Accurate simulation of the cracking process caused by rust expansion of reinforced concrete(RC)structures plays an intuitive role in revealing the corrosion-induced failure mechanism.Considering the quasi-brittle frac...Accurate simulation of the cracking process caused by rust expansion of reinforced concrete(RC)structures plays an intuitive role in revealing the corrosion-induced failure mechanism.Considering the quasi-brittle fracture of concrete,the fracture phase field driven by the compressive-shear term is constructed and added to the traditional brittle fracture phase field model.The rationality of the proposed model is verified by a mixed fracture example under a shear displacement load.Then,the extended fracture phase model is applied to simulate the corrosion-induced cracking process of RC.The cracking patterns caused by non-uniform corrosion expansion are discussed for RC specimens with homogeneous macroscopically or heterogeneous with different polygonal aggregate distributions at the mesoscopic scale.Then,the effects of the protective layer on the crack propagation trajectory and cracking resistance are investigated,illustrating that the cracking angle and cracking resistance increase with the increase of the protective layer thickness,consistent with the experimental observation.Finally,the corrosion-induced cracking process of concrete specimens with large and small spacing rebars is simulated,and the interaction of multiple corrosion cracking is easily influenced by the reinforcement spacing,which increases with the decrease of the steel bar interval.These conclusions play an important role in the design of engineering anti-corrosion measures.The fracture phase field model can provide strong support for the life assessment of RC structures.展开更多
This study proposes a comprehensive,coupled thermomechanical model that replaces local spatial derivatives in classical differential thermomechanical equations with nonlocal integral forms derived from the peridynamic...This study proposes a comprehensive,coupled thermomechanical model that replaces local spatial derivatives in classical differential thermomechanical equations with nonlocal integral forms derived from the peridynamic differential operator(PDDO),eliminating the need for calibration procedures.The model employs a multi-rate explicit time integration scheme to handle varying time scales in multi-physics systems.Through simulations conducted on granite and ceramic materials,this model demonstrates its effectiveness.It successfully simulates thermal damage behavior in granite arising from incompatible mineral expansion and accurately calculates thermal crack propagation in ceramic slabs during quenching.To account for material heterogeneity,the model utilizes the Shuffle algorithm andWeibull distribution,yielding results that align with numerical simulations and experimental observations.This coupled thermomechanical model shows great promise for analyzing intricate thermomechanical phenomena in brittle materials.展开更多
This paper analyzes the characteristics of emotion state and group behavior in the evacuation process.During the emergency evacuation,emotion state and group behavior are interacting with each other,and indivisible.Th...This paper analyzes the characteristics of emotion state and group behavior in the evacuation process.During the emergency evacuation,emotion state and group behavior are interacting with each other,and indivisible.The emotion spread model with the effect of group behavior,and the leader-follower model with the effect of emotion state are proposed.On this basis,exit choice strategies with the effect of emotion state and group behavior are proposed.Fusing emotion spread model,leader-follower model,and exit choice strategies into a cellular automata(CA)-based pedestrian simulation model,we simulate the evacuation process in a multi-exit case.Simulation results indicate that panic emotion and group behavior are two negative influence factors for pedestrian evacuation.Compared with panic emotion or group behavior only,pedestrian evacuation efficiency with the effects of both is lower.展开更多
