Wall Deformation Research Articles

Finite Element Analysis of Evolut Transcatheter Heart Valves: Effects of Aortic Geometries and Valve Sizes on Post-TAVI Wall Stresses and Deformations

Background/Objectives: For transcatheter aortic valve implantation (TAVI) therapy, a catheter-guided crimped valve is deployed into the aortic root. Valve types such as Edwards balloon-expandable valves and Medtronic self-expandable valves come in different sizes and are chosen based on patient-specific aortic anatomy, including aortic root diameter measurement. Complications may arise due to variations in anatomical characteristics and the implantation procedure, making pre-implantation assessment important for predicting complications. Methods: Computational modeling, particularly finite element analysis (FEA), has become popular for assessing wall stresses and deformations in TAVI. In this study, a finite element model including the aorta, native leaflets, and TAVI device was used to simulate procedures and assess patient-specific wall stresses and deformations. Results: Using the Medtronic Evolut R valve, we simulated TAVI for 14 patients to analyze the effects of geometrical variations on structural stresses. Virtual TAVIs with different valve sizes were also simulated to study the influence of TAV size on stresses. Our results show that variations in aortic wall geometries and TAV sizes significantly influence wall stresses and deformations. Conclusions: Our study is one of the first comprehensive FEA investigations of aortic geometrical variations and valve sizes on post-TAVI stresses, demonstrating the non-linear relationship between aortic dimensions, TAV sizes, and wall stresses.

The Resistance of Sandwich Cylinders With Density-Graded Foam Cores to Internal Blast Loadings

Abstract The resistance of sandwich cylinders with density-graded foam cores to internal blast loadings is investigated theoretically and numerically. Four kinds of density-graded foam core are designed, such as positive, negative, middle–high, and middle–low gradients. The deformation process of the sandwich cylinders is assumed to be split into three phases, i.e., fluid–structure interaction, combined deformation of core and inner wall, and sandwich stage of motion. Employing a rigid perfectly-plastic locking model of density-graded foam core, analytical models are proposed to predict the dynamic response of gradient sandwich cylinders. Finite element simulations of gradient sandwich cylinders subjected to internal blast loadings are carried out and agree well with the analytical predictions. Furthermore, the effects of the core density gradients and the wall thickness distributions on the blast resistance are explored and identified. It is shown that the thicker inner wall design can enhance the blast resistance of sandwich cylinders with the same mass.

Development of swelling pressure in paulownia and Norway spruce during moisture absorption

Wood hybrid materials have gained significant attention for advanced technical applications over the past decade. In contrast to other materials, wood’s hygroscopic nature causes swelling and shrinkage, leading to differential expansion in hybrid systems under varying humidity conditions. When wood’s swelling is restrained by surrounding materials, stresses develop within both the wood and its adjacent components. To study this phenomenon, swelling tests were conducted on kiln-dried paulownia (Paulownia elongata) and Norway spruce (Picea abies) in a climate chamber at 20 °C and 98% relative humidity, with expansion restricted in one direction. Moisture absorption initially exhibited a steep, linear increase, levelling off after approximately 2 h. Swelling pressures rose sharply, peaking after 30 h for paulownia and 19 h for spruce, before gradually decreasing due to increased moisture content and relaxation. The measured stresses were lower than the compressive strengths of both wood species at their respective moisture contents. Microscopic examinations showed no cellular damage in paulownia during moisture absorption due to swelling pressure. In contrast, spruce wood displayed cell wall deformations and ray’s kinking in the early wood region of radial samples, as well as cell wall bending in tangential samples. This indicates that maximum stress is determined by the localised failure of the wood’s cellular structure rather than its overall properties. Such local effects were more pronounced in spruce than in paulownia due to their different structure. As a result, paulownia shows excellent potential for use in hybrid structures due to its low swelling and shrinkage properties and uniform structure.

