Wall Stress Research Articles

PSO-BP model for assessing frost resistance in containment concrete with varying pipe diameters

The safety of containment concrete is of utmost importance for nuclear power plants. The presence of pipe openings in the containment concrete structure introduces weakened areas, which adversely impact the mechanical properties and durability of the concrete. However, little research has been done on the durability of containment concrete with embedded steel pipe (CCESP), and no studies are found on its frost resistance under single-side freezing and thawing conditions. In this paper, using single-side salt freeze-thaw experiment to simulate the practical situation of coastal containment concrete, the effect of different steel pipe diameters (d) on the frost resistance of containment concrete was investigated. Based on the experimental results and using backpropagation neural networks optimized by a particle swarm algorithm (PSO-BP), a model was established to predict the frost resistance of CCESP for varying values of d. The research results showed that wall effects and stress concentrations created an interface zone between the steel pipes and the concrete, leading to a decline of compressive strength. Freeze-thaw cycles had only a slight impact on the relative dynamic elastic modulus (E) of CCESP, while the exfoliation mass per unit area (M) of the concrete specimens increased linearly with d. It indicates that pipe opening adversely impacts the frost resistance of the concrete, and that M can be used to evaluate the frost resistance of CCESP. This study addresses the research gap in the frost resistance of containment concrete with steel pipe openings, and the proposed PSO-BP model can accurately predict the frost resistance of containment concrete with varying pipe diameters under different freeze-thaw cycles.

Turbulence from an Observer Perspective

Turbulence is often studied by tracking its spatiotemporal evolution and analyzing the dynamics of its different scales. The dual to this perspective is that of an observer who starts from measurements, or observations, of turbulence and attempts to identify their back-in-time origin, which is the foundation of data assimilation. This back-in-time search must contend with the action of chaos, which obfuscates the interpretation of the observations. When the available measurements satisfy a critical resolution threshold, the influence of chaos can be entirely mitigated and turbulence can be synchronized to the exact state–space trajectory that generated the observations. The critical threshold offers a new interpretation of the Taylor microscale, one that underscores its causal influence. Below the critical threshold, the origin of measurements becomes less definitive in regions where the flow is inconsequential to the observations. In contrast, flow events that influence the measurements, or are within their domain of dependence, are accurately captured. The implications for our understanding of wall turbulence are explored, starting with the highest density of measurements that entirely tame chaos and proceeding all the way to an isolated measurement of wall stress. The article concludes with a discussion of future opportunities and a call to action.

Penicillin-binding proteins exhibit catalytic redundancy during asymmetric cell division in Clostridioides difficile.

Peptidoglycan synthesis is an essential driver of bacterial growth and division. The final steps of this crucial process involve the activity of SEDS family glycosyltransferases that polymerize glycan strands and class B penicillin-binding protein (bPBP) transpeptidases that cross-link them. While most bacteria encode multiple bPBPs that perform specialized roles during specific cellular processes, some bPBPs can play redundant roles that are important for resistance against certain cell wall stresses. Our understanding of these compensatory mechanisms, however, remains incomplete. Endospore-forming bacteria typically encode multiple bPBPs that drive morphological changes required for sporulation. The sporulation-specific bPBP, SpoVD, is important for synthesizing the asymmetric division septum and spore cortex peptidoglycan during sporulation in the pathogen Clostridioides difficile. Although SpoVD catalytic activity is essential for cortex synthesis, we show that it is unexpectedly dispensable for SpoVD to mediate asymmetric division. The dispensability of SpoVD's catalytic activity requires the presence of its SEDS partner, SpoVE, and is facilitated by the catalytic activity of another sporulation-specific bPBP, PBP3. Our data further suggest that PBP3 interacts with components of the asymmetric division machinery, including SpoVD. These findings suggest a possible mechanism by which bPBPs can be functionally redundant in diverse bacteria and facilitate antibiotic resistance.