Vanadium-based compounds with high theoretical capacities and relatively stable crystal structures are potential cathodes for aqueous zinc-ion batteries(AZIBs).Nevertheless,their low electronic conductivity and sluggi...Vanadium-based compounds with high theoretical capacities and relatively stable crystal structures are potential cathodes for aqueous zinc-ion batteries(AZIBs).Nevertheless,their low electronic conductivity and sluggish zinc-ion diffusion kinetics in the crystal lattice are greatly obstructing their practical application.Herein,a general and simple nitrogen doping strategy is proposed to construct nitrogen-doped VO_(2)(B)nanobelts(denoted as VO_(2)-N)by the ammonia heat treatment.Compared with pure VO_(2)(B),VO_(2)-N shows an expanded lattice,reduced grain size,and disordered structure,which facilitates ion transport,provides additional ion storage sites,and improves structural durability,thus presenting much-enhanced zinc-ion storage performance.Density functional theory calculations demonstrate that nitrogen doping in VO_(2)(B)improves its electronic properties and reduces the zinc-ion diffusion barrier.The optimal VO_(2)-N400 electrode exhibits a high specific capacity of 373.7 mA h g^(-1)after 100 cycles at 0.1 A g^(-1)and stable cycling performance after 2000 cycles at 5 A g^(-1).The zinc-ion storage mechanism of VO_(2)-N is identified as a typical intercalation/de-intercalation process.展开更多
Dear Editor,Any fault of a battery system that is not handled timely can cause catastrophic consequences.Therefore,it is significant to diagnose battery faults early and accurately.Due to the complex nonlinear feature...Dear Editor,Any fault of a battery system that is not handled timely can cause catastrophic consequences.Therefore,it is significant to diagnose battery faults early and accurately.Due to the complex nonlinear features and inconsistency of lithium batteries,traditional fault diagnosis methods usually fail to detect battery minor faults in the early stages.展开更多
BACKGROUND The technique of percutaneous endoscopic lumbar discectomy(PELD)as a transforaminal approach has been used to treat highly migrated lower lumbar disc herniations.However,due to the different anatomic charac...BACKGROUND The technique of percutaneous endoscopic lumbar discectomy(PELD)as a transforaminal approach has been used to treat highly migrated lower lumbar disc herniations.However,due to the different anatomic characteristics of the upper lumbar spine,conventional transforaminal PELD may fail to remove the highly migrated upper lumbar disc nucleus pulposus.Therefore,the purpose of this study was to describe a novel surgical technique,two-level PELD,for the treatment of highly migrated upper lumbar disc herniations and to report its related clinical outcomes.CASE SUMMARY A 60-year-old male presented with a complaint of pain at his lower back and right lower limb.The patient received 3 mo of conservative treatments but the symptoms were not alleviated.Physical examination revealed a positive femoral nerve stretch test and a negative straight leg raise test for the right leg,and preoperative visual analog scale(VAS)score for the lower back was 6 points and for the right leg was 8 points.Magnetic resonance imaging(MRI)demonstrated L2-L3 disc herniation on the right side and the herniated nucleus pulposus migrated to the upper margin of L2 vertebral body.According to physical examination and imaging findings,surgery was the primary consideration.Therefore,the patient underwent surgical treatment with two-level PELD.The pain symptom was relieved and the VAS score for back and thigh pain was one point postoperatively.The patient was asymptomatic and follow-up MRI scan 1 year after operation revealed no residual nucleus pulposus.CONCLUSION Two-level PELD as a transforaminal approach can be a safe and effective procedure for highly migrated upper lumbar disc herniation.展开更多
BACKGROUND： Brain-derived neurotrophic factor （BDNF） provides nourishment to injured neurons. Neural stem cells can differentiate into neurons to repair neuronal injury in vivo. It has been hypothesized that contin...BACKGROUND： Brain-derived neurotrophic factor （BDNF） provides nourishment to injured neurons. Neural stem cells can differentiate into neurons to repair neuronal injury in vivo. It has been hypothesized that continuous secretion of BDNF from neural stem cells could benefit brain injury repair. OBJECTIVE： To transfect BDNF and enhanced green fluorescent protein （EGFP） into neural stem cells with adenovirus vector and to observe expression of BDNF and EGFP in transfected neural stem cells. DESIGN, TIME AND SETTING： Observational, cellular, molecular study was performed at the Biochemistry Laboratory, Tongji University School of Medicine, China from July 2004 to September 2006. MATERIALS： Neural stem cells were provided by the Anatomy and Histoembryology Laboratory of Fudan University Medical School, China. METHODS： BDNF cDNA was extracted by reverse transcription polymerase chain reaction from the rat hippocampus. Following gene cloning and packaging by HEK293.BDNF, the EGFP gene was transfected into cultured neural stem cells with the Ad-EGFP-BDNF vector. BDNF-expressing neural stem cell clones were selected