Apical Sparing of Longitudinal Strain as a Specific Pattern of Myocardial Fibrosis in Patients with Severe Left Ventricular Hypertrophy: A Comparison between Deformation Imaging and Histological Findings.

Objectives: This study aimed to investigate the correlation between apical sparing of longitudinal strain (LS), as measured by speckle-tracking echocardiography (STE), and the histological presence of myocardial fibrosis (MF), in patients with hypertrophic obstructive cardiomyopathy (HOCM). Methods: Twenty-seven HOCM patients who underwent elective Morrow procedures +/- aortic valve replacement (AVR) were included. All patients had standard echocardiography, with STE pre- and post-operatively. Intraoperative probes of the interventricular septum were sent for histological analysis. Correlation of different regional LS patterns with the histological findings of MF and with clinical outcome were analyzed. In addition, a logistic regression and ROC analysis were performed. Results: All patients underwent the Morrow procedure for HOCM, with 33.3% also undergoing AVR. A total of 74.1% showed evidence of MF in the histological analysis. Patients with MF had significantly lower GLS than patients without MF (-12.7 ± 2.7% vs. -23.0 ± 5.7%, p < 0.001). The LS in patients with MF was significantly lower at the basal regions of the LV segments and increased significantly towards the apex as compared to the patients without MF (mean basal-strain %: -10.6 ± 2.6 vs. -17.3 ± 4.6, p < 0.001; mean apical strain %: -21.8 ± 4.8 vs. -16.7 ± 5.6, p = 0.032). In the logistic regression, only the GLS remained as an independent predictor of MF with an Odds ratio of 1.07 (95%-CI: 1.05-1.09, p < 0.001). Conclusions: Our study highlights the significant correlation between GLS and MF in HOCM patients. These findings contribute to the growing understanding of MF in HOCM and may inform future approaches to patient management and risk stratification.

Blood eosinophil count is associated with early atherosclerotic artery changes in asthma.

OBJECTIVE: Asthma is linked to atherosclerosis, yet the underlying mediators remain elusive. Eosinophils may contribute to both asthmatic and atherosclerotic inflammation. Hence, this study aimed to explore the potential associations of eosinophils with artery changes among patients with asthma. METHODS: We assessed strain values of the common carotid arteries (CCAs) via vascular speckle tracking and compared asthma patients with low (< 300/µl) and high (≥ 300/µl) blood eosinophil counts (BEC). RESULTS: We enrolled 100 patients, 42 with a BEC of < 300 and 58 with a BEC of ≥ 300 n/µl. Patients with high BEC exhibited more severe disease, characterized, e.g., by a higher frequency of acute exacerbations (1.3 ± 2.1 vs. 2.6 ± 2.4 n/year, p = 0.005). Both groups presented similar profiles in terms of conventional cardiovascular risk. The high BEC group demonstrated elevated arterial stiffness, reflected by reduced radial strain (mean radial strain of the right CCA: 2.7 ± 1.4% for BEC ≥ 300 n/µl vs. 3.5 ± 1.7% for BEC < 300 n/µl, p = 0.008; left CCA: 2.6 ± 1.4% vs. 4.1 ± 2.2%, p < 0.001). A weak yet statistically significant negative correlation was observed between BEC and radial strain for the right CCA (R2 = 0.131, b=-0.001, p = 0.001) and left CCA (R2 = 0.086, b=-0.001, p = 0.015). However, the prevalence of cerebrovascular disease was similar in both groups (31,0% vs. 50,0%, p = 0.057). CONCLUSION: We identified a correlation between BEC and vascular stiffness, which supports the hypothesis that eosinophils may promote atherosclerosis. CLINICAL TRIAL NUMBER: Due to the exploratory and predominantly retrospective nature of the study, trial registration was not conducted. The only prospective procedure conducted was the angiological sonography to evaluate the current state. No ensuing health-related interventions were performed specifically for this study.

Advanced myocardial characterization and function with cardiac CT.

