Strain Rate Research Articles

Effect of Rate-Dependent Breakage on Strength and Deformation of Granular Sample—A DEM Study

The mechanical response of granular materials is influenced significantly by both the magnitude and strain rate. While traditionally considered rate-independent in the quasi-static regime, granular media can exhibit rate effects in certain instances. This research uses two-dimensional discrete element modelling (DEM) to investigate the rate effects in one-dimensional compression tests by comparing non-crushable with crushable granular samples. This study indicates that micromechanical properties such as particle breakage and contact force distributions are predominant factors in dictating the macroscopic responses of the material. The DEM simulations highlight differences in macroscopic changes between crushable and non-crushable samples, demonstrating a clear correlation between mechanical properties and underlying microstructural features. Notably, the distribution of contact forces varies with strain rates, influencing the degree of particle breakage and, consequently, the overall rate-dependent behaviour. Further, this study explores the impact of post-breakage contact creation and progressive force redistribution, which contributes to observable differences in macroscopic stress under varying loading rates, which is quantified using coordination number, particle velocity, and fabric tensor profiles at two loading rates.

Comparative study of creep in a disk of rubber/copper fitted with rigid shaft

The article deals with the comparative study of creep analysis in a rotating disk made of rubber/copper material and fitted with rigid shaft. The effects of different pertinent parameters (i.e., angular speed and density) are considered for the rotating disk of rubber/steel material. The behaviour of creep stress/strain rate distribution, and density rise are investigated. From the obtained results, it is noticed that the radial stress requires a maximum value at the inner surface of the disk fitted with rigid shaft made of rubber material in comparison to the disk made of copper material. The strain rates must be decreased with increasing density parameter. Results have been discussed numerically and graphically.

Stress-Dilatancy Behavior of Highly Elastic Rubber-Added Cohesionless Materials.

Dilatancy is commonly defined as the ratio of the rates of plastic volumetric strain to plastic deviatoric strain, denoted as Dp. Owing to the high modulus of elasticity, the elastic volumetric and deviatoric strain rates under shear stress in conventional cohesionless materials are negligible. Therefore, using the ratio of the rates of total volumetric to deviatoric strain (Dt) as an approximation is common in studying stress-dilatancy behavior and calibrating dilatancy model parameters. This approach is also common in the study of rubber-added cohesionless materials (RCM). However, RCM with a common range of rubber content exhibit a significantly lower modulus of elasticity compared to conventional cohesionless materials. Further research is needed to evaluate the potential impact of elastic strain rates in RCM on stress-dilatancy analysis. Therefore, comparisons were conducted on the stress-dilatancy responses of a series of tests on RCM, where dilatancy is calculated by Dp and Dt, respectively. Furthermore, a modified method for calibrating the parameters of a state-dependent dilatancy model considering Dp is presented. It turns out that Dp is better suited and more precise for dilatancy analysis on highly elastic RCM. Additionally, the dilatancy model can more precisely capture the test results of RCM with parameters calibrated by the proposed method.

Microstructure and dynamic deformation mechanism of laser powder bed fusion of 316L-containing Ti–6Al–4V with dual-phase heterostructure

In this paper, 316L-containing Ti–6Al–4V alloy was fabricated by laser powder bed fusion (LPBF) through mixing Ti–6Al–4V and 4.5 wt% 316L powders, and the dynamic compressive mechanical properties and deformation mechanism at different strain rates were studied. The results show that the volume fraction of β phase sharply increases from 1.8% (in TC4) to 61.4% (in HST), and micro- and submicron-sized grains coexist in the HST alloy, producing heterostructure in the form of bimodal grain size distribution. The presence of the heterostructure led to superior heterogeneous deformation induced stress, thus facilitating the additional strain hardening and deformation coordinating ability, thus made the HST alloy achieved ultimate compressive stress of ∼1750 MPa and fracture strain of ∼17%, showing excellent comprehensive mechanical properties. Under quasi-static load, the deformation mode of HST alloy is mainly attributed to progressive deformation-induced martensitic transformation. However, at high strain rates, the impact loading inhibited the activation of progressive DIMT, and thus the deformation mode changed to combination of dislocation slipping and deformation twinning.

