Mesh Selection Research Articles

Microgravity and Cardiovascular Health in Astronauts: A Narrative Review.

Space exploration has become a major interest for scientific and medical research. With increasing duration and frequency of manned space missions, it is crucial to understand the impact of microgravity on the cardiovascular health of astronauts. We focus on this relationship by reviewing literature that explores how microgravity affects several hemodynamic parameters and cardiovascular biomarkers. We conducted a search updated to November 2024 across several databases, including PubMed, Cochrane Library, ESA, NASA and DLR, using relevant MeSH terms and selection criteria. The 22 selected articles detail how microgravity impacts the cardiovascular system and its adaptations. We identify some clear patterns, such as loss of ventricular mass and increased QT intervals (corrected for heart rate) indicating increased risk of arrhythmias. Our analysis confirms that head-down tilt is an accurate analog of microgravity. While a direct link between microgravity and cardiovascular disease, such as coronary heart disease and myocardial infarction, remains elusive, the documented physiological changes pose a potential threat to the astronauts' health. We suggest that future research focus on long-term effects, particularly on female subjects.

The influence of time steps and turbulence model in numerical predicting total resistance on Japan Bulk Carrier with and without pre-duct

Abstract As a numerical fluid dynamic simulation method, Computational Fluid Dynamic (CFD) must guarantee the accuracy of the simulation results carried out, where the accuracy of the simulation results depends on: numerical method, grid generation, mesh independence, grid type, turbulence model, etc. This paper explains the influence of turbulence model and time step on the resistance prediction results of the Japan Bulk Carrier (JBC) ships, with CFD simulations using the ANSYS CFX software package. The model is simulated with several turbulence models including: k-Epsilon (k-ε), k-Omega (k-ω) and Shear Stress Transport k-ω (SST k-ω), apart from that the turbulence model is simulated in several time steps. From the results of the CFD modelling carried out, the influence of the turbulence model and time step on the accuracy of predicting ship resistance from the JBC ship was analysed, by comparing the CFD modelling results with experimental results from National Maritime Research Institute (NMRI). In general, the turbulence model and time step influence modelling and mesh selection, the correct time step provides accurate and convergent modelling results.

Rihi Mesh Placement Algorithm In Collocation Methods

Various adaptive mesh selection strategies for solving single higher order two-points boundary value problems (BVPs) by using collocation methods are intensively investigated for along time and they are now well established. In this work we concern with numerical investigations of adaptive mesh selection algorithms using the criterion function rihi for solving first order system of BVPs and developing some algorithms. The algorithms perform quite nicely and appear competitive with De Boor algorithm.

Constructions of innovative geodesic domes in terms of the sustainable and efficient cross-sections using

Geodesic domes are structures which deliver effective solutions, associated with cost savings, due to the lack of intermediate supports when roofing large-sized objects. The multitude of advantages of this type of construction was translated into the shaping of innovative lightweight objects of geodesic domes, constructed on a regular octahedron. In this article, the use of strut sections was applied to covers generated due to a regular octahedron. Two families of domes were compared, resulting from the use of two methods that differ from each other in their topology. Each family consist of 8 structures thus finally 16 geodesic domes were considered. The generated domes were compared in terms of the same section for all strut elements, and the optimized section for each group of struts. To find the design focused on obtaining optimal solution, a number of comparative analysis were carried out. The presented analysis is extremely important in the context of environmental impact, because it shows the steel consumption and the sense of optimization. It was indicated that by optimizing the cross-sections of the strut elements, the steel consumption, as well as their weight, decreased by approx. 10–25% for dome structures which were created using method 1 and 20–40% for domes generated using method 2. The article aims to provide suggestion on the selection of the appropriate innovative geodesic dome mesh. A mesh based on various methods of shaping the covers of geodesic domes created using a regular octahedron.

