Decrease In Stress Research Articles

Influences of strain rate on mechanical behaviors of unsaturated and quasi-saturated loess under varying drainage conditions

Although time-dependent deformation of geomaterials underpins slope-failure prediction models, the influence of strain rate on shearing strength and deformation behavior of loess remains unclear. The consolidated undrained (CU) and drained (CD) triaxial testing elucidated the impact of strain rate (0.005–0.3 mm/min) on strength envelopes, deformation moduli, pore pressures, and dilatancy characteristics of unsaturated and quasi-saturated loess. Under drained conditions with a controlled matric suction of 50 kPa, increasing strain rates from 0.005 mm/min to 0.011 mm/min induced decreases in failure deviatoric stress (qf), initial deformation modulus (Ei), and cohesion (c), while friction angles remained unaffected. Specimens displayed initial contractive volumetric strains transitioning to dilation across varying confining pressures. Higher rates diminished contractive volumetric strains and drainage volumes, indicating reduced densification and strength in the shear zone. Under undrained conditions, both unsaturated and quasi-saturated (pore pressure coefficient B = 0.75) loess exhibited deteriorating mechanical properties with increasing rates from 0.03 mm/min to 0.3 mm/min. For unsaturated loess, reduced contractive volumetric strains at higher rates manifested relatively looser structures in the pre-peak stress phase. The strength decrement in quasi-saturated loess arose from elevated excess porewater pressures diminishing effective stresses. Negative porewater pressures emerged in quasi-saturated loess at lower confining pressures and strain rates. Compared to previous studies, the qf and Ei exhibited rate sensitivity below threshold values before attaining minima with marginal subsequent influence. The underlying mechanism mirrors the transition from creep to accelerated deformation phase of landslides.

WHY HAPPENS A PROGRESSIVE DECREASE OF BLOOD PRESSURE AFTER RENAL DENERVATION

Objective: Long-term follow-up data from the SYMPLICITY 3 trial (Bhatt et al, Lancet, 2022) and the Global Symplicty Register data (Mahfoud et al, JACC, 2020) show a further decrease in BP over time up to 3 years post procedure. Yet these observations lack a mechanistic explanation. A decrease in vascular resistance could possibly explain the observed phenomenon. Scanning Laser Doppler Flowmetry (SLDF) allows the non-invasive assessment of vascular resistance and capillary density by using the retinal vasculature as a mirror of the systemic circulation. Design and method: Retinal parameters were assessed using SLDF together with office and 24-hour ambulatory BP before and 6 as well as 12 months after renal denervation in 63 patients with treatment resistant hypertension (TRH) (NCT01687725). SLDF allows the assessment of retinal capillary flow (RCF), pulsed retinal capillary flow (systolic retinal capillary flow – diastolic retinal capillary flow) (pRCF), retinal vascular resistance, capillary area (CapA) and intercapillary distance (ICD). Results: Mean age of the study cohort was 60±11 years, mean BMI 30.6±4.9 kg/m2. Patients took 5.8 antihypertensive medications on average. There was a significant reduction of systolic and diastolic 24-hour ambulatory as well office BP 6 as well as 12 months after RDN (table 1). There was no significant reduction in the number of antihypertensive medications taken between baseline and 12 months after RDN (5.8vs.5.7 antihypertensive pills, p=0.159). Retinal vascular resistance was reduced 6 months after RDN (table 1), pRCF was reduced 6 as well as 12 months after RDN and capillary density improved 12 months after RDN. Conclusions: In high-risk patients with TRH endovascular RDN improved vascular resistance and reversed capillary rarefaction in the retinal circulation, a prognostic marker of further end-organ damage. The reduction of pRCF indicates a decrease of shear stress on the vascular wall by the pulsed blood flow. Increment of capillary density was observed not already 6 months, but only 12 months after RDN. We conclude that, improvement of capillary rarefaction happens slowly after RDN and requires long-term effective BP control and, that reduction in vascular resistance might explain the prolonged BP reduction after RDN.

