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Sample records for mesh materials surgisis

  1. Comparison of three different mesh materials in tension-free inguinal hernia repair: prolene versus Vypro versus surgisis.

    PubMed

    Puccio, F; Solazzo, M; Marciano, P

    2005-01-01

    Using mesh or a synthetic prosthesis during tension-free inguinal hernia repair has been shown to be safe and effective. We compared the final outcome in treating inguinal hernia in 45 patients using three different prosthetic materials: 15 patients underwent tension-free inguinal hernia repair using Prolene (polypropylene) mesh, 15 using Vypro (polyglactin and polypropylene) mesh, and 15 with Surgisis-a new bioactive material derived from porcine small intestinal submucosa. The aim of this study was to evaluate the safety and efficacy of tension-free inguinal repair using Surgisis, comparing it with conventional prosthetic materials. From January 2003 to December 2003, 45 male patients underwent Lichtenstein inguinal hernia repair. Median follow-up was 12 months, with a range of 1-16 months. Each patient underwent ultrasound evaluation of the inguinal region 1 month after surgery. All the procedures were completed under local anesthesia. There were no intraoperative complications, and all patients were discharged home the same day of surgery. No recurrent hernias and wound infections were observed in our post-operative follow-up period. Postoperative pain (visual analog score) and discomfort were lower in patients with Surgisis mesh. There was no statistically significant difference between the groups in terms of overall early and late complications; however, there was a tendency toward a higher incidence of pain and discomfort in Vypro and Prolene group. The median time to full recovery was significantly shorter in the Surgisis group. Surgisis mesh seems to be a promising new prosthetic material for hernia repair. Long-term follow-up is necessary to confirm these preliminary results.

  2. Laparoscopic Repair of Inguinal Hernia Using Surgisis Mesh and Fibrin Sealant

    PubMed Central

    2006-01-01

    Objective: We tested the hypothesis that laparoscopic inguinal herniorrhaphy using Surgisis mesh secured with fibrin sealant is an effective long-term treatment for repair of inguinal hernia. This case series involved 38 adult patients with 51 inguinal hernias treated in a primary care center. Methods: Between December 2002 and May 2005, 38 patients with 45 primary and 6 recurrent inguinal hernias were treated with laparoscopic repair by the total extra-peritoneal mesh placement (TEP) technique using Surgisis mesh secured into place with fibrin sealant. Postoperative complications, incidence of pain, and recurrence were recorded, as evaluated at 2 weeks, 6 weeks, 1 year, and with a follow-up questionnaire and telephone interview conducted in May and June 2005. Results: The operations were successfully performed on all patients with no complications or revisions to an open procedure. Average follow-up was 13 months (range, 1 to 30). One hernia recurred (second recurrence of unilateral direct hernia), indicating a 2% recurrence rate. Conclusions: Laparoscopic repair of inguinal hernia using Surgisis mesh secured with fibrin sealant can be effectively used to treat primary, recurrent, direct, indirect, and bilateral inguinal hernias in adults without complications and minimal recurrence within 1-year of follow-up. PMID:17575758

  3. The use of Surgisis for abdominal wall reconstruction in the separation of omphalopagus conjoined twins.

    PubMed

    Dasgupta, Roshni; Wales, Paul W; Zuker, Ronald M; Fisher, David M; Langer, Jacob C

    2007-09-01

    Abdominal wall reconstruction in omphalopagus twins poses a difficult reconstructive challenge, as separation often results in a large abdominal wall defect. A number of options are available for closure, including tissue flaps, expanders and patches made of foreign material. Surgisis is a new biodegradable small intestine scaffolding substrate that permits tissue in-growth and results in a permanent durable scar. We describe its use in abdominal wall reconstruction after separation of a set of conjoined twins. A set of omphalopagus conjoined twins shared liver and abdominal wall. After separation at 6 months of age, Twin A's abdomen could be closed primarily, but Twin B could not. A 4-ply Surgisis mesh was used in the upper abdominal closure, and a skin flap was created, to completely cover the patch. Both twins survived the operation. A small portion of the skin flap over the Surgisis broke down, healing by secondary intention. In follow up of over 18 months post procedure, there have been no wound infections and the abdominal wall is intact with no evidence of a hernia. Surgisis can be successfully used for the reconstruction of complex abdominal wall defects in the pediatric patient, including reconstruction after separation of conjoined twins.

