Lower Strain Values Research Articles

Deformation analysis in post-hospitalised patients with moderate SARS-CoV-2 infection

Abstract Funding Acknowledgements Type of funding sources: None. Background SARS-CoV-2 infection is associated with multiple cardiac manifestations (1,2). Global longitudinal strain (GLS) by speckle tracking echocardiography (STE) is a novel transthoracic echocardiography (TTE) measure of myocardial deformation, which could early recognize subclinical cardiac injury in COVID-19 patients (3,4). Purpose We aimed to explore GLS profiles in post-hospitalized COVID-19 patients to identify features of eventual subclinical cardiac injury and to investigate the possible correlation with the severity of infection. Methods We enrolled 33 patients (mean age 59.2 ± 13, 64% men) with positive SARS-CoV-2 RT-PCR, hospitalized for moderate COVID-19 disease, with no admission to intensive care unit. Patients were submitted to TTE 1-2 months after discharge. Images were anonymised and analysed offline by two accredited cardiologists. Clinical parameters and laboratory findings from hospitalization were also collected. Acute myocardial infarction and pulmonary embolism were exclusion criteria. Results Mean duration of hospitalization was 12.9 ± 8.0 days. Study population had normal systolic function with a mean LV ejection fraction 58.6% (±3.6) while the majority of patients had relative low values of LV global longitudinal strain, mean 15.2% (±2.3). Arterial hypertension was present in 51.5% of patients and a history of previous myocardial infarction was referred in 6.1% of the population. Only 24.2% of patients had elevated troponin levels during the previous in-hospital period (mean maximal value of hs-troponin was 18.1 ±16.6 pg/mL) whereas 81.8% had abnormal D-Dimers values (mean 2424 μg /L, range ±2825) and 93.1% had high hs-CRP values (138.2 ±92.0 mg/L) . Duration of hospitalization had strong significant correlation with D-Dimers (rho: 0.708, p: <0.001) and hs CRP (rho:0383, p:0.028) and marginal association with troponin ( rho: 0.335, p:0.056). Moreover, global longitudinal strain showed significant association with duration of hospitalization (rho:-0.545, p: 0.007). Traditional systolic indices as LVEF and the various diastolic parameters showed no significant association with severity of disease reflected by the duration of hospitalization and the other clinical and laboratory biomarkers. Conclusion Cardiac manifestations of SARS-CoV-2 infections could be present in mild to moderate disease and seems to associate with the severity of infection. The novel echocardiographic parameters such as GLS could add valuable information and identify possible subclinical cardiac injury often unrecognized by traditional TTE examination.

Strain mapping of GaN substrates and epitaxial layers used for power electronic devices by synchrotron X-ray rocking curve topography

Strain and tilt maps of gallium nitride (GaN) materials including substrates, ion-implanted and annealed epilayers, and etched and regrown epilayers by different etching methods have been generated from synchrotron X-ray rocking curve topography. The strain map of the ammonothermal grown GaN substrate shows uniform low strain values, while that of the patterned hydride vapor phase epitaxy (HVPE) grown substrate shows high strain centers as well as uniformly distributed low strain between them. Strain variations within the as-implanted wafers and the annealed wafers are similar, while the tilt levels are significantly decreased for the annealed wafers. The inductively coupled plasma (ICP) etched and then regrown sample gives rise to the significant variations in strain values within the imaged region, while using tertiary butyl chloride (TBCl) to etch the sample does not affect the strain distribution compared to the continuously grown sample without etching and can remove some damage from a preceding ICP etching process.

Optimization and characterization of soybean oil-carnauba wax oleogel

Oleogel formulation based on soybean oil – carnauba wax was optimized using response surface methodology to achieve the desired oil binding capacity (OBC), textural and rheological attributes. Highly significant factors affecting the preparation of oleogel were the heating temperature and wax concentration. The best formulation was obtained at - carnauba wax: 8%, heating temperature: 92 °C, and storage temperature: 10.7 °C. The optimized oleogel had a high OBC (97.31%) and showed a shear-thinning behavior (n < 1). Amplitude sweep revealed that at low strain values the gel is stable and cross-over point occurred at 361.4 ± 0.6 Pa with a strain of 12.01 ± 0.2%. The frequency sweep showed that oleogel had a very low-frequency dependence. The oleogel FTIR spectra showed that the gel network formed via physical entanglements without any changes in its chemical properties. The spectrum of oil and oleogels exhibited specific peaks at 2922, 2855, 1743, 1460, 1159, and 718 cm-1. According to the DSC results, the oleogel had a single, broad melting peak with a melting temperature of about 75 °C. The smoke point of the oleogel (283 ± 2 °C) was higher than oil (232 ± 0.4 °C), which indicates its suitability as a frying medium.