Effect of Progressive Wetting on Permanent Deformation of Fouled Ballast under Cyclic Loading

Climate change in recent decades has increased the frequency and intensity of extreme rainfall events, causing varied moisture contents in the ballasted track, which greatly challenges railway operation and track maintenance. Currently, most research about permanent deformation of fouled ballast are under dry condition or with a moisture content in the individual tested sample, which could not fully represent varied moisture conditions in the field induced by varying rainfall intensities. In this paper, permanent deformation of field-sourced fouled ballast under progressive wetting condition was investigated using large-scale triaxial cyclic tests. The results indicate that, with progressively rising water contents (0% to 12%), the fouled ballast sample maintained their stability; however, the rate of permanent strain increases to a peak value before experiencing a slight decline, aligning with classified shakedown ranges. This observed phenomenon can be attributed to the interplay between wetting, densification, and interlocking under conditions of cyclic loading and progressive wetting, an aspect that existing research have not elaborated. To encapsulate the identified deformation characteristics, this study proposes and validates a new predictive model for the permanent deformation of fouled ballast, demonstrating high prediction accuracy for fouled ballast with varying water contents.

Correlation dependences between hardening in terms of yield strength and microhardness for austenitic and ferritic-martensitic steels

Instrumental measurements of microhardness were carried out using a Vickers indenter at a constant strain rate. The yield strength values were determined for austenitic chromium-nickel steels 08Kh18N10Т, 10Kh18N9 and 08Kh16N20M2Т in the initial (non-irradiated) state, after neutron irradiation at various regimes, as well as after plastic prestrain. Similar measurements were carried out for chromium stainless steels of the ferritic-martensitic class 07Kh12NMFB and 16Kh12MVSFBR (EP-823) in the initial (non-irradiated) state and after heat treatment, leading to hardening of the material and also after neutron irradiation. The relationships between microhardness and yield strength were determined for all studied states of all steels studied. A unified correlation has been established between hardening in terms of the yield strength and hardening in terms of Vickers micro-hardness, independently of the nature of the strengthening factor and the class of steel.

Prognostic impact of echocardiographic predictors of subclinical systolic dysfunction in patients with moderate aortic stenosis

Abstract Introduction Moderate aortic stenosis (AS) marks a critical point in AS severity spectrum, paralleled by significant cardiac structural changes. Concentric left ventricular (LV) hypertrophy, in response to the increased afterload, enables the preservation of a normal ejection fraction (EF) despite significant underlying myocardial dysfunction. Reductions in LVEF may serve as early indicators of the LV's diminished capacity to withstand this increased afterload, potentially leading to LV fibrosis and irreversible myocardial damage. Research has shown that LVEF may not recover in some patients following aortic valve replacement (AVR). Consequently, there is a growing debate concerning higher LVEF thresholds for triggering AVR in patients with severe AS, aiming to intervene before clinical systolic dysfunction ensues and irreversible damage occurs. Meanwhile, a combination of objective indicators may help to identify those patients AS at high risk before a decline in LVEF occurs. Aim To explore the role of baseline left ventricle global longitudinal strain (GLS) and strain rate (SR) as markers of subclinical LV dysfunction, as predictors of LVEF depression, and their impact on survival of patients with moderate AS. Methods Patients with moderate AS and LVEF ≥ 50% at least in 2 echocardiograms were retrospectively identified. Prosthetic and bicuspid valves were excluded. Baseline LV GLS and SR were used as covariates in cox regression models to predict the cumulative incidence of LVEF depression over 5 years and overall survival after multivariable adjustment including time-dependent AVR. Results 574 patients were included (age 76 ± 9 years; 51% female; median follow-up time of 8.97 years). The average baseline aortic peak velocity was 3.4±0.8 m/s, mean pressure gradient was 25±9 mmHg, aortic valve area was 1.1± 0.3 cm2, and LVEF 60±5%. The average GLS was -17±7 % while the peak systolic SR was 1.2 ± 0.5/s. Both baseline GLS (HR= 0.88 for each -1%; 95% CI= 079-0.99; p= 0.04) and SR (HR= 0.89 for each +0.1/s; 95% CI= 0.80-0.99; p=0.03) were associated with 5-year incidence of LVEF depression (<50%). Risk discrimination improved by incorporating SR on top of GLS (increase in area under curve from 0.78 to 0.84; 95% CI= 0.01-0.10; p= 0.04). Furthermore, a nonlinear relation was found between GLS (optimal boundary <-15.8%; p=0.35) and SR (optimal boundary >0.96/s; p=0.34) and overall survival. Conclusions This study identifies baseline GLS and SR as predictors of LVEF depression in moderate AS underscoring their importance in detecting subclinical LV dysfunction. The combination of GLS and SR may enhance the prediction of cardiac function decline, suggesting their potential utility in guiding early intervention strategies. Although their direct relationship with survival needs further exploration, these findings advocate for incorporating GLS and SR in AS management to inform timely AVR decisions and improve patient outcomes.