The Effectiveness of EduMind for Mental Health Promotion Among Youths.

Introduction The global surge in mental health issues, particularly among the youth, is evident. Despite the proliferation of digital mental health services, their adoption remains limited, hindered by various barriers. To address this issue, an evidence-based, validated digital mental health intervention is necessary. Although much research has explored the effectiveness of such interventions, there was limited evidence supporting those within the youth population. The objective of this research is to assess the effects of aninterventional module on depression, anxiety, and stress symptoms among youths. Methods The EduMind online mental health intervention contents were developed from a needs assessment and a scoping review of effective psychotherapies, achieving a high content validation index (CVI) of 0.96. The contents were integrated into a web application to assess its effectiveness among the target population which consisted of university students of a local institution. A quasi-experimental study compared the intervention group (n=264) to a waitlist-control group (n=200), evaluating changes in mental health status with the Depression, Anxiety and Stress Scale 21 (DASS-21) questionnaire using analysis of covariance (ANCOVA) to analyse mean differences. Results Participants in the intervention group indicated a significant decrease (p< 0.001) in depression, anxiety, and stress. The pre-test and post-test mean scores in the intervention group were 15.81 and 8.97 for depression, 11.46 and 7.02 for anxiety and 14.64 and 6.33 for stress, respectively. In the control group, there was no significant difference between the pre-test and post-test mean scores for depression. However, there was a slight significant reduction for anxiety with pre- and post-test scores of13.31 and 12.95. Stress mean scores exhibited a slight increase, rising from 13.55 to 14.24. The final phase revealed significant improvements in mental health status between groups, with significant effect sizes for stress (ƞp2= 0.57, p < 0.001), depression (ƞp2= 0.71, p < 0.001), and anxiety (ƞp2= 0.27, p < 0.001). Conclusion The findings contribute to the advancement of technology-assisted health services, facilitating greater uptake among the population.This study utilized a comprehensive module development framework and demonstrated the effectiveness of the expert-guided mental health intervention module.Furthermore, the study suggests potential integration with the National Strategic Plan for Mental Health 2020-2025 and the National Mental Health Policy, proposing the web application as a potential compulsory student screening tool administered by universities. The information gathered by this application could inform future research directions, propelling technological-assisted mental health services to new heights.

Energy-Based Assessment of Liquefaction Behavior of a Non-Plastic Silt Based on Cyclic Triaxial Tests

Earthquakes cause cyclic shear deformations in soil and build-up of excessive pore water pressure as a result of undrained loading, accompanied with rearrangement of soil particles and degradation in stiffness of the soil due to decrease in effective stresses. During loading, the onset of soil liquefaction is defined as a stress state in which the excess pore water pressure is equalized to the total stress. From this point of view, assessment of the pore water pressure development pattern under cyclic loading has been one of the most salient research topics in geotechnical and earthquake engineering. In this study, results of a series of cyclic triaxial tests on non-plastic silt specimens consolidated under 100 kPa effective isotropic consolidation pressure were used to question the modelling ability of pore pressure development models previously proposed for sands. Tests were performed on specimens of 6 different initial relative densities (Dr) ranging between 30-80% and 10 different cyclic stress ratios (CSR). The key parameters of pore water pressure development and shear deformation in the energy-based model used are relative density, cyclic stress ratio and number of cycles. The results revealed that, these energy-based models have a strong potential in evaluation of pore water pressure development pattern of non-plastic silts. Test results also show that the increase in relative density and decrease in CSR causes a ladderlike behavior among pore water pressure and cyclic shear strain, which is relevantly rendered by energy-based models.

