Due to the heterogeneity of rock masses and the variability of in situ stress,the traditional linear inversion method is insufficiently accurate to achieve high accuracy of the in situ stress field.To address this cha...Due to the heterogeneity of rock masses and the variability of in situ stress,the traditional linear inversion method is insufficiently accurate to achieve high accuracy of the in situ stress field.To address this challenge,nonlinear stress boundaries for a numerical model are determined through regression analysis of a series of nonlinear coefficient matrices,which are derived from the bubbling method.Considering the randomness and flexibility of the bubbling method,a parametric study is conducted to determine recommended ranges for these parameters,including the standard deviation(σb)of bubble radii,the non-uniform coefficient matrix number(λ)for nonlinear stress boundaries,and the number(m)and positions of in situ stress measurement points.A model case study provides a reference for the selection of these parameters.Additionally,when the nonlinear in situ stress inversion method is employed,stress distortion inevitably occurs near model boundaries,aligning with the Saint Venant's principle.Two strategies are proposed accordingly:employing a systematic reduction of nonlinear coefficients to achieve high inversion accuracy while minimizing significant stress distortion,and excluding regions with severe stress distortion near the model edges while utilizing the central part of the model for subsequent simulations.These two strategies have been successfully implemented in the nonlinear in situ stress inversion of the Xincheng Gold Mine and have achieved higher inversion accuracy than the linear method.Specifically,the linear and nonlinear inversion methods yield root mean square errors(RMSE)of 4.15 and 3.2,and inversion relative errors(δAve)of 22.08%and 17.55%,respectively.Therefore,the nonlinear inversion method outperforms the traditional multiple linear regression method,even in the presence of a systematic reduction in the nonlinear stress boundaries.展开更多
In the aerospace field, residual stress directly affects the strength, fatigue life and dimensional stability of thin-walled structural components, and is a key factor to ensure flight safety and reliability. At prese...In the aerospace field, residual stress directly affects the strength, fatigue life and dimensional stability of thin-walled structural components, and is a key factor to ensure flight safety and reliability. At present, research on residual stress at home and abroad mainly focuses on the optimization of traditional detection technology, stress control of manufacturing process and service performance evaluation, among which research on residual stress detection methods mainly focuses on the improvement of the accuracy, sensitivity, reliability and other performance of existing detection methods, but it still faces many challenges such as extremely small detection range, low efficiency, large error and limited application range.展开更多
The surrounding rock of the soft rock roadway is seriously deformed and damaged under the superposition of mining stress and fault tectonic stress.In this paper,taking the No.232206 intake roadway in Meihuajing Coal M...The surrounding rock of the soft rock roadway is seriously deformed and damaged under the superposition of mining stress and fault tectonic stress.In this paper,taking the No.232206 intake roadway in Meihuajing Coal Mine as the engineering background,the deformation and failure law of the surrounding rock of the roadway in different fault protection pillar widths were obtained by numerical simulation method.On this basis,the mechanical model of the roadway under the action of hanging wall overburden migration and fault slip in normal faults was established,and the energy-driven mechanism of large deformation of the surrounding rock of the roadway was revealed.The ratio T of the energy applying on anchoring surrounding rock to the resistant energy of the anchored surrounding rock was defined as the criterion for the deformation of the roadway.Finally,it was calculated according to the actual working conditions on site,and the control method of“stress relief-support reinforcement”was used to support the roadway with the risk of large deformation.The on-site monitoring results show that the control effect of the surrounding rock of the roadway is obvious.展开更多
To investigate the residual stress distribution and its influence on machining deformation in 6061-T651 aluminum alloy plates,this paper uses the crack compliance method to study the residual stress characteristics of...To investigate the residual stress distribution and its influence on machining deformation in 6061-T651 aluminum alloy plates,this paper uses the crack compliance method to study the residual stress characteristics of 6061-T651 aluminum alloy plates with a thickness of 75 mm produced by two domestic manufacturers in China.The results indicate that both types of plates exhibit highly consistent and symmetrical M-shaped residual stress profile along the thickness direction,manifested as surface layer compression and core tension.The strain energy density across all specimens ranges from 1.27 kJ/m^(3)to 1.43 kJ/m^(3).Machining deformation simulations of an aerospace component incorporating these measured stresses showed minimal final deformation difference between the material sources,with a maximum deviation of only 0.009 mm across specimens.These findings provide critical data for material selection and deformation control in aerospace manufacturing.展开更多
This study proposes an alternative calculation mode for stresses on the slip surface(SS).The calculation of the normal stress(NS)on the SS involves examining its composition and expanding its unknown using the Taylor ...This study proposes an alternative calculation mode for stresses on the slip surface(SS).The calculation of the normal stress(NS)on the SS involves examining its composition and expanding its unknown using the Taylor series.This expansion enables the reasonable construction of a function describing the NS on the SS.Additionally,by directly incorporating the nonlinear Generalized Hoke-Brown(GHB)strength criterion and utilizing the slope factor of safety(FOS)definition,a function of the shear stress on the SS is derived.This function considers the mutual feedback mechanism between the NS and strength parameters of the SS.The stress constraints conditions are then introduced at both ends of the SS based on the spatial stress relation of one point.Determining the slope FOS and stress solution for the SS involves considering the mechanical equilibrium conditions and the stress constraint conditions satisfied by the sliding body.The proposed approach successfully simulates the tension-shear stress zone near the slope top and provides an intuitive description of the concentration effect of compression-shear stress of the SS near the slope toe.Furthermore,compared to other methods,the present method demonstrates superior processing capabilities for the embedded nonlinear GHB strength criterion.展开更多
In this paper,we propose a multiphysics finite element method for a nonlinear poroelasticity model with nonlinear stress-strain relation.Firstly,we reformulate the original problem into a new coupled fluid system-a ge...In this paper,we propose a multiphysics finite element method for a nonlinear poroelasticity model with nonlinear stress-strain relation.Firstly,we reformulate the original problem into a new coupled fluid system-a generalized nonlinear Stokes problem of displacement vector field related to pseudo pressure and a diffusion problem of other pseudo pressure fields.Secondly,a fully discrete multiphysics finite element method is performed to solve the reformulated system numerically.Thirdly,existence and uniqueness of the weak solution of the reformulated model and stability analysis and optimal convergence order for the multiphysics finite element method are proven theoretically.Lastly,numerical tests are given to verify the theoretical results.展开更多