Weighing the benefits: Exploring the differential effects of light-weight and heavy-weight polypropylene meshes in inguinal hernia repair in a retrospective cohort study

BackgroundInguinal hernia repair is a common surgical procedure, with more than 20 million cases yearly. Choice between mesh types varies in clinical practice. To compare light-weight polypropylene (LW-PP, 34–36 g/m2) and heavy-weight polypropylene (HW-PP, 95 ​g/m2) meshes. MethodsData from patients who underwent open inguinal hernia repair between 2020 and 2022. Selection criteria ensured homogeneity. Endpoints were to assess the impact of different mesh weights on overall health-related quality of life (HRQoL), using Short Form 36 (SF-36), and to monitor postoperative complications. ResultsTwo hundred patients were included in both groups. Lateral and direct hernias occurred in 60.5 ​% and 39.5 ​%. According to EHS, 31.5 ​%, 22.3 ​% and 46.2 ​% were classified as size 1, 2, 3. Follow-up showed similar HRQoL at 30-days, with a favorable trend towards LW-PP mesh offering fewer limitations, better comfort, and improved general health after 12-months. No difference in postoperative paresthesia, wound hematoma, and interference with daily activities. Conclusion1-year after surgery HRQoL evaluation highlights the non-inferiority of LW-PP. Mesh selection should be tailored, aiming at improving outcomes and postoperative comfort.

Examining Clinical Practice and Short-Term Results in Ventral Hernia Repair

Background and Objectives: This prospective observational study conducted at Parul Sevashram Hospital, Vadodara aimed to examine the diversity in surgical techniques used for primary and incisional ventral hernia repair (VHR). Methods: Twenty-five elective VHR patients treated from January 1, 2023, to March 31, 2023, were enrolled. Patients were monitored for 90 days post-surgery. Exclusion criteria included patients under 18 years old and those undergoing emergency surgeries. The primary objective was to compare surgical approaches between primary and incisional hernia repairs. Secondary objectives focused on intraoperative procedures such as mesh selection, fixation techniques, and drain placement, as well as evaluating postoperative outcomes at 3 months, including infection rates, surgical site issues, mortality, and readmission rates within 90 days. Results: Data from 25 patients were analysed: 14 (58%) had primary hernias (PH) and 11 (42%) had incisional hernias (IH), including 1 (9.09%) recurrent case. – PH Group: Procedures included 6 (42.85%) open Onlay, 4 (28.57%) open Sublay, 1 (7.14%) intraperitoneal Onlay meshplasty (IPOM), and 3 (21.42%) suture repairs. Complications: 7% seroma, 0% surgical site infection (SSI), 0% recurrence. – IH Group: Procedures included 7 (63.63%) open Onlay, 3 (27.3%) open Sublay, and 1 (9.09%) suture repair. Complications: 9% seroma, 9% hematoma, 0% SSI, 9% wound sinus, 0% recurrence. Conclusion: Onlay meshplasty emerged as the predominant procedure for both primary and incisional hernias. However, open Sublay repair showed promising results with fewer seroma-related complications. Standardizing guidelines could optimize outcomes in VHR.

Construction of a new time-space two-grid method and its solution for the generalized Burgers’ equation

In this paper, we construct a new time-space two-grid method and apply it to the generalized Burgers’ (GB) equation. We prove that our proposed scheme is solvable, energy-preserving and convergent in the discrete L2-norm. Compared with previous studies on the two-grid method, the new time-space two-grid technique allows for a more flexible selection of the coarse grid in both temporal and spatial dimensions, resulting in greater computational efficiency and a simpler mesh selection. Finally, we compare our scheme with the general difference method (Zhang et al., 2021) and the time two-grid method (Shi and Yang, 2024), revealing that the proposed new time-space two-grid method is more efficient in computational time.