Analysis of the mechanical response of solid rocket engine propellant under acceleration shock

The increased-range solid rocket engine of new ammunition often needs to withstand extremely high acceleration overload, leading to damage to the propellant’s structural integrity. To address this issue, this paper constructs a nonlinear viscoelastic constitutive model for the CMDB propellant by using low- and high-strain rate mechanical property tests. Combined with the secondary development of explicit dynamics and numerical simulation technology, the mechanical response of a certain type of solid rocket propellant under different acceleration impacts is analyzed. The results show that under acceleration impact loads, the propellant will compress, rebound, and recover over time, continuously cycling. Its axial displacement, maximum equivalent stress, and maximum equivalent strain exhibit irregular sinusoidal wave-like periodic cycles. Looking at the time when the peaks appear, the time when the maximum equivalent stress appears always lags behind the time when the maximum axial displacement peak appears. Due to the viscous effect of the viscoelastic material of the propellant, the time when the equivalent strain peak appears will lag behind the equivalent stress. Because of the material’s damping effect, both the peak values of the maximum equivalent stress and equivalent strain decrease over time. Under continuous high acceleration impact loads, this viscous damping phenomenon continuously diminishes, and the peak value of the propellant’s axial displacement gradually increases.

DEM investigation on sandy soil behaviors under the influence of particle shape

The mechanical properties of sandy soil, a prevalent material in engineering construction, are affected by several factors, including the particle shape. This study utilized a rigid block unit for particle simulation and established specimens reflecting the real particle appearance based on μCT scanning geometry. Four simple particle types with varying roundness were designed according to the roundness definition, and corresponding numerical test models were developed. These models were employed to examine the effect of particle roundness on the macroscopic mechanical properties of sandy soil using triaxial shearing simulation tests, disregarding other shape parameters. The results demonstrate that particle roundness significantly affects the mechanical properties of sandy soil. Within a roundness range of [0,1], samples with varying particle roundness displayed different deviatoric stress–strain curves. As the roundness increases, the peak deviatoric stress decreases, and both the cohesive strength and friction angle of the samples reduce.

Study of Surface Chemistry, Temperature and Strain Rate on the Tensile Properties of Monolayer Graphene Oxide

The mechanical properties of graphene oxide (GO) during tensile fracture were studied using molecular dynamics methods, and the influence of hydroxyl and epoxy groups on the mechanical properties of GO was explored. In addition, the changes in mechanical properties of GO under different temperatures and strain rates were studied to gain a deeper understanding of its mechanical behavior. The results indicate that hydroxyl and epoxy groups have a significant influence on the elastic modulus, ultimate stress, and ultimate strain of GO. The presence of hydroxyl and epoxy groups can alter the molecular structure of GO, thereby affecting its ultimate stress and strain. When the number of hydroxyl groups is 16 and the number of epoxy groups is 20, the ultimate stress decreases by about 31% and the elastic modulus decreases by about 20%. The variation of elastic modulus, ultimate stress, and ultimate strain of GO with temperature was studied at three temperatures: 300[Formula: see text]K, 500[Formula: see text]K, and 800[Formula: see text]K. As the temperature increases, the amplitude of atomic vibration increases and internal defects and cracks in GO continue to form and expand. At the same time, its coefficient of thermal expansion also increases, causing deformation and loosening of the crystal structure, resulting in a decrease of about 10% in the ultimate stress of GO, and a slight decrease in the ultimate strain and elastic modulus. Finally, the influence of different strain rates on the mechanical properties of GO was studied. As the strain rate increases, the intermolecular interactions within GO are rapidly altered, and the previously loose structure gradually becomes tightly ordered, resulting in an increasing trend in the elastic modulus, ultimate stress, and ultimate strain of GO.