  4. Mesh materials and hernia repair

    PubMed Central

    Elango, Santhini; Perumalsamy, Sakthivel; Ramachandran, Krishnakumar; Vadodaria, Ketankumar

    2017-01-01

    Hernia incidence has been observed since ancient time. Advancement in the medical textile industry came up with the variety of mesh materials to repair hernia, but none of them are without complications including recurrence of hernia. Therefore individuals once developed with the hernia could not lead a healthy and comfortable life. This drawn attention of surgeons, patients, researchers and industry to know the exact mechanism behind its development, complications and recurrence. Recent investigations highlighted the role of genetic factors and connective tissue disorders being the reason for the development of hernia apart from the abnormal pressure that is known to develop during other disease conditions. This review discusses different mesh materials, their advantages and disadvantages and their biological response after its implantation. PMID:28840830

  5. Prosthetic mesh materials used in hernia surgery.

    PubMed

    Sanders, David L; Kingsnorth, Andrew N

    2012-03-01

    It is estimated that 20 million prosthetic meshes are implanted each year worldwide. It is clear that the evolution of meshes is not yet complete and the ideal mesh is yet to be found. There is a vast array of prosthetics available for hernia repair. This review outlines the properties of available meshes and the evidence to be considered when choosing a prosthetic for hernia repair.

  6. Surgisis acellular collagen matrix in aesthetic and reconstructive plastic surgery soft tissue applications.

    PubMed

    Centeno, Robert F

    2009-04-01

    Tissue engineering in aesthetic and reconstructive plastic surgery remains an elusive goal. The advent of Surgisis extracellular collagen matrix and its performance characteristics suggest that the use of a bioengineered tissue substitute can meet some of our reconstructive requirements. Incorporation and replacement by host tissue with minimal allergic or immune response seems to be achievable today. The ability to engineer the device, the ready availability of substrate, and its cost effectiveness support the use of Surgisis in aesthetic and reconstructive plastic surgery applications. Future product innovations and engineering seem promising. The permanent role of Surgisis in aesthetic and reconstructive plastic surgery will be determined by its documented long-term performance.

  7. Gentamicin supplementation of polyvinylidenfluoride mesh materials for infection prophylaxis.

    PubMed

    Junge, Karsten; Rosch, Raphael; Klinge, Uwe; Krones, Carsten; Klosterhalfen, Bernd; Mertens, Peter R; Lynen, Petra; Kunz, Dagmar; Preiss, Achim; Peltroche-Llacsahuanga, Heidrun; Schumpelick, Volker

    2005-03-01

    Hernia repair evolved from pure tissue repair to mesh repair due to decreased recurrence rates. However, concern exists about mesh-related infections occurring even several years after initial operation. Therefore, a polyvinylidenfluoride (PVDF) mesh material was constructed and surface modified by plasma-induced graft polymerization of acrylic acid (PVDF+PAAc). Antimicrobial treatment was sought by binding of gentamicin (PVDF+PAAc+Gentamicin). In vitro efficacy and cytotoxicity was measured by agar diffusion test, L929 cytotoxicity testing and by analyzing the amount of gentamicin release from the mesh surface. In vivo biocompatibility was evaluated in 45 Sprague-Dawley rats. 7, 21 and 90 days after mesh implantation the amount of inflammatory and connective tissue as well as the percentage of proliferating (Ki67) and apoptotic cells (TUNEL) were analyzed at the perifilamentary region. Agar diffusion tests showed sufficient local antimicrobiotic effects against the bacteria tested after 24h of incubation. No signs of cytotoxicity could be identified by L929 testing. Furthermore, surface modification did not affect the in vivo biocompatibility. At the end of the observation period, no significant differences were found for the perifilamentary amount of inflammatory cells and connective tissue and the percentage of Ki67 and TUNEL positive stained cells. The presented data confirm that an antibiotic surface modification of PVDF mesh samples is feasible. By analyzing cytotoxicity in vitro as well as biocompatibility in vivo no side effects were observed.

