the tunnel vault and bottom in the whole fracture zone. Besides, tectonic stress has apparent effects on the transverse displacement of the tunnel axis and the compressive damage range. The H-shaped tunnel behaves the worst, experiencing the largest cross-sectional deformation, the largest compressive damage range, and the smallest required fault deformation for compressive damage.

PAR4 Antagonism in Patients With Coronary Artery Disease Receiving Antiplatelet Therapies.

BMS-986141 is a novel potent highly selective antagonist of PAR (protease-activated receptor) type 4. PAR4 antagonism has been demonstrated to reduce thrombus formation in isolation and in combination with factor Xa inhibition in high shear conditions in healthy people. We sought to determine whether PAR4 antagonism had additive antithrombotic effects in patients with coronary artery disease who were receiving antiplatelet therapy. Forty-five patients with stable coronary heart disease and 10 healthy volunteers completed a phase 2a open-label 4-arm single-center study. Patients were allocated to 1 of 3 treatment arms for 7 days: (1) ticagrelor (90 mg BID), (2) aspirin (75 mg QD), or (3) the combination of ticagrelor and aspirin. Agonist-induced platelet aggregation, platelet activation, and ex vivo thrombus formation were measured before and 2 and 24 hours after a single oral 4-mg dose of BMS-986141 on the first study visit day in all participants. BMS-986141 demonstrated highly selective inhibition of PAR4-AP (agonist peptide)-induced platelet aggregation, P-selectin expression, and platelet-monocyte aggregate expression (P≤0.001 for all), which were unaffected by concomitant antiplatelet therapies. PAR4 antagonism reduced ex vivo thrombus area in high shear conditions in healthy volunteers (-21%; P=0.001) and in patients receiving ticagrelor alone (-28%; P=0.001), aspirin alone (-23%; P=0.018), or both in combination (-24%; P≤0.001). Plasma concentration of BMS-986141 correlated with PAR4-AP-induced platelet responses (P≤0.001 for all) and total thrombus area under high shear stress conditions (P≤0.01 for all). PAR4 antagonism has additive antithrombotic effects when used in addition to ticagrelor, aspirin, or their combination, in patients with stable coronary heart disease. URL: https://www.clinicaltrials.gov; Unique identifier: NCT05093790.

The impact of illegitimate tasks on burnout syndrome in a healthcare system: A cross-sectional study

BackgroundBurnout syndrome, characterized by physical, mental, and emotional exhaustion due to continuous exposure to high-stress work conditions, has been increasingly recognized as a serious occupational phenomenon, especially amongst healthcare professionals. Recent studies indicate that illegitimate tasks–activities unrelated to one's role are a significant factor contributing to burnout. However, given the variability of work environments across regions, these findings may not apply universally. ObjectiveTo investigate the behavior of the relationship between burnout and illegitimate tasks among healthcare professionals in Guayaquil, Ecuador. MethodsWe conducted a survey of 562 healthcare professionals, including physicians, nurses, and medical/nursing interns, employing the Copenhagen Burnout Inventory and Bern Illegitimate Task Scale. Regression models were developed to predict burnout levels based on multiple factors, including demographic characteristics, professional roles, and perceptions of illegitimate tasks. ResultsWe revealed a statistically significant positive correlation between burnout and illegitimate tasks, with correlation coefficients ranging from 0.320 to 0.588, with higher levels of illegitimate tasks leading to increased burnout. Interestingly, we also found that age and length of service were negatively correlated with burnout, suggesting that these factors may serve as protective elements against burnout. ConclusionsIllegitimate tasks had an impact on burnout amongst healthcare professionals and emphasized the need for organizational strategies aimed at better task management to mitigate burnout risk.