Key principles of stress control method

Underground excavation would cause two main excavation effects: (1) stress redistribution, including radial stress decrease and tangential stress concentration; and (2) surrounding rock degradation. Comprehensive consideration of excavation effects is crucial to prevent underground engineering disasters. However, the two excavation effects are not considered in the predominantly used Platts pressure arch theory, whereas the New Austrian tunneling method is focused on the full utilization of the strength of the surrounding rock. Construction designing using these methods could lead to disaster deep underground. Thus, in this study, the stress control method (SCM) was proposed to comprehensively consider the two excavation effects. The following two key SCM principles were introduced in this study: (1) adopt the largest possible prestressing force to increase the low radial stress caused by excavation; (2) timing of support should be as early as possible to minimize surrounding rock deterioration. The application principles of SCM in hard rock tunnels and soft rock tunnels are explained

The Effect of Five-Finger Relaxation Technique on Anxiety and Stress in Non-Hemorrhagic Stroke Patients at the Inpatient Installation of RSUD Cimacan Cianjur District

Aims: The purpose of this study was to examine the effect of five-finger relaxation technique on anxiety and stress in hemorrhagic stroke patients at Cimacan Hospital. Methods: This study used quasi-experiment with nonequivalent control group design. Sample collection using purposive sampling. The sample was 40 people and divided into two groups with 20 people each for the intervention group and control group. Data analysis using Paired Sample T-Test and Independent Sample T-Test. Results: The results showed that after the five-finger relaxation technique was performed on the intervention group, there was a decrease in anxiety levels (p = 0.000) and stress (p = 0.000) in stroke patients, while in the control group there was a decrease in anxiety (p = 0.000) and stress (p = 0.000), and there was a difference between anxiety levels (p = 0.000) and stress (p = 0.000) in the intervention and control groups. Conclusion: There is an effect of five-finger relaxation technique on anxiety and stress in non-hemorrhagic stroke patients, and there are differences in anxiety and stress in the control and intervention groups. It is hoped that this five-finger relaxation technique can be used as an evidence base nursing on non-pharmacological treatment as a form of independent nursing intervention by a nurse in providing nursing care to help in the process of reducing anxiety and stress in stroke patients.

EFFECT OF SEGMENT DISLOCATION ON THE MECHANICAL PROPERTIES OF LINED TUNNELS IN A COMPLEX ENVIRONMENT

In complex environments, tunnels with a lined structure are more affected by the dislocation of a segment. This study uses finite element simulations to further investigate the relationship between environmental changes and segments in lined tunnels. Tunnels with and without a lining are simulated under varying strata resistance, buried depth, and water level conditions. The horizontal and vertical displacements and stress changes in the two tunnels are compared when segment dislocation occurs. The results show that the lateral displacement of the tunnel is relatively stable and less influenced by external loads. However, the longitudinal displacement change is the opposite, and it increases significantly when the displacement exceeds 10 mm. When the lined tunnel is subjected to a large external load and misalignment occurs, the performance of the tube sheet joint bolts deteriorates, resulting in a stress decrease. Furthermore, the lined tunnel exhibits an increased ability to resist deformation and does not exactly follow the law of small displacements from small misalignments. When a large misalignment occurs, the lined tunnel may be damaged by elliptical deformation along the 45° direction, and its internal forces would be much larger than those of the unlined tunnel.

Investigation of mechanical properties in thin spray-on liner coated sandstone: Comparative study of unfilled and filled flaws

Thin spray-on liners (TSLs) are increasingly recognized as a potent skin support technology in underground engineering applications, particularly in mining. To better understand the coating and filling effects of TSL on the mechanical properties of the flawed specimens, a series of uniaxial compression tests were conducted on TSL-coated sandstone with unfilled and filled flaws. The experimental results showed that compared with the flawed specimen, the strength and peak strain of the TSL-coated and filled specimens increased, and the degree of improvement was more evident for the filled specimen coated with TSL. The specimens coated with TSL exhibited higher total, elastic, and dissipation energies compared to the uncoated specimens. Additionally, a greater proportion of the total input energy was transformed into dissipation energy after coating. For the filled specimens, more dissipation energy was generated during the failure process owing to the friction of the flaw surface provided by the filling effect. Moreover, the crack initiation and propagation behaviors of the flawed and filled sandstone specimens coated with TSL were analyzed by numerical simulation. For the specimens with an inclination angle of 45°, the TSL provided confinement to inhibit the initiation and propagation of tensile cracks, resulting in delayed crack initiation. The TSL filling plays a role in sharing part of the stress on the flaw surface, which weakens the stress concentration at the flaw tip. The effect of the TSL on the stress at the flaw tip was analyzed using a theoretical solution. The variation in SIF KII of the specimens with different flaw inclination angles was studied using a theoretical solution. Compared with the flawed specimens, the stress concentration in the filled flawed specimen was lower and the confinement effect could enhance the decrease in the flaw tip stress.

