Strain Values Research Articles

Antibacterial Power of Lemon Essential Oil, Ginger And Their Synergy With Neem Vegetable Oil On Mastitis Pathogenic Germs Dairy Cows From The Poro Region In Ivory Coast

Gas chromatography-mass spectrometry analysis of essential oils of (Citrus limon, Zingiber officinalis and Azadirachta indica vegetable oil), purchased, identified 32.80%, 42.40% and 47.10% of its constituents. This study consisted of evaluating the antimicrobial performance of some EOs obtained from three medicinal plants, considered to have a great bacterial effect. This is in order to standardize their use to apply them as an alternative remedy to antibiotics in the face of the advance of resistant bacteria and the failure of antibiotic therapy. The essential oils of these plants were tested alone or in combination on nine pathogenic microbial strains from cows suffering from mastitis and resistant to certain antibiotics, namely: four Gram (-) bacterial strains (Pseudomonas aeruginosa, E. coli ATCC25922, E. coli, Klebsiella spp) ; five Gram (+) bacterial strains (Staphylococcus aureus, Micrococcus spp, S. aureus ATCC19213, SCN (S. lentus and S. xylosus)); and E. coli ATCC25922, S. aureus ATCC19213 as reference strains. Reasonable antimicrobial activities of the studied EOs were observed on some of the germs tested. All the strains tested are sensitive to concentrations less than or equal to 100μg.ml -1 of essential oil. Enterobacteria (Escherichia coli, Klebsiella spp) are resistant to standard antibiotics with the exception of Colistin, which have been shown to be sensitive to all essential oils studied. This observation applies to Gram-positive cocci (Staphylococcus aureus, Micrococcus spp, Staphylococcus lentus and Staphylococcus sylosus) which are very sensitive to the oils studied but resistant to three types of standard antibiotics (Ampicillin, Colistin and Penicillin). The CMB/MIC ratios of Zingiber officinalis and Citrus limon oils have a bacteriostatic action while that of the combination of EO (Zingiber officinalis, Citrus limon and Azadirachta indica oil ) are bactericidal on all bacterial strains tested. There was no significant difference between the MIC and MBC values of the essential oil resistant strains. As a result of the study, an idea could be proposed for the development and upgrading of a new generation of combination of natural antimicrobial agents that can be used in humans and animals against infections with commonly used antibiotics.

Mechanical and autogenous shrinkage properties of coarse aggregate ultra-high performance concrete (CA-UHPC): The effect of mineral admixtures

To reduce the shrinkage and explore the best content of mineral admixtures of coarse aggregate ultra-high performance concrete (CA-UHPC), this study conducted 12 groups of autogenous shrinkage, basic material properties (compressive strength, tensile strength, and flowability), and X-ray diffraction experiments on CA-UHPC with coarse aggregate and different amounts of mineral admixtures (slag powder, limestone powder). The effects of coarse aggregate and mineral admixtures on the autogenous shrinkage and basic material properties of CA-UHPC were analyzed, and the measured values of CA-UHPC autogenous shrinkage strain were compared with the theoretical values calculated by six commonly used concrete shrinkage prediction models. The experimental results show that under the condition of 15 % coarse aggregate content and no steam curing, a CA-UHPC with a compressive strength greater than 110 MPa, a tensile strength greater than 11 MPa, a flowability greater than 290 mm, and an autogenous shrinkage of less than 700 after 120d can be obtained. The mineral admixture has a significant impact on the fundamental properties of CA-UHPC. The compressive strength, tensile strength, and flowability of CA-UHPC with 15 % limestone powder and 15 % S95 slag powder increased by 6.6 %, 5.4 %, and 27.6 % compared to UHPC with only coarse aggregate added, and the autogenous shrinkage after 120 days decreased by 10.5 %. However, when the dosage of limestone powder and S95 slag powder exceeds 30 %, the tensile and compressive strength of CA-UHPC will rapidly decrease. This study also revised the GL 2000 shrinkage prediction model based on the CA-UHPC autogenous shrinkage test results, introduced the influence coefficient of mineral admixture content on autogenous shrinkage strain, and established a theoretical calculation model suitable for CA-UHPC autogenous shrinkage strain.

