Granular behaviour under bi-directional shear with constant vertical stress and constant volume

This paper aims to investigate the role of bi-directional shear in the mechanical behaviour of granular materials and macro-micro relations by conducting experiments and discrete element method(DEM)modelling.The bi-directional shear consists of a static shear consolidation and subsequent shear under constant vertical stress and constant volume conditions.A side wall node loading method is used to exert bi-directional shear of various angles.The results show that bi-directional shear can significantly influence the mechanical behaviour of granular materials.However,the relationship between bidirectional shear and mechanical responses relies on loading conditions,i.e.constant vertical stress or constant volume conditions.The stress states induced by static shear consolidation are affected by loading angles,which are enlarged by subsequent shear,consistent with the relationship between bidirectional shear and principal stresses.It provides evidence for the dissipation of stresses accompanying static liquefaction of granular materials.The presence of bi-directional principal stress rotation(PSR)is demonstrated,which evidences why the bi-directional shear of loading angles with components in two directions results in faster dissipations of stresses with static liquefaction.Contant volume shearing leads to cross-anisotropic stress and fabric at micro-contacts,but constant vertical stress shearing leads to complete anisotropic stress and fabric at micro-contacts.It explains the differentiating relationship between stress-strain responses and fabric anisotropy under these two conditions.Micromechanical signatures such as the slip state of micro-contacts and coordination number are also examined,providing further insights into understanding granular behaviour under bi-directional shear.

Effect of safety valve types on the gas venting behavior and thermal runaway hazard severity of large-format prismatic lithium iron phosphate batteries

The safety valve is an important component to ensure the safe operation of lithium-ion batteries(LIBs).However,the effect of safety valve type on the thermal runaway(TR)and gas venting behavior of LIBs,as well as the TR hazard severity of LIBs,are not known.In this paper,the TR and gas venting behavior of three 100 A h lithium iron phosphate(LFP)batteries with different safety valves are investigated under overheating.Compared to previous studies,the main contribution of this work is in studying and evaluating the effect of gas venting behavior and TR hazard severity of LFP batteries with three safety valve types.Two significant results are obtained:(Ⅰ)the safety valve type dominates over gas venting pressure of battery during safety venting,the maximum gas venting pressure of LFP batteries with a round safety valve is 3320 Pa,which is one order of magnitude higher than other batteries with oval or cavity safety valve;(Ⅱ)the LFP battery with oval safety valve has the lowest TR hazard as shown by the TR hazard assessment model based on gray-fuzzy analytic hierarchy process.This study reveals the effect of safety valve type on TR and gas venting,providing a clear direction for the safety valve design.

Low-temperature characteristicsof rubbers and performance testsof type 120 emergencyvalve diaphragms

Purpose–The type 120 emergency valve is an essential braking component of railway freight trains,butcorresponding diaphragms consisting of natural rubber(NR)and chloroprene rubber(CR)exhibit insufficientaging resistance and low-temperature resistance,respectively.In order to develop type 120 emergency valverubber diaphragms with long-life and high-performance,low-temperatureresistant CR and NR were processed.Design/methodology/approach–The physical properties of the low-temperature-resistant CR and NRwere tested by low-temperature stretching,dynamic mechanical analysis,differential scanning calorimetryand thermogravimetric analysis.Single-valve and single-vehicle tests of type 120 emergency valves werecarried out for emergency diaphragms consisting of NR and CR.Findings–The low-temperature-resistant CR and NR exhibited excellent physical properties.The elasticityand low-temperature resistance of NR were superior to those of CR,whereas the mechanical properties of thetwo rubbers were similar in the temperature range of 0℃–150℃.The NR and CR emergency diaphragms metthe requirements of the single-valve test.In the low-temperature single-vehicle test,only the low-temperaturesensitivity test of the NR emergency diaphragm met the requirements.Originality/value–The innovation of this study is that it provides valuable data and experience for futuredevelopment of type 120 valve rubber diaphragms.

Current knowledge for the risk factors of early permanent pacemaker implantation following transcatheter aortic valve replacement and what is next for the primary prevention?