Biochemical state of brain-liver axis of rats under restraint-induced stress and 2-oxoglutarate impact

Environmental factors play a significant role in affecting the overall health of organisms, with stress being a notable contributor. The process of urbanization and globalization in modern society introduces additional stressors, exacerbating population health issues. Consequently, there is a need for thorough examination, analysis, and exploration of strategies to mitigate the adverse effects of stress. 2-Oxoglutarate, an essential intracellular metabolite and mediator with metabolite trophic properties, emerges as a promising candidate for intervention. In this study, we aimed to evaluate the combined impact of restraint-induced stress and 2-oxoglutarate on the oxidative-reducing balance, antioxidant system effectiveness, and the functional status of the liver and brain in rats. Restraint-induced stress was found to elevate oxidative stress levels, as evidenced by increased concentrations of malonic dialdehyde and oxidative-modified proteins, particularly in the brain. Additionally, signs of lactic acidosis were observed in the liver, indicating physiological changes in response to stress. Furthermore, restraint-induced stress significantly altered bioenergy components, with decreased superoxide dismutase activity and increased cytochrome C concentration, potentially indicating mitochondrial dysfunction and increased membrane permeability. The incorporation of a 2% solution of 2-oxoglutarate into the diet demonstrated a reduction in malonic dialdehyde and carbonylated protein formation, leading to more effective restoration of oxidative-reducing balance in the brain compared to the liver. Additionally, normalization of the lactate/pyruvate concentration ratio and decreased lactate dehydrogenase activity, alongside elevated alanine aminotransferase levels, suggested a decrease in oxidative stress in the liver. Moreover, exogenous 2-oxoglutarate exhibited a positive effect on superoxide dismutase activity and cytochrome C concentration, indicating a reduction in oxidative tension in the liver and progressive mitochondrial function recovery. Based on these findings, exogenous 2-oxoglutarate emerges as a promising metabolitotrope and adaptogen for managing oxidative stress and improving mitochondrial function.

Global tele-music therapy program reduces pain, discomfort and stress with enduring effects during COVID – 19: A pilot study

Abstract: Of particular need was access to easily applied modalities to improve recovery during the COVID-19 pandemic. The current state of knowledge regarding music therapy has allowed improvements among victims of stroke, dementia, spinal cord injuries, and so forth. The goal of this pilot study was to provide individuals with symptom reduction such as perceived pain, discomfort and anxiety, improved emotional processing, improved relaxation and well-being for participants with current, recent case or long haul COVID-19; those who had lost a loved one to COVID; those experiencing workplace burnt out, or symptoms related to getting the vaccine. Sixty-one individuals participated in a follow-up survey out of one hundred seventy one participants from twelve countries who were treated using one to one zoom sessions following a 30 minute protocol of live music using instruments chosen for soothing or activating energy. Recipients responded to assessment questions showing decrease in pain, anxiety and stress, sustained effect, most effective instruments, spontaneous imagery and open-ended narrative responses. The totality of all instruments were considered most helpful with the drum and Native American style flute considered the most beneficial. Many participants reported spontaneous healing imagery without any guidance demonstrating the power of sound and music to evoke individualized visualization.