Hot deformation behavior of an ignition resistance Mg–6Zn-0.6Zr-1.2Ca magnesium alloy

The addition of Ca could enhance the ignition point of magnesium alloys but impairing their workability, so it is essential to study the hot deformation behavior of new Ca-containing ignition resistance magnesium alloys. The hot deformation behavior of a new ignition resistance Mg–6Zn-0.6Zr-1.2Ca alloy was investigated by compression experiment in the temperature range of 240 °C–360 °C, strain rates of 10−3 s−1-1 s−1 and height reduction of 10%–60%. The true stress-strain curves show that flow stress decreases as the deformation temperature increases or the strain rate decreases. Microstructure analysis shows that higher temperatures and lower strain rates are favorable for DRX, while higher strain rates promote the fragmentation of the Ca2Mg6Zn3 phase. Meanwhile, the existence of Ca2Mg6Zn3 phase make the DRX process be dominated by the particle-induced subgrain nucleation mechanism. By superposition of the power dissipation map and the instability map, a hot processing map of true strain of 0.6 is generated. According to analyses on the processing map and microstructure evolution, the instability of processing map can be attributed to the greater dislocation motion resistances, insufficient DRX, and Ca2Mg6Zn3 phase with low-melting point. Conversely, the optimal processing parameters for the alloy were determined as 280–360 °C/0.001–0.01 s−1 in safe zone with a high η above 0.3, which can be due to the apparent DRX and good deformation coordination.

Left ventricular late diastolic strain rate predicts cardiovascular mortality in patients with heart failure with reduced ejection fraction

Abstract Background Left ventricular (LV) strain rate measures provide detailed information regarding LV contraction and filling pressures. These include global systolic strain rate (GSRs), early and late diastolic strain rates (GSRe and GSRa), and ratio of transmitral early filling velocity to GSRe (E/GSRe). Purpose To investigate the prognostic value of strain rate measures with regard to cardiovascular mortality in patients with heart failure with reduced ejection fraction (HFrEF). Methods The study population was retrospectively included from a HF clinic and consisted of patients with LV ejection fraction (LVEF) ≤45%. Echocardiography was obtained within 1 year of referral. The study endpoint was cardiovascular mortality, which was analysed using univariable and adjusted Cox proportional hazards models. Incremental prognostic information was assessed using Harrell’s C-index and continuous net reclassification improvement (NRI). Cubic spline analysis was used to dichotomise variables at a hazard ratio (HR) of 1 for better interpretability. Results The final study population consisted of 1160 patients with HFrEF (mean age 68±11.8 years, 72.7% male, LV ejection fraction (LVEF) 28.6±9.9%). During follow-up (median 10.1 years, IQR: 4.7-13.0), 333 (28.7%) met the outcome. Subjects who met the outcome generally had higher age and prevalence of male sex, a higher burden of comorbidities, and more severely impaired conventional echocardiographic parameters. All four strain rate measures were significantly associated with cardiovascular mortality (GSRs: HR 16.88 95% CI [8.42, 33.84] per 1 s-1 increase, GSRe: HR 0.29 [0.18, 0.47] per 1 s-1 increase, E/GSRe ratio: HR 1.31 [1.22, 1.41] per 1 unit increase, GSRa: HR 0.15 95% CI [0.23, 0.65] per 1 s-1 increase, p<0.0001 for all). However, only GSRa remained an independent predictor in multivariable Cox regression after adjustment for clinical risk factors including sex, age, mean arterial pressure, heart rate, body mass index, cigarette pack years, diabetes mellitus, total cholesterol, ischemic heart disease, and echocardiographic factors including LVEF, global longitudinal strain, tricuspid annular plane systolic excursion, LV mass index, LV internal diameter index, E/e’ ratio and left atrial volume index (HR 0.39 [0.23,0.65], p=0.0003). Furthermore, GSRa provided incremental prognostic information to a model containing all aforementioned parameters (Harrell’s C-index 0.789 vs. 0.792 and continuous NRI 0.158). GSRa was dichotomised at 0.5 s-1, and a Kaplan-Meier curve stratified according to this was plotted (log rank p<0.0001)(Figure 2). Conclusion GSRa is an independent predictor of cardiovascular mortality in patients with HFrEF after multivariable adjustment. GSRa provides incremental prognostic value over conventional echocardiographic measures in risk stratification of HFrEF patients. Our results suggest an increased risk of cardiovascular mortality associated with a GSRa below 0.5 s-1.Figure 1:Spline of HR according to GSRaFigure 2:Kaplan-Meier curve