Critical diameter for a single-tank molten salt storage – Parametric study on structural tank design

Molten salt thermal energy storage (TES) is a cost-effective option for grid-connected storage in both concentrating solar power (CSP) plants and retrofitted thermal power plants in a multimegawatt scale. Current systems use two tanks (hot and cold), but future systems may use a single tank with a transient temperature profile (hot in the top and cold in the bottom) to reduce costs and space. However, the structural and mechanical design of large-scale molten salt single-tank storages at 560 °C has not been fully explored, and the impact of increasing the operating temperature to 620 °C is still uncertain. The challenge presented by a single tank is the existence of a temperature profile that results in a varying thermal expansion of the tank shell along its height. In the case of larger tanks, this discrepancy can reach a magnitude of centimeters, which in turn gives rise to bending moments. To the best of our knowledge, this study addresses the issue of bending stresses in large-sized high-temperature tanks with thermal stratification for the first time. The modelling approach is applied to single-tank CSP TES systems as a case study to evaluate the constraints imposed by tank size and wall thickness.With the help of experimentally validated numerical methods, it is revealed that a low thermocline thickness can be a limiting factor for large tank diameters. It is shown that the temperature has a major influence on maximum possible tank size: if the operating temperature is raised from 560 °C to 620 °C, the permitted tank diameter is significantly reduced when using the same tank wall material. A possible approach is to use a more heat resistant steel for 620 °C. Results of the parametric study show that designing a single tank below a critical diameter only requires a moderate increase of the wall thickness compared to the two-tank system with constant temperature profiles. Based on this parametric study a formula for the critical tank diameter is developed and presented in this work. The paper concludes with recommendations on how increased wall stresses can be addressed by an appropriate design.

Modeling the deformation of thin-walled circular tubes filled with metallic foam under two lateral loading patterns

Thin-walled circular tubes with metallic foam fillers are widely used in various engineering fields. This work examines the plastic behavior of thin-walled circular tubes filled with metallic foam under two different lateral loading patterns, by using both analytical and numerical methods. Two types of loading indenters, including a line load and a rigid plane, are considered. There have been very few studies on the lateral compression of foam-filled circular tubes crushed by a line load or a rigid plane. The analytical models assume that the tubular wall material is rigid and ideally plastic, and that the metallic foam fillers maintain a constant resistance known as plateau stress. Using the principle of virtual velocities, we derive succinct explicit solutions for the crushing forces as well as deformation characteristics in regard with the radius of the tubes, the flow stress of the tubular wall and the plateau stress of the filled foam under the two loading conditions. Finite element analysis is performed using the ABAQUS2023/Explicit code to model aluminum alloy circular tubes filled with aluminum foam. A comparison and analysis of the deformation characteristics of the tubular top generator and foam cross-sections are conducted. The proposed analytical crushing forces and deformation properties obtained herein agree well with the numerical simulation results and outperform previous theoretical models, which may serve as valuable formulations for the engineering application.

A Genome-Wide Identification and Expression Analysis of the Xyloglucan Endotransglucosylase/Hydrolase Gene Family in Melon (Cucumis melo L.)

The xyloglucan endotransglucosylase/hydrolase (XTH) family is an important multigene family in plants that plays a key role in cell wall reconstruction and stress tolerance. However, the specific traits of XTH genes and their expression patterns under different stresses have not been systematically studied in melon. In this study, based on the genomic data of Cucumis melon, 29 XTH genes were identified; most of these genes contain two conserved domains (Glyco_hydro_16 and XET_C domains). Based on neighbor-joining phylogenetic analysis, the CmXTHs were divided into four subfamilies, I/II, IIIA, and IIIB, which are distributed across nine chromosomes of melon. Collinearity analysis showed that the melon XTH genes have an evolutionary history consistent with three species: Arabidopsis, tomato, and cucumber. The promoter regions of the CmXTH genes contain numerous cis-acting elements, which are associated with plant growth, hormonal response, and stress responses. RNA-Seq analysis indicated that CmXTH genes exhibit different expression patterns under drought and salt stress treatments, suggesting that this gene family plays an important role under abiotic stress. This study provides a theoretical basis for further studies on the molecular function of XTH genes in melon.

Influence of Augmented Fixation to Dynamic Hip Screw on Trochanteric Lateral Wall

This paper focused on lateral trochanteric wall stress which is a contributing factor for the success of complex trochanteric fracture management with loss of medical bone support. Its aim was to assess performance of augmented fixations to Dynamic Hip Screw (DHS). The analysis was performed using Finite Element (FE) method, where the femoral bone and fixations were developed from reverse engineering technique. The boundary conditions were physiological loads with constraints at distal condyle. It was revealed that lateral augmented fixation i.e. trochanteric stabilization plate raised the trochanteric lateral wall stress that could be at risk of bone breakage.