Comprehensive echocardiographic and speckle tracking strain analysis in rheumatic mitral stenosis patients before and after transvenous mitral commissurotomy.

Percutaneous Transvenous Mitral Commissurotomy (PTMC) is the first line treatment for rheumatic mitral stenosis (MS). We sought to evaluate (1) changes in 2-dimensional (2D) echocardiographic and strain values and (2) differences in these values for patients in atrial fibrillation (AF) and sinus rhythm (SR) pre, immediately and 6months post PTMC. Retrospective study of 136 patients who underwent PTMC between 2011 and 2021. We analyzed their 2D echocardiogram, Global Longitudinal Strain (GLS), Left Atrial Reservoir Strain (LAr-S) and Right Ventricle Free Wall Strain (RVFW-S) pre, immediately and 6months post PTMC. At 6months, mitral valve area increases from 0.94 ± 0.23cm2 to 1.50 ± 0.42cm2. Ejection fraction (EF) did not change post PTMC (pre; 55.56 ± 6.62%, immediate; 56.68 ± 7.83%, 6months; 56.28 ± 7.00%, p = 0.218). Even though EF is preserved, GLS is lower pre-procedure; -11.52 ± 3.74% with significant improvement at 6months; -15.16 ± 4.28% (p < 0.001). Tricuspid annular plane systolic excursion (TAPSE) improved at 6months from 1.95 ± 0.43 to 2.11 ± 0.49 (p = 0.004). RVFW-S increases at 6months from -17.37 ± 6.03% to -19.75 ± 7.19% (p = 0.011). LAr-S improved from 11.23 ± 6.83% pre PTMC to 16.80 ± 8.82% at 6months (p < 0.001) post PTMC. Pre-procedure patients with AF have lower strain values (More LV, RV and LA dysfunction) with statistically significant difference for LAr-S (p < 0.001), GLS (p < 0.001) and RVFW-S (p < 0.001) than patients in SR. Patients with severe rheumatic MS have subclinical left and right ventricle dysfunction despite preserved EF and relatively normal TAPSE with significant improvement seen at 6months post PTMC. AF patients have lower baseline strain values than SR patients.

Evaluation of comprehensive myocardial contractility in children with Kawasaki disease by cardiac magnetic resonance in a large single center.

Children with Kawasaki disease (KD) and coronary artery lesions (CALs) can develop myocardial ischemia, fibrosis, and abnormal contractility. We aimed to assess the association between myocardial mechanical deformation with myocardial fibrosis, ischemia, and CALs. In total, 76 KD and 20 healthy volunteers received cardiac magnetic resonance (CMR). Peak systolic left ventricular (LV) longitudinal, radial, and circumferential strain and strain rate [LV strain longitudinal (LVSL), LV strain radial (LVSR), LV strain circumferential (LVSC), LV strain rate longitudinal (LVSRL), LV strain rate radial (LVSRR), and LV strain rate circumferential (LVSRC)], along with late gadolinium enhancement (LGE), perfusion deficit, and CALs in related segments were analyzed. The KD group was subdivided by CALs, perfusion, and LGE results, and strain results were compared with controls and in subgroups. Cardiac fibrosis and ischemia were not confined to the territory of CALs. In a global analysis, strain and strain rates were lower in the KD group, especially in the subgroup with LGE and perfusion deficit. In segmental analysis, LVSR, LVSC, LVSL, and LVSRR decreased in the giant aneurysm group, and a lower LVSR (20.369%±10.603% vs. 26.071%±12.349%) and LVSC (-13.37%±5.365% vs. -15.847%±5.778%) were observed in thrombosed segments. The strain and strain rate were all lower in segments with LGE and perfusion deficit, and no obvious difference was found between groups with and without stenosis. LVSR had a better ability to identify giant aneurysm, thrombosis, stenosis, perfusion deficit, and LGE. We detected lower strain values in KD patients, which was more pronounced in segments with aneurysm, thrombi, LGE, and perfusion deficit. LVSR is useful to discern patients with higher risk.