Expanded polytetrafluoroethylene mesh in chest-wall reconstruction: A 27-year experience

ObjectiveThe study objective was to evaluate the success of expanded polytetrafluoroethylene mesh in chest-wall reconstruction. MethodsWe retrospectively reviewed patients who underwent expanded polytetrafluoroethylene (Gore-Tex) chest-wall reconstruction. The main outcome was a mesh-related event, defined as a mesh-related reoperation (eg, mesh infection requiring debridement with/without explant, tumor recurrence with explant) or structural dehiscence/mesh loosening with/without a hernia. Demographics and surgical outcomes were reported. ResultsA total of 246 reconstructions met inclusion (1994-2021). Fifty-five reconstructions (22.4%) had mesh-related events within a median of 1.08 years (interquartile range, 0.08-4.53) postoperatively; those without had a stable chest for a median of 3.9 years (interquartile range, 1.59-8.23, P < .001). Forty-one meshes (16.6%) became infected, requiring reoperation. Eighty-eight percent (36/41) were completely explanted; 8.3% (3/36) required additional mesh placement. Predictors of mesh-related events were prior chest-wall radiation (odds ratio, 9.73, CI, 3.47-30.10, P < .001), higher body mass index (odds ratio, 1.08, CI, 1.01-1.16, P = .019), and larger defects (odds ratio, 1.48, CI, 1.02-2.17, P = .042). The risk of mesh-related events with obesity was higher with prior chest-wall radiation. ConclusionsMost patients (78%) with an expanded polytetrafluoroethylene mesh had a stable reconstruction after a median of 4 years. Obesity, larger defects, and prior chest-wall radiation were associated with a higher risk of a mesh-related event mostly due to mesh infections. Seventeen percent of reconstructions had reoperation for mesh infection; 88% were completely explanted. Only 8% required replacement mesh, suggesting that experienced surgeons can safely manage them without replacement. Future studies should compare various meshes for high-risk patients to help guide the optimal mesh selection.

Fabrication of bioactive silk composite meshes for hernia repair and guided soft tissue remodeling: In silico, in vitro and in vivo models

ObjectivesPost-operative complications stemming from incompatible meshes often lead to delayed wound healing, seroma, infections, inappropriate tissue infiltration and pain. The present study was outlined to develop biocompatible composite hand-knitted silk meshes modified with polymers and natural extracts. Our study introduced hand-knitted B. mori silk fibroin as the primary mesh material, offering superior mechanical strength and biocompatibility. The spin-assisted dip coating achieved desirable morphology, internal structures, thickness, and surface roughness. Moreover, the application of biopolymeric composite coatings containing polymers and natural extracts introduced antimicrobial character, facilitated cell attachment, migration, proliferation, potentiating gene expression and accelerating the process of wound healing. These composite meshes are a viable solution for addressing post-op complications in hernia and soft tissue repair surgeries. MethodIn this study, 9 silk-based composite meshes (modified with polymeric-extract blends through spin-assisted dip coating) were successfully developed. Experimental variants were then subjected to various characterizations including SEM, DMA and chemical analysis (FTIR and GC-MS). Modified meshes were evaluated for their physiological characteristics and biological responses (the basic criterion for the selection of composite silk mesh). The biological testing included (antimicrobial susceptibility testing, in vitro cell viability assay, cell attachment assay (NIH3T3 and hUc-MSCs), in vitro cell migration, in vitro gene expression analysis with NIH3T3, in silico molecular docking with bioactive ligands of HE extract and in vivo analysis with PHBV-HE and PHBV-Control composite meshes in rat models. ResultsResults showed that all variants exhibited a multi-fiber morphology with significant surface coating, allowing for optimal drug release up to 72 h. This release facilitated antibacterial properties and biocompatibility, as evidenced by in vitro cell viability, migration assays and gene expression analysis. Among the variants, the PHBV-HE composite mesh demonstrated superior results. In the case of PHBV-coated polymeric controls, the SEM analysis concluded that the presence of coating reduced the pore size up to 39.62 % whereas, fiber diameter was increased by up to 19.89 % as compared to the control. The presence of a coating on the mesh improved the mechanical strength/modulus by 165.89 %, UTS by 185.38 % and reduced the % strain by 64.67 %. The fast release of HE from PHBV-HE composite mesh was 90.7% up to 72h, confirming that it can induce antibacterial activity against surgical infections. ConclusionPHBV-HE showed the highest cell viability, wound healing and gene expression. Based on appreciable biological evaluation results shown by PHBV-HE, in rat hernia models, only the PHBV-HE variant was tested for in-vivo analysis. Results confirmed its non-toxic nature and wound-healing abilities. Enhanced cell proliferation and wound healing observed both in vitro and in vivo indicated that PHBV-HE holds promise as a biomedical implant suggesting its potential for effective hernia and soft tissue repair and regeneration.