Chromatin accessibility profile and the role of PeAtf1 transcription factor in the postharvest pathogen Penicillium expansum

Abstract Gene transcription is governed by a complex regulatory system involving changes in chromatin structure, action of transcription factors, and activation of cis-regulatory elements. Postharvest fruits are threatened by Penicillium expansum, a leading causal agent of blue mold disease and one of the most economically significant postharvest pathogens worldwide. However, the information on its transcription regulatory mechanism is lagging. Here, we conducted an assay for transposase accessible chromatin sequencing (ATAC-seq) for P. expansum during vegetative growth and infection phase and then studied the function of a bZIP transcription factor PeAtf1. Results highlighted the role of promoter regions in gene transcription and the significant difference in P. expansum between the two phases. Six footprint-supported cis-regulatory elements of active transcription factors were obtained and analyzed. We then identified a homolog of the bZIP regulator Atf1, PeAtf1, and found it positively regulated vegetative growth, reproduction and osmotic stress response in P. expansum. Conversely, PeAtf1 deletion enhanced fungal tolerance to oxidative, cell wall and membrane stresses, which might contribute to the virulence of P. expansum in apple fruits, leading to similar pathogenicity between mutants and the wild type. Overall, this study provides new insights into the transcription regulatory mechanism of P. expansum, aiding in the future development of strategies to control P. expansum.

Dynamic Responses in a Pipe Surrounded by Compacted Soil Suffering from Water Hammer with Fluid–Structure–Soil Interactions

The current literature analyzing the dynamic response of coupled pipelines neglects the crucial interplay between the pipelines themselves and these constraints. This overlooked interaction has substantial influence on the fluid–structure coupling response, particularly in scenarios involving continuous constraints. We focus on a piping system surrounded by compacted soil, which is regarded as unbounded homogeneous elastic soil that suffers from water hammer. This study established a one-dimensional model for water pipe-embedded compacted soil with fluid–structure–soil interaction. Taking fluid–structure–soil interaction into account, fluid–structure interactions (FSIs) include Poisson coupling, junction coupling emerging at the fluid–structure interface, and pipe–soil coupling (PSC) emerging at the pipe–soil interface. In this study, as soil is assumed to be a homogeneous, isotropic elastic material, the coupling responses are more complex than those of an exposed pipe, and the relevant mechanisms justify further exploration to obtain well-predicted results. To mathematically describe this system considering fluid–structure–soil interaction, the four-equation FSI model was modified to accommodate the piping system surrounded by unbounded homogeneous elastic soil, employing the finite volume method (FVM) as a means to tackle and solve the dynamic problems with FSI and PSC, which partitions the computational domain into a finite number of control volumes and discretizes governing equations within each volume. The results were validated by the experimental and numerical results. Then, dynamic FSI responses to water hammer were studied in a reservoir–pipe–reservoir physical system. The hydraulic pressure, pipe wall stress, and axial motion were discussed with respect to different parameters. With the PSC and FSI taken into account, fluid, soil, and pipe signals were obviously observed. The results revealed the structural and fluid modes. Dynamic responses have been proven to be difficult to understand and predict. Despite this, this study provides a tractable method to capture more accurate systematic characteristics of a water pipe embedded in soil.

GpsB Coordinates StkP Signaling as a PASTA Kinase Adaptor in Streptococcus pneumoniae Cell Division