by G418 selection. MAIN OUTCOME MEASURES： EGFP expression and cell morphology were observed by fluorescent microscopy; neural stem cell expressing BDNF mRNA was examined by reverse transcription polymerase chain reaction; BDNF expression was detected by enzyme-linked immunosorbent assay from supematant of infected neural stem cells. RESULTS： High transfection efficiency was obtained using 5×10^8 virus titers to transfect neural stem cells. G418-resistant neural stem cell clones integrated BDNF mRNA fragments. Enzyme-linked immunosorbent assay results showed that BDNF expression in the supernatant increased with increasing culture time and peaked at 72 hours. CONCLUSION： Adenovirus-mediated BDNF and EGFP genes were successfully transfected into neural stem cells and were expressed in neural stem cells for a long period of time.展开更多
Temporal variation of rock mass properties,especially the strength degradation due to drying-wetting cycles as well as the acidic wetting fluid(rainfall or reservoir water)is crucial to stability of reservoir rock slo...Temporal variation of rock mass properties,especially the strength degradation due to drying-wetting cycles as well as the acidic wetting fluid(rainfall or reservoir water)is crucial to stability of reservoir rock slopes.Based on a series of drying-wetting cycling and experiments considering the influences of pH values,the degradation degree models of the reduced cohesion𝑐𝑐′,friction angle𝜑𝜑′are developed.2D stability analysis of the slope is subsequently carried out to calculate the factor of safety(Fs)via limit equilibrium method(LEM)and a predictive model of Fs is built using multivariate adaptive regression splines(MARS),revealing the effect of the drying-wetting cycles and pH value.The reliability analysis by Monte Carlo simulation is performed to rationally consider the uncertainty and the temporal variation of the shear strength parameters of rock mass.Results indicate that the MARS-based model can estimate the Fs accurately.The Fs and the reliability indexβdecrease with increase of drying-wetting cycles,and the temporal variation of rock mass properties has significant influence on the slope reliability.Overlooking the temporal variation of rock properties may overestimate the Fs and reliability indexβin the longer term.展开更多
Objective: Contrast induced nephropathy (CIN) is the third leading cause of hospital acquired renal failure. The mechanism of CIN is not fully understood. The objectives of this study were to investigate the expressio...Objective: Contrast induced nephropathy (CIN) is the third leading cause of hospital acquired renal failure. The mechanism of CIN is not fully understood. The objectives of this study were to investigate the expression changes of the four subtypes of adenosine receptors (A1AR, A2AAR, A2BAR, and A3AR) following administration of contrast media in mice. Methods: C57BL/6J mice were randomized into treatment and control groups. Iodixanol (IDX) was administered to two treatment groups through retroorbital injection at two different dosages, 0.75 gI/kg and 2.75 gI/kg. Phosphate buffered saline (PBS) was given to the control group. Mice kidneys were harvested at day 3 and day 7 after Iodixanol administration. Kidney injuries and function were evaluated according to Hematoxylin and eosin stain, Ki67 protein expression, and TUNEL assay of paraffin embedded kidney sections, and plasma creatinine assay. RNA and protein were extracted from the kidney specimens. A1AR, A2AAR, A2BAR, and A3AR RNA and protein level of the samples were assessed using qRT-PCR and Western blotting, with GAPDH as an endogenous control. Results: H&E staining showed no significant histopathology injuries after Iodixanol administration. No evidence of kidney injury and functional impairment was found. However, there was an increased number of A1AR, A2AAR, A2BAR, and A3AR RNA transcripts detected in the kidney 3 days after Iodixanol injection. The RNA levels in all the four subtypes of adenosine receptors were increased 2-3 fold in the day 3 specimens and back to normal at day 7. Western blot demonstrated that A1AR, A2AAR, and A3AR expression increased 1.5 to 2 fold at day 3 and day 7 following Iodixanol injection. A2BAR baseline expression was low in normal physiological conditions and no significant change was detected by Western blot. Conclusions: Iodixanol significantly increases adenosine receptors gene expression in mice. This suggests that adenosine receptors may play a role in the development of CIN.展开更多
基金the National Natural Science Foundation of China(Qing Zhang,Nos.11932006,U1934206,12172121)the Fundamental Research Funds for the Central Universities(Xin Gu,No.B210201031).