Quantitative Analysis of Myocardial Work in Gestational Diabetes Mellitus Using Noninvasive Left Ventricular Pressure-Strain Loop Measurement.

Gestational diabetes mellitus (GDM) poses a risk for cardiovascular damage during pregnancy. This study focused on evaluating changes in left ventricular myocardial performance in GDM patients using the left ventricular pressure-strain loop (LV-PSL) method and examining risk factors associated with reduced myocardial function. A prospective, randomized study involving 112 pregnant women diagnosed with GDM was conducted from June 2021 to June 2024. Additionally, 84 healthy pregnant women from the same period served as the control group. Utilizing both conventional echocardiography and two-dimensional speckle tracking echocardiography, left ventricular myocardial work metrics were assessed using LV-PSL technology. GDM patients demonstrated significantly reduced values for global longitudinal strain (GLS), global work index (GWI), global work efficiency (GWE), and global constructive work (GCW) (p < 0.05), while conventional ultrasound measures showed no significant difference between GDM and control groups. GWI, GWE, GCW, and GLS had high predictive value for cardiac function changes in GDM patients, with GWE showing the highest predictive value {Area under curve (AUC)=0.866, cutoff value=95.5%, specificity=0.77, sensitivity=0.87}. GWI, GWE, and GCW were negatively correlated with GLS (r=-0.532, -0.411, -0.425, all p < 0.001), whereas global wasted work (GWW) showed a positive correlation with GLS (r=0.325 and p < 0.001). These parameters were also correlated with HbA1c levels (r=-0.316, -0.256, -0.260, all p < 0.001 for negative correlations, and r=0.172, p < 0.05 for positive correlations). Multivariate logistic regression indicated that 1-h OGTT (mmol/L), 2-h OGTT (mmol/L), and HbA1c (%) were significant predictors of left ventricular systolic function (GWE) in GDM patients. LV-PSL is an effective tool for early detection of left ventricular systolic function impairment in GDM patients.

Molecular dynamics study of mechanical stability of Ti4C3 MXene subjected to chirality, temperature, strain rate, and point-vacancy for Lithium-ion batteries

Two-dimensional Ti4C3 MXene has recently emerged as a promising electrode for Lithium-ion batteries (LIBs) because of its outstanding ion-transport abilities and high Li-absorbability. This study employed molecular dynamics simulation to explore the mechanical stability of Ti4C3 MXene subjected to various temperatures, strain rates, and vacancy concentrations. A slightly superior tensile strength and elasticity modulus have been observed along zigzag directions, measuring 148.14 GPa and 29.17 GPa, respectively. On the other hand, armchair-oriented Ti4C3 MXene shows a considerably greater fracture strain of 0.259 due to its strain-hardening tendency at lower temperatures. Elevated temperature decreases both fracture strength and fracture strain, which is opposite to the effect of strain rate. Armchair loading has been revealed to be more sensitive to strain rate than its counter direction. Unlike temperature and strain rate, point vacancy significantly deteriorates the elastic modulus of Ti4C3 MXene. Carbon vacancies are more probable than titanium vacancies, which have less formation energy. The atomistic deformation profile supports the predicted values of fracture strain from stress-strain behavior. This in-depth study offers a detailed understanding of the mechanical behavior of Ti4C3 MXene under diverse circumstances, which will aid further experimental study and be beneficial for adopting Ti4C3 as anode materials in LIBs.