Cocoa flavanols alleviate early diastolic dysfunction by decreasing left atrial volume in healthy elderly individuals

Abstract Background Enlargement of the left atrium (LA) predicts future cardiovascular events. Current guidelines recommend cocoa flavanol (CF) intake as it provides cardiovascular and metabolic benefits, although underlying mechanisms are not fully revealed. In this study, we hypothesized that CF intake reverses LA enlargement as a surrogate marker for diastolic dysfunction in elderly individuals without cardiovascular diseases. Methods and Results In a randomized, double-blinded trial, we investigated the effects of CF on systolic and diastolic heart function in healthy elderly individuals. Precise assessment of left-atrial and left-ventricular volume as well as strain rates, all together as emblems of early subclinical cardiac impairment, and markers of systolic function were measured by high-resolution cardiac magnetic resonance (CMR) imaging before and after CF intake. Sixty-three participants (59% male) aged ≥ 55 years received either 500 mg CF (n=30) or a placebo (n=33) twice daily for 30 days. CF counteracted subclinical cardiac dysfunction, evidenced by a reduction in maximal LA volume and LA volume index by 12.6±3.5% (p=0.0063 and p=0.0067) and LV end-diastolic volume (LVEDV) and LVEDV index by ~4.9±1.9% (p=0.049 and p=0.0413). CF intake did not influence strain, strain rate, and systolic function parameters, while the systolic blood pressure decreased by 7 mmHg [~4.7±1.9% (p=0.04)]. Conclusion We provide evidence that CF intake mitigates early changes of diastolic dysfunction and improves cardiovascular health by reversing left atrial and left ventricular remodeling. Cocoa flavanol consumption may prevent age-related cardiac changes in healthy elderly individuals and promote a health span free from cardiovascular diseases.

Investigating the Effects of Boron Nitride on Mechanical Properties of CoCrFeNiMn Composites

High‐entropy alloys (HEAs) are gaining attention for their exceptional properties but achieving precision and surface quality in powder metallurgy (PM) can be challenging. This study investigates the mechanical properties of CoCrFeNiMn HEAs produced through the flake powder metallurgy (FPM) technique and laser powder bed fusion (LPBF) preservative industrial, which established outstanding antiwear properties. To assess the enhancement of mechanical behavior and wear resistance by incorporating boron nitride (BN) into CoCrFeNiMn composites is fabricated via FPM. By incorporating BN into the composites, the mechanical behavior is significantly enhanced, leading to improved resistance against wear. Furthermore, the study delivers comprehensions into the serration behavior microstructure and shear localization in a high‐strain‐rate‐deformed CoCrFeMnNi entropy‐high alloy produces through metallurgy in powder. The serration behavior of the CoCrFeMnNi HEA is discussed concerning strain rate and temperature. Accordingly, the study employs the LPBF technique to fabricate the CoCrFeMnNi alloy from the prepared flakes. Microstructural characterization using scanning electron microscopy and X‐ray diffraction techniques to explore phase distribution, grain size, and possible segregation in the CoCrFeMnNi alloy produced through FPM‐LPBF is performed. In this particular investigation, a gradient microstructure is achieved through fusion in a laser‐powder bed of CoCrFeMnNi HEA onto highly deformed equal‐atomic HEA sheets. The resulting combination of partially recrystallized regions, exhibiting elevated yield strength, and fully recrystallized regions, demonstrates enhanced strain hardenability and elongation, and yields superior mechanical properties. The results obtained from the FPM‐LPBF CoCrFeMnNi alloy will be compared with those of conventionally processed CoCrFeMnNi to highlight the advantages and improvements achieved through the proposed method. The study findings reveal that the fundamental understanding of HEAs’ behavior under LPBF with FPM affords valuable insights into optimizing the processing parameters and achieving superior mechanical attributes.