Evaluation of surgical and non-surgical interventions in pectus excavatum management: nuss procedure vs. vacuum bell therapy

Pectus excavatum (PE) is a congenital chest wall deformity affecting 1 in 400 to 1 in 1,000 live births, predominantly males. The Nuss procedure, a minimally invasive surgery, and vacuum bell therapy (VBT), a non-surgical alternative, are primary treatments. The Nuss procedure is effective for severe PE but carries risks like bar displacement and potential damage to the heart and lungs. VBT, suitable for milder cases and younger patients, offers fewer complications but requires consistent long-term use for optimal results. Comparing these modalities highlights their distinct advantages and limitations. Comprehensive, randomized controlled trials are needed to refine treatment guidelines and enhance patient care in pediatric surgery.

Quality of life assessment after minimally invasive operative treatment in children with pectus excavatum: A single-center study and literature review.

Most patients with chest wall deformities have a negative body image, which affects their self-esteem and quality of life (QoL). The aim of this study was to evaluate changes in patients' QoL after minimally invasive repair of pectus excavatum (MIRPE). A prospective, single-center study was conducted between 2019 and 2023. We included 20 pediatric patients at a median age of 15 years and 9 months who underwent MIRPE. Two QoL questionnaires were used: the KIDSCREEN-52 and the EQ-5D-Y. The data were statistically analyzed with the Wilcoxon and Mann-Whitney tests. All patients and their parents were asked to complete questionnaires preoperatively and 12 months after surgical treatment. All patients were followed up during the 12-month study period. The study group was comprised of 65% male patients. The median Haller index was 5.0 standard deviation (SD) = 1.58). The assessment of general health condition was higher among the boys (with postoperative improvement), though this finding was not statistically significant. Routine daily activities were easier for all patients after MIRPE (p = 0.048). The patients showed improved physical activity (p = 0.038) and psychological wellbeing (p = 0.013) after elevation of the anterior chest wall. There was no impact on relations with parents, free time or school environment, but we found better patient contact with peers in the postoperative period. A high correlation was confirmed between the parents' and the patients' responses in each questionnaire. Chest wall deformities can have a strong impact on the patient's wellbeing, which is a very important part of psychological development in adolescents. Our study showed that improved QoL should be always considered as an indication for surgical treatment of chest wall deformities in children.

Large-eddy simulation of high-Reynolds-number turbulent channel flow controlled using streamwise travelling wave-like wall deformation for drag reduction

Large-eddy simulation of high-Reynolds-number turbulent channel flow controlled using streamwise travelling wave-like wall deformation for drag reduction

Monitoring Excavation-Induced Deformation of a Secant Pile Wall Using Distributed Fiber Optic Sensors.

This paper investigates the use of the BOTDA (Brillouin Optical Time-Domain Analysis) technology to monitor a large-scale bored pile wall in the field. Distributed fiber optic sensors (DFOSs) were deployed to measure internal temperature and strain changes during cement grouting, hardening, and excavation-induced deformation of a secant pile wall. The study details the geological conditions and DFOS installation process. During grouting, the temperature increased by approximately 69 °C due to cement hydration 30 min post-grouting, while the strain decreased by 0.5% on average due to cement slurry shrinkage. During excavation, the temperature changes were minimal, but the excavation depth significantly influenced the strain distribution, with continuous compressive deformation observed in two monitored boreholes. Two analytical methods, the numerical integration method (NIM) and the finite difference method (FDM), were used to calculate the lateral pile displacement based on the monitored strain data. The results were compared with previous monitoring data, showing that the lateral displacement of the pile was minimal after excavation and was attributed to the high stiffness of the secant pile wall. This study demonstrates the effectiveness of DFOSs and BOTDA technology for monitoring complex pile wall behaviors during construction.

Development and performance assessment of a novel self-centering damper for slotted RC walls