Determination of Structural Elements of Hydrothermally Synthesized CeO₂ Nanoparticles by Monshi, Williamson–Hall, Halder–Wagner, and Size–Strain Plot Methods, and Effect of Annealing Temperature

AbstractCeO₂ nanoparticles are synthesized hydrothermally using CTAB as a surfactant, cerium nitrate hexahydrate (Ce(NO3)3·6H₂O) as a precursor and urea. The synthesized CeO₂ nanoparticles are characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction peak profile analysis (XRD), Scanning electron microscopy (SEM), and UV–vis. The X‐ray diffraction results revealed that the sample is crystalline with a face centered cubic (fcc) phase having cubic fluorite structure. The structural elements of prepared samples have been investigated by various methods. The Monshi, W–H analysis, size–strain plot, and H–W methods are used to study crystallite sizes and lattice strain on the peak broadening of CeO₂ nanoparticles. Further, the lattice constant of the cubic fluorite has also been estimated from the Nelson–Riley plot. The parameters, including strain, stress, and energy density value, are calculated for all the reflection peaks of X‐ray diffraction corresponding to cubic fluorite phase of CeO₂ lying in the range 20°–80° and at different temperatures.

Clinical significance of echocardiographic left ventricular hypertrophy for predicting left atrial appendage thrombotic milieu in patients with atrial fibrillation and CHA2DS2-VASc scores of 0–2

BackgroundThe clinical significance of echocardiographic left ventricular hypertrophy (LVH) in risk stratification of left atrial appendage (LAA) thrombogenic milieu, as a surrogate for cardioembolic risk, in patients with atrial fibrillation (AF) and HA2DS2-VASc scores of 0–2 is unknown. Methods and resultsWe enrolled 707 consecutive patients with AF and CHA2DS2-VASc scores of 0–2 who underwent transesophageal echocardiography. LAA thrombogenic milieu was defined as the presence of a thrombus, severe spontaneous echo contrast, sludge in the LAA, or LAA flow velocity ≤ 20 cm/s. Alongside conventional parameters, longitudinal strain values for the left ventricle (LV) and left atrium were obtained using transthoracic echocardiography. Among the 707 patients, 77 (10.9 %) exhibited LVH. The LVH group exhibited a significantly higher prevalence of LAA thrombogenic milieu than the non-LVH group (32.5 % vs. 2.5 %, p < 0.001). LVH independently associated with LAA thrombogenic milieu after adjusting for clinical factors (including CHA2DS2-VASc score, AF type, and serum brain natriuretic peptide levels) and conventional echocardiographic parameters (including LV ejection fraction, LV end-diastolic volume index, and left atrium volume index) (odds ratio [OR]: 7.54, 95 % confidence interval [CI]: 3.49–16.29, p < 0.001 and OR: 7.16, 95 % CI: 3.26–15.73, p < 0.001, respectively). Moreover, LVH provided incremental value for predicting LAA thrombogenic milieu, even when added to the longitudinal strain of the LV and left atrium reservoir strains (p < 0.001). ConclusionEchocardiographic LVH significantly improves the prediction of LAA thrombogenic milieu, offering potential utility in further cardioembolic risk stratification for patients with AF and CHA2DS2-VASc scores of 0–2.

Utilizing echocardiography and unsupervised machine learning for heart failure risk identification

BackgroundGlobal longitudinal strain (GLS) is recognized as a powerful predictor of heart failure (HF). However, the entire strain curve may entail important prognostic information regarding HF risk that might be undiscovered by only focusing on the peak strain value. ObjectiveThe hypothesis of the present study was, that analysis of the entire strain curve using unsupervised machine learning (uML) would reveal novel ventricular deformation patterns capable of predicting incident HF independently of GLS. MethodsLongitudinal strain curves from 3710 subjects from the general population without prevalent HF were analyzed using uML. ResultsMean age was 56 years and 43 % were male. During a median follow-up of 5.3 years, 92 subjects (2.5 %) developed HF. The uML algorithm generated a hierarchical clustering tree (HCT) resulting in 10 different clusters. Generally, the strain curves displayed reduced early diastolic strain to peak-strain ratio with an increasing incidence rate of HF. In multivariable Cox regressions, cluster 9 was significantly associated with increased risk of HF when compared to cluster 2–5, and 7–8 [For cluster 3: HR 8.95, 95 %CI: 2.08;38.48, P = 0.003] even though the subjects of cluster 9 were younger, displayed healthier clinical baseline characteristics, and only had slightly reduced GLS. The mean strain curve of cluster 9 displayed an early systolic lengthening followed by a late and reduced contraction specifically related to the basal lateral segment. ConclusionThe unsupervised machine learning algorithm identified unknown strain patterns beyond GLS presumably related to increased risk of HF.