Non-invasive imaging with characterization and quantification of the myocardium with computed tomography (CT) became feasible owing to recent technical developments in CT technology. Cardiac CT can serve as an alternative modality when cardiac magnetic resonance imaging and/or echocardiography are contraindicated, not feasible, inconclusive, or non-diagnostic. This review summarizes the current and potential future role of cardiac CT for myocardial characterization including a summary of late enhancement techniques, extracellular volume quantification, and strain analysis. In addition, this review highlights potential fields for research about myocardial characterization with CT to possibly include it in clinical routine in the future.

The development of bend clamp of carbon-based fiber offshore gas lift pipelines: A primary experimental approach.

The work reports the proposed development of the laminated carbon fiber-reinforced polymer composites (CFRP), at a uniaxial angle as a primary bend clamp material assembly of the offshore gas lift pipelines. Generally, the clamps are utilized to repair the defect of the metallic pipelines due to their practical and mechanical strength. The existing bend clamp model poses challenges especially when applied to the J-tube bending side due to mechanical buckling and corrosion. This study evaluates the effect of laminated CFRP subjected to uniform uniaxial and in-plane compression on API 5 L X52. Several tests, including tensile, bend, and impact tests, are chosen to assess the effect of multiple and thick carbon layers to improve the clamp's mechanical properties. Scanning electronic microscope (SEM) intends to reveal the surface characterization of carbon fiber clamp. The result shows that laminated carbon fiber increases the durability and mechanical properties of the bend clamp for two weeks. The tensile test result shows that the uniaxial orientation has the highest tensile strength of about 2000N and is affected by the strong interfacial bond between the fiber and metal layers. The high impact energy of 2242 ± 0.001 J of the same orientation shows the stability of the clamp under unprecedented dynamic load and enhances the safety. The SEM result at uniaxial shows the resistance towards fracture has increased and was initiated from the air pocket in the composite.

Effect of Atrial Septostomy on Left Ventricular Function in Pediatric Dilated Cardiomyopathy Requiring ECMO.

Balloon atrial septostomy (BAS) reduces left ventricular (LV) hypertension during extracorporeal membrane oxygenation (ECMO). However, the acute effect of BAS on LV function as measured by echocardiography is unknown. This was a Retrospective analysis of clinical outcome, LV dimensions, and LV function in dilated cardiomyopathy patients 0-18 years old who underwent BAS on ECMO. In 13 patients with median (IQR) age of 2.3 (0.6-10.9) years, there were no differences in clinical markers of cardiac output at intervals between 12 h before and 6 days after BAS. In addition, BAS was associated with a low rate of periprocedural complications (0.0%), acute kidney injury (7.7%), and worsening radiographic pulmonary vascular congestion (30.7%). There was a significant worsening in LV end systolic diameter (LVIDs; 3.6 [2.9-4.8] cm vs 4.2 [3.2-5.6] cm vs 3.3 [2.6-4.6] cm, p = 0.025), LV end systolic posterior wall thickness (LVPWs; 0.7 [0.5-0.9] cm vs 0.6 [0.5-0.9] cm vs 0.8 [0.6-1.2] cm, p = 0.038), fractional shortening (FS; 17.6% [8.4-20.4%] vs 6.3% [2.0-9.9%] vs 13.2% [3.6-23.4%], p = 0.013), and ejection fraction (EF; 13.1% [8.7-18.9%] vs 5.3% [2.5-11.1%] vs 9.2% [6.0-16.3%], p = 0.039) following BAS that improved in approximately 1 week. There were no differences in LV global longitudinal strain following BAS. We conclude that BAS was associated with low procedural and clinical adverse event rates in our cohort. The worsening LVIDs, LVPWs, FS, and EF seen immediately after the procedure suggests that BAS causes altered loading conditions affecting LV function in pediatric patients with dilated cardiomyopathy requiring ECMO.

Reliability Assessment of Wireless Sensor Networks by Strain-Based Region Analysis for Redundancy Estimation in Measurements on the Example of an Aircraft Wing Box.