Contemporary Abdominal Wall Reconstruction: Emerging Techniques and Trends.

Abdominal wall reconstruction is a common and necessary surgery, two factors that drive innovation. This review article examines recent developments in ventral hernia repair including primary fascial closure, mesh selection between biologic, permanent synthetic, and biosynthetic meshes, component separation, and functional abdominal wall reconstruction from a plastic surgery perspective, exploring the full range of hernia repair's own reconstructive ladder. New materials and techniques are examined to explore the ever-increasing options available to surgeons who work within the sphere of ventral hernia repair and provide updates for evolving trends in the field.

Selectivity in snow crab (Chionoecetes opilio) pot fishery: Effect of escape gap shape and size for conservation of fishery resources

Conical pots are commonly used fishing gear for capturing snow crab (Chionoecetes opilio). In these fisheries, optimal snow crab size selection is important for reducing unintended mortality of undersized individuals aiming at conserving fisheries resources and reducing sorting time onboard fishing vessels. Size selection in snow crab pot fisheries commonly takes place through pot netting meshes during deployment. The diamond mesh netting has varying opening angles affecting retention of snow crab of different sizes, and often large proportions of catches consist of undersized crab challenging natural resource conservation. Some commercial snow crab fisheries use rigid escape gaps in addition to mesh selection to improve size selectivity. In this study, we predict the size selection potential of escape gaps with different shape and size and investigated whether such additional size selection mechanism can have a potential to improve selectivity compared to mesh selection. Results showed that circular escape gaps have potential to provide sharper size selection compared to netting meshes and thus could be used to limit the capture of undersized snow crab which is relevant for management and conservation of snow crab resources. However, a similar positive effect cannot be obtained to the same extent with elliptical and rectangular escape gaps.

Regression estimation for continuous-time functional data processes with missing at random response

In this paper, we are interested in nonparametric kernel estimation of a generalised regression function based on an incomplete sample ( X t , Y t , ζ t ) t ∈ [ 0 , T ] copies of a continuous-time stationary and ergodic process ( X , Y , ζ ) . The predictor X is valued in some infinite-dimensional space, whereas the real-valued process Y is observed when the Bernoulli process ζ = 1 and missing whenever ζ = 0 . Uniform almost sure consistency rate as well as the evaluation of the conditional bias and asymptotic mean square error are established. The asymptotic distribution of the estimator is provided with a discussion on its use in building asymptotic confidence intervals. To illustrate the performance of the proposed estimator, a first simulation is performed to compare the efficiency of discrete-time and continuous-time estimators. A second simulation is conducted to discuss the selection of the optimal sampling mesh in the continuous-time case. Then, a third simulation is considered to build asymptotic confidence intervals. An application to financial time series is used to study the performance of the proposed estimator in terms of point and interval prediction of the IBM asset price log-returns. Finally, a second application is introduced to discuss the usage of the initial estimator to impute missing household-level peak electricity demand.

Effect of microcarbon particle size and dispersion on the electrical conductivity of LLDPE-carbon composite

This experimental research aimed to develop a conductive polymer composite (CPC) material for electromechanical devices. The composite was made by incorporating conductive micro carbon derived from rice husks into a Linear Low-Density Polyethylene (LLDPE) polymer matrix using hot compaction. Variations of filler composition were used, with carbon loading of 50%, 45%, and 40%, and mesh sizes of #150, #200, and #250. The experimental results showed that particle size variations did not significantly affect composite density, but higher mesh selection improved filler dispersion within the matrix, resulting in higher electrical conductivity values. The optimal conductivity value of 9.43E-04 S/cm was achieved with a micro-carbon composition of 50% loading. However, decreasing micro carbon loading had a more significant impact on reducing electrical conductivity values.