Slotted RC walls exhibit better ductility compared to conventional RC walls, but inevitably lead to a reduction in lateral stiffness and load-bearing capacity. In order to improve the seismic performance and reduce the residual deformation of slotted RC walls, a novel self-centering damper (SCD) suitable for the connection of slotted RC wall is proposed. The novel SCD is composed of two diagonally intersecting disc spring devices (DSD) and multiple slit steel plate (MSSP) arranged in parallel. The construction and working principle of the novel SCD were thoroughly explained, and its theoretical model was established. Through cyclic loading tests and numerical simulations, the collaborative working mechanism of the two components was analyzed. The influence of the pre-pressed force and arrangement angle of the DSD on the energy-dissipating and self-centering capacities of the SCD was investigated. It was found that increasing the pre-pressed force and arrangement angle of the DSD would reduce residual deformation and equivalent viscous damping ratio. Then, the seismic performance of the slotted RC wall with the novel SCDs was analyzed. The results demonstrated that the slotted RC wall incorporating the SCDs exhibited superior deformation and energy-dissipating capabilities, while maintaining a relatively high level of load- bearing capacity and stiffness. Notably, the residual deformation rate of the SCDs was only 0.4 % at the design threshold, enabling disassembly and replacement after seismic events.

Hygromechanical deformation of wood cell walls regulated by the microfibril angle

Microfibril angle regulates wood cell wall deformation by influencing moisture diffusion, while hydrogen bonding competition between CNFs and hemicellulose directs water movement.

Intracranial aneurysm wall displacement depicted by amplified Flow predicts growth

BackgroundAbnormal intracranial aneurysm (IA) wall motion has been associated with IA growth and rupture. Recently, a new image processing algorithm called amplified Flow (aFlow) has been used to successfully track...

Application of the simulation-graphic method for the computational modeling of the cross-section characteristics of foundations made of T-beams installed on keelsons with deformed walls

The object of the study is a composite beam made of an existing T-beam on a vessel - a keelson, with a web deformed within the standard values and an additional T-beam added to its free flange, which allows forming a foundation beam during the modernization of the vessel. The task is to obtain the geometric characteristics of the cross-section of such a beam. First, analytical expressions are given for a deformed T-beam with modeling of the wall in one case as a broken line, and in the other case as an undeformed beam with a height of the deformed and additional vertical element of the residual area compared to the original undeformed beam and a height equal to the height of the wall deformation. For both modeling options, it is convenient to obtain initial information on the beam wall deformation by fixing the maximum arrows of deviation from the normal position on both sides of the wall and the height of such deformation on the modernized vessel. Based on these expressions, analytical expressions are then obtained for the geometric parameters of the cross-section of the formed foundation beam. The values of the moments of resistance and inertia of the cross-sectional area of the formed beam are obtained, which allow further calculations of the bending strength and rigidity, as well as the frequencies of natural vibrations, which provide the possibility of assessing vibration. The extended T-beam is adopted as having both a solid and a perforated wall.

Assessing intra- and interfraction motion and its dosimetric impacts on cervical cancer adaptive radiotherapy based on 1.5T MR-Linac

PurposeThe purpose of this study was to quantify the intra- and interfraction motion of the target volume and organs at risk (OARs) during adaptive radiotherapy (ART) for uterine cervical cancer (UCC) using MR-Linac and to identify appropriate UCC target volume margins for adapt-to-shape (ATS) and adapt-to-position (ATP) workflows. Then, the dosimetric differences caused by motion were analyzed.MethodsThirty-two UCC patients were included. Magnetic resonance (MR) images were obtained before and after each treatment. The maximum and average shifts in the centroid of the target volume and OARs along the anterior/posterior (A/P: Y axes), cranial/caudal (Cr/C: Z axes), and right/left (R/L: X axes) directions were analyzed through image contours. The bladder wall deformation in six directions and the differences in the volume of the organs were also analyzed. Additionally, the motion of the upper, middle and lower rectum was quantified. The correlation between OAR displacement/deformation and target volume displacement was evaluated. The planning CT dose distribution was mapped to the MR image to generate a plan based on the new anatomy, and the dosimetric differences caused by motion were analyzed.ResultsFor intrafraction motion, the clinical tumor volume (CTV) range of motion along the XYZ axes was within 5 mm; for interfraction motion, the range of motion along the X axis was within 5 mm, and the maximum distances of motion along the Y axis and Z axis were 7.45 and 6.59 mm, respectively. Additionally, deformation of the superior and anterior walls of the bladder was most noticeable. The largest magnitude of motion was observed in the upper segment of the rectum. Posterior bladder wall displacement was correlated with rectal and CTV centroid Y-axis displacement (r = 0.63, r = 0.50, P < 0.05). Compared with the interfractional plan, a significant decrease in the planning target volume (PTV) D98 (7.5 Gy, 7.54 Gy) was observed. However, there were no significant differences within the intrafraction.ConclusionDuring ART for UCC patients using MR-Linac, we recommend an ATS workflow using isotropic PTV margins of 5 mm based on intrafraction motion. Based on interfraction motion, the recommended ATP workflow uses anisotropic PTV margins of 5 mm in the R/L direction, 8 mm in the A/P direction, and 7 mm in the Cr/C direction to compensate for dosimetric errors due to motion.