Fatigue failure caused by vibration is the most common type of pipeline failure.The core of this research is to obtain the nonlinear dynamic stress of a pipeline system accurately and efficiently,a topic that needs to...Fatigue failure caused by vibration is the most common type of pipeline failure.The core of this research is to obtain the nonlinear dynamic stress of a pipeline system accurately and efficiently,a topic that needs to be explored in the existing literature.The shell theory can better simulate the circumferential stress distribution,and thus the Mindlin-Reissner shell theory is used to model the pipeline.In this paper,the continuous pipeline system is combined with clamps through modal expansion for the first time,which realizes the coupling problem between a shell and a clamp.While the Bouc-Wen model is used to simulate the nonlinear external force generated by a clamp,the nonlinear coupling characteristics of the system are effectively captured.Then,the dynamic equation of the clamp-pipeline system is established according to the Lagrange energy equation.Based on the resonance frequency and stress amplitude obtained from the experiment,the nonlinear parameters of the clamp are identified with the semi-analytical method(SAM)and particle swarm optimization(PSO)algorithm.This study provides a theoretical basis for the clamp-pipeline system and an efficient and universal solution for stress prediction and analysis of pipelines in engineering.展开更多
The surrounding rock is prone to large-scale loosening and failure after the excavation of shallow large-span caverns because of the thin overlying strata and large cross-section span.The rational design of bolt suppo...The surrounding rock is prone to large-scale loosening and failure after the excavation of shallow large-span caverns because of the thin overlying strata and large cross-section span.The rational design of bolt support is very important to the safety control of surrounding rock as a common support means.The control mechanism and design method of bolt support for shallow-buried large-span caverns is carried out.The calculation method of bolt prestress and length based on arched failure and collapsed failure mode is established.The influence mechanism of different influencing factors on the bolt prestress and length is clarified.At the same time,the constant resistance energy-absorbing bolt with high strength and high toughness is developed,and the comparative test of mechanical properties is carried out.On this basis,the design method of high prestressed bolt support for shallow-buried large-span caverns is put forward,and the field test is carried out in Qingdao metro station in China.The monitoring results show that the maximum roof settlement is 6.8 mm after the new design method is adopted,and the effective control of the shallow-buried large-span caverns is realized.The research results can provide theoretical and technical support for the safety control of shallow-buried large-span caverns.展开更多
Existing evidence has demonstrated the association between exposure to volatile organic compounds(VOCs)and osteoporosis(OP)risk,but the underlying mechanistic framework remains unclear.This study aimed to explore pote...Existing evidence has demonstrated the association between exposure to volatile organic compounds(VOCs)and osteoporosis(OP)risk,but the underlying mechanistic framework remains unclear.This study aimed to explore potential pathways using adverse outcome pathway(AOP)analysis,and evidence this association in middle-to-old-aged American adults using the updated National Health and Nutrition Examination Survey data.Multivariable-adjusted general linear and weighted quantile sum models were employed to analyze associations of VOC metabolites(VOCMs),representing internal VOCs exposure levels,with OP-related phenotypes.An AOP framework based on network analysis was developed by extracting target genes and phenotypes.Among 3555 American adults aged≥40 years(539 OP participants),we found that increasing urinary 3-and 4-methylhippuric acid,N-acetyl-S-(n-propyl)-l-cysteine(BPMA),and N-acetyl-S-(3-hydroxypropyl)-l-cysteine were associated with elevated OP odds with odds ratios(ORs)(95%confidence intervals,95%CIs)being 1.254(1.016 to 1.548),1.182(1.014 to 1.377),and 1.244(1.029 to 1.505),respectively,per standard deviation.Urinary BPMA and N-acetyl-S-(2-cyanoethyl)-l-cysteine were inversely associated with lumbar spine bone mineral density(BMD),while urinary N-acetyl-S-(2-hydroxypropyl)-l-cysteine was positively associated with hip BMD.Additionally,OP odds increased by 46.0%(95%CI:3.9%to 105.1%)per quartile increment in the VOC mixture.AOP analysis identified 53 target genes and 9 target phenotypes,and 5 of 9 target phenotypes were oxidative stress(OS)-related.Literature and the“AOP 482”framework implied the core role of OS in the VOC exposure and prevalent OP association,with the interleukin-6 as themolecular initiating event.Our findings provided a theoretical basis for further investigation.展开更多
Axial chain rockbursts(ACRs)repeatedly occur in deep tunnels during drilling and blasting methodology(D&B)within locked-in stress zones,severely hindering construction progress.In extremely cases,ACRs can persist ...Axial chain rockbursts(ACRs)repeatedly occur in deep tunnels during drilling and blasting methodology(D&B)within locked-in stress zones,severely hindering construction progress.In extremely cases,ACRs can persist for 7−10 d and affect areas exceeding 20 m along tunnel axis.Through integrated geological investigations and microseismic(MS)monitoring,the geological characteristics,MS activity patterns,and formation mechanisms of ACRs were analyzed.In tectonically active regions,locked-in stress zones arise from interactions between multiple structural planes.Blasting dynamic disturbances during tunnel excavation in these zones trigger early slippage along structural planes and fractures in the surrounding rock,with MS events developing ahead of the working face.High-energy MS events dominate during the development and occurrence stages of ACRs,extending 20−30 m(3−4 tunnel diameters)ahead of the working face.Following the ACRs,low-energy MS events primarily occur behind the working face.Tensile fracturing is the predominant failure mode during ACRs.Shear and mixed fractures primarily occur within the ACRs zone during the intra-ACR phase.Monitoring MS event locations ahead of the working face provides a reliable approach for prewarning potential ACR-prone zones.展开更多
The presence of residual stresses in materials or engineering structures can significantly influence their mechanical per-formance.Accurate measurement of residual stresses is of great importance to ensure their in-se...The presence of residual stresses in materials or engineering structures can significantly influence their mechanical per-formance.Accurate measurement of residual stresses is of great importance to ensure their in-service reliability.Although numerous instrumented indentation methods have been proposed to evaluate residual stresses,the majority of them require a stress-free reference sample as a comparison benchmark,thereby limiting their applicability in scenarios where obtaining stress-free reference samples is challenging.In this work,through a number of finite element simulations,it was found that the loading exponent of the loading load-depth curve and the recovered depth during unloading are insensitive to residual stresses.The loading curve of the stress-free specimen was virtually reconstructed using such stress-insensitive parameters extracted from the load-depth curves of the stressed state,thus eliminating the requirement for stress-free reference samples.The residual stress was then correlated with the fractional change in loading work between stressed and stress-free loading curves through dimensional analysis and finite element simulations.Based on this correlation,an instrumented sharp indentation method for measuring equibiaxial residual stress without requiring a stress-free specimen was established.Both numerical and experimental verifications were carried out to demonstrate the accuracy and reliability of the newly proposed method.The maximum relative error and absolute error in measured residual stresses are typically within±20%and±20 MPa,respectively.展开更多