Graphite-Based Bioinspired Piezoresistive Soft Strain Sensors with Performance Optimized for Low Strain Values.

This paper presents the custom-made graphite-based piezoresistive strain sensor with gecko foot-inspired macroscopic features realized using a Velcro tape on Ecoflex substrate. The Velcro-based design provides an inexpensive and easy approach for the development of soft sensors with appreciable improvement in the performance even at low strain values. The sensor demonstrated excellent response (sensitivity of ∼16 500%, gauge factor of ∼3800) for 24% linear strain. The fabricated device showed a high gauge factor (>100) even for very low strain values. The sensor has been extensively characterized with a view to potentially use in soft robotics applications where high performance is needed at lower strain values. It is observed that the piezoresistive behavior of strain sensors is governed by several factors such as the supporting elastic medium, architecture of the strain sensor, material properties, strain rate and deformation sequence, and direction.

Shifting LED emission from blue to the green gap spectral range using In0.12Ga0.88N relaxed templates

In y Ga 1-y N templates are grown with y ≤ 13.5% and a few nm surface roughness . These templates are used successfully to address two of the main issues facing long wavelength emitting LEDs, mainly the low growth temperature and high values of strain in the quantum wells (QWs). In this work, three LED structures are investigated: the first is a blue LED grown on GaN, the second and third are green LEDs grown on relaxed In y Ga 1-y N templates with y of about 10% and 12%, respectively. The same multiple quantum wells (MQWs) were used in the three LED structures, with the same well width, barrier width, and growth temperature. The reduced strain in the QWs due to the use of InGaN templates enhances the indium incorporation rate in the QWs. Red shift in emission wavelength of about 100 nm, from 470 nm to 570 nm, was achieved, at low injection current. Optical output power and external quantum efficiency (EQE) measurements showed that at high level of current injection, performance of the blue LED is about twice of the green emitting LEDs on InGaN templates. The current results indicate the potential of the InGaN template approach, with high values of y , in addressing problems facing long wavelength InGaN LEDs. • Relaxed InGaN templates are used to shift blue LED emission from blue to the green gap spectral range. • Indium content>10% shows surface roughness of few nanometers and pit density in the 10 7 cm −2 to the mid 10 8 cm −2 range. • Performance of the blue the blue LED on GaN is about twice that of green LED on InGaN templates.

Comparison between Nondedicated and Novel Dedicated Tracking Tool for Right Ventricular and Left Atrial Strain

Recently, dedicated speckle-tracking solutions for right ventricular (RV) and left atrial (LA) strain assessment have become commercially available. The purpose of this study was to assess the level of agreement between nondedicated (left ventricular [LV] tracking software) and novel dedicated tracking software for RV and LA strain. In 200 patients with various cardiovascular pathologies, we measured global longitudinal strain (GLS), free wall strain (FWS), and segmental values, as well as LA strain during reservoir, conduit, and contraction phases, by using the (1) LV-tracking software and (2) the novel dedicated tracking software for RV or LA strain analysis. Agreement between corresponding measurements obtained with the LV and dedicated RV or LA software was determined by using mean absolute difference (MAD) and Bland-Altman test. The intra- and interobserver reproducibility related to the nondedicated and novel dedicated tracking software was tested in 30 randomly selected subjects. The dedicated RV-tracking software provided slightly lower strain values without reaching statistical significance. The agreement between software was best for RV GLS (MAD, 2.4±1.8) and significantly poorer for segmental values (MAD ranging from 4.5±3.8 to 5.1±4.0; analysis of variance, P<.05). The intra- and interobserver reproducibility for RV measurements was similar with both software (P>.05 for all parameters). Left atrial mean values showed no statistical difference when obtained with the two tracking tools. The use of LA dedicated tracking software increased significantly the intra- and interobserver reproducibility for LA strain during reservoir and atrial contraction (P<.01 for both). Our results suggest that the choice of tracking software does not significantly impact RV strain measurements. Nonetheless, the use of the same tracking software is recommended when performing serial measurements. The use of the dedicated software for LA strain analysis significantly improved the intra- and interobserver reproducibility.