Wireless sensor networks (WSNs) are attracting increasing research interest due to their ability to monitor large areas independently. Their reliability is a crucial issue, as it is influenced by hardware, data, and energy-related factors such as loading conditions, signal attenuation, and battery lifetime. Proper selection of sensor node positions is essential to maximise system reliability during the development of products equipped with WSNs. For this purpose, this paper presents an approach to estimate WSN system reliability during the development phase based on the analysis of measurements, using strain measurements in finite element (FE) models as an example. The approach involves dividing the part under consideration into regions with similar strains using a region growing algorithm (RGA). The WSN configuration is then analysed for reliability based on data paths and measurement redundancy resulting from the sensor positions in the identified measuring regions. This methodology was tested on an exemplary WSN configuration at an aircraft wing box under bending load and found to effectively estimate the hardware perspective on system reliability. Therefore, the methodology and algorithm show potential for optimising sensor node positions to achieve better reliability results.

Assessment of Digital Image Correlation Effectiveness and Quality in Determination of Surface Strains of Hybrid Steel/Composite Structures.

The application of the digital image correlation (DIC) contactless method has extended the possibilities of reliable assessment of structure strain fields and deformations throughout the last years. However, certain weak points in the analyses using the DIC method still exist. The fluctuations of the results caused by different factors as well as certain deficiencies in the evaluation of DIC accuracy in applications for hybrid steel/composite structures with adhesive joints are one of them. In the proposed paper, the assessment of DIC accuracy based on the range of strain fluctuation is proposed. This relies on the use of a polynomial approximation imposed on the results obtained from the DIC method. Such a proposal has been used for a certain correction of the DIC solution and has been verified by the introduction of different error measures. The evaluation of DIC possibilities and accuracy are presented on the examples of the static tensile tests of adhesively bonded steel/composite joints with three different adhesives applied. The obtained results clearly show that in a non-disturbed area, very good agreement between approximated DIC and FEM results is achieved. The relative average errors in an area, determined by comparison of DIC and FEM strains, are below 15%. It is also observed that the use of approximated strains by polynomial function leads to a more accurate solution with respect to FEM results. It is concluded that DIC can be successfully applied for the analyses of hybrid steel/adhesive/composite samples, such as determination of strain fields, non-contact visual detection of faults of manufacturing and their development and influence on the whole structure behavior during the strength tests, including the elastic response of materials.

Intraoperative Assessment of Noninvasive Left Ventricular Myocardial Work Indices in Patients Undergoing Aortic Valve Replacement.

OBJECTIVE: Evaluation of noninvasive left ventricular (LV) myocardial work (MW) enables insights into cardiac contractility and efficacy beyond conventional echocardiography. However, there is limited intraoperative data on patients undergoing surgical aortic valve replacement (AVR). The aim of this study was to describe the feasibility and the intraoperative course of this technique of ventricular function assessment in these patients and compare it to conventional two (2D)- and three-dimensional (3D) echocardiographic measurements and strain analysis. DESIGN: Prospective observational study. SETTING: Single university hospital. PARTICIPANTS: Twenty-five patients scheduled for isolated AVR with preoperative preserved left and right ventricular function, sinus rhythm, without significant other heart valve disease or pulmonary hypertension, and an uneventful intraoperative course. INTERVENTIONS: Transesophageal echocardiography was performed after induction of anesthesia (T1), after termination of cardiopulmonary bypass (T2), and after sternal closure (T3). Evaluation was performed in stable hemodynamics, in sinus rhythm or atrial pacing and vasopressor support with norepinephrine ≤ 0.1 µg/kg/min. MEASUREMENTS AND MAIN RESULTS: EchoPAC v206 software (GE Vingmed Ultrasound AS, Norway) was used for analysis of 2D and 3D LV ejection fraction (EF), LV global longitudinal strain (GLS), LV global work index (GWI), LV global constructive work (GCW), LV global wasted work (GWW), and LV global work efficiency (GWE). Estimation of myocardial work was feasible in all patients. Although there was no significant difference in the values of 2D and 3D EF, GWI and GCW decreased significantly after AVR (T1 v T2, 1,647 ± 380 mmHg% v 1,021 ± 233 mmHg%, p < 0.001; T1 v T2, 2,095 ± 433 mmHg% v 1,402 ± 242 mmHg%, p < 0.001, respectively), while GWW remained unchanged (T1 v T2, 296 mmHg% [IQR 178-452) v 309 mmHg% [IQR 255-438), p = 0.97). This resulted in a decreased GWE directly after bypass (T1 v T2, 84% ± 6% v 78% ± 5%, p < 0.001), but GWE already improved at the end of surgery (T2 v T3, 78% ± 5% v 81% ± 5%, p = 0.003). There was no significant change in the values of GWI, GCW, or 2D and 3D LVEF before and after sternal closure (T2 v T3). CONCLUSION: LV MW analysis showed a reduction of LV workload after bypass in our group of patients, which was not detected by conventional echocardiographic measures. This evolving technique provides deeper insights into cardiac energetics and efficiency in the perioperative course of aortic valve replacement surgery.