  8. Adaptive mesh refinement for shocks and material interfaces

    SciTech Connect

    Dai, William Wenlong

    2010-01-01

    There are three kinds of adaptive mesh refinement (AMR) in structured meshes. Block-based AMR sometimes over refines meshes. Cell-based AMR treats cells cell by cell and thus loses the advantage of the nature of structured meshes. Patch-based AMR is intended to combine advantages of block- and cell-based AMR, i.e., the nature of structured meshes and sharp regions of refinement. But, patch-based AMR has its own difficulties. For example, patch-based AMR typically cannot preserve symmetries of physics problems. In this paper, we will present an approach for a patch-based AMR for hydrodynamics simulations. The approach consists of clustering, symmetry preserving, mesh continuity, flux correction, communications, management of patches, and load balance. The special features of this patch-based AMR include symmetry preserving, efficiency of refinement across shock fronts and material interfaces, special implementation of flux correction, and patch management in parallel computing environments. To demonstrate the capability of the AMR framework, we will show both two- and three-dimensional hydrodynamics simulations with many levels of refinement.

  9. Quality Partitioned Meshing of Multi-Material Objects

    PubMed Central

    Zhang, Qin; Cha, Deukhyun; Bajaj, Chandrajit

    2016-01-01

    We present a simple but effective algorithm for generating topologically and geometrically consistent quality triangular surface meshing of compactly packed multiple heterogeneous domains in R3. By compact packing we imply that adjacent homogeneous domains or materials share some 0, 1, and/or 2 dimensional boundary. Such packed multiple material (or multi-material) solids arise naturally from classification/partitioning/segmentation of homogeneous domains in R3 into different sub-regions. The multi-materials may also represent separate functionally classified sections or just be multiple component copies tightly fused together as perhaps by layered manufacturing processes. The input to our algorithm is a geometric representation of the entire multi-material solid, and a volumetric classification map identifying the individual materials. As output, each individual material region is represented by a triangulated 2-manifold boundary, with adjacent material regions having shared boundaries. Our algorithm has been implemented, and applied to different multi-material solids, and the results are additionally presented with quantitative analysis of detection and cure of non-manifold interfaces as well as spurious small components. These meshes are useful for combined boundary element analysis, however these simulation results are not presented. PMID:27563367

  10. Quality Partitioned Meshing of Multi-Material Objects.

    PubMed

    Zhang, Qin; Cha, Deukhyun; Bajaj, Chandrajit

    We present a simple but effective algorithm for generating topologically and geometrically consistent quality triangular surface meshing of compactly packed multiple heterogeneous domains in [Formula: see text]. By compact packing we imply that adjacent homogeneous domains or materials share some 0, 1, and/or 2 dimensional boundary. Such packed multiple material (or multi-material) solids arise naturally from classification/partitioning/segmentation of homogeneous domains in [Formula: see text] into different sub-regions. The multi-materials may also represent separate functionally classified sections or just be multiple component copies tightly fused together as perhaps by layered manufacturing processes. The input to our algorithm is a geometric representation of the entire multi-material solid, and a volumetric classification map identifying the individual materials. As output, each individual material region is represented by a triangulated 2-manifold boundary, with adjacent material regions having shared boundaries. Our algorithm has been implemented, and applied to different multi-material solids, and the results are additionally presented with quantitative analysis of detection and cure of non-manifold interfaces as well as spurious small components. These meshes are useful for combined boundary element analysis, however these simulation results are not presented.

  11. An Automatic 3D Mesh Generation Method for Domains with Multiple Materials

    PubMed Central

    Zhang, Yongjie; Hughes, Thomas J.R.; Bajaj, Chandrajit L.

    2009-01-01

    This paper describes an automatic and efficient approach to construct unstructured tetrahedral and hexahedral meshes for a composite domain made up of heterogeneous materials. The boundaries of these material regions form non-manifold surfaces. In earlier papers, we developed an octree-based isocontouring method to construct unstructured 3D meshes for a single-material (homogeneous) domain with manifold boundary. In this paper, we introduce the notion of a material change edge and use it to identify the interface between two or several different materials. A novel method to calculate the minimizer point for a cell shared by more than two materials is provided, which forms a non-manifold node on the boundary. We then mesh all the material regions simultaneously and automatically while conforming to their boundaries directly from volumetric data. Both material change edges and interior edges are analyzed to construct tetrahedral meshes, and interior grid points are analyzed for proper hexahedral mesh construction. Finally, edge-contraction and smoothing methods are used to improve the quality of tetrahedral meshes, and a combination of pillowing, geometric flow and optimization techniques is used for hexahedral mesh quality improvement. The shrink set of pillowing schemes is defined automatically as the boundary of each material region. Several application results of our multi-material mesh generation method are also provided. PMID:20161555