StkP, the Ser/Thr protein kinase of the major human pathogen Streptococcus pneumoniae, monitors cell wall signals and regulates growth and division in response. In vivo, StkP interacts with GpsB, a cell division protein required for septal ring formation and closure, that affects StkP-dependent phosphorylation. Here, we report that although StkP has basal intrinsic kinase activity, GpsB promotes efficient autophosphorylation of StkP and phosphorylation of StkP substrates. Phosphoproteomic analyzes showed that GpsB is phosphorylated at several Ser and Thr residues. We confirmed that StkP directly phosphorylates GpsB in vitro and in vivo, with T79 and T83 being the major phosphorylation sites. In vitro, phosphoablative GpsB substitutions had a lower potential to stimulate StkP activity, whereas phosphomimetic substitutions were functional in terms of StkP activation. In vivo, substitutions of GpsB phosphoacceptor residues, either phosphoablative or mimetic, had a negative effect on GpsB function, resulting in reduced StkP-dependent phosphorylation and impaired cell division. The bacterial two-hybrid assay and co-immunoprecipitation of GpsB from cells with differentially active StkP indicated that increased phosphorylation of GpsB resulted in a more efficient interaction of GpsB with StkP. Our data suggest that GpsB acts as an adaptor that directly promotes StkP activity by mediating interactions within the StkP signaling hub, ensuring StkP recruitment into the complex and substrate specificity. We present a model that interaction of StkP with GpsB and its phosphorylation and dephosphorylation dynamically modulate kinase activity during exponential growth and under cell wall stress of S. pneumoniae, ensuring the proper functioning of the StkP signaling pathway.

Thermal-mechanical coupling characteristics of large-scale molten salt storage tanks under stable operating conditions with varying liquid levels

The large-scale molten salt storage tank is a critical component of the thermal storage system employed in concentrating solar power (CSP) plants. The storage tank is subjected to complex conditions, including high temperature, fluctuating hydrostatic pressure, and thermal stress. Therefore, it is imperative to investigate the thermal-mechanical coupling characteristics of the tank during stable operation under varying liquid levels to comprehensively understand its behavior. The study commences by establishing thermal and stress analysis models for the tank, laying the foundation for subsequent investigation. Subsequently, a comprehensive thermal-mechanical coupling model is constructed using a sequential coupling approach, enabling a more accurate representation of the system's behavior. Finally, an in-depth study is conducted to explore the thermal-mechanical coupling characteristics of storage tanks at various liquid levels. The results indicate that radiation emitted by high-temperature air, confined in the top space of the tank, induces a temperature differential of approximately 5 °C between the tank's roof and the molten salt confined within it. Furthermore, heat loss from the roof accounts for 53 % of the overall heat loss. Thermal stress analysis of each weld seam connecting the tank into an integration reveals that the inner surface experiences tensile stress, while the outer surface undergoes compressive stress, primarily influenced by radial stress. Under the influence of thermal-mechanical, the coupling effect leads to compressive stress in the form of thermal stress, resulting in a decreasing trend in stress on the inner surface of the weld seam. The radial compressive stress on the outer surface reaches approximately 140 MPa, while the tank wall is primarily subjected to circumferential forces. The temperature exerts a negligible impact on the stress of the tank wall, yet it significantly affects its deformation. The stress evaluation of hydrostatic pressure and thermodynamic coupling under different liquid levels is carried out, and the results meet the strength requirements.

The nuclear pore protein Nup2 is essential for growth and development, stress response, pathogenicity and deoxynivalenol biosynthesis in Fusarium graminearum.

Wheat is an important grain crop that has been under serious threat from Fusarium graminearum. Nup2, a member of the nuclear pore complex, plays an important role in regulating eukaryotic nuclear protein transport and participates in gene regulation. Dissecting the function of nuclear pore proteins in pathogenic fungi may provide effective targets for novel fungicides. Mutants exhibited nutritional growth defects, asexual/sexual developmental abnormalities. Deficiency of FgNup2 resulted in increased resistance of Fusarium graminearum to cell wall disruptors and increased sensitivity to metal ions. Pathogenicity analyses showed that the mutant was significantly less virulent on flowering wheat ears, consistent with the observed decrease in deoxynivalenol (DON) production. Furthermore, we showed that FgNup2 interacts synergistically with FgTri6, a transcription factor of the TRI family, to regulate the expression of toxin-producing genes, which, in turn, affects the biosynthesis of DON and related toxins. This study revealed that FgNup2 plays important roles in the growth and development, cell wall integrity, stress response, pathogenicity, and DON synthesis of F. graminearum. © 2024 Society of Chemical Industry.

The Kelch Repeat Protein VdKeR1 Is Essential for Development, Ergosterol Metabolism, and Virulence in Verticillium dahliae.