A Reduced Sparse Dictionary Reconstruction Algorithm Based on Grid Selection

A sparse dictionary reconstruction algorithm based on grid selection is introduced to solve the grid mismatch when using the sparse recovery space time adaptive processing (SR-STAP) algorithm. First, the atom most closely related to clutter is selected from the traditional dictionary through the spectral value dimensionality reduction method. The local mesh is divided around the selected atoms to create mesh cells, and the mesh cells that are most likely to appear in the real clutter points are judged according to the local selection iteration criteria. In this way, the mesh spacing is refined, the local mesh selection is carried out step by step, and the optimal atoms in the local region are constantly adjusted and selected to narrow the search region until the iteration termination condition is met. Finally, the space-time plane is divided using a novel meshing technique that centers around the optimal atom. By removing atoms beyond the maximum range of spatial and Doppler frequencies, the simplified sparse dictionary can overcome the mesh mismatch problem. The simulation results demonstrate that the algorithm enhances the sparse recovery accuracy of clutter space-time spectrum, mitigates the mesh mismatch effect, and boosts STAP performance.

Component separation repair of incisional hernia: evolution of practice and review of long-term outcomes in a single center.

To review the long-term outcomes of complex abdominal wall reconstruction using anterior and posterior component separation (CS) techniques in our center. This was a descriptive analytical study. Analysis of data from a prospectively collected database of patients who had undergone Component Separation (CS) repair of incisional hernias was performed. Two techniques were used. Anterior component separation (ACS) and posterior component separation with transversus abdominis release (PCS/TAR). Follow-up was clinical review at 6 weeks, 6 months, and 12 months with direct access telephone review thereafter. Long-term outcome data was obtained from electronic records and based on either clinical or CT assessment. Minimum physical follow-up was 6 months for all patients. 89 patients with large incisional hernias underwent CS repair. 29 patients had ACS while 60 underwent PCS/TAR. Mean follow-up was 60 months (range 6-140 months) in the ACS group and 20 months (range 6-72 months) in the PCS group. Twenty-five patients (28%) had simultaneous major procedures including 21 intestinal anastomoses. Twenty-six (29%) of patients had associated stomas. Twenty-seven (30.3%) of the patients had undergone previous hernia repairs. Seromas occurred in 24 (26.97%) patients. Wound infections were more common after ACS. There have been 10 (11.2%) recurrences to date. Component separation repair techniques result in good long-term outcomes with acceptable complication rates. They can be performed simultaneously with gastrointestinal procedures with low morbidity. Appropriate patient selection and use of appropriate mesh are important.

In-Silico Model Validation of Impact on a Composite Helmet Shell

Abstract Numerical impact simulation plays a critical role in the development and improvement of helmet systems. Due to the curvature of the helmet, the selection of impact position on the helmet may affect the ability to correlate results between numerical models and experimental results. In this study, high-velocity impact simulations were performed on composite plates, as well as a model of a modern composite helmet to validate helmet model performance. Results of the composite plate simulation show a non-converging increase in composite deformation with mesh refinement, indicating that model validation is a function of both material properties and mesh selection. Results of impact on the helmet model show that the calculated deformation of the helmet increases by up to 35% with a 20 mm change in impact position. The positional variation of helmet deformation is most pronounced on the front of the helmet. Due to the significant effect that impact position has on helmet deformation, the numerical model validation cannot be performed against experimental tests of a “small” sample size.

Numerical Simulation of Helical Coil Tube in Tube Heat Exchangers with Grooved Internal Tube

Abstract: The goal of this work is to analyse the heat transfer effects of providing inner tube with formed groove in helical coil tube in tube HE. In order to investigate further heat transmission improvements, the groove depth was increased to find the comparative study of Nusselt number in different cases analysed in this work. This was performed by use of Ansys CFD Fluent Software package by configuring and employing a compact 3-D model of a real and complex system to solve for the case studies in this research. The context for the topic is discussed, as well as explanation of process breakthroughs in CFD analysis. In order to improve the computational fluid dynamics simulations, information on proper mesh selection and geometry was generated with respect to theoretical concerns and finite CFD practises of element size, nodes, and shape appropriateness. The hot fluid flows through the annulus region and the cold fluid flows through the inner tube in the examined model with counterflow setup. After simulating fluid flow and performing a heat transfer study for a helical coil tube in tube HE with structural configuration as mentioned, post processing techniques is applied to produce the results as furnished by means of graphical representation. Moreover, upon discussion on the impact of variation of Nusselt number and friction factor were established, the analysed results create recommendations with the purpose of better understanding the impact of helical coil grooved tube heat transfer capacity in tube heat exchangers and future research. As a result, grooved inner tube treatment can significantly improve heat exchanger total heat transfer capacity, and the findings of this research can provide assistance theoretically for the development and design of helically coiled tubes in HEs.