Analysis of Right Ventricular Strain in Heart Failure with Preserved Ejection Fraction

Introduction: The complexity of the geometry and the unique architecture of the right ventricular (RV) myocardial fibers make the study of its function a significant challenge. However, the advent of new imaging techniques, such as RV strain imaging, has improved our understanding of its function. The aim of our study is to specify the principles of studying right ventricular deformation and its impact on the prognosis of patients with heart failure with preserved ejection fraction (HFpEF). Materials and Methods: This is a two-year prospective study comparing echocardiographic parameters of right ventricular function in 87 patients followed in our unit for HFpEF at the Cardiology Department of ERRAZI Hospital, CHU Mohammed VI, Marrakech. Results: Over the past two years, our unit has hosted 87 patients diagnosed with HFpEF. The average age was 68 years and 5 months, with a female predominance. The most common cardiovascular risk factors were hypertension and obesity (BMI &gt; 30). Symptomatic presentations were dominated by exertional dyspnea, observed in 84% of cases, with resting dyspnea and cough affecting about half of the patients. Signs of left heart failure, such as crackling rales, were present in 44% of patients, while signs of right heart failure, such as lower limb edema, were noted in 41%, with jugular distension and hepatojugular reflux in 19%. Echocardiography revealed left ventricular hypertrophy in 57% of patients and left atrial dilatation in 65%. Right ventricular function was markedly impaired, with significant abnormalities in TAPSE (Tricuspid Annular Plane Systolic Excursion), S' wave, and Tei index values, highlighting a marked correlation between the Tei index and the deformation of the right ventricular lateral wall. Rehospitalization for heart failure occurred in 40.2% of the cohort, emphasizing the severe clinical implications of right ventricular dysfunction in this patient population. Discussion and Conclusion: RV strain in HFpEF is an analysis that has not yet revealed all its intricacies. This study demonstrates that there is an alteration in RV strain in patients with HFpEF, which has a prognostic impact on mortality and rehospitalization for cardiac decompensation. This suggests that this parameter should be integrated into routine evaluations of RV systolic function.

Effect of Insecticides Imidacloprid and Alpha-Cypermethrin on the Development of Pea (Pisum sativum L.) Nodules.

Insecticides are used commonly in agricultural production to defend plants, including legumes, from insect pests. It is a known fact that insecticides can have a harmful effect on the legume-rhizobial symbiosis. In this study, the effects of systemic seed treatment insecticide Imidor Pro (imidacloprid) and foliar insecticide Faskord (alpha-cypermethrin) on the structural organization of pea (Pisum sativum L.) nodules and their transcriptomic activity were investigated. The plants were treated as recommended by the manufacturer (10 mg/mL for Imidor Pro and 50 µg/mL for Faskord) and twofold concentrations were used for both insecticides. Insecticides had no visible effect on the growth of pea plants. The nodules also showed no visible changes, except for the variant treated with twofold concentration of Imidor Pro. However, the dry weight of shoots and roots differed significantly in insecticide-treated plants compared to untreated plants in almost all treatments. The number of nodules decreased in variants with Imidor Pro treatment. At the ultrastructural level, both insecticides caused cell wall deformation, poly-β-hydroxybutyrate accumulation in bacteroids, expansion of the peribacteroid space in symbiosomes, and inclusions in vacuoles. Treatment with Faskord caused chromatin condensation in nucleus. Imidor Pro treatment caused hypertrophy of infection droplets by increasing the amount of matrix, as confirmed by immunofluorescence analysis of extensins. Transcriptome analysis revealed upregulation of expression of a number of extensin-like protein-coding genes in nodules after the Imidor Pro treatment. Overall, both insecticides caused some minor changes in the legume-rhizobial system when used at recommended doses, but Faskord, an enteric contact insecticide, has fewer negative effects on symbiotic nodules and legume plants; of these two insecticides, it is preferred in pea agricultural production.