Reactivity of Zinc Fingers in Oxidizing Environments: Insight from Molecular Models Through Activation Strain Analysis.

The reactivity of Zn2+ tetrahedral complexes with H2O2 was investigated in silico, as a first step in their disruption process. The substrates were chosen to represent the cores of three different zinc finger protein motifs, i. e., a Zn2+ ion coordinated to four cysteines (CCCC), to three cysteines and one histidine (CCCH), and to two cysteines and two histidines (CCHH). The cysteine and histidine ligands were further simplified to methyl thiolate and imidazole, respectively. H2O2 was chosen as an oxidizing agent due to its biological role as a metabolic product and species involved in signaling processes. The mechanism of oxidation of a coordinated cysteinate to sulfenate-κS and the trends for the different substrates were rationalized through activation strain analysis and energy decomposition analysis in the framework of scalar relativistic Density Functional Theory (DFT) calculations at ZORA-M06/TZ2P ae // ZORA-BLYP-D3(BJ)/TZ2P. CCCC is oxidized most easily, an outcome explained considering both electrostatic and orbital interactions. The isomerization to sulfenate-κO was attempted to assess whether this step may affect the ligand dissociation; however, it was found to introduce a kinetic barrier without improving the energetics of the dissociation. Lastly, ligand exchange with free thiolates and selenolates was investigated as a trigger for ligand dissociation, possibly leading to metal ejection; molecular docking simulations also support this hypothesis.

Optical coherence elastography with osmotically induced strains: Preliminary demonstration for express detection of cartilage degradation.

Optical coherence elastography (OCE) demonstrated impressive abilities for diagnosing tissue types/states using differences in their biomechanics. Usually, OCE visualizes tissue deformation induced by some additional stimulus (e.g., contact compression or auxiliary elastic-wave excitation). We propose a new variant of OCE with osmotically induced straining (OIS-OCE) and demonstrate its application to assess various stages of proteoglycan content degradation in cartilage. The information-bearing signatures in OIS-OCE are the magnitude and rate of strains caused by the application of osmotically active solutions onto the sample surface. OCE examination of the induced strains does not require special tissue preparation, the osmotic stimulation is highly reproducible, and strains are observed in noncontact mode. Several minutes suffice to obtain a conclusion. These features are promising for intraoperative method usage when express assessment of tissue state is required during surgical operations. The "waterfall" images demonstrate the development of cumulative osmotic strains in control and degraded cartilage samples.

Strain visualization using large-angle convergent-beam electron diffraction.