Additive effect of metabolic dysfunction-associated fatty liver disease on left ventricular function and global strain in type 2 diabetes mellitus patients: a 3.0 T CMR feature tracking study

Abstract Purpose Type 2 diabetes mellitus (T2DM) represents the most prevalent form of diabetes, exerting a significant influence on cardiovascular health. Concurrently, metabolic dysfunction-associated fatty liver disease (MAFLD) is closely linked to heightened cardiac dysfunction risk. Our study aimed to explore the additive effect of MAFLD on left ventricular (LV) deformation among T2DM patients, utilizing cardiac magnetic resonance (CMR) feature tracking technology. Methods This study retrospectively included 270 patients with T2DM, comprising 110 individuals with MAFLD and 160 without, alongside 80 age- and sex-matched healthy controls, all of whom underwent CMR examination. Parameters derived from CMR encompass those related to LV function and global strain metrics. LV global strain parameters include global radial peak strain (GRPS), longitudinal peak strain (GLPS), and circumferential peak strain (GCPS), peak systolic strain rate (PSSR), and peak diastolic strain rate (PDSR), measured across radial, circumferential, and longitudinal directions. Intergroup analysis, employing the Mann-Whitney U test, was utilized to compare LV function and global strain parameters. Results The LV function parameters, including LV end-diastolic volume (LVEDV), LVEDV index, LV end-systolic volume (LVESV), LVESVI, LV mass, and LV mass index, displayed a progressive augmentation from controls through T2DM patients without MAFLD, to those with MAFLD. In parallel, LVEF showed a declining trajectory across these groups. In contrast, LVSV and LVSVI were comparable among the three groups. In a similar vein, when examining global strain parameters derived from CMR, a significant and progressive deterioration is observed across the groups. GRPS, GCPS and GLPS, along with PSSR and PDSR in radial, circumferential, and longitudinal directions, manifest a pronounced decline moving from control subjects to T2DM patients without MAFLD, and further deteriorating in those with T2DM and MAFLD (All p-values < 0.05). To assess the effect of MAFLD severity on global peak strain, patients with T2DM and MAFLD were stratified into two groups: a mild MAFLD group (N=77) and a moderate to severe MAFLD group (N=33). Although there was a noticeable decline in GRPS, GCPS and GLPS, as well as in PSSR and PDSR across the three groups—from those without MAFLD to those with mild and then moderate to severe MAFLD—the observed differences did not reach statistical significance. The absence of statistical significance is likely due to the small sample sizes of the groups categorized by severity of MAFLD. Conclusions This study revealed that MAFLD has additive worsening effects on LV function and LV global strains in T2DM patients evaluated by CMR. Besides, moderate to severe MAFLD, compared to mild MAFLD, exhibits worse global strain parameters. Early detection and intervention of MAFLD might improve the prognosis of T2DM patients.

Verification of intra- and inter-atrial conduction during Bachmann's bundle pacing using longitudinal bi-atrial strain