Multilayer global longitudinal strain assessment of subclinical myocardial dysfunction related to insulin resistance

Abstract Myocardial tissue is sensitive to insulin resistance (IR) due to its interactions with insulin levels. Previous studies demonstrated that heart failure prevalence was higher in IR patients. Evaluation of myocardial deformation by multilayer global longitudinal strain (MGLS) might provide more information about IR related left ventricular dysfunction. In this study, we aimed to investigate subclinical LV dysfunction with MGLS in patients with IR. The study was designed as a prospective cross-sectional study. The present study included 64 patients with IR(+), and 54 subjects without IR(−) prospectively. The homeostasis model of insulin resistance (HOMA-IR) was used to quantify insulin resistance. Specific analysis for endocardial, mid-myocardial and epicardial layers were performed by two-dimensional (2D) speckle tracking echocardiography (STE) for multilayer global longitudinal strain. MGLS (Endocard-Mid-myocard-Epicard) values were significantly lower in the IR(+) group compared to IR(−) group ((GLS-endocard; −15.1±1.5 vs. −18.7±1.3, p&amp;lt;0.001), (GLS-mid-myocard; −16.0±2.0 vs. −18.0±2.0, p&amp;lt;0.001), (GLS-epicard; −17.0±1.7 vs. −18.01±1.94, p=0.004)). GLS-endocard levels were significantly and positively correlated with HOMA-IR levels (r=0.643, p&amp;lt;0.001). HOMA-IR and age were found to be independent factors in detecting a decrease in GLS-endocard level in regression analysis. In conclusion, our data reveal that IR(+) patients had significantly lower strain values compared to IR(−) group. Besides, we presented that the HOMAIR value was an independent predictor of subclinical left ventricular dysfunction. Funding Acknowledgement Type of funding sources: None.

Auto combustion synthesis and characterization of Co doped ZnO nanoparticles with boosted photocatalytic performance

In this report, pure ZnO and Co doped ZnO (1, 2.5, 5, 7.5 wt% of Co) nanoparticles were synthesized by using one-pot flash combustion synthesis technique. Structural, morphological, optical and photocatalytic properties of the prepared samples were analyzed by using different characterization techniques. The X-ray diffraction results shows the pure ZnO and Co:ZnO samples exhibits hexagonal wurtzite structure having preferential growth along the (101) plane without the presence of secondary phase impurities. The crystalline size of the 7.5% Co:ZnO sample was found to be higher with a value of 27.14 nm with low dislocation density and strain values of 1.36 × 10−3 and 4.38 × 10−3, respectively compared to the other prepared samples. The morphology of the prepared samples were obtained using FESEM analysis which revealed a non-uniform spherical shaped nanoparticles for pure ZnO and the morphology becomes uniform with the incorporation of the Co dopants. The e-mapping and the EDX results confirms the presence of Zn, O and Co elements. UV–Vis. absorption spectrum revealed that the inclusion of Co dopants in ZnO incorporation leads to higher absorption and decrease in band gap. The band gap values of ZnO are noticed to be reduced from 3.27 eV 2.81 eV with Co doping from 0 to 7.5 wt%. Photocatalytic performance of the prepared samples was evaluated in the decolourization reaction of methyl green aqueous solution under the illumination. The prepared Co doped ZnO samples exhibited several times higher photocatalytic activity than bare ZnO. The kinetic model was proposed and the rate constant for the decolourization reactions was calculated. The best performed sample was 5 wt% Co, in which the rate constant was 2.6 times higher than that of bare ZnO.

Home-based exercise program improves normal right ventricle function in renal transplant recipients.

Right ventricular function is strongly associated with clinical outcomes in populations at high cardiovascular risk. Renal Transplant Recipients have multiple coexisting comorbidities potentially involved in the biventricular dysfunction including the right ventricular chamber. Speckle tracking echocardiography is recently used to investigate the normal function of this chamber. The study aims to verify whether global longitudinal strain carries clinical and prognosis implications in the renal transplant recipients during 1 year of regular unsupervised physical activity and compared to a control group. A group of 50 transplant recipients, aged 49.6±11.5 was submitted for 1 year to a moderate intensity of mixed exercise. All the subjects were followed by echocardiographic exam every 6 months, only 25 subjects with a high quality of image were investigated by 2D Speckle tracking strain analysis with the measurement calculated at T0, T6, and T12 months. Renal transplant recipients started with low values of right ventricle global longitudinal strain compared to health controls; it increased significantly (P<0.01) after 12 months of exercise, restoring the normal range. Moderate intensity of physical exercise, despite unsupervised, support a normal RV ventricular performance in renal transplant recipients' strain analysis contribute to plan a correct follow-up, with prognostic impact in these patients practicing physical exercise.