Hydraulic fracturing plays a critical role in enhancing shale gas production in deep shale reservoirs.Conventional hydraulic fracturing simulation methods rely on prefabricated grids,which can be hindered by the chall...Hydraulic fracturing plays a critical role in enhancing shale gas production in deep shale reservoirs.Conventional hydraulic fracturing simulation methods rely on prefabricated grids,which can be hindered by the challenge of being computationally overpowered.This study proposes an efficient fracturing simulator to analyze fracture morphology during hydraulic fracturing processes in deep shale gas reservoirs.The simulator integrates the boundary element displacement discontinuity method and the finite volume method to model the fluid-solid coupling process by employing a pseudo-3D fracture model to calculate the fracture height.In particular,the Broyden iteration method was introduced to improve the computational efficiency and model robustness;it achieved a 46.6%reduction in computation time compared to the Newton-Raphson method.The influences of horizontal stress differences,natural fracture density,and natural fracture angle on the modified zone of the reservoir were simulated,and the following results were observed.(1)High stress difference reservoirs have smaller stimulated reservoir area than low stress difference reservoirs.(2)A higher natural fracture angle resulted in larger modification zones at low stress differences,while the effect of a natural fracture angle at high stress differences was not significant.(3)High-density and long natural fracture zones played a significant role in enhancing the stimulated reservoir area.These findings are critical for comprehending the impact of geological parameters on deep shale reservoirs.展开更多
Accurate prediction of coal and gas outburst(CGO)hazards is paramount in gas disaster prevention and control.This paper endeavors to overcome the constraints posed by traditional prediction indexes when dealing with C...Accurate prediction of coal and gas outburst(CGO)hazards is paramount in gas disaster prevention and control.This paper endeavors to overcome the constraints posed by traditional prediction indexes when dealing with CGO incidents under low gas pressure conditions.In pursuit of this objective,we have studied and established a mechanical model of the working face under abnormal stress and the excitation energy conditions of CGO,and proposed a method for predicting the risk of CGO under abnormal stress.On site application verification shows that when a strong outburst hazard level prediction is issued,there is a high possibility of outburst disasters occurring.In one of the three locations where we predicted strong outburst hazards,a small outburst occurred,and the accuracy of the prediction was higher than the traditional drilling cuttings index S and drilling cuttings gas desorption index q.Finally,we discuss the mechanism of CGO under the action of stress anomalies.Based on the analysis of stress distribution changes and energy accumulation characteristics of coal under abnormal stress,this article believes that the increase in outburst risk caused by high stress abnormal gradient is mainly due to two reasons:(1)The high stress abnormal gradient leads to an increase in the plastic zone of the coal seam.After the working face advances,it indirectly leads to an increase in the gas expansion energy that can be released from the coal seam before reaching a new stress equilibrium.(2)Abnormal stress leads to increased peak stress of coal body in front of working face.When coal body in elastic area transforms to plastic area,its failure speed is accelerated,which induces accelerated gas desorption and aggravates the risk of outburst.展开更多
To investigate the influence of the shear lag effect on the bending shear stress of single-box multicell box gird-ers(MCBG),the shear lag warping additional deflection is selected as the generalized displacement.The g...To investigate the influence of the shear lag effect on the bending shear stress of single-box multicell box gird-ers(MCBG),the shear lag warping additional deflection is selected as the generalized displacement.The governing dif-ferential equations and boundary conditions for the shear lag of the MCBG are derived using the energy variational method.Based on the shear lag warping deformation state of the MCBG and by employing the microelement equilib-rium differential equation and the coordination conditions for shear lag warping deformation,the calculation method for the bending-warping shear stress of the MCBG is de-rived,and the influence of the width-to-span and height-to span ratios on bending-warping shear stress is analyzed.Ex-ample analysis shows that the bending-warping shear stress of the MCBG calculated by the proposed calculation method coincides with the finite element solution,and the warping shear stress satisfies the self-balancing condition of shear warping,thus verifying the accuracy of the proposed method.The warping shear stress exhibits an antisymmetric distribution about the vertical axis of symmetry and has a weakening effect on the shear stress of the elementary beam(EB).The larger the width-to-span ratio is,the larger the proportion of the warping shear stress of the EB.The larger the height-to-span ratio is,the smaller the proportion of the warping shear stress and the more significant the influence of the width-to-span ratio.The more the number of cells is,the smaller the influence of the warping shear stress on the total bending shear stress.The influence of the shear lag ef-fect can be ignored in the calculation of the bending shear stress of three or more cells in the MCBG.展开更多
Background Environmental hypoxia is a common phenomenon in aquaculture,which causes gill tissue injury in fish.Glutathione(GSH)is a vital antioxidant in animal tissues,and its levels decrease under hypoxic conditions....Background Environmental hypoxia is a common phenomenon in aquaculture,which causes gill tissue injury in fish.Glutathione(GSH)is a vital antioxidant in animal tissues,and its levels decrease under hypoxic conditions.However,the effects of glutathione on fish under hypoxic stress remain poorly understood.This study aimed to investigate the impact of glutathione on gill tissue damage in fish under hypoxic stress and explore the underlying mechanisms.Methods Six experimental diets with varying glutathione concentrations.The actual glutathione levels in these diets,measured by high-performance liquid chromatography,were 0.00,145.95,291.90,437.85,583.80,and 729.75 mg/kg,respectively.Fish were fed these diets for 70 d,after which a 96-h hypoxic stress experiment was conducted.The experiment was set up with normoxic and hypoxic groups,in which the dissolved oxygen in the group was 6 mg/L,and that in the group was 1 mg/L.Results This research revealed that glutathione could enhance the growth performance and antioxidant capability of juvenile grass carp while mitigating the structural damage to gill tissues induced by hypoxia stress.Mechanistic investigations further indicated that glutathione mitigated hypoxia-induced oxidative injury in gill tissues and improved their antioxidant capacity.In addition,glutathione attenuated gill apoptosis induced by hypoxia stress.Glutathione also inhibited the initiation,nucleation,elongation,and degradation phases of autophagy,thereby attenuating hypoxia-induced gill autophagy.Moreover,glutathione was found to alleviate hypoxia-induced endoplasmic reticulum stress(ERS)in gills,a response potentially linked to the suppression of PERK,IRE1,and ATF6 signaling pathways.Finally,based on the ROS and PC contents in gill tissue,the optimum glutathione supplementation levels for juvenile grass carp under hypoxia stress were 437.10 and 495.00 mg/kg,respectively.Conclusions In conclusion,our experimental results demonstrated the effectiveness of glutathione in alleviating gill tissue damage caused by hypoxic stress.This study confirms the feasibility and effectiveness of dietary glutathione addition to alleviate hypoxic stress in fish.展开更多
Protein aggregates,mitochondrial import stress and neurodegenerative disorders:A salient hallmark of several neurodegenerative diseases,including Parkinson’s disease,is the abundance of protein aggregates(Goiran et a...Protein aggregates,mitochondrial import stress and neurodegenerative disorders:A salient hallmark of several neurodegenerative diseases,including Parkinson’s disease,is the abundance of protein aggregates(Goiran et al.,2022).This molecular event is believed to lead to activation of stress pathways ultimately resulting in cellular dysfunction(Eldeeb et al.,2022).Accordingly,many lines of research investigations focused on dampening the formation of protein aggregates or augmenting the clearance of protein aggregates as a potential therapeutic strategy to counteract the progression of neurodegenerative diseases,albeit with little success(Costa-Mattioli and Walter,2020).Cell stress cues such as the accumulation of protein aggregates lead to the activation of stress response pathways that aid cells in responding to the damage.Despite the notion that the transient activation of these pathways helps cells cope with stressors,persistent activation can induce unwanted apoptosis of cells and reduce overall tissue strength as well as lead to an accumulation of aggregation-prone proteins(Hetz and Papa,2018).Mutations in proteins involved in stress signaling termination can cause conditions like ataxia and early-onset dementia(Conroy et al.,2014).Therefore,it is crucial for stress response signaling to be turned off once conditions have improved.Nevertheless,the mechanisms by which cells silence these signals are still elusive.展开更多