Abstract Introduction Although atrial septal pacing has been reported to reduce atrial fibrillation (AF) burden, there is less evidence regarding its effect on the prevention of permanent AF and the improvement of long-term clinical outcomes. However, Bachmann's bundle pacing (BBp), which features P-wave morphology similar to sinus rhythm and shortened P-wave duration (PWD), was reported to significantly reduce permanent AF recurrences and occurrences compared with right atrial appendage pacing (RAAp) and non-specific right septal pacing. Purpose Possible mechanisms for AF suppression with BBp are that fast inter-atrial conduction through BB decreases global atrial activation time and the dispersion of the overall atrial refractoriness, and it prevents the decrease in left ventricular filling and increase in left atrial pressure associated with delayed left atrial contraction. Intra-and inter-atrial conduction during BBp was evaluated using longitudinal bi-atrial strain. Methods In patients with successful BBp implantation defined by electrocardiographic criteria using SelectSecure pacing lead and C315 delivery catheter (Medtronic, Inc), both left atrium (LA) and right atrium (RA) global longitudinal strain (GLS) in simultaneous phases were measured using Philips Ultrasound Workspace 2D Strain in apical 4-chamber view during atrial pacing to assess intra- and inter-atrial conduction delay. The atrial GLS were measured semi-automatically, and the strain rate was analyzed in the three segments of septal wall, lateral wall, and roof and their average. The negative peak of strain rate during atrial systole was the starting point of atrial contraction, and time to peak (TTP) was measured. The difference in TTP between septal and lateral walls in each atrium was measured as intra-atrial conduction delay and the difference in average TTP between LA and RA as inter-atrial conduction delay. Results Ten patients who underwent successful BBp were enrolled (Sick sinus syndrome: 3, advanced atrioventricular block: 2, complete atrioventricular block: 5). At implantation, bipolar atrial electrogram amplitude was 2.03±0.93 mV, atrial lead impedance was 632.7±157.6 Ω, and atrial pacing threshold was 0.7±0.2 V at 0.4 ms. The PWD during sinus rhythm on the 12-lead ECG was 132.8±10.6 ms, while during BBp it was 108.0±11.9 ms, which was significantly shorter in the BBp group (p<0.001). The intra-atrial conduction delay in RA and LA was 10.9 ± 12.1 ms and 12.1 ± 17.3 ms, respectively, and the inter-atrial conduction delay was 6.6 ± 8.6 ms. On the other hand, for the 10 RAAp and 10 sinus rhythm patients as control groups, the inter-atrial conduction delay was 29.7±13.8 ms and 8.5±9.5 ms, respectively. BBp had significantly less inter-atrial conduction delay than RAAp (p=0.005) and was comparable to sinus rhythm (p=0.719). Conclusion Longitudinal bi-atrial strain suggested that BBp significantly reduced inter-atrial delay and it might be effective in AF suppression.Longitudinal bi-atrial strain

Interaction between right atrial function reserve and liver stiffness after complete repair of tetralogy of fallot: a pilot study

Abstract Background Impaired right atrial mechanics is reported in patients with repaired tetralogy of Fallot (TOF) and is associated with liver stiffness. However, whether right atrial functional reserve correlates with liver stiffness is unknown. Purpose This study tested the hypothesis that right atrial reserve capacity is limited in patients with repaired TOF and explore its relationships with right ventricular function and liver stiffness. Methods 10 patients (45% male) aged 19.04 ± 3.76 at 16.70 ± 4.30 years after repair and 15 controls (60% male, aged 20.31 ± 1.25 years) were studied. RA mechanics was assessed by speckle-tracking echocardiography (STE) at rest and during bicycle exercise, with quantification of positive, negative, and total strain, and strain rates at ventricular systole (aSRs), early diastole (aSRed), and atrial contraction (aSRac). Right atrial function reserve (RAFR) is calculated as (∆RA total strain x [1-1/ RA total strain at baseline]). RV systolic and diastolic function was quantified using Doppler interrogation and STE. Hepatic shear wave velocity (c) and tissue elasticity (E) were measured using two-dimensional shear wave elastography. Results At rest, patients had significantly lower RA positive, negative and total strain, aSRs and aSRed than control subjects (all P<0.02). Shear wave velocity and hepatic E value were significantly higher in patients than controls (both P<0.02). Compared with controls, patients had significantly lower RA positive, negative and total strain, aSRs, aSRed, and aSRac at exercise (all P<0.05). No significant difference in hepatic shear wave velocity and tissue elasticity were found between patients and control subjects at exercise (all P>0.05). Both baseline liver stiffness indices correlated negatively with RAFR, RA positive and total strain and aSRed at exercise (p<0.05 for all). RV function parameters, including baseline trans-tricuspid early and late diastolic inflow velocity (E, A), systolic, early and late diastolic tricuspid annular velocity (s, e, a), isovolumetric acceleration (IVA), RV systolic and diastolic reserve correlated significantly with RA positive and total strain at exercise (P<0.05 for all). Conclusions In young adults with repaired TOF, right atrial function reserve is impaired, and is associated with increased liver stiffness and RV dysfunction.RA mechanics from rest to exerciseStress RA mechanics and liver stiffness

Echocardiographic assessment of the right heart pulmonary circulation unit in mitral regurgitation due to mitral valve prolapse