In this editorial,we comprehensively summarized the preoperative risk factors of early permanent pacemaker implantation after transcatheter aortic valve replacement(TAVR)among patients with severe aortic stenosis from several renowned clinical studies and focused on the primary prevention of managing the modifiable factors,e.g.,paroxysmal atrial fibrillation before the TAVR.

A novel mouse model of calcific aortic valve stenosis

Background:Calcific aortic valve stenosis(CAVS)is one of the most challenging heart diseases in clinical with rapidly increasing prevalence.However,study of the mecha-nism and treatment of CAVS is hampered by the lack of suitable,robust and efficient models that develop hemodynamically significant stenosis and typical calcium deposi-tion.Here,we aim to establish a mouse model to mimic the development and features of CAVS.Methods:The model was established via aortic valve wire injury(AVWI)combined with vitamin D subcutaneous injected in wild type C57/BL6 mice.Serial transthoracic echocardiography was applied to evaluate aortic jet peak velocity and mean gradi-ent.Histopathological specimens were collected and examined in respect of valve thickening,calcium deposition,collagen accumulation,osteogenic differentiation and inflammation.Results:Serial transthoracic echocardiography revealed that aortic jet peak velocity and mean gradient increased from 7 days post model establishment in a time depend-ent manner and tended to be stable at 28 days.Compared with the sham group,sim-ple AVWI or the vitamin D group,the hybrid model group showed typical pathological features of CAVS,including hemodynamic alterations,increased aortic valve thicken-ing,calcium deposition,collagen accumulation at 28 days.In addition,osteogenic dif-ferentiation,fibrosis and inflammation,which play critical roles in the development of CAVS,were observed in the hybrid model.Conclusions:We established a novel mouse model of CAVS that could be induced efficiently,robustly and economically,and without genetic intervention.It provides a fast track to explore the underlying mechanisms of CAVS and to identify more effec-tive pharmacological targets.

The use of fluoroscopy for detecting hypertensive lung edema due to prosthetic valve dysfunction: a case report

Heart valve diseases affect more than one hundred million people around the world,which are a serious cause of illness and mortality.[1]Among the valve diseases,mitral valve insufficiency ranks second in the list of valve diseases requiring surgical repair in Europe.[2]Prosthetic valve replacement is the standard treatment in cases where repair is not sufficient for valve diseases.[3]Mechanical and bioprosthetic valves can be preferred for replacement,mechanical valves are more durable and require lifelong use of anticoagulants.The disadvantage of bioprosthetic valves is early degeneration,and infective reoperation is required due to the formation of endocarditis.[4-5]The risk of thromboembolism,lifetime anticoagulant use and complications related to anticoagulation remain disadvantages of valve surgery.[3]The most important complication requiring urgent intervention is valve dysfunction due to thrombosis.It usually occurs due to inappropriate use of the anticoagulants.[6]Surgical treatment is used for severe obstructions,such as thrombi larger than 10 mm.Thrombolytic therapy can be applied in small thrombi and in cases where surgical intervention is risky.

Application of CFD and FEA Coupling to Predict Structural Dynamic Responses of A Trimaran in Uni-and Bi-Directional Waves

To predict the wave loads of a flexible trimaran in different wave fields,a one-way interaction numerical simulation method is proposed by integrating the fluid solver(Star-CCM+)and structural solver(Abaqus).Differing from the existing coupled CFD-FEA method for monohull ships in head waves,the presented method equates the mass and stiffness of the whole ship to the hull shell so that any transverse and longitudinal section stress of the hull in oblique waves can be obtained.Firstly,verification study and sensitivity analysis are carried out by comparing the trimaran motions using different mesh sizes and time step schemes.Discussion on the wave elevation of uni-and bi-directional waves is also carried out.Then a comprehensive analysis on the structural responses of the trimaran in different uni-directional regular wave and bi-directional cross sea conditions is carried out,respectively.Finally,the differences in structural response characteristics of trimaran in different wave fields are studied.The results show that the present method can reduce the computational burden of the two-way fluid-structure interaction simulations.