Excavation causes stress redistribution and affects the stress path during the shearing process of rock.The shear strength of rock varies under different stress paths,and the presence of defects reduces the shear stre...Excavation causes stress redistribution and affects the stress path during the shearing process of rock.The shear strength of rock varies under different stress paths,and the presence of defects reduces the shear strength.To further investigate this phenomenon,this study investigates the shear behaviour of rocks with different shear surface integrities under the influenceof different stress paths through laboratory tests and numerical simulations.The results indicate that the shear strength depends on the stress path and a decrease in the shear surface integrity reduces the degree of dependence.The cohesion and friction angle of the Mohr‒Coulomb criterion decrease with weakening of the shear surface integrity.For different stress paths,the direct shear strength is always greater than that of other shear stress paths.The pattern of changes in the acoustic emission count and cumulative count indirectly reflectsthe above findings.Numerical simulations further indicate that the different principal stress states and normal suppression effects during the shearing process lead to changes in the factors of crack propagation,resulting in different mechanical behaviours under various stress paths.For rocks with different integrity levels,the main reason for the different path dependences of shear strength is that the size of the area affected by shear is different.Shear failure will concentrate on the shear plane when the normal inhibition effect is greater.This study explores the mechanism of rock shear behaviour,providing a theoretical basis for establishing more accurate constitutive models and strength criteria.展开更多
In-situ stress is a key parameter for underground mine design and rock stability analysis.The borehole overcoring technique is widely used for in-situ stress measurement,but the rheological recovery deformation of roc...In-situ stress is a key parameter for underground mine design and rock stability analysis.The borehole overcoring technique is widely used for in-situ stress measurement,but the rheological recovery deformation of rocks after stress relief introduces errors.To improve accuracy,this study proposes an in-situ stress solution theory that incorporates time-dependent stress relief effects.Triaxial stepwise loadingunloading rheological tests on granite and siltstone established quantitative relationships between instantaneous elastic recovery and viscoelastic recovery under different stress levels,confirming their impact on measurement accuracy.By integrating a dual-class elastic deformation recovery model,an improved in-situ stress solution theory was derived.Additionally,accounting for the nonlinear characteristics of rock masses,a determination method for time-dependent nonlinear mechanical parameters was proposed.Based on the CSIRO hollow inclusion strain cell,time-dependent strain correction equations and long-term confining pressure calibration equations were formulated.Finally,the proposed theory was successfully applied at one iron mine(736 m depth)in Xinjiang,China,and one coal mine(510 m depth)in Ningxia,China.Compared to classical theory,the calculated mean stress values showed accuracy improvements of 6.0%and 9.4%,respectively,validating the applicability and reliability of the proposed theory.展开更多
Global population pressures have necessitated increased focus on protecting and developing resilient plant species that can maintain productivity despite environmental challenges.Environmental degradation,driven by cl...Global population pressures have necessitated increased focus on protecting and developing resilient plant species that can maintain productivity despite environmental challenges.Environmental degradation,driven by climate change and anthropogenic activities,poses significant threats to global food security through various forms of physical stress.Major environmental constraints affecting agricultural yields worldwide include salinity,water scarcity,nutritional imbalances(encompassing mineral toxicity and deficiencies),and extreme temperatures.Crop yield is influenced by multiple abiotic factors,including agronomic conditions,climatic variables,and soil nutrient availability.Plants develop various survival mechanisms at molecular,cellular,and physiological levels in response to stress.Abiotic stress,whether occurring individually or in combination,significantly impacts crop growth and productivity.For instance,drought stress reduces leaf area,plant height,and overall crop development.Cold stress inhibits plant development and crop efficiency,leading to diminished productivity.Salinity stress not only induces water stress in plants but also negatively affects cytosolic metabolism,cell development,membrane function,and increases reactive oxygen species(ROS)production.Elevated CO_(2)concentrations may enhance global precipitation patterns,potentially resulting in increased rainfall that can adversely affect crop development.Plants under excessive water stress exhibit reduced amylose content but increased crude protein levels.This affects both quality and quantity of crop production by inhibiting seed germination and causing growth impairment through combined effects of elevated osmotic potential and ion toxicity.Plants have evolved various escape-avoidance and tolerance mechanisms in response to abiotic stress,including physiological adaptations and integrated cellular or molecular responses.This review paper examines the impact of abiotic stress on morpho-physiological,biochemical,and molecular activities across various crops.Additionally,it analyzes crop interactions with abiotic stress regarding response and adaptation mechanisms,providing a fundamental framework for species selection and development of stress-tolerant varieties in the future.展开更多
Background:Childhood leukemia,a malignant proliferative disorder of the hematopoietic system and the most common childhood cancer,poses a significant threat to the lives and health of affected children.For parents,a l...Background:Childhood leukemia,a malignant proliferative disorder of the hematopoietic system and the most common childhood cancer,poses a significant threat to the lives and health of affected children.For parents,a leukemia diagnosis in their child is a profoundly traumatic event.As primary caregivers,they endure immense psychological distress and caregiving stress throughout the prolonged and demanding treatment process,which can adversely affect their own well-being and caregiving capacity.However,the psychological mechanisms,such as the role of mindfulness,linking caregiver stress to parental coping strategies remain underexplored,and evidence-based interventions to support these parents are needed.Methods:In Study 1,we administered a cross-sectional survey to 242 parents of children with leukemia who were hospitalized at the Affiliated Hospital of Qingdao University between January and August 2024.Participants completed measures assessing caregiver burden,mindful attention awareness,and parental coping style.In Study 2,we further evaluated the effects of a Mindfulness-Based Stress Reduction(MBSR)intervention.Results:The results of Study 1 revealed:(1)The caregiving stress significantly and negatively predicted coping style(β=−1.18,95%CI[−2.18,−0.18],p<0.01).(2)Caregiving stress also significantly and negatively predicted mindfulness(β=−1.90,95%CI[−2.43,−1.38],p<0.01).(3)Conversely,mindfulness significantly and positively predicted coping style(β=0.85,95%CI[0.62,1.07],p<0.01).These findings suggest that mindfulness mediates the relationship between caregiver burden and coping style.In Study 2,the experimental group showed a significant decrease in caregiver stress post-intervention(t=2.24,p<0.05),a significant increase in mindfulness(t=−4.61,p<0.001),and a significant improvement in coping style(t=−2.36,p<0.01).No significant changes were observed in the control group.Conclusion:MBSR can effectively enhance mindfulness and promote adaptive coping strategies,while reducing caregiver burden among parents of children with leukemia.展开更多
基金funded by the National Key R&D Program of China(Grant No.2022YFC2903904)the National Natural Science Foundation of China(Grant Nos.51904057 and U1906208).