Numerical Simulation Study on the Mechanics and Pore Characteristics of Tectonically Deformed Coal under Multi-Level and Multi-Cycle Loading and Unloading Conditions

Horizontal well cavern completion and stress release is considered a potential technique for efficient development of coalbed methane in tectonically deformed coal (TDC). Pulsating loading and unloading is a key technique for the controlled expansion of caverns and broader stress release within the reservoir. However, current understanding of the mechanical characteristics and pore network structure evolution of TDC under cyclic loading and unloading conditions is still limited. This paper employs numerical simulation methods to study the mechanical behavior and damage characteristics of TDC under cyclic loading and unloading. After obtaining a set of micromechanical parameters reflecting the behavior of TDC samples under triaxial compression in high-stress states, the effects of different stress gradients and cyclic amplitudes on the stress–strain curve, porosity changes, and crack propagation in TDC samples were analyzed. The study results indicate that under various cyclic loading and unloading conditions, the mechanical response characteristics of TDC samples are broadly similar, primarily divided into compression, slow expansion, and accelerated expansion phases. Under low unloading level conditions, the volume expansion of TDC samples is minimal. Also, at the same unloading level, the strain increment decreases with an increasing number of cycles. Correspondingly, under these conditions, the porosity and microcrack expansion in TDC are less than in high-stress gradient scenarios. Under the same unloading level but different amplitudes, the volume expansion rate at 50% unloading amplitude is higher than at 1 MPa unloading amplitude for TDC, with an increased number of crack expansions. Therefore, under cyclic loading conditions, the sensitivity of crack propagation within TDC samples to amplitude is greater than that to unloading level. Under actual pulsating excitation conditions, a low-amplitude, low-stress gradient pulsation method should be used to maintain the stability of horizontal well caverns, and gradually increase the cyclic amplitude to achieve the efficient extraction of coalbed methane in TDC reservoirs. The findings of this study can serve as an important reference for optimizing process parameters in cyclic pulsating stress release engineering for TDC.

Induced seismic activity and source parameter characteristics in the Datong coal mine, China

To clarify the activity patterns and source characteristics of coal mining–induced microseismicity, this study analyzed the spatial distribution characteristics of microseismic events in the Datong coal mining area based on records from the regional digital seismic network. We conducted a detailed characterization of the depth distribution characteristics of microseismic events using the double-difference localization method. Additionally, the source parameters, including corner frequency ( fc), source rupture radius ( r), seismic moment ( M0), source radiated energy ( Es), and stress drop (Δσ), were calculated for 136 mine-induced earthquakes with magnitudes ranging from ML1.3 to ML3.2. The results show that ML ≥ 2.0 mining-induced seismic events occur mainly within numerous microfractures in the Datong mining area. The depth of the seismic sources in the mining area is concentrated at 200∼500 m, with significant north–south differences and a close correlation with the mining depth. The displacement spectra of microseismic sources show agreement with the Brune source model [Formula: see text] attenuation pattern. As M0 gradually increases, r, Δσ, and Es show an increasing trend, while fc gradually decreases, exhibiting characteristics similar to those of tectonic earthquakes. Compared to tectonic earthquakes, coal mining-induced earthquakes have lower corner frequencies and stress drop levels mainly because mining activities alter the originally stable geological structure and stress state, leading to weakened rock strength, decreased elastic modulus, and shallower source depths. These factors contribute to the reduction in corner frequencies. As mining operations continue, microfracturing occurs in the coal and surrounding rock mass, intensifying the dynamic instability of the rock mass that was already under high stress conditions. This situation triggers larger-magnitude, mining-induced seismic events under lower stress conditions.

Investigating the Path Dependent Aging Behavior of Nickel Cobalt Aluminum Oxide Cathode Batteries During High C-rate Cycling Conditions