Abstract Background Right ventricular evaluation is essential in the context of chronic mitral regurgitation (MR). Chronic MR is associated with a progressive cardiac remodeling with enlargement and dysfunction of all cardiac chambers, and the development of functional tricuspid regurgitation (TR). Besides, right ventricle (RV) dysfunction and functional TR have been shown to influence patient prognosis. Purpose The aim of this study was to evaluate simple and combined echocardiographic parameters analysing the right heart – pulmonary circulation unit, according to the severity of MR. Methods In this monocentric retrospective study, echocardiographic studies of patients followed for a mitral valve prolapse (with or without MR) were reviewed. Usual parameters analysing RV morphology, load and function were obtained. Combined parameters of RV – pulmonary artery (RV-PA) coupling were calculated: TAPSE/PASP and RVFWS/PASP. Comparison between MR grades were performed with ANOVA or Kruskal Wallis tests as appropriate. Two-by-two post-hoc comparisons of continuous variables across the 5 groups were made using the Bonferroni correction. Results 158 patients with mitral valve prolapse (MVP) were included: 37 without MR, 28 with mild MR, 23 with mild-to-moderate MR, 21 with moderate-to-severe MR and 49 with severe MR. Clinical and echocardiographic results are presented in Table 1. Patients with a higher-grade MR tended to be older and were more likely to be men. They were also significantly more symptomatic. Most echocardiographic parameters were significantly different between grades of MR. RV remodeling, studied with morphologic parameters, started with the first grade of MR and had a linear progression between levels of MR severity (Figure 1A). Load parameters were stable until grade 2 and then showed progressive increase of RV afterload. RV free wall strain slightly increased with MR grade 1, and then decreased with each grade of MR (Figure 1B). RV fractional area change, Tissue Doppler MPI and RV free wall strain rate tended to stagnate between grade 0 and 2, and then they progressively decreased. Combined parameters of RV-PA coupling including load and function, increased with the first grade of MR, and then gradually decreased (Figure 1C). Conclusion In this study, multiparametric assessment of the cardiopulmonary unit in patients with MVP showed that RV morphologic remodeling starts with the first grades of MR, before any significant increase of pulmonary pressure. This remodeling seemed to initially enhance RV function (evaluated with parameters of RV – pulmonary artery coupling) in the first grade of MR and was then followed by a progressive decrease of RV function with the increasing severity of MR.

3D geometry of the Dugald River Shear Zone, Mount Isa Inlier, Australia

The Dugald River Shear Zone is a structurally complex, anastomosing shear zone that hosts high-grade Zn mineralisation within the Dugald River Slate. The Dugald River Zn–Pb–Ag mine is situated within the Mount Isa Inlier, Australia and developed through two phases of mineralisation with high-grade Zn mineralisation intimately associated with the development of the brittle–ductile Dugald River Shear Zone. The first phase of mineralisation occurred during the regionally extensive, D2 ductile fold and axial planar cleavage forming event and resulted in the development of a sulfide horizon. This horizon was a preferential site for strain partitioning during early D4 ductile deformation, which resulted in transposition-related concentration and thickening of a sulfide horizon marking the second phase of mineralisation. The Dugald River Shear Zone developed during D4 wherein strain rate incompatibilities between a ductile-deforming sulfide horizon and the brittle-deforming Dugald River Slate resulted in the development of a Riedel shear zone. A high-resolution 3D model of the shear zone was constructed from robust drilling and mapping datasets in which releasing and restraining bends highlight the thickening and thinning of ore lenses, respectively. The 3D model with detailed structural analysis and observations allows for predictive modelling of dilational zones within throughgoing Y-shears, which are prospective sites for remobilisation of high-grade Zn sulfides as the ore body developed coevally with progressive shearing.