文摘Accurate simulation of the cracking process caused by rust expansion of reinforced concrete(RC)structures plays an intuitive role in revealing the corrosion-induced failure mechanism.Considering the quasi-brittle fracture of concrete,the fracture phase field driven by the compressive-shear term is constructed and added to the traditional brittle fracture phase field model.The rationality of the proposed model is verified by a mixed fracture example under a shear displacement load.Then,the extended fracture phase model is applied to simulate the corrosion-induced cracking process of RC.The cracking patterns caused by non-uniform corrosion expansion are discussed for RC specimens with homogeneous macroscopically or heterogeneous with different polygonal aggregate distributions at the mesoscopic scale.Then,the effects of the protective layer on the crack propagation trajectory and cracking resistance are investigated,illustrating that the cracking angle and cracking resistance increase with the increase of the protective layer thickness,consistent with the experimental observation.Finally,the corrosion-induced cracking process of concrete specimens with large and small spacing rebars is simulated,and the interaction of multiple corrosion cracking is easily influenced by the reinforcement spacing,which increases with the decrease of the steel bar interval.These conclusions play an important role in the design of engineering anti-corrosion measures.The fracture phase field model can provide strong support for the life assessment of RC structures.
基金supported by the University Natural Science Foundation of Jiangsu Province(Grant No.23KJB130004)the National Natural Science Foundation of China(Grant Nos.11932006,U1934206,12172121,12002118).
文摘This study proposes a comprehensive,coupled thermomechanical model that replaces local spatial derivatives in classical differential thermomechanical equations with nonlocal integral forms derived from the peridynamic differential operator(PDDO),eliminating the need for calibration procedures.The model employs a multi-rate explicit time integration scheme to handle varying time scales in multi-physics systems.Through simulations conducted on granite and ceramic materials,this model demonstrates its effectiveness.It successfully simulates thermal damage behavior in granite arising from incompatible mineral expansion and accurately calculates thermal crack propagation in ceramic slabs during quenching.To account for material heterogeneity,the model utilizes the Shuffle algorithm andWeibull distribution,yielding results that align with numerical simulations and experimental observations.This coupled thermomechanical model shows great promise for analyzing intricate thermomechanical phenomena in brittle materials.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFC0803903)the National Natural Science Foundation of China(Grant No.62003182)。
文摘This paper analyzes the characteristics of emotion state and group behavior in the evacuation process.During the emergency evacuation,emotion state and group behavior are interacting with each other,and indivisible.The emotion spread model with the effect of group behavior,and the leader-follower model with the effect of emotion state are proposed.On this basis,exit choice strategies with the effect of emotion state and group behavior are proposed.Fusing emotion spread model,leader-follower model,and exit choice strategies into a cellular automata(CA)-based pedestrian simulation model,we simulate the evacuation process in a multi-exit case.Simulation results indicate that panic emotion and group behavior are two negative influence factors for pedestrian evacuation.Compared with panic emotion or group behavior only,pedestrian evacuation efficiency with the effects of both is lower.
基金supported from the Natural Science Foundation of Shandong Province(ZR2022MB088)the National Natural Science Foundation of China(22138013)+1 种基金the Taishan Scholar Project(ts201712020)the Innovation and Entrepreneurship Training Program for college students of the China University of Petroleum(East China)(202207011)。
文摘Vanadium-based compounds with high theoretical capacities and relatively stable crystal structures are potential cathodes for aqueous zinc-ion batteries(AZIBs).Nevertheless,their low electronic conductivity and sluggish zinc-ion diffusion kinetics in the crystal lattice are greatly obstructing their practical application.Herein,a general and simple nitrogen doping strategy is proposed to construct nitrogen-doped VO_(2)(B)nanobelts(denoted as VO_(2)-N)by the ammonia heat treatment.Compared with pure VO_(2)(B),VO_(2)-N shows an expanded lattice,reduced grain size,and disordered structure,which facilitates ion transport,provides additional ion storage sites,and improves structural durability,thus presenting much-enhanced zinc-ion storage performance.Density functional theory calculations demonstrate that nitrogen doping in VO_(2)(B)improves its electronic properties and reduces the zinc-ion diffusion barrier.The optimal VO_(2)-N400 electrode exhibits a high specific capacity of 373.7 mA h g^(-1)after 100 cycles at 0.1 A g^(-1)and stable cycling performance after 2000 cycles at 5 A g^(-1).The zinc-ion storage mechanism of VO_(2)-N is identified as a typical intercalation/de-intercalation process.