Mechanistic Characteristics of HRS-WC Mixture Using Tabas Stone Waste Coated With Plastic Waste As Aggregate

Utilization of tabas stone waste and polypropylene (PP) plastic waste has not been carried out massively and optimally because it lacks economic value. The Tabas stone waste can be used as an aggregate for pavement. The porous characteristic of tabas stone results in a high rate of absorption and abrasion, so modifications are made by coating the aggregate with an PP plastic. The aim of this experiment was to determine the characteristics of the HRS-WC mixture with the aggregate of tabas stone coated with plastic. The initial step of this research was testing the tabas stone aggregates, bitumen material, and PP plastic according to the SNI procedure, the next step was Marshall test to find the Optimum Bitumen Content (OBC), the OBC value was obtained by 10%. Coating the aggregate with shredded plastic measuring ± 1 cm2 was done on coarse aggregate only using the dry method with the proportions of plastic are 5% and 10% of the total weight of coarse aggregate. The characteristics of the aggregate coated with plastic decrease in the value of absorption and abrasion, but only 10% of the plastic content met the specifications with a value of 2.5% and 19.63%. The Marshall testing on the HRS-WC mixture with plastic-coated aggregates was done at variations in bitumen content of 8.5%; 9%; 9.5%. The mixture at 5% plastic content only 9.5% bitumen content met the specifications, namely: stability 1352.72 kg, flow 3.39 mm, MQ 402.23 kg/mm, VIM 5.75%, VMA 18.62% , and VFB 69.16%. When at 10% plastic content, only 9% and 9.5% bitumen content met the specifications, namely the stability of 1370.06 kg; 1456.21 kg, flow 3.81 mm; 3.98 mm, MQ 365.31 kg/mm; 370.06 kg/mm, VIM 5.77%; 4.89%, VMA 18.07%; 18; 15%, and VFB 68.05%; 73.04%. Asphalt mixture of 9% bitumen content, 10% plastic content has more ITSM value compared to 5% plastic content. This is due to the plastic content in the mixture of 10% plastic content which causes the mixture to be stiffness. Asphalt mixture with a plastic content of 5%, with an bitumen content of 9.5% faster than the mixture with an bitumen content of 8.5% and 9% in the ITFT test. Asphalt mixture with a plastic content of 5%, with a variation of bitumen of 8.5% experienced a decrease in the dynamic creep strain value until the bitumen content was 9.5%. A mixture with a plastic content of 5% aggregate coating is recommended for HRS WC that uses tabas stone.

The Predictive Value of Global Longitudinal and Circumferential Strains in Hypertensive Patients: 10-Year Follow-Up

Background: The aim of the current study was to investigate the predictive value of a multidirectional LV strain on adverse outcomes in a large population of uncomplicated hypertensive patients who were followed for a mean period of 10 years. Methods: This retrospective study included 591 recently diagnosed hypertensive patients who underwent clinically indicated echocardiography between January 2010 and December 2014 and were followed for a mean period of 10 years. Global longitudinal, circumferential and radial strains (GLS, GCS and GRS) were measured by 2D speckle tracking imaging. The primary outcome was a MACE occurrence defined by all-cause mortality, cardiovascular mortality, myocardial infarction, coronary artery by-pass, coronary stent implantation, stroke, development of heart failure and the occurrence of atrial fibrillation during follow-up. Results: Our results showed that GLS, GCS and GRS were significantly lower in patients who experienced MACE. Age, male gender, systolic blood pressure, left ventricular hypertrophy (LVH) and left atrial enlargement (LAE) were associated with MACE occurrence. Reduced GLS [OR 1.15; 95%CI: 1.01–1.30] and reduced GCS [OR 1.1; 95%CI: 1.02–1.22] were related with MACE independently of clinical characteristics, LV systolic and diastolic function, as well as LVH. Reduced GRS was not independently associated with adverse outcomes. Conclusions: Reduced GLS and GCS were independently associated with adverse outcomes during 10-year follow-up in patients who were recently diagnosed and uncomplicated hypertensive patients at the baseline.