Verticillium dahliae is a soil-borne fungal pathogen that can cause severe vascular wilt in many plant species. Kelch repeat proteins are essential for fungal growth, resistance, and virulence. However, the function of the Kelch repeat protein family in V. dahliae is unclear. In this study, a Kelch repeat domain-containing protein DK185_4252 (VdLs.17 VDAG_08647) included in the conserved VdPKS9 gene cluster was identified and named VdKeR1. Phylogenetic analysis demonstrated a high degree of evolutionary conservation of VdKeR1 and its homologs among fungi. The experimental results showed that the absence of VdKeR1 impaired vegetative growth, microsclerotia development, and pathogenicity of V. dahliae. Osmotic and cell wall stress analyses suggested that VdKeR1-deleted mutants were more tolerant to NaCl, sorbitol, CR, and CFW, while more sensitive to H2O2 and SDS. In addition, analyses of the relative expression level of sqe and the content of squalene and ergosterol showed that VdKeR1 mediates the synthesis of squalene and ergosterol by positively regulating the activity of squalene epoxidase. In conclusion, these results indicated that VdKeR1 was involved in the growth, stress resistance, pathogenicity, and ergosterol metabolism of V. dahliae. Investigating VdKeR1 provided theoretical and experimental foundations for subsequent control of Verticillium wilt.

Sex-related disparities in aortic stenosis from disease awareness to treatment: a state-of-the-art review.

This state-of-the-art review aimed to synthesize evidence from various sex-stratified studies on aortic stenosis (AS), focusing on the difference in clinical presentation, anatomical characteristics, pathophysiology, and management of AS. In comparison to men, women with AS are present at later stages, are older, more symptomatic, frailer, and exhibit higher operative risk [Society of Thoracic Surgeons (STS) score]. Women tend to have smaller aortic valve (AV) areas and left ventricular (LV) outflow tract, leading to lower stroke volumes (SVs) than men and have a higher prevalence of paradoxical, low-flow, low-gradient AS. In women, chronic pressure overload due to AS results in concentric LV remodelling and hypertrophy, characterized by reduced LV cavities, higher filling pressures, lower wall stress, and more diastolic dysfunction. Conversely, men exhibit more dilated eccentric LV remodelling and hypertrophy. AVs in women are less calcified but more fibrotic. Moreover, women are often underdiagnosed, have severity underestimated, and experience delays or receive fewer referrals for AV replacement (AVR). However, women tend to benefit from transcatheter AVR (TAVR) with a long-term survival advantage over men, although the incidence of vascular complications and bleeding events in 30 days after TAVR is higher in women. Surgical AVR (SAVR) in women has high operative risk, is technically demanding and has poorer outcomes with increased mortality at 30 days compared to men. According to the STS score and EuroSCORE, the female sex itself is considered a risk factor for SAVR. Therefore, addressing sex-related disparities in AS and increasing awareness among physicians promises improved diagnosis and treatment, facilitating equitable care and the development of sex-specific personalized medicine.

Overexpression of CBK1 or deletion of SSD1 confers fludioxonil resistance in yeast by suppressing Hog1 activation

Group III hybrid histidine kinases (HHK3) are known molecular targets of the widely used fungicidal agent fludioxonil which indirectly converts these kinases to a phosphatase form that causes constitutive activation of Hog1 MAPK. To better understand the fungicidal effect of fludioxonil we have screened S. cerevisiae haploid deletion collection for fludioxonil resistant mutant and identified Ssd1 as a critical factor for this. Deletion of SSD1 not only promoted resistance to fludioxonil but also abrogated Hog1 activation and other cellular damages caused by fludioxonil. Our results showed that fludioxonil perturbed the localization of Cbk1 kinase, an essential protein in yeast, at the bud neck triggering the accumulation of Ssd1 in P-bodies. As a result, localized synthesis of Ssd1 bound mRNA encoding cell wall proteins at the polarized growth site was impaired which created a sustained cell wall stress causing constitutive activation of Hog1. Our data, for the first time, clearly indicated the role of Cbk1 upstream of Hog1 and provided a novel paradigm in the mechanism of action of fludioxonil.