Animal Model of Aortic Valve Calcification: Their Methodology Helps Us Understand Aortic Valve Calcification

Aortic valve calcification disease (CAVD) is the most prevalent degenerative valve disease in humans, leading to significant morbidity and mortality. Despite its common occurrence, our understanding of the underlying mechanisms remains incomplete, and available treatment options are limited and risky. A more comprehensive understanding of the biology of CAVD is essential to identify new therapeutic strategies. Animal models have played a crucial role in advancing our knowledge of CAVD and exploring potential treatments. However, these models have inherent limitations as they cannot fully replicate the complex physiological mechanisms of human CAVD. In this review, we examine various CAVD models ranging from pigs to mice, highlighting the unique characteristics of each model to enhance our understanding of CAVD. While these models offer valuable insights, they also have limitations and shortcomings. We propose that the guide wire model shows promise for future CAVD research, and streamlining the methodology could enhance our understanding and expand the research scope in this field.

Psychological Status and Warfarin Therapy in Patients after Valve Replacement during the COVID-19 Pandemic:A Cross-sectional Study

Objective The standardization of warfarin anticoagulant therapy is the key to lifelong treatment for patients after heart valve replacement.The present study explored the possible risk factors for anxiety and depression during the coronavirus disease 2019(COVID-19)pandemic and analyzed the influence of psychological state on medication safety.Methods Eligible patients received a web-based questionnaire survey via the Wenjuanxing platform during outpatient visits.Depression was evaluated by the Self-Rating Depression Scale(SDS).Anxiety was evaluated by the Self-Rating Anxiety Scale(SAS).Medication adherence was evaluated by the Morisky scale.Results A total of 309 patients(aged 52.2±11.4 years)were included in the present study.The SDS score of all included patients was 36.9±9.4 points,of which 11(3.6%)patients were diagnosed as having depression.The SAS score of all included patients was 43.1±9.3 points,of which 71(23%)patients were diagnosed as having anxiety.Seven patients(2.3%)had both anxiety and depression.Logistic regression analysis revealed that only monthly income was an independent influencing factor for depression.Regarding anxiety,patients who underwent repeated operations had a 2.264-fold greater risk,and patients who received combination medication had a 2.140-fold greater risk.More bleeding events and coagulation disorders could be observed in patients with anxiety,depression or both.When anxiety occurred,patients showed worse medication adherence.However,depression had no significant effect on medication adherence.Conclusion During the COVID-19 pandemic,the detection rate of mental illnesses such as anxiety and depression was high,which seriously affected the medication safety of warfarin.Analysis of its influencing factors will provide a reference for further standardized regulation of warfarin anticoagulant therapy after valve replacement.

Transcatheter aortic valve replacement in low-risk young population:A double edge sword?

Since the advent of transcatheter aortic valve replacement(TAVR)in 2002,it has now become the default interventional strategy for symptomatic patients presenting with severe aortic stenosis,particularly in intermediate to highsurgical risk patients.In 2019,the United States Food and Drug Administration approved TAVR in low-risk patients based on two randomized trials.However,these breakthrough trials excluded patients with certain unfavorable anatomies and odd profiles.While currently there is no randomized study of TAVR in young patients,it may be preferred by the young population given the benefits of early discharge,shorter hospital stay,and expedite recovery.Nonetheless,it is important to ruminate various factors including lifetime expectancy,risk of pacemaker implantation,and the need for future valve or coronary interventions in young cohorts before considering TAVR in these patients.Furthermore,the data on long-term durability(>10 years)of TAVR is still unknown given most of the procedures were initially performed in the high or prohibitive surgical risk population.Thus,this editorial aims to highlight the importance of considering an individualized approach in young patients with consideration of various factors including lifetime expectancy while choosing TAVR against surgical aortic valve replacement.