文摘Due to the heterogeneity of rock masses and the variability of in situ stress,the traditional linear inversion method is insufficiently accurate to achieve high accuracy of the in situ stress field.To address this challenge,nonlinear stress boundaries for a numerical model are determined through regression analysis of a series of nonlinear coefficient matrices,which are derived from the bubbling method.Considering the randomness and flexibility of the bubbling method,a parametric study is conducted to determine recommended ranges for these parameters,including the standard deviation(σb)of bubble radii,the non-uniform coefficient matrix number(λ)for nonlinear stress boundaries,and the number(m)and positions of in situ stress measurement points.A model case study provides a reference for the selection of these parameters.Additionally,when the nonlinear in situ stress inversion method is employed,stress distortion inevitably occurs near model boundaries,aligning with the Saint Venant's principle.Two strategies are proposed accordingly:employing a systematic reduction of nonlinear coefficients to achieve high inversion accuracy while minimizing significant stress distortion,and excluding regions with severe stress distortion near the model edges while utilizing the central part of the model for subsequent simulations.These two strategies have been successfully implemented in the nonlinear in situ stress inversion of the Xincheng Gold Mine and have achieved higher inversion accuracy than the linear method.Specifically,the linear and nonlinear inversion methods yield root mean square errors(RMSE)of 4.15 and 3.2,and inversion relative errors(δAve)of 22.08%and 17.55%,respectively.Therefore,the nonlinear inversion method outperforms the traditional multiple linear regression method,even in the presence of a systematic reduction in the nonlinear stress boundaries.
文摘In the aerospace field, residual stress directly affects the strength, fatigue life and dimensional stability of thin-walled structural components, and is a key factor to ensure flight safety and reliability. At present, research on residual stress at home and abroad mainly focuses on the optimization of traditional detection technology, stress control of manufacturing process and service performance evaluation, among which research on residual stress detection methods mainly focuses on the improvement of the accuracy, sensitivity, reliability and other performance of existing detection methods, but it still faces many challenges such as extremely small detection range, low efficiency, large error and limited application range.
基金Projects(52374094,52374218,52174122)supported by the National Natural Science Foundation of ChinaProject(ZR2022YQ49)supported by the Excellent Youth Fund of Shandong Natural Science Foundation,ChinaProjects(tspd20210313,tsqn202211150)supported by the Taishan Scholar Project in Shandong Province,China。
文摘The surrounding rock of the soft rock roadway is seriously deformed and damaged under the superposition of mining stress and fault tectonic stress.In this paper,taking the No.232206 intake roadway in Meihuajing Coal Mine as the engineering background,the deformation and failure law of the surrounding rock of the roadway in different fault protection pillar widths were obtained by numerical simulation method.On this basis,the mechanical model of the roadway under the action of hanging wall overburden migration and fault slip in normal faults was established,and the energy-driven mechanism of large deformation of the surrounding rock of the roadway was revealed.The ratio T of the energy applying on anchoring surrounding rock to the resistant energy of the anchored surrounding rock was defined as the criterion for the deformation of the roadway.Finally,it was calculated according to the actual working conditions on site,and the control method of“stress relief-support reinforcement”was used to support the roadway with the risk of large deformation.The on-site monitoring results show that the control effect of the surrounding rock of the roadway is obvious.
基金supported in part by the National Natural Science Foundation of China(Nos.61201048,61107063)the National Science and Technology Major Project(No.2017-VI-001-0094).
文摘To investigate the residual stress distribution and its influence on machining deformation in 6061-T651 aluminum alloy plates,this paper uses the crack compliance method to study the residual stress characteristics of 6061-T651 aluminum alloy plates with a thickness of 75 mm produced by two domestic manufacturers in China.The results indicate that both types of plates exhibit highly consistent and symmetrical M-shaped residual stress profile along the thickness direction,manifested as surface layer compression and core tension.The strain energy density across all specimens ranges from 1.27 kJ/m^(3)to 1.43 kJ/m^(3).Machining deformation simulations of an aerospace component incorporating these measured stresses showed minimal final deformation difference between the material sources,with a maximum deviation of only 0.009 mm across specimens.These findings provide critical data for material selection and deformation control in aerospace manufacturing.
基金Project(52278380)supported by the National Natural Science Foundation of ChinaProject(2023JJ30670)supported by the National Science Foundation of and Technology Major Project of Hunan Province,China。
文摘This study proposes an alternative calculation mode for stresses on the slip surface(SS).The calculation of the normal stress(NS)on the SS involves examining its composition and expanding its unknown using the Taylor series.This expansion enables the reasonable construction of a function describing the NS on the SS.Additionally,by directly incorporating the nonlinear Generalized Hoke-Brown(GHB)strength criterion and utilizing the slope factor of safety(FOS)definition,a function of the shear stress on the SS is derived.This function considers the mutual feedback mechanism between the NS and strength parameters of the SS.The stress constraints conditions are then introduced at both ends of the SS based on the spatial stress relation of one point.Determining the slope FOS and stress solution for the SS involves considering the mechanical equilibrium conditions and the stress constraint conditions satisfied by the sliding body.The proposed approach successfully simulates the tension-shear stress zone near the slope top and provides an intuitive description of the concentration effect of compression-shear stress of the SS near the slope toe.Furthermore,compared to other methods,the present method demonstrates superior processing capabilities for the embedded nonlinear GHB strength criterion.
基金Supported by the National Natural Science Foundation of China(Grant Nos.12371393,11971150 and 11801143)Natural Science Foundation of Henan Province(Grant No.242300421047).
文摘In this paper,we propose a multiphysics finite element method for a nonlinear poroelasticity model with nonlinear stress-strain relation.Firstly,we reformulate the original problem into a new coupled fluid system-a generalized nonlinear Stokes problem of displacement vector field related to pseudo pressure and a diffusion problem of other pseudo pressure fields.Secondly,a fully discrete multiphysics finite element method is performed to solve the reformulated system numerically.Thirdly,existence and uniqueness of the weak solution of the reformulated model and stability analysis and optimal convergence order for the multiphysics finite element method are proven theoretically.Lastly,numerical tests are given to verify the theoretical results.
基金Project supported by the National Science and Technology Major Project(No.J2019-I-0008-0008)the National Natural Science Foundation of China(No.52305096)the Chinese Postdoctoral Science Foundation(No.GZB20230117)。
文摘Fatigue failure caused by vibration is the most common type of pipeline failure.The core of this research is to obtain the nonlinear dynamic stress of a pipeline system accurately and efficiently,a topic that needs to be explored in the existing literature.The shell theory can better simulate the circumferential stress distribution,and thus the Mindlin-Reissner shell theory is used to model the pipeline.In this paper,the continuous pipeline system is combined with clamps through modal expansion for the first time,which realizes the coupling problem between a shell and a clamp.While the Bouc-Wen model is used to simulate the nonlinear external force generated by a clamp,the nonlinear coupling characteristics of the system are effectively captured.Then,the dynamic equation of the clamp-pipeline system is established according to the Lagrange energy equation.Based on the resonance frequency and stress amplitude obtained from the experiment,the nonlinear parameters of the clamp are identified with the semi-analytical method(SAM)and particle swarm optimization(PSO)algorithm.This study provides a theoretical basis for the clamp-pipeline system and an efficient and universal solution for stress prediction and analysis of pipelines in engineering.