Less-deformable erythrocyte subpopulations biomechanically induce endothelial inflammation in sickle cell disease

AbstractSickle cell disease (SCD) is canonically characterized by reduced red blood cell (RBC) deformability, leading to microvascular obstruction and inflammation. Although the biophysical properties of sickle RBCs are known to influence SCD vasculopathy, the contribution of poor RBC deformability to endothelial dysfunction has yet to be fully explored. Leveraging interrelated in vitro and in silico approaches, we introduce a new paradigm of SCD vasculopathy in which poorly deformable sickle RBCs directly cause endothelial dysfunction via mechanotransduction, during which endothelial cells sense and pathophysiologically respond to aberrant physical forces independently of microvascular obstruction, adhesion, or hemolysis. We demonstrate that perfusion of sickle RBCs or pharmacologically-dehydrated healthy RBCs into small venule-sized “endothelialized” microfluidics leads to pathologic physical interactions with endothelial cells that directly induce inflammatory pathways. Using a combination of computational simulations and large venule-sized endothelialized microfluidics, we observed that perfusion of heterogeneous sickle RBC subpopulations with varying deformability, as well as suspensions of dehydrated normal RBCs admixed with normal RBCs, leads to aberrant margination of the less-deformable RBC subpopulations toward the vessel walls, causing localized, increased shear stress. Increased wall stress is dependent on the degree of subpopulation heterogeneity and oxygen tension and leads to inflammatory endothelial gene expression via mechanotransductive pathways. Our multifaceted approach demonstrates that the presence of sickle RBCs with reduced deformability leads directly to pathological physical (ie, direct collisions and/or compressive forces) and shear-mediated interactions with endothelial cells and induces an inflammatory response, thereby elucidating the ubiquity of vascular dysfunction in SCD.

Differential association of abdominal, liver, and epicardial adiposity with anthropometry, diabetes, and cardiac remodeling in Asians.

Heterogenous deposition and homeostasis roles of physiologic and ectopic adipose tissues underscore the impact of fat compartmentalization on cardiometabolic risk. We aimed to characterize the distribution of abdominal visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), epicardial adipose tissue (EAT), and liver fat on magnetic resonance imaging (MRI), and evaluate their associations with anthropometric indices and adverse cardiac remodeling. In this cross-sectional observational study, 149 Asian adults (57.0 ± 12.8 years; 65% males) with at least one cardiometabolic risk factor underwent multiparametric fat and cardiovascular MRI. Anthropometric indices included body mass index (BMI), waist circumference (WC), waist-hip ratio (WHR), and bioimpedance body fat mass (BFM). Associations between fat depots and anthropometric measures as well as cardiac remodeling features were examined as a single cohort and stratified by type 2 diabetes mellitus (T2DM) status. VAT and SAT had opposing associations with liver fat and EAT. Therefore the VAT/SAT ratio was explored as an integrated marker of visceral adiposity. VAT/SAT was positively associated with EAT (β=0.35, P<0.001) and liver fat (β=0.32, P=0.003) independent of confounders. Of the anthropometric measurements assessed, only WHR was independently associated with VAT/SAT (β=0.17, P=0.021). Individuals with T2DM had higher VAT and lower SAT compared to those without T2DM, translating to a significantly higher VAT/SAT ratio. EAT volume was independently associated with adverse features of cardiac remodeling: increased left ventricular (LV) mass (β=0.24, P=0.005), larger myocyte volume (β=0.26, P=0.001), increased myocardial fibrosis (β=0.19, P=0.023), higher concentricity (β=0.18, P=0.035), and elevated wall stress (β=-0.18, P=0.023). Multiparametric MRI revealed abdominal VAT and SAT have differential associations with anthropometric indices and ectopic fats in a single cohort of Asians at risk of cardiometabolic disease. People with T2DM have expanded VAT and diminished SAT, endorsing the VAT/SAT ratio beyond usual anthropometric measurements as a marker for multiorgan visceral fat composition. Among the fat depots examined, EAT is uniquely associated with adverse cardiac remodeling, suggesting its distinctive cardiometabolic properties and implications.