基金supported by the National Natural Science Foundation of China(62173211,61821004,62122041)Natural Science Foundation of Shandong Province,China(ZR2021JQ25,ZR2019ZD09)。
文摘Dear Editor,Any fault of a battery system that is not handled timely can cause catastrophic consequences.Therefore,it is significant to diagnose battery faults early and accurately.Due to the complex nonlinear features and inconsistency of lithium batteries,traditional fault diagnosis methods usually fail to detect battery minor faults in the early stages.
文摘BACKGROUND The technique of percutaneous endoscopic lumbar discectomy(PELD)as a transforaminal approach has been used to treat highly migrated lower lumbar disc herniations.However,due to the different anatomic characteristics of the upper lumbar spine,conventional transforaminal PELD may fail to remove the highly migrated upper lumbar disc nucleus pulposus.Therefore,the purpose of this study was to describe a novel surgical technique,two-level PELD,for the treatment of highly migrated upper lumbar disc herniations and to report its related clinical outcomes.CASE SUMMARY A 60-year-old male presented with a complaint of pain at his lower back and right lower limb.The patient received 3 mo of conservative treatments but the symptoms were not alleviated.Physical examination revealed a positive femoral nerve stretch test and a negative straight leg raise test for the right leg,and preoperative visual analog scale(VAS)score for the lower back was 6 points and for the right leg was 8 points.Magnetic resonance imaging(MRI)demonstrated L2-L3 disc herniation on the right side and the herniated nucleus pulposus migrated to the upper margin of L2 vertebral body.According to physical examination and imaging findings,surgery was the primary consideration.Therefore,the patient underwent surgical treatment with two-level PELD.The pain symptom was relieved and the VAS score for back and thigh pain was one point postoperatively.The patient was asymptomatic and follow-up MRI scan 1 year after operation revealed no residual nucleus pulposus.CONCLUSION Two-level PELD as a transforaminal approach can be a safe and effective procedure for highly migrated upper lumbar disc herniation.
基金the Natural Science Foundation of Shanghai,No.04ZR14107the Science and Technology Developmental Fund of Shanghai Railway Station,No.2003Y04
文摘BACKGROUND： Brain-derived neurotrophic factor （BDNF） provides nourishment to injured neurons. Neural stem cells can differentiate into neurons to repair neuronal injury in vivo. It has been hypothesized that continuous secretion of BDNF from neural stem cells could benefit brain injury repair. OBJECTIVE： To transfect BDNF and enhanced green fluorescent protein （EGFP） into neural stem cells with adenovirus vector and to observe expression of BDNF and EGFP in transfected neural stem cells. DESIGN, TIME AND SETTING： Observational, cellular, molecular study was performed at the Biochemistry Laboratory, Tongji University School of Medicine, China from July 2004 to September 2006. MATERIALS： Neural stem cells were provided by the Anatomy and Histoembryology Laboratory of Fudan University Medical School, China. METHODS： BDNF cDNA was extracted by reverse transcription polymerase chain reaction from the rat hippocampus. Following gene cloning and packaging by HEK293.BDNF, the EGFP gene was transfected into cultured neural stem cells with the Ad-EGFP-BDNF vector. BDNF-expressing neural stem cell clones were selected by G418 selection. MAIN OUTCOME MEASURES： EGFP expression and cell morphology were observed by fluorescent microscopy; neural stem cell expressing BDNF mRNA was examined by reverse transcription polymerase chain reaction; BDNF expression was detected by enzyme-linked immunosorbent assay from supematant of infected neural stem cells. RESULTS： High transfection efficiency was obtained using 5×10^8 virus titers to transfect neural stem cells. G418-resistant neural stem cell clones integrated BDNF mRNA fragments. Enzyme-linked immunosorbent assay results showed that BDNF expression in the supernatant increased with increasing culture time and peaked at 72 hours. CONCLUSION： Adenovirus-mediated BDNF and EGFP genes were successfully transfected into neural stem cells and were expressed in neural stem cells for a long period of time.