Electric-controlled pressure relief valve for enhanced safety in liquid-cooled lithium-ion battery packs

The liquid-cooled battery energy sto rage system(LCBESS) has gained significant attention due to its superior thermal management capacity.However,liquid-cooled battery pack(LCBP) usually has a high sealing level above IP65,which can trap flammable and explosive gases from battery thermal runaway and cause explosions.This poses serious safety risks and challenges for LCBESS.In this study,we tested overcharged battery inside a commercial LCBP and found that the conventionally mechanical pressure relief valve(PRV) on the LCBP had a delayed response and low-pressure relief efficiency.A realistic 20-foot model of an energy storage cabin was constructed using the Flacs finite element simulation software.Comparative studies were conducted to evaluate the pressure relief efficiency and the influence on neighboring battery packs in case of internal explosions,considering different sizes and installation positions of the PRV.Here,a newly developed electric-controlled PRV integrated with battery fault detection is introduced,capable of starting within 50 ms of the battery safety valve opening.Furthermore,the PRV was integrated with the battery management system and changed the battery charging and discharging strategy after the PRV was opened.Experimental tests confirmed the efficacy of this method in preventing explosions.This paper addresses the safety concerns associated with LCBPs and proposes an effective solution for explosion relief.

A chaotic hierarchical encryption/watermark embedding scheme for multi-medical images based on row-column confusion and closed-loop bi-directional diffusion

Security during remote transmission has been an important concern for researchers in recent years.In this paper,a hierarchical encryption multi-image encryption scheme for people with different security levels is designed,and a multiimage encryption(MIE)algorithm with row and column confusion and closed-loop bi-directional diffusion is adopted in the paper.While ensuring secure communication of medical image information,people with different security levels have different levels of decryption keys,and differentiated visual effects can be obtained by using the strong sensitivity of chaotic keys.The highest security level can obtain decrypted images without watermarks,and at the same time,patient information and copyright attribution can be verified by obtaining watermark images.The experimental results show that the scheme is sufficiently secure as an MIE scheme with visualized differences and the encryption and decryption efficiency is significantly improved compared to other works.

Patient-specific bicuspid aortic valve hemodynamics study based on computer simulation and in vitro experiment

Bicuspid aortic valve(BAV)is a common congenital malformation of the aortic valve with various structural characteristics.Different types of BAV can cause secondary aortic diseases,including calcific aortic valve stenosis and aortic dilation,although their pathogenesis remains unclear.In this study,we first established patient-specific BAV simulation models and silicone models(Type 0 A-P,Type 1 R-N,and Type 1 L-R)based on clinical computed tomography angiography(CTA)and pressure data.Next,we applied a research method combining fluid-structure interaction(FSI)simulation and digital particle image velocimetry(DPIV)experiment to quantitatively analyze the hemodynamic,structural mechanical,and flow field characteristics of patients with different BAV types.Simulation-based hemodynamic parameters and experimental results were consistent with clinical data,affirming the accuracy of the model.The location of the maximum principal strain in the patientspecific model was associated with the calcification site,which characterized the mechanism of secondary aortic valve stenosis.The maximum wall shear stress(WSS)of the patient-specific model(>67.1 Pa)exceeded 37.9 Pa and could cause endothelial surface injury as well as remodeling under long-term exposure,thus increasing the risk of aortic dilation.The distribution of WSS was mainly caused by BAV type,resulting in different degrees of dilation in different parts guided by the type.The patient-specific model revealed a maximum viscous shear stress(VSS)value of 5.23 Pa,which was smaller than the threshold for shear-induced hemolysis of red blood cells(150 Pa)and platelet activation(10 Pa),but close to the threshold for platelet sensitization(6 Pa).The results of flow field characteristics revealed a low risk of hemolysis but a relative high risk of thrombus formation in the patient-specific model.This study not only provides a basis for future comprehensive research on BAV diseases,but also generates relevant insights for theoretical guidance for calcific aortic valve stenosis and aortic dilation caused by different types of BAV,as well as biomechanical evidence for the potential risk of hemolysis and thrombus formation in BAV,which is of great value for clinical diagnosis and treatment of BAV.