In this study, we report a strain visualization method using large-angle convergent-beam electron diffraction (LACBED).1 We compare the proposed method with the strain maps acquired via STEM-NBD, a combination of scanning transmission electron microscopy (STEM) and nanobeam electron diffraction (NBD). Although STEM-NBD can precisely measure the lattice parameters, it requires a large amount of data and personal computer (PC) resources to obtain a two-dimensional strain map. Deficiency lines in the transmitted disk of LACBED reflect the crystalline structure information and move, curve, or disappear in the deformed area. Properly setting the optical conditions makes it possible to acquire real-space images over a broad area in conjunction with deficiency lines on the transmitted disk. The proposed method acquires images by changing the relative position between the specimen and the deficiency line and can grasp the strain information with a small number of images. In addition, the proposed method does not require high-resolution images. It can reduce the required PC memory or storage consumption in comparison with that of STEM-NBD, which requires a high-resolution diffraction pattern (DP) from each point of the region of interest. Compared with the two-dimensional maps of LACBED and NBD, NBD could detect large distortions in the area where the deficiency line curved, moved, or disappeared. The curving or moving direction of the deficiency line is qualitatively consistent with the NBD results. If quantitative strain values are not essential, strain visualization using LACBED can be considered an effective technique. We believe that the strain information of a sample can be obtained effectively using both methods.

Improvement in right heart function following kidney transplantation in esrd patients: insights from speckle tracking echocardiography analysis.

Chronic kidney disease (CKD) is commonly associated with unfavorable cardiovascular outcomes and remains the leading cause of mortality in individuals with end-stage renal disease (ESRD). Despite substantial knowledge about the impact of CKD on the left heart, the right heart, which holds significant clinical relevance, has often been overlooked and inadequately assessed in ESRD patients who have undergone kidney transplant (KTx). This study aimed to evaluate the effects of KTx on the right heart chambers in ESRD patients. 57 adult KTx candidates were enrolled in this prospective longitudinal study, while 49 of them were included in the final assessment. Patients underwent a comprehensive cardiac assessment, including conventional echocardiography, speckle tracking echocardiography, and three-dimensional heart modeling both before and after surgery. Echocardiographic assessments showed significant increases in right ventricular (RV) ejection fraction, RV fractional area change (RVFAC), tricuspid annular plain systolic excursion, RV fractional shortening, right atrial (RA) reservoir, conduit, and booster strains, and RV global longitudinal strain (RVGLS). Moreover, significant reductions in RV end-diastolic volume (RVEDV), RV end-systolic volume (RVESV), RV stroke volume, RV end-diastolic diameter (RVEDD) in mid-cavity view, systolic pulmonary artery pressure was observed (all P values < 0.05). However, no significant difference was found in S velocity, as well as RVEDD in basal and apex-to-annulus view. Moreover, pre-KTx measurements of RVGLS, RVEDD (apex-to-annulus diameter), RV fractional shortening, and S velocity were predictors of RVGLS after KTx. RA conduit strain was also identified as a predictor of RA conduit strain after KTx. Additionally, age, RVEDV, RVESV, RVFAC, and RA reservoir strain before KTx were identified as independent predictors of RA reservoir strain after KTx. The findings of this study demonstrate a significant improvement in right heart function following KTx. Furthermore, strain analysis can provide valuable insights for predicting right heart function after KTx.

Experimental research and application of drilling and blasting with directional damage-reduction shaped charge.

In this research, a directional reduction charging structure was proposed to solve the problems caused by drilling and blasting method such as serious damage to surrounding rocks, working face low contour flatness and serious over-under break of root base c. Drilling and blasting tests, numerical calculations and field applications were designed and performed for the verification of the blasting advantages of charge structure. Test results showed that the peak positive strain along the protection direction of directional protection shaped charge was significantly smaller than that of ordinary charge, where PVC material presented the strongest effect such that the peak positive strain of specimen 1 at measuring point 4 (protection direction) was only 0.27 times that at measuring point 9 (non-protected direction). Numerical simulations indicated shaped jet formation, damage-reduction and charge penetration process and obtained the force law of cement target plate. Experimental results revealed that application of charge in tunnel controlled blasting achieved a clear controlling effect on contour line excavation. Compared with ordinary smooth blasting method, all technical indicators of the developed method were improved such that half hole mark rate was increased by about 33% and the amount of over-under break was decreased by about two times. Research results are of certain significance for the stability of surrounding reserved rocks and formation of roadway in blasting engineering and the developed method was found to be applicable to mining, shaft excavation and other projects.

Case Studies about Finite Element Modeling and Wireless Sensing of Three Pennsylvania Bridges.