Modeling of Creep Closure of Salt Rocks Drilled by Directional Wells

This paper presents a strategy for three-dimensional modelling of directional wells penetrating salt rocks, aiming at predicting the closure of these rocks due to creep. One of the major challenges in oil production in the pre-salt region is drilling through thick layers of salt rocks. During drilling, these rocks deform in the direction of the wellbore closure due to creep. The accumulated deformation of the wellbore wall over a given time interval can lead to the restriction of the drilling string's passage and even its irretrievably trapped. Directional wells in salt regions present an even greater complexity, as changes in inclination alter the stress distribution around the well, changing the configuration of the deviatoric stress, with no symmetry around the well's central axis (as in vertical wells). This paper discusses a strategy for modelling directional wells in salt regions using the commercial software Abaqus. This software implements the Finite Element Method, including its three-dimensional formulation, and allows modeling of creep deformation of materials, enabling the implementation of constitutive models different from traditional ones through subroutines. The adopted constitutive equation is the most recurrent in the literature to describe the creep phenomenon in wells through Brazilian salt rock. To verify the developed strategy, a vertical well is modelled, and the obtained results are compared with those presented by axisymmetric modeling, already consolidated in other works developed by the group. After verification, directional wells are modelled and studied, and their behavior is discussed regarding the observed displacement and stress fields, mainly along the region near the wellbore wall. This work contributes to the understanding of the creep behavior in salt rocks when drilled by directional wells, and discusses some strategies that can contribute to the stability of the rock formation, aiming at the safe and efficient construction of wells in salt regions.

A Comprehensive Finite Element and Reliability-Based Analysis of Hybrid Reinforced Earth Retaining Wall Stability and Deformation

A Comprehensive Finite Element and Reliability-Based Analysis of Hybrid Reinforced Earth Retaining Wall Stability and Deformation

Experimental Study on Damage of Ship Multi-cabin Protective Structure with Arc-shaped Supports Subjected to Underwater Contact Explosion

Abstract Underwater contact explosion will cause serious damage to the multi-cabin protective structure (MPS) of large ships. In order to improve the protective performance of MPS, an effective way is to set arc-shaped supports behind the main protective wall to reduce the risk of damage. In order to explore the damage mechanism of multi-cabin protective structure with arc-shaped supports under contact explosion, a large-scale cabin model was designed and the underwater contact explosion test was carried out. The experimental data of the multi-cabin protective structure model after the test were obtained, such as model breach size, deformation and impact acceleration. The results show that underwater contact explosions will cause significant damage to the outer structure of the MPS, with main forms of damage including tearing of the outer plate, buckling of internal components, and production of fragments. The calculation method for breach size based on panel energy is in good agreement with the experimental results. Additionally, setting arc-shaped supports behind the main protective wall can significantly reduce the deformation of the main defensive wall and mitigate the risk of tensile failure at the upper and lower joints.

Thermal–structural response and life prediction of lattice regenerative cooling thrust chambers in liquid rocket engines based on a simplified viscoplastic model

With advances in aerospace technology, the reusability of liquid rocket engines has become the focus of considerable research interest. Traditional channel-type regenerative cooling thrust chambers often experience plastic deformation and microcracks, which limit their lifespan. This study proposed a novel lattice regenerative cooling thrust chamber using a simplified viscoplastic model and ABAQUS finite element software to simulate thermal–structural responses under different pressure conditions. The lattice structure not only enhanced the cooling efficiency and reduced the structural weight but also mitigated the plastic deformation and high-temperature creep of the inner wall. At an inner-wall temperature of 820 K, creep damage was significant. Compared to that of traditional chambers, the lattice structure of the proposed chamber exhibited different mechanical behavior and failure modes, with a more uniform stress distribution and initial failure occurring at the lattice nodes. The proposed design avoided the “doghouse” effect evident in traditional chambers, achieving an inner-wall lifespan of up to 202 cycles, a 359 % improvement. The high design flexibility of the lattice structure in the cooling channels enabled enhanced thrust chamber longevity. The study results provide new insights and technical support for next-generation liquid rocket engine designs.