Fabrication and testing of re-entrant auxetic samples and sensor: Numerically and experimentally

Auxetic structures (negative Poisson’s ratio) are a group of materials that expand (contract) under tensile (compression) longitudinal loading. In this work, the effect of re-entrant auxetic structure geometry on Poisson’s ratio was investigated under large tensile loading experimentally and numerically and showed that the location and stiffness of rotation joints are two new important parameters affecting the value of Poisson’s ratio. Poisson's ratio increases as the rotation joints tighten and move away from the center of the structure. Therefore, by changing the location and stiffness of the rotation joints, it will be easy to obtain re-entrant auxetic structures with different Poisson's ratios, which makes it possible to build piezoresistant auxetic sensors with different sensitivities. A highly sensitive, stretchable piezoresistant auxetic sensor made of silicon rubber and chopped carbon fibers is proposed for low strain values. The main feature of this sensor is its high sensitivity for strains less than 6%, which previous works have been unable to detect this range of strains. Shifting strain is the value of strain in which the Poisson's ratio of the structure changes from negative to positive. The provided auxetic sensor performs exceptionally well until the shifting strain and then performs as conventional sensors. This improvement in sensing performance is about 150% (in terms of gauge factor).

Contractile Differences Detected by Speckle Tracking Echocardiography in Pediatric Patients with Mitral Valve Prolapse

Mitral valve prolapse (MVP) is the most common valvar dysfunction in children. There is emerging evidence that MVP is not always a benign entity, hence identification of underlying mechanisms is pertinent to clinical management. Our group previously identified a ventricular contraction abnormality named end-systolic basal eversion (ESBE) in adults that contributed to MVP. The aim of this study was to evaluate regional circumferential strain in pediatric patients with MVP and ESBE compared to normal controls. Left ventricular circumferential strain was assessed in 16 pediatric patients referred for clinical echocardiographic examination with MVP and ESBE (MVP group) and compared to age-gender-matched healthy subjects. ESBE has been previously described as late systolic bileaflet mitral valve prolapse, papillary traction, and concomitant late systolic outward movement of the basal inferior myocardium. The mean age of the MVP group was 13.8 ± 4.6year and 75% were female. All patients with MVP and controls had qualitatively normal systolic cardiac function. The MVP group had significantly lower regional strain values for 11/16 of the segments including all 6 basal segments. Importantly, the basal inferior (- 17.02 ± 8.32% vs. - 26.10 ± 3.18, p = 0.001) and basal inferolateral (- 19.53 ± 9.76 vs. - 26.10 ± 3.18, p = 0.03) had the lowest strain values compared to the average of all other segments suggesting weaker contraction in the basal inferior segments. Pediatric patients with MVP and ESBE are subject to a similar left ventricular mechanical dysfunction previously described in adults. ESBE was evident by decreased basal circumferential strain values. These findings denoted weaker contraction which is believed to propagate the late systolic outward movement of the basal ventricular myocardium.

Using digital image correlation for in situ strain and damage monitoring in hybrid fiber laminates under in‐plane shear loading

AbstractUtilizing resistive strain gauges for V‐notch shear tests in fiber reinforced laminates is usually limited to low strain values due to technical uncertainties imposed by the measurement technique and also the progressive damage development in the notched region of the composite. Therefore, this study investigates an alternative approach by using digital image correlation system and further comparison with resistive strain gauge to identify the effect of heterogenous nature of damage development on measurement results. Moreover, glass/carbon fiber hybrid and non‐hybrid laminates are tested in two major directions through the same approach to determine the effect of stacking sequence in spatial microdamage accumulation. It is shown that tailoring appropriate region of interest for full field strain measurement at various stages of loading enables proper monitoring of microdamage accumulation and thereby delivers a precise stress–strain behavior for hybrid and non‐hybrid laminates. Comparison of the strain maps for hybrid laminates tested in 0° direction, shows that the presence of carbon plies at the surface results in uniform strain distribution between the notches of the test sample. In contrast, a non‐homogeneous strain map with separate regions of high strain gradient are observed for hybrid specimens with glass plies at surface, which can cause underestimation of average shear strain by resistive strain gauges. On the other hand, it is shown that strain maps for hybrid samples tested at 90° configuration is analogous regardless of the stacking sequence, and damage accumulation in these samples is most likely related to relative volume fraction of various fibers in hybrid laminate.