Three Pennsylvanian bridges were studied using finite element and wireless sensor technology. A detailed finite element model of each bridge was created using a commercial software in order to calculate the strains generated by a load that simulates the presence of a standard truck. Pristine and damage scenarios were simulated, and the computed strains were compared to the experimental strains measured with proprietary wireless sensors during a truck test performed by companies not involved in the study presented in this article. The comparison demonstrated the accuracy of the model and the presence of a few non-critical anomalies in terms of load redistribution. In addition, the comparison proved the reliability of the wireless sensing system installed on the bridges, although some drift was observed. The structural monitoring program for the three bridges was also evaluated by processing more than two years of data streamed to a repository.

Comparative assessment of myocardial function between late premature newborns and term neonates using the 2D speckle tracking method.

Introduction: Assessment of myocardial function through speckle tracking echocardiography (STE) can bring benefits to conventional echocardiography in premature newborns, a particular vulnerable group in terms of adaptation to extra-uterine life. Furthermore, it represents a non-invasive imagistic method which can guide therapeutic approach in the hemodynamically unstable newborn. This study aims to highlight the particularities of myocardial function in late premature newborns, by conducting a comparison with a group of healthy neonates, by using STE. Methods: Conducted over a timespan of two years, this prospective study enrolled 64 term neonates and 21 premature newborns, with gestational ages ranging between 28 and 36 weeks, who prior to discharge underwent a cardiac ultrasound, involving two-dimensional image acquisitions of the apical four-chamber view of both ventricles. Afterwards, the images were offline analyzed, by using the autostrain function. Results: After segmental strain analysis, no significant discrepancies between the two groups in terms of interventricular values were found. However, left ventricle and right ventricle strain measurements differed significantly (p < 0.01), for each of the analyzed segments (basal, medial or apical). Moreover, a linear increase in interventricular (IV) basal strain with corrected gestational age progression was noted (p = 0.04). Peak global longitudinal strain (pGLS) and EF were similar between the two study groups. Premature newborns presented significantly more negative mean values of right ventricular free wall longitudinal strain (RVFWSL), (-24.19 ± 4.95 vs. -18.05 ± 5.88, p < 0.01) and of right ventricle global four chamber longitudinal strain (RV4CSL), (-19.71 ± 3.62 vs. -15.46 ± 5.59, p < 0.01), when compared to term neonates. Conclusions: The 2D STE is a reliable method for cardiac assessment of late preterm newborns. The evaluation of two-dimensional global longitudinal LV and RV strains might represent a useful tool in clinical practice. A better response of the right ventricle to the longitudinal deformation within premature neonates was noted. Thus, this study facilitates the identification of accurate reference values for this particular population segment, which will enable the evaluation of ventricular function in premature newborns with concurring disorders. Future longitudinal studies, assessing the fetal heart, could provide more insight into the development of myocardial function.

Stereo Camera Setup for 360° Digital Image Correlation to Reveal Smart Structures of Hakea Fruits.

About forty years after its first application, digital image correlation (DIC) has become an established method for measuring surface displacements and deformations of objects under stress. To date, DIC has been used in a variety of in vitro and in vivo studies to biomechanically characterise biological samples in order to reveal biomimetic principles. However, when surfaces of samples strongly deform or twist, they cannot be thoroughly traced. To overcome this challenge, different DIC setups have been developed to provide additional sensor perspectives and, thus, capture larger parts of an object's surface. Herein, we discuss current solutions for this multi-perspective DIC, and we present our own approach to a 360° DIC system based on a single stereo-camera setup. Using this setup, we are able to characterise the desiccation-driven opening mechanism of two woody Hakea fruits over their entire surfaces. Both the breaking mechanism and the actuation of the two valves in predominantly dead plant material are models for smart materials. Based on these results, an evaluation of the setup for 360° DIC regarding its use in deducing biomimetic principles is given. Furthermore, we propose a way to improve and apply the method for future measurements.

New avenues for residual stress analysis in ultrathin atomic layer deposited free-standing membranes through release of micro-cantilevers.