Dynamic statistical damage constitutive model based on the Hoek–Brown criterion at high strain rates

Dynamic statistical damage constitutive model based on the Hoek–Brown criterion at high strain rates

Fenofibrate modulates cardiac energy metabolism in moderate-severe aortic stenosis: a mechanistic double-blinded randomised controlled MR trial

Abstract Background Aortic stenosis (AS) is associated with impaired cardiac metabolism and high-energy phosphate production which can further exacerbate the progression to HF. Myocardial lipid accumulation and reduced production of high-energy phosphates have important implications for both systolic and diastolic heart function in AS. Peroxisome proliferator-activated receptor alpha (PPAR-alpha agonist, has the potential to optimise cardiac substrate metabolism, thereby, may be effective in improving cardiac dysfunction and functional capacity in AS. Methods In this prospective, randomized, double-blind, placebo-controlled study, patients with moderate-to-severe asymptomatic AS (n=72) were randomly assigned to Fenofibrate 200 mg daily or matching placebo for 6 months in 4:1 fashion. Of the total 72 participants, 59 received Fenofibrate and 13 received placebo. All subjects underwent cardiac magnetic resonance (CMR) and exercise testing at 0 and 6 months, with follow-up data available in 47 patients. The primary end point was change in myocardial triglyceride content (MTG) determined by proton magnetic resonance spectroscopy (1H-MRS). Secondary outcome measures included change in cardiac energetics (PCr/ATP) determined by phosphorus magnetic resonance spectroscopy (31P-MRS), left ventricular strain determined by myocardial tagging and exercise capacity i.e. peak VO2 assessment via cardiopulmonary exercise testing. Results Cardiac energetics (PCr/ATP) showed statistically significant improvement in the Fenofibrate group (0.14 ± 0.48; CI: - 0.03, 0.30; p=0.05) vs placebo group (0.11 ± 0.75; CI -0.42, 0.65; p=0.64). There was also significant reduction in MTG in the Fenofibrate group (mean change -0.40 ± 0.97; 95% CI -0.74, -0.06; p=0.02). MTG content also reduced in the placebo group (mean change -0.41 ± 0.26, 95% CI -1.10, 0.18, p 0.13), but the reduction was not statistically significant. Though no significant changes were seen in the systolic function parameters, there was a significant improvement in diastolic function in the fenofibrate group only (peak diastolic longitudinal strain rate 9.6, 95% CI: 1.13, 18.1; p = 0.02). Peak VO2 did not show any significant improvement in either group. Conclusions Fenofibrate works as a metabolic modulator upregulating fatty acid metabolism in pressure overload AS hearts. Such modulation is associated with an improvement in cardiac energetics and diastolic function in moderate-severe AS.Main results from baseline to 6 monthsBaseline demographic and CMR parameters

Inclined bending seismic reflection layer in the crust illuminated by distributed fibre-optic-sensing measurements in western Japan

Distributed acoustic sensing (DAS), which enables a single fibre-optic cable to function as multiple sensors, is a technique to measure the strain rate distributed along the cable. This technique is applied to record ground motions in western Japan via a 50 km-long fibre-optic cable beneath a national road. The measured values are strain changes along the cable every 5 m, corresponding to 9788 sensor deployments. This high-density measurement along the long cable successfully recorded the 2021 M2.8 and M3.2 earthquakes that occurred in the crust within the distance of the cable in southern Kyoto. The direct S waves were followed by seismic waves approximately 8–14 s later, which were reflected by lower crustal structures. These waveforms were previously reported by observing many earthquakes via multiple seismometers, but the DAS observations clearly illuminate reflected wavefields from single earthquake observations for the first time. The numerical simulation of the strain-rate wavefields of these earthquakes reveals the existence of a north-dipping thin layer with a slow seismic velocity in the lower crust, which becomes steeper in the shallower part. This layer might represent the path of slab-derived fluid to the shallow fault zone.

Thermal processing behaviour and microstructural evolution of high W and high γ’ content extruded nickel-based powder metallurgy superalloy FGH4109

ABSTRACT Nickel-based powder metallurgy superalloys with high W and high γ’ content exhibit excellent high-temperature properties, but their high deformation resistance poses significant challenges for hot processing. In this study, the hot compression behaviour of an extruded nickel-based powder superalloy FGH4109 with high W (6.1%) and high γ’ phase contents (60%) was systematically investigated at temperatures ranging from 1060 ℃ ~ 1140 ℃, strain rates from 0.001 s−1 ~1 s−1, and maximum true strains of 0.7. Combined with the hot working map and the microstructure evolution in different hot working zones, the optimal hot working window for the alloy was determined to be in the temperature range of 1060 ℃ ~ 1140 ℃ and strain rates of 0.001 s−1 ~0.012 s−1, where the power dissipation efficiency η was greater than 0.5, and the dominant deformation mechanism was discontinuous dynamic recrystallisation.