Isogeometric Analysis of Hyperelastic Material Characteristics for Calcified Aortic Valve

This study explores the implementation of computed tomography(CT)reconstruction and simulation techniques for patient-specific valves,aiming to dissect the mechanical attributes of calcified valves within transcatheter heart valve replacement(TAVR)procedures.In order to facilitate this exploration,it derives pertinent formulas for 3D multi-material isogeometric hyperelastic analysis based on Hounsfield unit(HU)values,thereby unlocking foundational capabilities for isogeometric analysis in calcified aortic valves.A series of uniaxial and biaxial tensile tests is executed to obtain an accurate constitutive model for calcified active valves.To mitigate discretization errors,methodologies for reconstructing volumetric parametric models,integrating both geometric and material attributes,are introduced.Applying these analytical formulas,constitutive models,and precise analytical models to isogeometric analyses of calcified valves,the research ascertains their close alignment with experimental results through the close fit in displacement-stress curves,compellingly validating the accuracy and reliability of the method.This study presents a step-by-step approach to analyzing themechanical characteristics of patient-specific valves obtained fromCT images,holding significant clinical implications and assisting in the selection of treatment strategies and surgical intervention approaches in TAVR procedures.

Early Prosthetic Valve Endocarditis with Mycobacterium Tuberculosis after Mitral Valve Replacement: A Case Report

Background: Tuberculous endocarditis is a rare but serious complication of heart valve replacement surgery. We report the case of a 24-year-old patient, who presented with tuberculous endocarditis after mechanical mitral valve replacement, with a favorable clinical course following anti-tuberculosis treatment. Case Presentation: We report a 24-year-old male patient, admitted to the cardiac surgery department of the Fann Hospital (Dakar, Senegal), for the management of severe mixed (rheumatic and endocarditic) mitral insufficiency with associated tricuspid insufficiency. He had a history of recurrent angina and polyarthralgia in childhood, was hospitalized several times for refractory global cardiac decompensation, and for a suspected infective endocarditis a month before his admission. On admission, the clinical examination revealed signs suggestive of mitral and tricuspid insufficiency. Transthoracic echocardiography revealed severe post-endocarditic mitral insufficiency with A3 amputation, highly mobile 15 mm vegetations on the free edge of the large valve, moderate tricuspid insufficiency, and severe pulmonary artery hypertension. Mechanical mitral valve replacement and tricuspid valve annuloplasty using autologous pericardial strip were performed via median sternotomy. After ten days, the patient presented with global cardiac decompensation associated with a clinico-biological infectious syndrome, and tans-oesophageal echography revealed an abscess at the sinotubular junction, communicating with the aorta. A thoraco-abdomino-pelvic CT scan was done, which revealed a bilateral alveolar-interstitial syndrome with mediastinal lymphadenopathy. Anti-tuberculosis treatment with RHZE was initiated for 06 months. The clinical course was favorable. Conclusion: Tuberculous endocarditis in prostheses is a serious complication of heart valve replacement surgery, which may evolve favorably under medical treatment.

Navigating postoperative complications:Uveitis-glaucoma-hyphema syndrome after Ahmed glaucoma valve implantation

Altwijri and Alsirhy reported a case of uveitis-glaucoma-hyphema syndrome after an Ahmed glaucoma valve implantation surgery in an advanced primary open-angle glaucoma patient,being the first ever recorded of its kind.The author describes the position of the tube as the origin of the anterior chamber inflam-mation and hyphema,which resolved shortly after shortening and relocating it.This publication emphasizes the importance of precise implant positioning and close-up patient follow-up after glaucoma filtration surgery as an important standard for healthcare providers.

Rates, predictors, and causes of readmission after transcatheter aortic valve replacement in patients with chronic kidney disease

BACKGROUND Transcatheter aortic valve replacement(TAVR)is a revolutionary procedure for severe aortic stenosis.The coexistence of chronic kidney disease(CKD)and TAVR introduces a challenge that significantly impacts patient outcomes.AIM To define readmission rates,predictors,and causes after TAVR procedure in CKD stage 1-4 patients.METHODS We used the national readmission database 2018 and 2020 to look into readmission rates,causes and predictors after TAVR procedure in patients with CKD stage 1-4.RESULTS Out of 24758 who underwent TAVR and had CKD,7892(32.4%)patients were readmitted within 90 days,and had higher adjusted odds of being females(adjusted odds ratio:1.17,95%CI:1.02-1.31,P=0.02)with longer length of hospital stay>6 days,and more comorbidities including but not limited to diabetes mellitus,anemia,and congestive heart failure(CHF).CONCLUSION Most common causes of readmission included CHF(18.0%),sepsis,and complete atrioventricular block.Controlling readmission predictors with very close followup is warranted to prevent such high rate of readmission.