基金Project(2023YFC3805700) supported by the National Key Research and Development Program of ChinaProjects(42477166,42277174) supported by the National Natural Science Foundation of China+2 种基金Project(2024JCCXSB01) supported by the Fundamental Research Funds for the Central Universities,ChinaProject(KFJJ24-01M) supported by the State Key Laboratory of Explosion Science and Safety Protection,Beijing Institute of Technology,ChinaProject(HLCX-2024-04) supported by the Open Foundation of Collaborative Innovation Center of Green Development and Ecological Restoration of Mineral Resources,China。
文摘The surrounding rock is prone to large-scale loosening and failure after the excavation of shallow large-span caverns because of the thin overlying strata and large cross-section span.The rational design of bolt support is very important to the safety control of surrounding rock as a common support means.The control mechanism and design method of bolt support for shallow-buried large-span caverns is carried out.The calculation method of bolt prestress and length based on arched failure and collapsed failure mode is established.The influence mechanism of different influencing factors on the bolt prestress and length is clarified.At the same time,the constant resistance energy-absorbing bolt with high strength and high toughness is developed,and the comparative test of mechanical properties is carried out.On this basis,the design method of high prestressed bolt support for shallow-buried large-span caverns is put forward,and the field test is carried out in Qingdao metro station in China.The monitoring results show that the maximum roof settlement is 6.8 mm after the new design method is adopted,and the effective control of the shallow-buried large-span caverns is realized.The research results can provide theoretical and technical support for the safety control of shallow-buried large-span caverns.
基金supported by the National Natural Science Foundation of China(No.82273711).
文摘Existing evidence has demonstrated the association between exposure to volatile organic compounds(VOCs)and osteoporosis(OP)risk,but the underlying mechanistic framework remains unclear.This study aimed to explore potential pathways using adverse outcome pathway(AOP)analysis,and evidence this association in middle-to-old-aged American adults using the updated National Health and Nutrition Examination Survey data.Multivariable-adjusted general linear and weighted quantile sum models were employed to analyze associations of VOC metabolites(VOCMs),representing internal VOCs exposure levels,with OP-related phenotypes.An AOP framework based on network analysis was developed by extracting target genes and phenotypes.Among 3555 American adults aged≥40 years(539 OP participants),we found that increasing urinary 3-and 4-methylhippuric acid,N-acetyl-S-(n-propyl)-l-cysteine(BPMA),and N-acetyl-S-(3-hydroxypropyl)-l-cysteine were associated with elevated OP odds with odds ratios(ORs)(95%confidence intervals,95%CIs)being 1.254(1.016 to 1.548),1.182(1.014 to 1.377),and 1.244(1.029 to 1.505),respectively,per standard deviation.Urinary BPMA and N-acetyl-S-(2-cyanoethyl)-l-cysteine were inversely associated with lumbar spine bone mineral density(BMD),while urinary N-acetyl-S-(2-hydroxypropyl)-l-cysteine was positively associated with hip BMD.Additionally,OP odds increased by 46.0%(95%CI:3.9%to 105.1%)per quartile increment in the VOC mixture.AOP analysis identified 53 target genes and 9 target phenotypes,and 5 of 9 target phenotypes were oxidative stress(OS)-related.Literature and the“AOP 482”framework implied the core role of OS in the VOC exposure and prevalent OP association,with the interleukin-6 as themolecular initiating event.Our findings provided a theoretical basis for further investigation.
基金Projects(52222810,52178383)supported by the National Natural Science Foundation of China。
文摘Axial chain rockbursts(ACRs)repeatedly occur in deep tunnels during drilling and blasting methodology(D&B)within locked-in stress zones,severely hindering construction progress.In extremely cases,ACRs can persist for 7−10 d and affect areas exceeding 20 m along tunnel axis.Through integrated geological investigations and microseismic(MS)monitoring,the geological characteristics,MS activity patterns,and formation mechanisms of ACRs were analyzed.In tectonically active regions,locked-in stress zones arise from interactions between multiple structural planes.Blasting dynamic disturbances during tunnel excavation in these zones trigger early slippage along structural planes and fractures in the surrounding rock,with MS events developing ahead of the working face.High-energy MS events dominate during the development and occurrence stages of ACRs,extending 20−30 m(3−4 tunnel diameters)ahead of the working face.Following the ACRs,low-energy MS events primarily occur behind the working face.Tensile fracturing is the predominant failure mode during ACRs.Shear and mixed fractures primarily occur within the ACRs zone during the intra-ACR phase.Monitoring MS event locations ahead of the working face provides a reliable approach for prewarning potential ACR-prone zones.
基金support from the National Natural Science Foundation of China(Grant Nos.12172332,11727803 and 12072009)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LZ23A020007)the Fundamental Research Funds for the Provincial Universities of Zhejiang(Grant No.RF-C2022003).
文摘The presence of residual stresses in materials or engineering structures can significantly influence their mechanical per-formance.Accurate measurement of residual stresses is of great importance to ensure their in-service reliability.Although numerous instrumented indentation methods have been proposed to evaluate residual stresses,the majority of them require a stress-free reference sample as a comparison benchmark,thereby limiting their applicability in scenarios where obtaining stress-free reference samples is challenging.In this work,through a number of finite element simulations,it was found that the loading exponent of the loading load-depth curve and the recovered depth during unloading are insensitive to residual stresses.The loading curve of the stress-free specimen was virtually reconstructed using such stress-insensitive parameters extracted from the load-depth curves of the stressed state,thus eliminating the requirement for stress-free reference samples.The residual stress was then correlated with the fractional change in loading work between stressed and stress-free loading curves through dimensional analysis and finite element simulations.Based on this correlation,an instrumented sharp indentation method for measuring equibiaxial residual stress without requiring a stress-free specimen was established.Both numerical and experimental verifications were carried out to demonstrate the accuracy and reliability of the newly proposed method.The maximum relative error and absolute error in measured residual stresses are typically within±20%and±20 MPa,respectively.
文摘Hydraulic fracturing plays a critical role in enhancing shale gas production in deep shale reservoirs.Conventional hydraulic fracturing simulation methods rely on prefabricated grids,which can be hindered by the challenge of being computationally overpowered.This study proposes an efficient fracturing simulator to analyze fracture morphology during hydraulic fracturing processes in deep shale gas reservoirs.The simulator integrates the boundary element displacement discontinuity method and the finite volume method to model the fluid-solid coupling process by employing a pseudo-3D fracture model to calculate the fracture height.In particular,the Broyden iteration method was introduced to improve the computational efficiency and model robustness;it achieved a 46.6%reduction in computation time compared to the Newton-Raphson method.The influences of horizontal stress differences,natural fracture density,and natural fracture angle on the modified zone of the reservoir were simulated,and the following results were observed.(1)High stress difference reservoirs have smaller stimulated reservoir area than low stress difference reservoirs.(2)A higher natural fracture angle resulted in larger modification zones at low stress differences,while the effect of a natural fracture angle at high stress differences was not significant.(3)High-density and long natural fracture zones played a significant role in enhancing the stimulated reservoir area.These findings are critical for comprehending the impact of geological parameters on deep shale reservoirs.