  12. Coated mesh photocatalytic reactor for air treatment applications: comparative study of support materials.

    PubMed

    Passalía, Claudio; Nocetti, Emanuel; Alfano, Orlando; Brandi, Rodolfo

    2017-03-01

    An experimental comparative study of different meshes as support materials for photocatalytic applications in gas phase is presented. The photocatalytic oxidation of dichloromethane in air was addressed employing different coated meshes in a laboratory-scale, continuous reactor. Two fiberglass meshes and a stainless steel mesh were studied regarding the catalyst load, adherence, and catalytic activity. Titanium dioxide photocatalyst was immobilized on the meshes by dip-coating cycles. Results indicate the feasibility of the dichloromethane elimination in the three cases. When the number of coating cycles was doubled, the achieved conversion levels were increased twofold for stainless steel and threefold for the fiberglass meshes. One of the fiberglass meshes (FG2) showed the highest reactivity per mass of catalyst and per catalytic surface area.

  13. Successful closure of gastrocutaneous fistulas using the Surgisis® anal fistula plug

    PubMed Central

    Kasem, H

    2014-01-01

    Introduction Gastrocutaneous fistulas remain an uncommon complication of upper gastrointestinal surgery. Less common but equally problematic are gastrocutaneous fistulas secondary to non-healing gastrostomies. Both are associated with considerable morbidity and mortality. Surgical repair remains the gold standard of care. For those unfit for surgical intervention, results from conservative management can be disappointing. We describe a case series of seven patients with gastrocutaneous fistulas who were unfit for surgical intervention. These patients were managed successfully in a minimally invasive manner using the Surgisis® (Cook Surgical, Bloomington, IN, US) anal fistula plug. Methods Between September 2008 and January 2009, seven patients with gastrocutaneous fistulas presented to Wishaw General Hospital. Four gastrocutaneous fistulas represented non-healing gastrostomies, two followed an anastomotic leak after an oesophagectomy and one following an anastomotic leak after a distal gastrectomy. All patients had poor nutritional reserve with no other identifiable reason for failure to heal. All were deemed unfit for surgical intervention. Five gastrocutaneous fistulas were closed successfully using the Surgisis® anal fistula plug positioned directly into the fistula tract under local anaesthesia and two gastrocutaneous fistulas were closed successfully using the Surgisis® anal fistula positioned endoscopically using a rendezvous technique. Results For the five patients with gastrocutaneous fistulas closed directly under local anaesthesia, oral alimentation was reinstated immediately. Fistula output ceased on day 12 with complete epithelialisation occurring at a median of day 26. For the two gastrocutaneous fistulas closed endoscopically using the rendezvous technique, oral alimentation was reinstated on day 5 with immediate cessation of fistula output. Follow-up upper gastrointestinal endoscopy confirmed re-epithelialisation at eight weeks. In none of the

  14. Successful closure of gastrocutaneous fistulas using the Surgisis(®) anal fistula plug.

    PubMed

    Darrien, J H; Kasem, H

    2014-05-01

    Gastrocutaneous fistulas remain an uncommon complication of upper gastrointestinal surgery. Less common but equally problematic are gastrocutaneous fistulas secondary to non-healing gastrostomies. Both are associated with considerable morbidity and mortality. Surgical repair remains the gold standard of care. For those unfit for surgical intervention, results from conservative management can be disappointing. We describe a case series of seven patients with gastrocutaneous fistulas who were unfit for surgical intervention. These patients were managed successfully in a minimally invasive manner using the Surgisis(®) (Cook Surgical, Bloomington, IN, US) anal fistula plug. Between September 2008 and January 2009, seven patients with gastrocutaneous fistulas presented to Wishaw General Hospital. Four gastrocutaneous fistulas represented non-healing gastrostomies, two followed an anastomotic leak after an oesophagectomy and one following an anastomotic leak after a distal gastrectomy. All patients had poor nutritional reserve with no other identifiable reason for failure to heal. All were deemed unfit for surgical intervention. Five gastrocutaneous fistulas were closed successfully using the Surgisis(®) anal fistula plug positioned directly into the fistula tract under local anaesthesia and two gastrocutaneous fistulas were closed successfully using the Surgisis(®) anal fistula positioned endoscopically using a rendezvous technique. For the five patients with gastrocutaneous fistulas closed directly under local anaesthesia, oral alimentation was reinstated immediately. Fistula output ceased on day 12 with complete epithelialisation occurring at a median of day 26. For the two gastrocutaneous fistulas closed endoscopically using the rendezvous technique, oral alimentation was reinstated on day 5 with immediate cessation of fistula output. Follow-up upper gastrointestinal endoscopy confirmed re-epithelialisation at eight weeks. In none of the cases has there been