An experimental and theoretical investigation on residual stress of 7075-T651 aluminum alloy hole under electromagnetic cold expansion

The electromagnetic cold expansion process (ECE) was adopted in this work. The theoretical plastic radius, hole wall stress, radial stress, circumferential stress and release stress under different expansion rates (ER) were studied based on thick cylinder theory and ECE experiments. The released strain, residual stress (RS) and failure force were measured. The tensile fracture morphology was characterized. The results showed that the theoretical plastic radius (maximum 15.87 mm), internal stress (maximum 982.9 MPa), radial stress (maximum −820.9 MPa) and circumferential stress (maximum −271.4 MPa) increased with the increase of ER. The absolute radial and circumferential stress decreased and increased in negative and positive ranges respectively with distance increased. The release strain (maximum −3033 με, 10−6 microstrain), radial RS (maximum 600.9 MPa) and circumferential RS (maximum 601.1 MPa) also increased with the increase of ER, and the minimum relative error of the plastic zone radius of the theoretical model was 3.78 % proving the reliability of the model. In addition, ECE increased the release stress (the maximum radial and circumferential release stresses were 1402.6 MPa and 747.5 MPa) and decreased the failure force (minimum 44.7kN) with increased ER. The initial crack position tended to transition from the inlet and outlet surfaces to the middle position, and the crack propagation angle and axial crack size gradually decreased with the decreased ER and stress level.

Dissecting contributions of pulmonary arterial remodeling to right ventricular afterload in pulmonary hypertension.

Pulmonary hypertension (PH) is defined as an elevation in the right ventricle (RV) afterload, characterized by increased hemodynamic pressure in the main pulmonary artery (PA). Elevations in RV afterload increase RV wall stress, resulting in RV remodeling and potentially RV failure. From a biomechanical standpoint, the primary drivers for RV afterload elevations include increases in pulmonary vascular resistance (PVR) in the distal vasculature and decreases in vessel compliance in the proximal PA. However, the individual contributions of the various vascular remodeling events toward the progression of PA pressure elevations and altered vascular hemodynamics remain elusive. In this study, we used a subject-specific one-dimensional (1D) fluid-structure interaction (FSI) model to investigate the alteration of pulmonary hemodynamics in PH and to quantify the contributions of vascular stiffening and increased resistance towards increased main pulmonary artery (MPA) pressure. We used a combination of subject-specific hemodynamic measurements, ex-vivo mechanical testing of arterial tissue specimens, and ex-vivo X-ray micro-tomography imaging to develop the 1D-FSI model and dissect the contribution of PA remodeling events towards alterations in the MPA pressure waveform. Both the amplitude and pulsatility of the MPA pressure waveform were analyzed. Our results indicated that increased distal resistance has the greatest effect on the increase in maximum MPA pressure, while increased stiffness caused significant elevations in the characteristic impedance. The method presented in this study will serve as an essential step toward understanding the complex interplay between PA remodeling events that leads to the most severe adverse effect on RV dysfunction.

Reynolds-Number-Dependence of Length Scales Governing Turbulent-Flow Separation in Wall-Modeled Large Eddy Simulation

This paper proposes a Reynolds number Re scaling for the number of grid points Ncv required in wall-modeled Large Eddy Simulation (WMLES) of turbulent boundary layers (TBL) to accurately capture the regions of flow separation. Based on the various time scales in a nonequilibrium TBL, a definition of the near-wall “underequilibrium” scales is proposed (in which “equilibrium” refers to a quasi balance between the viscous and the pressure gradient terms). This length scale is shown to vary with Reynolds number as lp∼Re−2/3. A-priori analysis demonstrates that the resolution (Δ) required to reasonably predict the wall stress in several nonequilibrium flows is at least O(10)lp, irrespective of the Reynolds number and Clauser parameter. Further, a-posteriori studies (on the Boeing speed bump, Song– Eaton diffuser, Notre-Dame Ramp, and the backward-facing step) show that scaling Δ such that Δ/lp is independent of Reynolds number results in accurate predictions of separation for the same “nominal” grid across different Reynolds numbers. Finally, we suggest that near separation and reattachment points, Ncv for WMLES scale as Re4/3, which is more restrictive than the previous estimates (∼Re1) by Choi and Moin (Choi, H., and Moin, P., “Grid-Point Requirements for Large Eddy Simulation: Chapman’s Estimates Revisited,” Physics of Fluids, Vol. 24, No. 1, 2012, Paper 011702) and Yang and Griffin (Yang, X. I. A., and Griffin, K. P., “Grid-Point and Time-Step Requirements for Direct Numerical Simulation and Large-Eddy Simulation,” Physics of Fluids, Vol. 33, No. 1, 2021, Paper 015108).