基金supported by the National Natural Science Foundation of China(52174162)the Fundamental Research Funds for the Central Universities(FRF-TP-20-002A3).
文摘Accurate prediction of coal and gas outburst(CGO)hazards is paramount in gas disaster prevention and control.This paper endeavors to overcome the constraints posed by traditional prediction indexes when dealing with CGO incidents under low gas pressure conditions.In pursuit of this objective,we have studied and established a mechanical model of the working face under abnormal stress and the excitation energy conditions of CGO,and proposed a method for predicting the risk of CGO under abnormal stress.On site application verification shows that when a strong outburst hazard level prediction is issued,there is a high possibility of outburst disasters occurring.In one of the three locations where we predicted strong outburst hazards,a small outburst occurred,and the accuracy of the prediction was higher than the traditional drilling cuttings index S and drilling cuttings gas desorption index q.Finally,we discuss the mechanism of CGO under the action of stress anomalies.Based on the analysis of stress distribution changes and energy accumulation characteristics of coal under abnormal stress,this article believes that the increase in outburst risk caused by high stress abnormal gradient is mainly due to two reasons:(1)The high stress abnormal gradient leads to an increase in the plastic zone of the coal seam.After the working face advances,it indirectly leads to an increase in the gas expansion energy that can be released from the coal seam before reaching a new stress equilibrium.(2)Abnormal stress leads to increased peak stress of coal body in front of working face.When coal body in elastic area transforms to plastic area,its failure speed is accelerated,which induces accelerated gas desorption and aggravates the risk of outburst.
基金The National Natural Science Foundation of China (No. 52368020)Gansu Provincial Universities Young Doctor Support Project (No. 2024QB-047)Gansu Province postdoctoral Fund (No. 386824)。
文摘To investigate the influence of the shear lag effect on the bending shear stress of single-box multicell box gird-ers(MCBG),the shear lag warping additional deflection is selected as the generalized displacement.The governing dif-ferential equations and boundary conditions for the shear lag of the MCBG are derived using the energy variational method.Based on the shear lag warping deformation state of the MCBG and by employing the microelement equilib-rium differential equation and the coordination conditions for shear lag warping deformation,the calculation method for the bending-warping shear stress of the MCBG is de-rived,and the influence of the width-to-span and height-to span ratios on bending-warping shear stress is analyzed.Ex-ample analysis shows that the bending-warping shear stress of the MCBG calculated by the proposed calculation method coincides with the finite element solution,and the warping shear stress satisfies the self-balancing condition of shear warping,thus verifying the accuracy of the proposed method.The warping shear stress exhibits an antisymmetric distribution about the vertical axis of symmetry and has a weakening effect on the shear stress of the elementary beam(EB).The larger the width-to-span ratio is,the larger the proportion of the warping shear stress of the EB.The larger the height-to-span ratio is,the smaller the proportion of the warping shear stress and the more significant the influence of the width-to-span ratio.The more the number of cells is,the smaller the influence of the warping shear stress on the total bending shear stress.The influence of the shear lag ef-fect can be ignored in the calculation of the bending shear stress of three or more cells in the MCBG.
基金financially supported by the Sichuan Science and Technology Program(2024YFNH0016,2024NSFSC2072)the earmarked fund for CARS(CARS-45)+2 种基金the National Science Fund for Distinguished Young Scholars of China(32425056)the National Key Research and Development Program of China(2023YFD2400600)Sichuan Innovation Team of National Modern Agricultural Industry Technology System(SCCXTD-2024-15)。
文摘Background Environmental hypoxia is a common phenomenon in aquaculture,which causes gill tissue injury in fish.Glutathione(GSH)is a vital antioxidant in animal tissues,and its levels decrease under hypoxic conditions.However,the effects of glutathione on fish under hypoxic stress remain poorly understood.This study aimed to investigate the impact of glutathione on gill tissue damage in fish under hypoxic stress and explore the underlying mechanisms.Methods Six experimental diets with varying glutathione concentrations.The actual glutathione levels in these diets,measured by high-performance liquid chromatography,were 0.00,145.95,291.90,437.85,583.80,and 729.75 mg/kg,respectively.Fish were fed these diets for 70 d,after which a 96-h hypoxic stress experiment was conducted.The experiment was set up with normoxic and hypoxic groups,in which the dissolved oxygen in the group was 6 mg/L,and that in the group was 1 mg/L.Results This research revealed that glutathione could enhance the growth performance and antioxidant capability of juvenile grass carp while mitigating the structural damage to gill tissues induced by hypoxia stress.Mechanistic investigations further indicated that glutathione mitigated hypoxia-induced oxidative injury in gill tissues and improved their antioxidant capacity.In addition,glutathione attenuated gill apoptosis induced by hypoxia stress.Glutathione also inhibited the initiation,nucleation,elongation,and degradation phases of autophagy,thereby attenuating hypoxia-induced gill autophagy.Moreover,glutathione was found to alleviate hypoxia-induced endoplasmic reticulum stress(ERS)in gills,a response potentially linked to the suppression of PERK,IRE1,and ATF6 signaling pathways.Finally,based on the ROS and PC contents in gill tissue,the optimum glutathione supplementation levels for juvenile grass carp under hypoxia stress were 437.10 and 495.00 mg/kg,respectively.Conclusions In conclusion,our experimental results demonstrated the effectiveness of glutathione in alleviating gill tissue damage caused by hypoxic stress.This study confirms the feasibility and effectiveness of dietary glutathione addition to alleviate hypoxic stress in fish.
文摘Protein aggregates,mitochondrial import stress and neurodegenerative disorders:A salient hallmark of several neurodegenerative diseases,including Parkinson’s disease,is the abundance of protein aggregates(Goiran et al.,2022).This molecular event is believed to lead to activation of stress pathways ultimately resulting in cellular dysfunction(Eldeeb et al.,2022).Accordingly,many lines of research investigations focused on dampening the formation of protein aggregates or augmenting the clearance of protein aggregates as a potential therapeutic strategy to counteract the progression of neurodegenerative diseases,albeit with little success(Costa-Mattioli and Walter,2020).Cell stress cues such as the accumulation of protein aggregates lead to the activation of stress response pathways that aid cells in responding to the damage.Despite the notion that the transient activation of these pathways helps cells cope with stressors,persistent activation can induce unwanted apoptosis of cells and reduce overall tissue strength as well as lead to an accumulation of aggregation-prone proteins(Hetz and Papa,2018).Mutations in proteins involved in stress signaling termination can cause conditions like ataxia and early-onset dementia(Conroy et al.,2014).Therefore,it is crucial for stress response signaling to be turned off once conditions have improved.Nevertheless,the mechanisms by which cells silence these signals are still elusive.