The fabrication of thinnest, yet undeformed membrane structures with nanometer resolution is a prerequisite for a variety of Microelectromechanical systems (MEMS). However, functionally relevant thin films are susceptible to growth-generated stress. To tune the performance and reach large aspect ratios, knowledge of the intrinsic material properties is indispensable. Here, we present a new method for stress evaluation through releasing defined micro-cantilever segments by focused ion beam (FIB) milling from a predefined free-standing membrane structure. Thereby, the cantilever segment is allowed to equilibrate to a stress-released state through measurable strain in the form of a resulting radius of curvature. This radius can be back-calculated to the residual stress state. The method was tested on a 20 nm and 50 nm thick tunnel-like ALD Image 1 membrane structure, revealing a significant amount of residual stress with 866 MPa and 6104 MPa, respectively. Complementary finite element analysis to estimate the stress distribution in the structure showed a 97% and 90% agreement in out-of-plane deflection for the 20 nm and 50 nm membranes, respectively. This work reveals the possibilities of releasing entire membrane segments from thin film membranes with a significant amount of residual stress and to use the resulting bending behavior for evaluating stress and strain by measuring their deformation.

Research on directional rock blasting based on different slotted pipe materials of the combined charge structure.

For shaped charge blasting projects in mining, civil engineering, and similar fields, it is proposed to modify the charge structure by combining slotted tubes and shaped charge liners to obtain a new type of charge structure. This aims to achieve directional rock breaking through the focused action of the shaped charge. The influence of different slotted pipe materials on the directional rock-breaking effect of concentrated energy using a new charge structure is explored through theoretical analysis combined with model test study, high-speed camera, stress-strain gauge, and other equipment. A comparison is made between slotted pipes made of aluminum, kraft paper, and PVC, with the cutting width of 2 mm. Based on the characteristics of the cracks formed after blasting, the new charge structure made of aluminum slotted pipe produces a penetrating crack that is almost consistent with the pre-cracking direction. Based on the corresponding characteristics of successively released blasting energy, the guiding and convergence effect of the new charge structure made of aluminum slotted pipe on the explosion energy is greater than that of the new charge structure made of the other two types of slotted pipe material. According to the strain data measured after blasting, the peak arrival time of the strain peak in the direction of the slotted pipe on one side of the shaped hood is shorter than that in the other two directions, and the peak strain is greater than that in the other two directions while having a better energy gathering effect. Based on the findings, the new charge structure with directional energy concentration has a damage reduction effect. Furthermore, the material of aluminum slotted pipe is found to be better than PVC slotted pipe, whereas the material of PVC slotted pipe is better than kraft paper slotted pipe in achieving directional rock breaking.

In vivo strain measurements in the human buttock during sitting using MR-based digital volume correlation.

Advancements in systems for prevention and management of pressure ulcers require a more detailed understanding of the complex response of soft tissues to compressive loads. This study aimed at quantifying the progressive deformation of the buttock based on 3D measurements of soft tissue displacements from MR scans of 10 healthy subjects in a semi-recumbent position. Measurements were obtained using digital volume correlation (DVC) and released as a public dataset. A first parametric optimisation of the global registration step aimed at aligning skeletal elements showed acceptable values of Dice coefficient (around 80%). A second parametric optimisation on the deformable registration method showed errors of 0.99mm and 1.78mm against two simulated fields with magnitude 7.30±3.15mm and 19.37±9.58mm, respectively, generated with a finite element model of the buttock under sitting loads. Measurements allowed the quantification of the slide of the gluteus maximus away from the ischial tuberosity (IT, average 13.74 mm) that was only qualitatively identified in the literature, highlighting the importance of the ischial bursa in allowing sliding. Spatial evolution of the maximus shear strain on a path from the IT to the seating interface showed a peak of compression in the fat, close to the interface with the muscle. Obtained peak values were above the proposed damage threshold in the literature. Results in the study showed the complexity of the deformation of the soft tissues in the buttock and the need for further investigations aimed at isolating factors such as tissue geometry, duration and extent of load, sitting posture and tissue properties.