Are Ratings of Perceived Exertion during Endurance Tasks of Predictive Value? Findings in Trunk Muscles Require Special Attention.

Background: Subjective rating scales of perceived exertion are often used to quantify effort levels during various endurance exercises, particularly submaximal tasks. The aim of the current study was to determine whether predictive conclusions can be drawn from perceived exertion levels surveyed at the start of defined submaximal endurance tasks. Methods: In this study, healthy participants performed a 10-min endurance task at 50% of their upper body weight, targeting either the back muscles (n = 47, 24 women) or abdominal muscles (n = 32, 17 women). At the end of each minute, participants were asked to rate their perceived exertion (RPE) using the 14-points Borg Scale. Based on their initial and final RPE levels, and for each muscle group separately, participants were divided into subgroups reflecting low (good start/good end) and high (bad start/bad end) strain levels. These values were then compared over the duration of the exercise. Comparisons of RPE levels between subgroups were made using the Mann-Whitney U-test for independent samples, with Bonferroni-Holm correction to account for multiple comparisons. Results: Overall, strain levels increased throughout the duration of the exercise. For the abdominal muscles, the difference between the two RPE groups remained constant over time: participants with good start/end ratings consistently showed different strain levels from those with bad start/end ratings, regardless of whether the grouping was based on initial or final exertion levels. In contrast, for the back muscles, the initial grouping showed a crossover in strain values: by the end of the task, participants in the good start group tended to report higher strain than those in the bad start group. No differences were found in initial RPE values when the grouping was based on final exertion levels. Conclusions: For endurance tasks involving the abdominal muscles, initial strain levels have strong predictive value, whereas this is not the case for the back muscles. Because back muscles are frequently loaded, continuous monitoring of RPE levels is necessary to prevent unexpected task failure, as initial RPE values are not predictive. In contrast, RPE values of 11 or higher on the 14-points Borg scale predict complete exhaustion or even premature task failure with high certainty for abdominal muscle exercises, while lower RPE levels indicate that exercise intensity can be increased.

Impact of smoking on procedural outcomes and all-cause mortality following acute myocardial infarction: A misleading early-stage pseudoparadox with ultimately reduced survival

BackgroundSmoking has conflicting results on outcomes following acute myocardial infarction (AMI). We evaluated the independent influence of smoking status on patient outcomes. MethodsWe included patients with AMI undergoing invasive coronary angiography with available self-reported smoking status. The incidence of death of any cause was evaluated during a median follow-up of 1.14 years (range 0.36–3.40 years). Association between smoking status and long-term mortality was evaluated using multivariable adjusted Cox regression analysis. ResultsFrom 1612 AMI patients (aged 65.7 ± 13.3 years, 72.1 % male), 378 patients (23.4 %) were current-smokers, 311 (19.3 %) ex-smokers, and 923 (57.3 %) non-smokers. Compared with non-smokers, current-smokers were younger (68.5 ± 13.0 vs. 58.6 ± 12.5, p < 0.0001) and more frequently presented with STEMI (21.6 % vs. 35,4 %, p < 0.0001), while ex-smokers with similar frequency of STEMI-manifestation as non-smokers (22.5 %, p = 0.79) constituted an intermediate-group in terms of age (65.8 ± 11,6 years). Although smoking status was not significantly associated with long-term survival in unadjusted-analysis, active-smokers had 56 % higher long-term mortality than non-smokers when adjusting for age, gender, medications and other traditional risk factors, whereas ex-smokers possessed comparable survival probability (current-smokers: 1.56[1.14–2.14], p = 0.006, ex-smokers 1.16[0.84–1.59], p = 0.37). Current-smokers had unadjusted lower NT-proBNP and modestly higher absolute in-hospital left ventricular global longitudinal strain (LV GLS) values that did not differ among groups after the same adjustments (NT-proBNP: −0.08[-0.31; 0.15], p = 0.5, LV GLS: 0.65[-0.26; 1.55], p = 0.16). ConclusionActive smoking is associated with increased adjusted long-term mortality, earlier onset and more frequent manifestation as STEMI, compared to non-smoking. Comparable adjusted results for LV GLS and NT-proBNP between groups support the presence of the pseudoparadox.