基金support from the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX24_2822)the Graduate Innovation Program of China University of Mining and Technology(Grant No.2024WLKXJ205)the National Natural Science Foundation of China(Grant No.52474157).
文摘Excavation causes stress redistribution and affects the stress path during the shearing process of rock.The shear strength of rock varies under different stress paths,and the presence of defects reduces the shear strength.To further investigate this phenomenon,this study investigates the shear behaviour of rocks with different shear surface integrities under the influenceof different stress paths through laboratory tests and numerical simulations.The results indicate that the shear strength depends on the stress path and a decrease in the shear surface integrity reduces the degree of dependence.The cohesion and friction angle of the Mohr‒Coulomb criterion decrease with weakening of the shear surface integrity.For different stress paths,the direct shear strength is always greater than that of other shear stress paths.The pattern of changes in the acoustic emission count and cumulative count indirectly reflectsthe above findings.Numerical simulations further indicate that the different principal stress states and normal suppression effects during the shearing process lead to changes in the factors of crack propagation,resulting in different mechanical behaviours under various stress paths.For rocks with different integrity levels,the main reason for the different path dependences of shear strength is that the size of the area affected by shear is different.Shear failure will concentrate on the shear plane when the normal inhibition effect is greater.This study explores the mechanism of rock shear behaviour,providing a theoretical basis for establishing more accurate constitutive models and strength criteria.
基金supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China(No.2024ZD1700201)the National Natural Science Foundation of China(Nos.U2034206,51974014 and 51574014)+1 种基金the Guangdong Basic and Applied Basic Research Foundation(No.2024A1515011631)the National Key Research and Development Project of China(No.2022YFC3004601)。
文摘In-situ stress is a key parameter for underground mine design and rock stability analysis.The borehole overcoring technique is widely used for in-situ stress measurement,but the rheological recovery deformation of rocks after stress relief introduces errors.To improve accuracy,this study proposes an in-situ stress solution theory that incorporates time-dependent stress relief effects.Triaxial stepwise loadingunloading rheological tests on granite and siltstone established quantitative relationships between instantaneous elastic recovery and viscoelastic recovery under different stress levels,confirming their impact on measurement accuracy.By integrating a dual-class elastic deformation recovery model,an improved in-situ stress solution theory was derived.Additionally,accounting for the nonlinear characteristics of rock masses,a determination method for time-dependent nonlinear mechanical parameters was proposed.Based on the CSIRO hollow inclusion strain cell,time-dependent strain correction equations and long-term confining pressure calibration equations were formulated.Finally,the proposed theory was successfully applied at one iron mine(736 m depth)in Xinjiang,China,and one coal mine(510 m depth)in Ningxia,China.Compared to classical theory,the calculated mean stress values showed accuracy improvements of 6.0%and 9.4%,respectively,validating the applicability and reliability of the proposed theory.
基金financially supported by the National Key R&D Program of China(2022YFE0113400)the Jiangsu Provincial Fund for Realizing Carbon Emission Peaking and Neutralization,China(BE2022305)+1 种基金the National Natural Science Fundation of China(32102411)the Project funded by China Postdoctoral Science Foundation(2022M722698)。
文摘Global population pressures have necessitated increased focus on protecting and developing resilient plant species that can maintain productivity despite environmental challenges.Environmental degradation,driven by climate change and anthropogenic activities,poses significant threats to global food security through various forms of physical stress.Major environmental constraints affecting agricultural yields worldwide include salinity,water scarcity,nutritional imbalances(encompassing mineral toxicity and deficiencies),and extreme temperatures.Crop yield is influenced by multiple abiotic factors,including agronomic conditions,climatic variables,and soil nutrient availability.Plants develop various survival mechanisms at molecular,cellular,and physiological levels in response to stress.Abiotic stress,whether occurring individually or in combination,significantly impacts crop growth and productivity.For instance,drought stress reduces leaf area,plant height,and overall crop development.Cold stress inhibits plant development and crop efficiency,leading to diminished productivity.Salinity stress not only induces water stress in plants but also negatively affects cytosolic metabolism,cell development,membrane function,and increases reactive oxygen species(ROS)production.Elevated CO_(2)concentrations may enhance global precipitation patterns,potentially resulting in increased rainfall that can adversely affect crop development.Plants under excessive water stress exhibit reduced amylose content but increased crude protein levels.This affects both quality and quantity of crop production by inhibiting seed germination and causing growth impairment through combined effects of elevated osmotic potential and ion toxicity.Plants have evolved various escape-avoidance and tolerance mechanisms in response to abiotic stress,including physiological adaptations and integrated cellular or molecular responses.This review paper examines the impact of abiotic stress on morpho-physiological,biochemical,and molecular activities across various crops.Additionally,it analyzes crop interactions with abiotic stress regarding response and adaptation mechanisms,providing a fundamental framework for species selection and development of stress-tolerant varieties in the future.
基金approved by the Ethics Review Committee of Northwest Normal University(Approval No.:[2023028]).All participants signed the informed consent in this study.
文摘Background:Childhood leukemia,a malignant proliferative disorder of the hematopoietic system and the most common childhood cancer,poses a significant threat to the lives and health of affected children.For parents,a leukemia diagnosis in their child is a profoundly traumatic event.As primary caregivers,they endure immense psychological distress and caregiving stress throughout the prolonged and demanding treatment process,which can adversely affect their own well-being and caregiving capacity.However,the psychological mechanisms,such as the role of mindfulness,linking caregiver stress to parental coping strategies remain underexplored,and evidence-based interventions to support these parents are needed.Methods:In Study 1,we administered a cross-sectional survey to 242 parents of children with leukemia who were hospitalized at the Affiliated Hospital of Qingdao University between January and August 2024.Participants completed measures assessing caregiver burden,mindful attention awareness,and parental coping style.In Study 2,we further evaluated the effects of a Mindfulness-Based Stress Reduction(MBSR)intervention.Results:The results of Study 1 revealed:(1)The caregiving stress significantly and negatively predicted coping style(β=−1.18,95%CI[−2.18,−0.18],p<0.01).(2)Caregiving stress also significantly and negatively predicted mindfulness(β=−1.90,95%CI[−2.43,−1.38],p<0.01).(3)Conversely,mindfulness significantly and positively predicted coping style(β=0.85,95%CI[0.62,1.07],p<0.01).These findings suggest that mindfulness mediates the relationship between caregiver burden and coping style.In Study 2,the experimental group showed a significant decrease in caregiver stress post-intervention(t=2.24,p<0.05),a significant increase in mindfulness(t=−4.61,p<0.001),and a significant improvement in coping style(t=−2.36,p<0.01).No significant changes were observed in the control group.Conclusion:MBSR can effectively enhance mindfulness and promote adaptive coping strategies,while reducing caregiver burden among parents of children with leukemia.