Incorporation of metal-doped silicate microparticles into collagen scaffolds combines chemical and architectural cues for endochondral bone healing.

Regeneration of large bone defects remains a clinical challenge until today. While existing biomaterials are predominantly addressing bone healing via direct, intramembranous ossification (IO), bone tissue formation via a cartilage phase, so-called endochondral ossification (EO) has been shown to be a promising alternative strategy. However, pure biomaterial approaches for EO induction are sparse and the knowledge how material components can have bioactive contribution to the required cartilage formation is limited. Here, we combined a previously developed purely architecture-driven biomaterial approach with the release of therapeutic metal ions from tailored silicate microparticles. The delivery platform was free of calcium phosphates (CaP) that are known to support IO but not EO and was employed for the release of lithium (Li), magnesium (Mg), strontium (Sr) or zinc (Zn) ions. We identified an ion-specific cellular response in which certain metal ions strongly enhanced cell recruitment into the material and showed superior chondrogenesis and deposition collagen II by human mesenchymal stromal cells (MSCs). At the same time, in some cases microparticle incorporation altered the mechanical properties of the biomaterial with consequences for cell-induced biomaterial contraction and scaffold wall deformation. Collectively, the results suggest that the incorporation of metal-doped silicate microparticles has the potential to further improve the bioactivity of architectured biomaterials for bone defect healing via EO. STATEMENT OF SIGNIFICANCE: Endochondral bone healing, a process that resembles embryonic skeletal development, has gained prominence in regenerative medicine. However, most therapeutic biomaterial strategies are not optimized for endochondral bone healing but instead target direct bone formation through IO. Here, we report on a novel approach to accelerate biomaterial-guided endochondral bone healing by combining cell-guiding collagen scaffolds with therapeutic metal-doped silicate microparticles. While other strategies, such as hypoxia-mimic drugs and iron-chelating biomaterials, have been documented in the literature before to enhance EO, our approach uniquely implements enhanced bioactivity into a previously developed biomaterial strategy for bone defect regeneration. Enhanced cell recruitment into the material and more pronounced chondrogenesis were observed for specific hybrid scaffold formulations, suggesting a high relevance of this new biomaterial for improved endochondral bone healing.

DIEP Flap Weights in Immediate 1-stage and 2-stage Breast Reconstruction: Considering Chest Wall Deformity

Background: There are advantages and disadvantages to both immediate 1-stage and 2-stage autologous-breast reconstruction. The 2-stage procedure may suffer from a hitherto overlooked difficulty: the tissue expander may induce chest wall depression that may require using a heavier-than-expected flap to generate symmetrical breasts. We conducted a retrospective observational study to assess this phenomenon. Methods: Consecutive patients who underwent 1-stage or 2-stage unilateral autologous-breast reconstruction with a deep inferior epigastric perforator flap were included. The 2 groups were compared in terms of age, body mass index, mastectomized tissue weight, inset-flap weight, and percentage additional flap weight (defined as [inset-mastectomy]/mastectomy × 100). The latter reflects the amount of additional flap tissue relative to mastectomized tissue that was needed to generate symmetrical breasts. The chest wall deformity after tissue expansion in the 2-stage patients was quantitated with computed tomography. Results: Patients’ healthy and affected breasts were symmetrical before surgery (P &gt; 0.05). Compared with the 1-stage patients (n = 37), the 2-stage patients (n = 31) only differed in terms of a significantly higher mean percentage additional flap weight (28% versus 12%, P = 0.0077). Relative to preoperative values, nearly all 2-stage patients had mild (74%) or moderate (19%) chest wall deformity before tissue expander removal. Conclusions: Due to tissue expander-induced chest wall deformity, 2-stage breast reconstruction may require a larger flap volume than is anticipated on the basis of preoperative volumetric measurements. Considering this phenomenon when choosing between immediate 1-stage and 2-stage reconstruction could potentially help improve patient outcomes.