Switching Frequency Improvement of a High Speed on/off Valve Based on Pre-excitation Control Algorithm

The high-speed on/off valve(HSV)serves as the fundamental component responsible for generating discrete fluids within digital hydraulic systems.As the switching frequency of the HSV increases,the properties of the generated discrete fluid approach those of continuous fluids.Therefore,a higher frequency response characteristic of HSV is the key to ensure the control accuracy of digital hydraulic systems.However,the current research mainly focuses on its dynamic performance,but neglect its FRC.This paper presents a theoretical analysis demonstrating that the FRC of the HSV can be enhanced by minimizing its switching time.The maximum switching frequency(MSF)is mainly determined by opening dynamic performance when HSV operates with low switching duty ratio(SDR),whereas the closing dynamic performance limits the MSF when HSV operates with high SDR.Building upon these findings,the pre-excitation control algorithm(PECA)is proposed to reduce the switching time of the HSV,and consequently enhance its FRC.Experimental results demonstrate that PECA shortens the opening delay time of HSV by 1.12 ms,the closing delay time by 2.54 ms,and the closing moving time by 0.47 ms in comparison to the existing advanced control algorithms.As a result,a larger MSF of 417 Hz and a wider controllable SDR range from 20%to 70%were achieved at a switching frequency of 250 Hz.Thus,the proposed PFCA in this paper has been verified as an effective and promising approach for enhancing the control performance of digital hydraulic systems.

Risk of permanent pacemaker implantation following transcatheter aortic valve replacement:Which factors are most relevant?

Transcatheter aortic valve replacement(TAVR)has emerged as a formidable treatment option for severe symptomatic aortic stenosis ahead of surgical aortic valve replacement.The encouraging results from large randomized controlled trials has resulted in an exponential rise in the use of TAVR even in the low-risk patients.However,this is not without challenges.Need for permanent pacemaker(PPM)post-TAVR remains the most frequent and clinically relevant challenge.Naturally,identifying risk factors which predispose an individual to develop high grade conduction block post-TAVR is important.Various demographic factors,electrocardiographic features,anatomic factors and procedural characteristics have all been linked to the development of advanced conduction block and need for PPM following TAVR.Amongst these electrophysiological variables,most notably a prolonged QRS>120 ms regardless of the type of conduction block seems to be one of the strongest predictors on logistic regression models.The index study by Nwaedozie et al highlights that patients requiring PPM post-TAVR had higher odds of having a baseline QRS>120 ms and were more likely to be having diabetes mellitus that those who did not require PPM.

Predictors of permanent pacemaker implantation following transcatheter aortic valve replacement-the search is still on!

Several anatomical,demographic,clinical,electrocardiographic,procedural,and valve-related variables can be used to predict the probability of developing con-duction abnormalities after transcatheter aortic valve replacement(TAVR)that necessitate permanent pacemaker(PPM)implantation.These variables include calcifications around the device landing zone and in the mitral annulus;pre-existing electrocardiographic abnormalities such as left and right bundle branch blocks(BBB),first-and second-degree atrioventricular blocks,as well as bifas-cicular and trifascicular blocks;male sex;diabetes mellitus(DM);hypertension;history of atrial fibrillation;renal failure;dementia;and use of self-expanding valves.The current study supports existing literature by demonstrating that type 2 DM and baseline right BBB are significant predictors of PPM implantation post-TAVR.Regardless of the side of the BBB,this study demonstrated,for the first time,a linear association between the incidence of PPM implantation post-TAVR and every 20 ms increase in baseline QRS duration(above 100 ms).After a 1-year follow-up,patients who received PPM post-TAVR had a higher rate of hospital-ization for heart failure and nonfatal myocardial infarction.