EXPERIMENTAL STUDY OF NON-EQUILIBRIUM RHEOLOGICAL EFFECTS DURING THE FLOW OF PARAFFINIC OILS OF TIMAN-PECHORA BASIN. THIXOTROPY, SUPER ANOMALOUS VISCOSITY, OSCILLATIONS OF SHEAR STRESS

Laboratory experiments were carried out to study the non-stationary and non-equilibrium flow regimes of some paraffinic and high paraffinic crude oils of the Timan-Pechora Basin in a rotational viscometer. The presence of thixotropic properties (shear thinnig and hy steresis loops on the flow curves) is shown. The threshold character of the dependence of the area of the hysteresis loop on the oil tempera ture is demonstrated. Experiments have shown that under certain conditions on the flow curves of the studied oils, there are areas of a decrease in shear stress with an increase in shear rate, similar to areas of a «super anomalous» viscosity (SAV) in plastic lubricants. The shape and size of these areas, i.e. the intensity of the «superanomality» manifestation strongly depends on the experiment conditions and are poorly reproducible from experiment to experiment. In experiments, the SAV phenomenon at temperatures below the gelation temperature was always observed when the sample of paraffinic oil was at rest for a sufficiently long time before deformation. If, however, it was in the gap between the viscometer cylinders after the end of the next measurement cycle for a short time (no more than a few minutes), then at the next cycle of recording the flow curve, the SAV phenomenon can be practically imperceptible, although the hysteresis remains. Experiments show that if a sample of high paraffinic oil is deformed at a constant low shear rate, i.e. constant angular velocity of rotation of the device cylinder, and a temperature below the temperature of gelation, then on the falling curve of the dependence of shear stress on time («shear thinning»), oscillations in shear stress with a period equal to the period of rotation of the viscometer cylinder can be observed.

Methanolic extract of Merremia emarginata (Burm. f.) Hallier f. attenuates renal damage in streptozotocin-induced diabetic nephropathy in rats

IntroductionMerremia emarginata (syn: Ipomoea reniformis) is used by the traditional healers of the Tirunelveli district of Tamil Nadu and Nelliampathy hills of Kerala for the treatment of diabetes. It contains important phytoconstituents like scopoletin, quercetin, and kaempferol and is reported to have pharmacological activities like antidiabetic antioxidant, antihyperlipidemic, ACE inhibitory, and hypotensive. Diabetic kidney disease is a common microvascular complication seen in patients with long-term diabetes. This study aimed to investigate the efficacy of Merremia emarginata in attenuating diabetic kidney disease. Materials and methodsDiabetes was induced by a single i.p. injection of 55 mg/kg streptozotocin (STZ). The animals were divided into seven groups with six rats in the control group and seven each in the STZ, STZ + Standard drug Ramipril (STD), STZ + Low dose (LD) methanolic extract of Merremia emarginata (MEME), STZ + High dose (HD) MEME, STZ + STD + LD, and STZ + STD + HD groups. The renal function was assessed by estimating various parameters viz, blood glucose, serum and urine creatinine, urine albumin, blood urea nitrogen (BUN), glycosylated haemoglobin (HbA1c) levels, oxidative stress, and kidney hypertrophy. ResultsTreatment with Ramipril and HD MEME showed a decrease in blood glucose levels, urine albumin, a decrease in serum creatinine, an increase in urine creatinine, a decrease in BUN, HbA1c, kidney hypertrophy, and oxidative stress. The combination treatment of Ramipril and HD MEME showed a synergistic effect. ConclusionThe study revealed that MEME attenuates diabetic nephropathy and has the potential to be used in diabetic nephropathy either alone or as an adjuvant.