Hot Torsion Tests of AA6082 Alloy

Materials characterization and the knowledge of their elastic-plastic behavior are of fundamental importance for the design of industrial manufacturing processes. Nowadays, FEM simulation is the main tool used to optimize product quality and minimize scraps, and the numerical codes have evolved over the years to obtain accurate solutions with reduced computational times. Nevertheless, in order to perform reliable simulations, it is necessary to include accurate modeling of the material flow stress. Hot torsion is a powerful method for the characterization of the material flow stress because, tests can be carried out at constant speeds and temperatures, reaching large strain values, and thus getting over the limits of compression and tensile tests. In this paper the hot torsion characterization applied to AA6082 alloy is presented: tests were performed with equivalent strain rates of 0.01, 0.1, 1, and 10 s-1, in the temperature range from 440 to 550 °C (from 713.15 to 823.15 K). The results are presented in terms of equivalent stress vs equivalent strain. Finally, the material flow stress curve was predicted by the Hyperbolic sine model and Hensel-Spittel law, and the material parameters A, m1-9 are provided for the temperature expressed in °C and K.

The influence of gamma radiation on the structure and morphology of AgNWs/GO nanocomposites

In this study, AgNWs/GO nanocomposites were prepared by mechanically mixing graphene oxide (GO) synthesized using a modified Hummers' method and silver nanowires (AgNWs) synthesized using a modified polyol method. These nanocomposites were subjected to gamma radiation at three different doses (8, 25, and 50 kGy). Modification of materials by gamma radiation is a very important issue in materials science. The effects of gamma radiation on the structure of the nanocomposites were investigated through X-Ray diffraction (XRD) analyses. Changes in morphology depending on the radiation dose were examined using transmission electron microscope (TEM) images. Elemental analysis was performed before and after irradiation. For GO irradiated at a dose of 25 kGy, the strain and dislocation density values reached their highest levels (ε = 0.065 and σ = 3.33 × 1012 cm−2). Following gamma radiation exposure, the strain and dislocation density of AgNWs showed a non-linear decrease compared to the initial sample. The highest values for both strain and dislocation density were recorded at the 0 kGy dose (ε = 0.0064 and σ = 0.0036 × 1012cm−2). Elemental analysis (EDS) indicated that reduction processes occurred depending on the radiation dose, with the highest reduction observed in the sample irradiated at 25 kGy. Studies indicate that gamma radiation can modify the structural and physical properties of the AgNWs/GO nanocomposite.

Machine learning approaches in designing anti-HIV nitroimidazoles: 2D/3D QSAR, kNN-MFA, docking, dynamics, PCA analysis and MMGBSA studies

In this study, newly synthesized 20 nitroimidazole derivatives were subjected to 2D and 3D Quantitative Structure-Activity Relationship (QSAR) study to investigate their anti-HIV activity against both ROD and IIIB strains. Later, proposed hypothesis was virtually proved by further in-silico studies. In statistically significant 2D-QSAR models r2 values for IIIB strains 0.9241 and for ROD strains 0.9412 with corresponding q2 values of 0.7706 and 0.8299, were obtained, respectively. Different models were constructed using three different kNN-MFA 3D QSAR approaches such as SW-FB, SA score, and GA. By using the generated hypothesis, newer analogues of nitroimidazole derivatives was designed and molecular modelling studies were conducted to prove the hypothesis. The three molecules were displayed the good docking scores compared to the reference molecule. The stabilities of docked complexes were analyzed by MD simulations and MMGB/SA calculations. These results offer insightful design guidance for novel anti-HIV compounds synthesis and suggest interesting directions for future pharmaceutical research.