Left Ventricular Function Assessment of Patients with Postoperative Ventricular Septal Defect Closure by Longitudinal Strain on Two-Dimensional Echocardiography 1 Year after Surgery

Background: Patients with large perimembranous ventricular septal defects (pm-VSDs) undergo surgical repair with prosthetic material during infancy. However, the effect of the presence of akinetic patch in the ventricular septum on the left ventricular (LV) mechanical synchrony and ventricular function has not been studied. In our study, we assessed LV function in postoperative pm-VSD closure patients on two-dimensional (2D) echocardiography (echo) after 1 year of surgery using biplane Simspon's method, fractional shortening (FS), and global longitudinal strain (GLS) to assess the regional strain pattern. Methods: This was a a single-institution observational study. Patients following up 1 year after surgical ventricular septal defect closure at our institute were enrolled. On follow-up, detailed 2D echo was done with special emphasis on left atrial size, LV size (by M-mode), and presence of any residual shunt. LV function was assessed using biplane Simpson's method and longitudinal strain on 2D echo. GLS was measured in three standard apical views. Results: Of the 121 patients enrolled, 101 patients fulfilling the inclusion and exclusion criteria were analyzed. Of these 101 patients, 75.2% were males. The median age at follow-up after surgery was 3.67 ± 2.7 years. About 92.1% of patients did not have residual VSD lesion. No patient had pulmonary arterial hypertension. All except one patient had normal ventricular function. Patients with ventricular dysfunction had LV ejection fraction (LVEF) of 47%, GLS –17.4%, and FS −20.5%. The mean values of FS, LVEF, and GLS were 32.0 ± 5.28%, 62.2% ± 4.2%, and −26.53 ± 2.93%, respectively, in pm-VSD closure patients. Regional strain pattern analysis showed significantly lower strain values in basal anteroseptal segment with a mean of −21.4 ± 2.7%. FS and GLS were noted to have significant correlation with each other (P = 0.01) and LVEF by biplane Simpson's method and GLS had significant correlation with each other (P = 0.0001). Conclusions: GLS has strong correlation with LVEF by Simson's method and FS. Basal anteroseptal segment in pm-VSD patients had significantly lower strain values compared to other segments. There is no significant correlation between age at surgery and GLS in pm-VSD closure patients who were operated within 1 year of age. The type of VSD closure does not have significant influence on GLS.

Optimized strain properties with small hysteresis in BNT-based ceramics with ergodic relaxor state

Electric field-induced high strain with small hysteresis and good temperature stability is necessary for piezoactuators devices. Most of previous works focus on the giant strain achieved in Bi0.5Na0.5TiO3 (BNT)-based ceramics through electric field-induced transition from nonergodic relaxor to ferroelectric state, while the high remnant strain or/and large hysteresis are always accompanying. In this work, through enhancing the local polarization by rare earth ions doping (e.g., La3+), we propose to improve the strain properties of BNT-based lead-free ceramics with ergodic relaxor state which displays the near zero remnant strain, small hysteresis, high temperature stability but the low strain value. The addition of La3+ would not change the ergodic relaxor state, but can improve the short-range correlation of local polar nanoregions, cut down the critical electric field of transition between relaxor and ferroelectric states, and elevate the electrostrictive effect of ceramics. Finally, high strain of ∼0.3 % with low hysteresis of ∼8−30 % was obtained in the broad temperature range from room temperature to 100 °C, which is superior to previous BNT-based ceramics and other lead-based/lead-free ceramics. This work affords a paradigm to regulate the ergodic relaxor state to optimize the strain properties, which give the significant guide for strain developments.

Dynamic recrystallization's role in strength-ductility trade-off in polycrystalline Fe–Cr–Ni stainless steels produced by laser powder bed fusion

Abstract The deformation mechanisms and reasons for excellent ductility in additively manufactured Fe–Cr–Ni stainless steels by laser powder bed fusion (L-PBF) were disclosed by an interrupted tensile test at room temperature, electron backscattered diffraction, and transmission electron microscopy. The results showed dislocation (DL) slip starts at low strain values, resulting in a rearrangement of DLs and reorientation of low angle grain boundaries along with shear bands. At higher strain values, deformation twins intersect with other twins, DLs, stacking faults, and grain boundaries. In addition to planar slip and twining-induced plasticity (TWIP), dynamic recrystallization (DRX) was observed during deformation due to the formation of a high density of DLs during L-PBF. Different deformation and DRX mechanisms are disclosed in detail, including their origin, sequences, and interplay. The results presented in this paper opens a new operation window for the other types of TWIP steels, such as medium and high Mn steels to be manufactured by the L-PBF to maximize their energy impact.