Energy characteristics of saturated Jurassic sandstone in western China under different stress paths

AbstractTo study the energy evolution and failure characteristics of saturated sandstone under unloading conditions, rock unloading tests under different stress paths were conducted. The energy evolution mechanism of the unloading failure of saturated sandstone was systematically explored from the perspectives of the stress path, the initial confining pressure, and the energy conversion rate. The results show that (1) before the peak stress, the elastic energy increases with an increase in deviatoric stress, while the dissipated energy slowly increases first. After the peak stress, the elastic energy decreases with the decrease of deviatoric stress, and the dissipated energy suddenly increases. The energy release intensity during rock failure is positively correlated with the axial stress. (2) When the initial confining pressure is below a certain threshold, the stress path is the main factor influencing the total energy difference. When the axial stress remains constant and the confining pressure is unloading, the total energy is more sensitive to changes in the confining pressure. When the axial stress remains constant, the compressive deformation ability of the rock cannot be significantly improved by the increase in the initial confining pressure. The initial confining pressure is positively correlated with the rock's energy storage limit. (3) The initial confining pressure increases the energy conversion rate of the rock; the initial confining pressure is positively correlated with the energy conversion rate; and the energy conversion rate has a high confining pressure effect. The increase in the axial stress has a much greater impact on the elastic energy than the confining pressure. (4) When the deviatoric stress is small, the confining pressure mainly plays a protective role. Compared with the case of triaxial compression paths, the rock damage is more severe under unloading paths, and compared with the case of constant axial stress, the rock damage is more severe under increasing axial stress.

Xyloglucan deficiency leads to a reduction in turgor pressure and changes in cell wall properties, affecting early seedling establishment

Xyloglucan is believed to play a significant role in cell wall mechanics of dicot plants. Surprisingly, Arabidopsis plants defective in xyloglucan biosynthesis exhibit nearly normal growth and development. We investigated a mutant line, cslc-Δ5, lacking activity in all five Arabidopsis cellulose synthase like-C (CSLC) genes responsible for xyloglucan backbone biosynthesis. We observed that this xyloglucan-deficient line exhibited reduced cellulose crystallinity and increased pectin levels, suggesting the existence of feedback mechanisms that regulate wall composition to compensate for the absence of xyloglucan. These alterations in cell wall composition in the xyloglucan-absent plants were further linked to a decrease in cell wall elastic modulus and rupture stress, as observed through atomic force microscopy (AFM) and extensometer-based techniques. This raised questions about how plants with such modified cell wall properties can maintain normal growth. Our investigation revealed two key factors contributing to this phenomenon. First, measurements of turgor pressure, a primary driver of plant growth, revealed that cslc-Δ5 plants have reduced turgor, preventing the compromised walls from bursting while still allowing growth to occur. Second, we discovered the conservation of elastic asymmetry (ratio of axial to transverse wall elasticity) in the mutant, suggesting an additional mechanism contributing to the maintenance of normal growth. This novel feedback mechanism between cell wall composition and mechanical properties, coupled with turgor pressure regulation, plays a central role in the control of plant growth and is critical for seedling establishment in a mechanically challenging environment by affecting shoot emergence and root penetration.

Effects of h-BN content and heat treatment temperature on the tribological behavior and toughness of laser-clad Mo2FeB2/WC/h-BN coatings

In this study, h-BN-modified Mo2FeB2/WC composite coatings were fabricated via laser cladding. The Mo2FeB2/WC/10 wt% h-BN composite coatings were heat-treated at 400, 600, and 800 °C. The microstructure, microhardness, tribological properties, residual stress, fracture toughness and fracture morphology of the coatings were investigated. The results showed that h-BN addition combined with heat treatment promoted the distribution of elements and finer microstructure. The Mo2FeB2/WC/10 wt% h-BN coating heat-treated at 600 °C showed the highest microhardness (1416.8 HV0.5) among the prepared coatings. The pristine and 600 °C heat-treated Mo2FeB2/WC/10 wt% h-BN coating showed excellent wear rates (1.97 and 1.84 × 10−5 mm3/Nm, respectively). The composite coatings modified with h-BN exhibited an abrasive wear mechanism after heat treatment. As the h-BN content and heat treatment temperature increased, there was a notable decrease in residual stress. Specifically, the coating subjected to heat treatment at 800 °C demonstrated the lowest residual tensile stress recorded at 168 MPa. Conversely, when heat-treated at 600 °C, the coating exhibited an optimal fracture toughness of 14.96 MPa⋅m1/2, with fracture behavior consistent with typical brittle fracture characteristics.