Simulation and Measurement of Strain Waveform under Vibration Using Fiber Bragg Gratings.

The work is devoted to the consideration of methods for determining the strain of objects using fiber Bragg gratings under a high-frequency vibration or pulsed mechanical action, which is difficult to perform using widespread methods and devices. The methods are based on numerical processing of the time dependence of the radiation power reflected from the fiber Bragg grating at various wavelengths, which makes it possible to measure strain parameters in a wide range of magnitude and frequencies. The efficiency of the proposed methods is demonstrated by numerical simulation. It is shown that it is possible to restore the strain dependence on time in the range ±1000 μϵ or more from simultaneously measured power dependencies reflected by the fiber Bragg grating using common fiber-optic components. The case of sequential registration of reflected radiation power at different wavelengths to determine the probability density of the distribution of the strain values is also considered. The results of signal processing obtained both by numerical simulation and experimentally for the case of a linear vibration are presented. The technical problems of using the proposed methods are discussed.

Fatigue damage mechanics approach to predict the end of incubation and breakthrough of leading edge protection coatings for wind turbine blades

The state of the surface of the leading edge of wind turbine blades is important for optimal aerodynamic performance. Rain erosion leads to damage and roughness on the leading edge. In this study, we present an approach to predict the level of roughness of the leading edge based on fatigue damage accumulation due to impacts of rain droplets. Impact simulations of droplets on the protective coating layer are coupled with rain erosion test data and fatigue S-N curves. Fatigue damage values are then related to surface roughness levels. An approach to extract S-N curve parameters from a rain erosion test and then make predictions for other coatings based only on the output of impact simulations is presented and tested against test data. Both the end of incubation and coating breakthrough times are predicted with this approach. Stress, strain and energy density values were used as fatigue damage indicators and the respective predictions were compared to each other. It was found that the maximum principal strain gave the best predictions and matched the experimental trends.

Subacute and long-term effects of COVID-19 on cardiac health and function in German elite athletes assessed by strain analysis: a speckle tracking echocardiography observational trial

Abstract Introduction During the COVID-19-pandemic, most elite athletes were infected with the novel severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). Initial worries of high rates of multi-organ complications including the heart and ending sporting careers were disproved by large studies. However, the effects of COVID-19 on the heart and its function in elite athletes remains unclear, especially in the prolonged post-infection follow-up and during and after return to competition. Methods In the year 2020, a cohort of 127 elite athletes (boasting an accumulated 58 Olympic and world championship medals) was recruited, 76 of them recently having undergone a SARS-CoV-2 infection. Echocardiography was conducted 1 (T0), 5 (T1) and 9 (T2) months after the infection in the infected cohort and at baseline for the control cohort. Left-ventricular global longitudinal, circumferential, and radial strain was compared cross-sectionally at baseline between athletes after a COVID-19-infection and control athletes, as well as longitudinally in the COVID-19-cohort. Results At baseline, global longitudinal strain (reported as absolute %-values) was significantly higher in the COVID-19-cohort in comparison to control-cohort (20.37 ± 1.98% vs. 19.41 ± 2.11%, respectively, p = 0.042). In the longitudinal assessment within the COVID-19-cohort the global longitudinal strain was significantly higher shortly after the infection (T0) than at the two follow-up measurements (T0: 20.37 ± 1.98%; T1: 19.34 ± 1.65%; T2: 19.30 ± 1.68% (p = 0.0052 and p = 0.0044, respectively)). No significant differences for any of the comparisons were found for circumferential or radial strain. Discussion The significantly elevated values in the COVID-19-cohort at T0 may be due to an affectation of the autonomic nervous system, which has previously been documented as a result of COVID-19-disease. No cardiac injury after COVID-19 was detected using strain analysis. All documented global longitudinal strain values were within the normal range for athletes. A return to training and competition had no deleterious effect on cardiac health in athletes after a COVID-19-infection in this trial.