The Use of Contravariant Tensors to Model Anisotropic Soft Tissues

Biological tissues have been shown to behave isotropically at lower strain values, while at higher strains the fibers embedded in the tissue straighten and tend to take up the load. Thus, the anisotropy induced at higher loads can be mathematically modeled by incorporating the strains experienced by the fibers. From histological studies on soft tissues it is evident that for a wide range of tissues the fibers have an oblique mean orientation about the physiological loading directions. Thus, we require a mathematical framework of tensors defined in nonorthogonal basis to capture the direction-dependent response of fibers under high induced loads. In this work, we propose a novel approach to determine the fiber strains with the aid of the contravariant tensors defined in an oblique coordinate system. To determine the fiber strains, we introduce a fourth-order contravariant fiber orientation transformation tensor. The approach helps us successfully in determining the fiber strains, for a family of symmetrically and asymmetrically oriented fibers, with the aid of a single anisotropic invariant. The proposed model was fitted with the experimental data from literature to determine the corresponding material parameters.

Prognostic Utility of Echocardiographic Atrial and Ventricular Strain Imaging in Patients With Cardiac Amyloidosis

ObjectivesThe prognostic value of echocardiographic atrial and ventricular strain imaging in patients with biopsy-proven cardiac amyloidosis was assessed. BackgroundAlthough left ventricular global longitudinal strain (GLS) is known to be predictive of outcome, the additive prognostic value of left (LA), right atrial (RA), and right ventricular (RV) strain is unclear. MethodsOne hundred thirty-six patients with cardiac amyloidosis and available follow-up data were studied by endomyocardial biopsy, noncardiac biopsy with supportive cardiac imaging, or autopsy confirmation. One hundred nine patients (80%) had light-chain, 23 (17%) had transthyretin, and 4 (3%) had amyloid A type cardiac amyloidosis. GLS, RV free wall strain, peak longitudinal LA strain, and peak longitudinal RA strain were measured from apical views. Clinical and routine echocardiographic data were compared. All-cause mortality was followed (median 5 years). ResultsStrain data were feasible for GLS in 127 (93%), LA strain in 119 (88%), RA strain in 117 (86%), and RV strain in 102 (75%). Strain values from all 4 chambers were significantly associated with survival. Hazard ratio (HR) and 95% confidence interval (CI) for low median strain values were as follows: GLS, HR: 2.3; 95% CI: 1.3 to 3.8 (p < 0.01); LA strain, HR: 7.5; 95% CI: 3.8 to 14.7 (p < 0.001); RA strain, HR: 3.5; 95% CI: 2.0 to 6.2 (p < 0.001); and RV free wall strain, HR: 2.8; 95% CI: 1.5 to 5.1 (p < 0.001). Peak longitudinal LA strain and RV strain remained independently associated with survival in multivariable analysis. Peak LA strain had the strongest association with survival (p < 0.001), and LA strain combined with GLS and RV free wall strain had the highest prognostic value (p < 0.001). ConclusionsStrain data from all 4 chambers had important prognostic associations with survival in patients with biopsy-confirmed cardiac amyloidosis. Peak longitudinal LA strain was particularly associated with prognosis. Atrial and ventricular strain have promise for clinical utility.

Spin-thermoelectric transport in nonuniform strained zigzag graphene nanoribbons

We study a nonuniform strain in zigzag graphene nanoribbons for producing the spin-thermoelectric effects, using the mean-field Hubbard approximation and a Green's function approach. Our theoretical results show that a sinusoidal-shaped inhomogeneous strain with electron-electron interaction could induce a different effect on each edge of zigzag nanoribbons and finally generate a spin semiconductor with a tunable spin-dependent band gap. The strength of strain also controls the magnitude of magnetization in each edge. Interestingly, pure spin current and a giant spin Seebeck coefficient can be produced even at low values of strain by applying a thermal gradient and without magnetic elements. These results pave a practical way toward improved design for spin-thermoelectric applications through strain engineering.