Numerical investigation of mechanical responses and failure features of coal measure strata using combined finite-discrete element method

Investigating the mechanical responses and failure features of the deep coal measure strata (CMS) is essential for designing hydraulic fracturing treatments and preventing geological dynamic hazards in underground engineering. In this paper, a three-dimensional CMS model is established by the combined finite-discrete element method (FDEM). The mechanical properties, stress evolutions and failure features of the CMS with different lithological combinations (sandstone-coal-sandstone (SCS), sandstone-coal-mudstone (SCM) and mudstone-coal-mudstone (MCM)) and thickness ratios are investigated under the uniaxial compressive condition. Results indicate that the SCS combination exhibits the highest uniaxial compressive strength (UCS) and elastic modulus, followed by the SCM and MCM combinations. The mechanical properties of the CMS are predominantly determined by the softer coal layer. The mechanical contrasts in elastic modulus and Poisson’s ratio between adjacent layers cause the generation of additional compressive stress in the softer layer and additional tensile stress in the stiffer layer. Therefore, the softer coal layer exhibits the shear-dominated failure pattern while the stiffer sandstone/mudstone layer displays the tensile-dominated failure pattern in the CMS. Furthermore, as the thickness ratio of the coal layer increases, the UCS, elastic modulus, and interfacial constraint stress decrease in the CMS. Additionally, the UCS and stress–strain relationship in the post-peak stage exhibit the noticeable size effect, whereas the mechanical behaviors in the pre-peak stage and the ultimate fracture patterns show the opposite. The elastic modulus and interfacial constraint stress obtained by the FDEM simulation match well with those calculated by theoretical models. The key findings of this paper can provide fundamental understanding and reliable parameters for multi-scale geomechanical modeling in petroleum and mining engineering.

Evaluation method of the synergistic service performance between ultrahigh-performance concrete and normal strength concrete based on the parameter of environmental equivalent force ratio

This study investigated the synergistic service performances of ultrahigh-performance concrete (UHPC) and normal-strength concrete (NSC). Restrained specimens used in this study were designed to assess the non-equivalent deformation of a substrate and UHPC under specific service conditions and shrinkage. Various UHPC repair materials characterized by different shrinkage deformation gradients were developed using expansive agents and lightweight aggregates. The study explored the effects of shrinkage on the synergistic service properties of UHPC-NSC. In addition, the bond fatigue performance of UHPC-NSC was investigated, and a bond fatigue-life equation was formulated. Under static loads and a stress ratio of 0.9, specimens exhibited both substrate and bond failures. By contrast, specimens under stress ratios of 0.8 and 0.7 displayed substrate failure. The synergistic effect of a 10 % dosage of expansive agent and a 15 % dosage of lightweight aggregate resulted in a 67.2 % reduction in UHPC shrinkage after 28 d. Internal stress derived from the non-equivalent deformation of the substrate and UHPC due to shrinkage was quantified. A reduction in UHPC shrinkage led to a 33.0–67.3 % decrease in tensile stress for repair materials. Internal stresses in the UHPC-NSC under alternating environments, including wet–dry, hot–cool, and freeze–thaw cycles, were calculated, where the ratio of internal stress to interfacial strength was defined as the interfacial stress-intensity ratio. This study presents an evaluation method for the synergistic service performance of UHPC-NSC based on an environmental equivalent-force ratio, thereby providing guidance for practical concrete-repair service-life design.