Nickel-rich cathode material batteries such as the nickel cobalt aluminum oxide with graphite anode are common in the automotive sector due to their high energy density and power performance capabilities, however, they are limited in lifetime performance. Accelerated degradation in specific operation conditions, such as high C-rates are known to significantly contribute to this issue. To better understand a chronological dependence of these high-stress conditions occurring during battery lifetime, a path dependent aging study is performed using profiles inspired by high-performance race operation. The focus on C-rates >1C during charging and discharging using real-world inspired profiles- known to induce particle cracking or lithium plating- addresses the need to understand aging behavior in less studied, but highly relevant high-performance automotive context. The aging conditions were tailored to induce specific degradation modes to better identify potential degradation mode coupling. Using differential voltage and capacity analysis techniques, degradation modes were identified which likely contributed to path dependent aging behavior, including loss of lithium inventory and loss of active material in the positive electrode. Two critical paths were identified in this study where later high C-rate conditions in the form of fast-charging at temperatures of 25 °C resulted in accelerated aging and where loss of lithium inventory induced stresses in the positive electrode, accelerating loss of active material.

Anomalous transport and upscaling in critically-connected fracture networks under stress conditions

Anomalous transport in fractured rocks is of high importance for numerous research fields and applications in hydrogeology and has been widely studied in the last decades. This phenomenon is due to the structural heterogeneities of fractured rocks and the high contrast between the fractures and matrix properties. At the same time, the fracture properties in terms of fracture density and geometrical characteristics are related to in-situ stress conditions that impact the connectivity of the system and the distributions of fracture aperture and length, including the creation of new cracks when the differential stress conditions are strong enough. In order to understand how all these features impact the observed anomalous transport, we study the role of in-situ stress in mass transport through a two-dimensional fractured rock. The fracture network is based on a real outcrop with a connectivity state around the percolation threshold, over which we simulate stress-dependent fracture deformation and propagation, and perform hydrodynamic transport through the deformed rock mass. The impact of the changes in aperture and the creation of new cracks on transport behavior is evaluated for various stress scenarios and reproduced with upscaled representations of transport processes. We also consider matrix diffusion as a source of anomalous transport and demonstrate that this process can be incorporated into the proposed upscaled models. Results showed that traditional upscaling methods with space-Lagrangian velocities description capture well the Gaussian-like breakthrough curves (BTCs) under low-stress ratio conditions, but fail under high-stress ratio conditions with multiple-peak early-times BTCs. To characterize the emergence of strong anomalous transport, we extend the Random Walk model Directed by a Markov Process with space-Lagrangian velocity sampling by incorporating multiple transition matrices conditioned by different initial velocity states. This new transport upscaling model shows high accuracy in predicting complex transport behaviors in critically connected fracture networks.

Effect of cyclic overload on deformation, crack growth behavior and crack initiation/growth lives of a C(T) specimen for 12Cr steel under creep-fatigue condition

ABSTRACT In this study, using a C(T) specimen for 12Cr steel used for a steam turbine rotor, crack growth tests under creep-fatigue conditions with and without overloading were conducted and the fundamental behaviours of deformation and crack growth were investigated experimentally. As a result, load line displacement was found to be suppressed under overload condition regardless of temperature and stress holding time. Crack initiation life under high temperature and low stress condition with overloading was delayed as compared with no overload condition. However, under low temperature and high stress condition with short stress holding time, crack initiation was accelerated remarkably. Furthermore, although crack growth life under creep-fatigue conditions with overloading was found to be shortened as compared with no overloading, the effect of overloading on crack growth life was decreased with an increase in stress holding time.

A Street-Specific Analysis of Level of Traffic Stress Trends in Strava Bicycle Ridership and its Implications for Low-Stress Bicycling Routes in Toronto

This study uses Strava bicycling data to investigate network level patterns of bicycle ridership in Toronto, Canada based on Level of Traffic Stress (LTS). We found that most bicycling occurred on a small fraction of the network, with just 10% of all roads and paths accounting for 75% of all bicycle kilometres travelled in 2022. Low-stress routes (LTS 1 and LTS 2) were more popular than high-stress routes for the top 80% most popular streets. The majority of bicycle kilometres travelled (84%) in LTS 2 occurred on routes with no bicycle infrastructure, highlighting the importance of quiet residential streets in forming a low-stress bike network. Despite high-stress conditions, some LTS 3 and LTS 4 streets were heavily used, suggesting infrastructure gaps in Toronto’s bicycle network.