  15. Materials characterization of explanted polypropylene hernia mesh: Patient factor correlation.

    PubMed

    Smith, Sarah E; Cozad, Matthew J; Grant, David A; Ramshaw, Bruce J; Grant, Sheila A

    2016-02-01

    This study quantitatively assessed polypropylene (PP) hernia mesh degradation and its correlation with patient factors including body mass index, tobacco use, and diabetes status with the goal of improving hernia repair outcomes through patient-matched mesh. Thirty PP hernia mesh explants were subjected to a tissue removal process followed by assessment of their in vivo degradation using Fourier transform infrared, differential scanning calorimetry, and thermogravimetric analysis analyses. Results were then analyzed with respect to patient factors (body mass index, tobacco use, and diabetes status) to determine their influence on in vivo hernia mesh oxidation and degradation. Twenty of the explants show significant surface oxidation. Tobacco use exhibits a positive correlation with modulated differential scanning calorimetry melt temperature and exhibits significantly lower TGA decomposition temperatures than non-/past users. Chemical and thermal characterization of the explanted meshes indicate measurable degradation while in vivo regardless of the patient population; however, tobacco use is correlated with less oxidation and degradation of the polymeric mesh possibly due to a reduced inflammatory response.

  16. Infection susceptibility of crosslinked and non-crosslinked biological meshes in an experimental contaminated environment.

    PubMed

    Mulder, Irene M; Deerenberg, Eva B; Bemelman, Willem A; Jeekel, Johannes; Lange, Johan F

    2015-07-01

    This experimental study investigates infectious complications and functional outcome of biological meshes in a contaminated environment. In 90 rats peritonitis was induced, and after 24 hours, a biological mesh was implanted intraperitoneally including 2 non-crosslinked mesh groups (Strattice and Surgisis) and 2 crosslinked mesh groups (CollaMendFM and Permacol). Sacrifice was after 90 and 180 days. More mesh infections occurred in crosslinked meshes compared with non-crosslinked meshes (70% vs 4%; P < .001). Mesh infection was the highest in crosslinked CollaMendFM (81.2%) and lowest in non-crosslinked Strattice groups (0%). Incorporation into the abdominal wall was poor in all meshes (0% to 39%). After 180 days no residue of non-crosslinked Surgisis mesh was found. After 180 days, shrinkage was .8% in crosslinked Permacol and 20% in Strattice groups. Strattice showed the least adhesion formation (median 5%). Infection rate of biological meshes in a contaminated field was the highest in crosslinked meshes. All biological meshes showed poor incorporation, which makes long-term abdominal wall repair questionable. Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Synthetic surgical meshes used in abdominal wall surgery: Part I-materials and structural conformation.

    PubMed

    Todros, S; Pavan, P G; Natali, A N

    2017-04-01

    Surgical implants are commonly used in abdominal wall surgery for hernia repair. Many different prostheses are currently offered to surgeons, comprising permanent synthetic polymer meshes and biologic scaffolds. There is a wide range of synthetic meshes currently available on the market with differing chemical compositions, fiber conformations, and mesh textures. These chemical and structural characteristics determine a specific biochemical and mechanical behavior and play a crucial role in guaranteeing a successful post-operative outcome. Although an increasing number of studies report on the structural and mechanical properties of synthetic surgical meshes, nowadays there are no consistent guidelines for the evaluation of mechanical biocompatibility or common criteria for the selection of prostheses. The aim of this work is to review synthetic meshes by considering the extensive bibliography documentation of their use in abdominal wall surgery, taking into account their material and structural properties, in Part I, and their mechanical behavior, in Part II. The main materials available for the manufacture of polymeric meshes are described, including references to their chemical composition, fiber conformation, and textile structural properties. These characteristics are decisive for the evaluation of mesh-tissue interaction process, including foreign body response, mesh encapsulation, infection, and adhesion formation. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 689-699, 2017. © 2015 Wiley Periodicals, Inc.