Tensile Deformability of Shotcrete in Tunnel Primary Support: A Case Study

Shotcrete strain in the primary support of a tunnel will produce non-loading strain at an early age due to the influence of its own temperature change, hardening shrinkage, spraying force, and other factors, which means that current strain-monitoring results fail to reflect the real strain, and the strain value after stabilization is high. In addition, tensile strain may be evident in the final result, even exceeding the tensile warning value, but, in actuality, the on-site lining is very stable, with no cracks or damage. Therefore, it is necessary to understand the strain characteristics of shotcrete in the primary support of a tunnel. Based on the long-span tunnel project at Shishan Road Station on the Qingdao Metro Line 6, in situ and indoor pull tests of concrete strain were designed while only considering temperature change, hardening shrinkage, and spraying force. This study shows the following: (1) The strain in shotcrete is greatly affected by temperature changes, hardening shrinkage, and shotcrete force in the first three days, reaching its peak value in the second to third days, while tending to be stable at about the seventh day. (2) The real strain of the shotcrete was tested, and the warning value was adjusted from 90 με to 120 με. (3) The strain value at the third day was taken as the initial value, and the previous monitoring results were revised. The revised results align with the trends shown during real tests performed on-site, providing guidance for tunnel engineering support monitoring.

Stress Echocardiography in the Follow-Up of Young Patients with Repaired Aortic Coarctation.

Background: Aortic coarctation (CoA) is a congenital heart disease affecting 5-8% of patients, with long-term complications persisting despite successful correction. Stress echocardiography (SE) is increasingly used for evaluating cardiac function under stress, yet its role in repaired CoA remains under-explored. Objective: This study aimed to assess the predictive value of SE and myocardial strain in repaired CoA patients with a history of hypertension without significant gradients or with borderline gradients at rest. Methods: Between June 2020 and March 2024, we enrolled 35 consecutive CoA patients with successful repairs and either a history of hypertension or borderline Doppler gradients. Baseline and peak exercise echocardiographic measurements, including left ventricular mass index (LVMi) and global longitudinal strain (LVGLS), were recorded. Patients were followed for up to 4 years. Results: At baseline, the positive SE group had higher systolic blood pressure (SBP) and diastolic blood pressure (DBP) compared to the negative SE group. The positive SE group also exhibited significantly higher basal and peak trans-isthmic gradients. Positive SE was found in 45.7% of patients, with 68.7% of these requiring re-intervention during follow-up. A peak trans-isthmic gradient > 61 mmHg during exercise predicted recoarctation with 100% sensitivity and 71% specificity (AUC = 0.836, p < 0.004). Conclusions: SE identifies at-risk patients post-CoA repair, aiding in early intervention. A peak trans-isthmic gradient > 61 mmHg during exercise is a strong predictor of recoarctation. These findings support incorporating SE into routine follow-up protocols for CoA patients, particularly those with a history of hypertension and borderline gradients, to improve long-term outcomes and quality of life.

FRACTURE MECHANISM ANALYSIS OF HIGH-DENSITY FIBREBOARD BASED ON DIGITAL IMAGE CORRELATION TECHNOLOGY

This paper analyses the scattering images of the bending deformation of high-density fibreboards based on the digital image correlation (DIC) technique, so as to study its mechanical deformation law. Three-point bending tests were carried out on fibreboards using a mechanical testing machine with a non-contact measuring system. The measured values of the displacements of the grid nodes in the region of interest (ROI) were combined with the Moving least squares (MLS) method to construct the strains of the high-density fibreboards at different loading forces, thus deriving the strain values of the fibreboards during the bending deformation process. To further analyze its force deformation mechanism, this paper used a portable electron microscope and scanning electron microscope to analyze the damage situation at the fracture damage, and at the same time, it verified that the constructed strain field model was accurate.