PyMERRY: A Python solution for an improved interpretation of electrical resistivity tomography images

Electrical resistivity tomography (ERT) is a widely used geophysical method for studying geologic hazards, civil engineering, and environmental remediation. It provides information about the subsurface’s resistivity distribution by analyzing electrical data collected at the surface or in boreholes. However, interpreting ERT images can be complex due to ambiguities in their resolution. To address this issue, we develop a postprocessing method called Python iMprovement of Electrical Resistivity tomography ReliabilitY (PyMERRY) to improve the reliability of ERT images. The PyMERRY code can be applied to any 2D resistivity model obtained from ERT inversion software. It computes a coverage mask that defines the domain well constrained by the data and the inversion process. It also evaluates the resistivity uncertainties in the ERT models. In addition to the sensitivity approaches, PyMERRY provides low- and high-resistivity values for all covered cells. Synthetic tests indicate that the approach is efficient and highlight the importance of resistivity contrasts, mesh selection, electrode spacing, and profile length in the reliability of ERT images. Compared with previous studies, using PyMERRY in south-central Bhutan allows a more accurate interpretation of ERT images. It confirms a high-resistivity contrast across the topographic frontal thrust and reveals the existence of small-scale variations.

Hernia repair techniques: a comparative analysis of mesh types

A hernia is a condition characterized by the protrusion of an internal organ, often part of the intestine, through a weakened area in the surrounding muscle and tissue. Surgical intervention is the primary treatment option for most hernias, with procedures known as herniorrhaphy or hernioplasty. Traditional open surgery involves a sizable abdominal incision, granting direct access to the herniated tissue. Alternatively, minimally invasive laparoscopic surgery utilizes small incisions and specialized instruments, including a camera, for repair. Synthetic or biological mesh is frequently employed to reinforce weakened muscle or tissue, reducing hernia recurrence risk. Mesh is integral to hernia treatment, providing critical reinforcement and enabling tension-free closure. This article's rationale lies in the necessity for a comprehensive comparative analysis of hernia repair techniques, with a particular focus on the influence of different mesh types in abdominal hernia surgery. This research, initiated on 17 October 2023, involved an exhaustive review of existing literature via databases like PubMed, Web of Science, and Cochrane, employing a broad range of medical terminology combinations. The management of hernias has evolved significantly, and open hernia repair, especially using the Shouldice technique, remains valuable when the mesh is unavailable or undesired. Modern tension-free repair techniques, such as Lichtenstein and plug and patch, provide similar outcomes. Laparoscopic hernia repair, despite the longer surgery duration, offers advantages in terms of recurrence, recovery, and postoperative discomfort. Mesh selection is vital, with options like polypropylene, polyester, composite, biological, and 3D offering tailored attributes. The choice should consider patient history, hernia type, and surgeon expertise, necessitating awareness of evolving techniques and materials for optimal outcomes in hernia repair.

A variable step-size implementation of a new one-step block method for integrating Burgers' model equation

This article proposes a variable stepsize implementation of an improved one-step block method (OBM) that uses two intermediate points to solve Burgers' equation. The model's problems under consideration are semi-discretized by reducing them into an equivalent differential system using the method of lines. The OBM is improved with an embedding-like method executed in variable stepsize mode. A few of Burgers' real-life model problems are numerically solved to test the accuracy of our error estimation and mesh selection strategy. The numerical results confirmed that the variable stepsize implementation used in this manuscript performed better than the fixed stepsize implementation.