  18. Approximate static condensation algorithm for solving multi-material diffusion problems on meshes non-aligned with material interfaces

    DOE PAGES

    Kikinzon, Evgeny; Kuznetsov, Yuri; Lipnikov, Konstatin; ...

    2017-07-08

    In this study, we describe a new algorithm for solving multi-material diffusion problem when material interfaces are not aligned with the mesh. In this case interface reconstruction methods are used to construct approximate representation of interfaces between materials. They produce so-called multi-material cells, in which materials are represented by material polygons that contain only one material. The reconstructed interface is not continuous between cells. Finally, we suggest the new method for solving multi-material diffusion problems on such meshes and compare its performance with known homogenization methods.

  19. Do collagen meshes offer any benefits over preclude® ePTFE implants in contaminated surgical fields? A comparative in vitro and in vivo study.

    PubMed

    García-Pumarino, Rubén; Pascual, Gemma; Rodríguez, Marta; Pérez-Köhler, Bárbara; Bellón, Juan Manuel

    2014-02-01

    The surgical repair of an abdominal wall defect may be complicated by infection. We examined the in vitro and in vivo behavior of Staphylococcus aureus (Sa) and Staphylococcus epidermidis (Se) when placed in contact with three collagen bioprostheses. For the in vitro study, 1 cm(2) fragments of the collagen meshes (Collamend®, Surgisis®, and Permacol®) and a control polytetrafluoroethylene mesh, Preclude®(ePTFE) were incubated on blood agar plates inoculated with Sa or Se. In the in vivo study, 2 partial 3 × 3 cm defects were created in the abdominal wall of 72 rabbits and infected with a suspension-containing 10(6) Colony-forming unit (CFU) of Sa or Se. The defects were then repaired using the above materials. At 14 and 30 days postimplant, mesh specimens were obtained for histological, morphometric, and biomechanical analysis. The incubated collagen meshes showed significantly greater bacterial loads than the ePTFE. In vivo, large abscesses comprised of bacteria (Sa/Se), detritus and white cells could be seen 14 days post-implant. At 30 days, the bacterial infiltrate was reduced in the Se group. In conclusion, in presence of bacterial contamination, no benefits were observed of the use of the collagen bioprostheses tested over the use of a non porous ePTFE mesh (Preclude®). Copyright © 2013 Wiley Periodicals, Inc.

  20. Kull ALE: I. Unstructured Mesh Advection, Interface Capturing, and Multiphase 2T RHD with Material Interfaces

    SciTech Connect

    Anninos, P

    2002-02-11

    Several advection algorithms are presented within the remap framework for unstructured mesh ALE codes. The methods discussed include a generic advection scheme based on a finite volume approach, and three groups of algorithms for the treatment of material boundary interfaces. The interface capturing algorithms belong to the Volume of Fluid (VoF) class of methods to approximate material interfaces from the local fractional volume of fluid distribution in arbitrary unstructured polyhedral meshes appropriate for the Kull code. Also presented are several schemes for extending single material radiation diffusion solvers to account for multi-material interfaces.

  1. High-Fidelity Geometric Modeling and Mesh Generation for Mechanics Characterization of Polycrystalline Materials

    DTIC Science & Technology

    2015-01-07

    AFRL-OSR-VA-TR-2015-0039 High-Fidelity Geometric Modeling and Mesh Generation for Mechanics Characterization of Polycrystalline Materials Yongjie...0188 The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing...From - To) Oct 1, 2011-Sep 30, 2014 4. TITLE AND SUBTITLE High-Fidelity Geometric Modeling and Mesh Generation for Mechanics Characterization of

  2. Biomechanics and biocompatibility of woven spider silk meshes during remodeling in a rodent fascia replacement model.

    PubMed

    Schäfer-Nolte, Franziska; Hennecke, Kathleen; Reimers, Kerstin; Schnabel, Reinhild; Allmeling, Christina; Vogt, Peter M; Kuhbier, Joern W; Mirastschijski, Ursula