基金the financial support from Natural Science Foundation of Chongqing,China(cstc2018jcyjAX0632)the Venture&Innovation Support Program for Chongqing Overseas Returnees(cx2017123)+1 种基金as well as Chongqing Engineering Research Center of Disaster Prevention&Control for Banks and Structures in Three Gorges Reservoir Area(SXAPGC18ZD01,SXAPGC18YB03)In addition,the authors would like to express their appreciation to Liu et al.[Liu,Zhang and Fu(2014)]for making their test results available for this work.
文摘Temporal variation of rock mass properties,especially the strength degradation due to drying-wetting cycles as well as the acidic wetting fluid(rainfall or reservoir water)is crucial to stability of reservoir rock slopes.Based on a series of drying-wetting cycling and experiments considering the influences of pH values,the degradation degree models of the reduced cohesion𝑐𝑐′,friction angle𝜑𝜑′are developed.2D stability analysis of the slope is subsequently carried out to calculate the factor of safety(Fs)via limit equilibrium method(LEM)and a predictive model of Fs is built using multivariate adaptive regression splines(MARS),revealing the effect of the drying-wetting cycles and pH value.The reliability analysis by Monte Carlo simulation is performed to rationally consider the uncertainty and the temporal variation of the shear strength parameters of rock mass.Results indicate that the MARS-based model can estimate the Fs accurately.The Fs and the reliability indexβdecrease with increase of drying-wetting cycles,and the temporal variation of rock mass properties has significant influence on the slope reliability.Overlooking the temporal variation of rock properties may overestimate the Fs and reliability indexβin the longer term.
文摘Objective: Contrast induced nephropathy (CIN) is the third leading cause of hospital acquired renal failure. The mechanism of CIN is not fully understood. The objectives of this study were to investigate the expression changes of the four subtypes of adenosine receptors (A1AR, A2AAR, A2BAR, and A3AR) following administration of contrast media in mice. Methods: C57BL/6J mice were randomized into treatment and control groups. Iodixanol (IDX) was administered to two treatment groups through retroorbital injection at two different dosages, 0.75 gI/kg and 2.75 gI/kg. Phosphate buffered saline (PBS) was given to the control group. Mice kidneys were harvested at day 3 and day 7 after Iodixanol administration. Kidney injuries and function were evaluated according to Hematoxylin and eosin stain, Ki67 protein expression, and TUNEL assay of paraffin embedded kidney sections, and plasma creatinine assay. RNA and protein were extracted from the kidney specimens. A1AR, A2AAR, A2BAR, and A3AR RNA and protein level of the samples were assessed using qRT-PCR and Western blotting, with GAPDH as an endogenous control. Results: H&E staining showed no significant histopathology injuries after Iodixanol administration. No evidence of kidney injury and functional impairment was found. However, there was an increased number of A1AR, A2AAR, A2BAR, and A3AR RNA transcripts detected in the kidney 3 days after Iodixanol injection. The RNA levels in all the four subtypes of adenosine receptors were increased 2-3 fold in the day 3 specimens and back to normal at day 7. Western blot demonstrated that A1AR, A2AAR, and A3AR expression increased 1.5 to 2 fold at day 3 and day 7 following Iodixanol injection. A2BAR baseline expression was low in normal physiological conditions and no significant change was detected by Western blot. Conclusions: Iodixanol significantly increases adenosine receptors gene expression in mice. This suggests that adenosine receptors may play a role in the development of CIN.