    2014-04-01

    The aim of this study was to investigate biomechanical and immunogenic properties of spider silk meshes implanted as fascia replacement in a rat in vivo model. Meshes for hernia repair require optimal characteristics with regard to strength, elasticity, and cytocompatibility. Spider silk as a biomaterial with outstanding mechanical properties is potentially suitable for this application. Commercially available meshes used for hernia repair (Surgisis and Ultrapro) were compared with handwoven meshes manufactured from native dragline silk of Nephila spp. All meshes were tied onto the paravertebral fascia, whereas sham-operated rats were sutured without mesh implantation. After 4 or 14 days, 4 weeks, and 4 or 8 months, tissue samples were analyzed concerning inflammation and biointegration both by histological and biochemical methods and by biomechanical stability tests. Histological sections revealed rapid cell migration into the spider silk meshes with increased numbers of giant cells compared with controls with initial decomposition of silk fibers after 4 weeks. Four months postoperatively, spider silk was completely degraded with the formation of a stable scar verified by constant tensile strength values. Surgisis elicited excessive stability loss from day 4 to day 14 (P < 0.001), with distinct inflammatory reaction demonstrated by lymphocyte and neutrophil invasion. Ultrapro also showed decreasing strength and poor elongation behavior, whereas spider silk samples had the highest relative elongation (P < 0.05). Hand-manufactured spider silk meshes with good biocompatibility and beneficial mechanical properties seem superior to standard biological and synthetic meshes, implying an innovative alternative to currently used meshes for hernia repair.

  3. Multiphase Advection and Radiation Diffusion with Material Interfaces on Unstructured Meshes

    SciTech Connect

    Anninos, P

    2002-10-03

    A collection of numerical methods are presented for the advection or remapping of material properties on unstructured and staggered polyhedral meshes in arbitrary Lagrange-Eulerian calculations. The methods include several new procedures to track and capture sharp interface boundaries, and to partition radiation energy into multi-material thermal states. The latter is useful for extending and applying consistently single material radiation diffusion solvers to multi-material problems.

  4. Materials characterization and histological analysis of explanted polypropylene, PTFE, and PET hernia meshes from an individual patient

    PubMed Central

    Wood, A. J.; Cozad, M. J.; Grant, D. A.; Ostdiek, A. M.; Bachman, S. L.

    2014-01-01

    During its tenure in vivo, synthetic mesh materials are exposed to foreign body responses, which can alter physicochemical properties of the material. Three different synthetic meshes comprised of polypropylene, expanded polytetrafluoroethylene (ePTFE), and polyethylene terephthalate (PET) materials were explanted from a single patient providing an opportunity to compare physicochemical changes between three different mesh materials in the same host. Results from infrared spectroscopy demonstrated significant oxidation in polypropylene mesh while ePTFE and PET showed slight chemical changes that may be caused by adherent scar tissue. Differential scanning calorimetry results showed a significant decrease in the heat of enthalpy and melt temperature in the polypropylene mesh while the ePTFE and PET showed little change. The presence of giant cells and plasma cells surrounding the ePTFE and PET were indicative of an active foreign body response. Scanning electron micrographs and photo micrographs displayed tissue entrapment and distortion of all three mesh materials. PMID:23371769

  5. Mechanical Properties of Mesh Materials Used for Hernia Repair and Soft Tissue Augmentation

    PubMed Central

    Pott, Peter P.; Schwarz, Markus L. R.; Gundling, Ralf; Nowak, Kai; Hohenberger, Peter; Roessner, Eric D.

    2012-01-01

    Background Hernia repair is the most common surgical procedure in the world. Augmentation with synthetic meshes has gained importance in recent decades. Most of the published work about hernia meshes focuses on the surgical technique, outcome in terms of mortality and morbidity and the recurrence rate. Appropriate biomechanical and engineering terminology is frequently absent. Meshes are under continuous development but there is little knowledge in the public domain about their mechanical properties. In the presented experimental study we investigated the mechanical properties of several widely available meshes according to German Industrial Standards (DIN ISO). Methodology/Principal Findings Six different meshes were assessed considering longitudinal and transverse direction in a uni-axial tensile test. Based on the force/displacement curve, the maximum force, breaking strain, and stiffness were computed. According to the maximum force the values were assigned to the groups weak and strong to determine a base for comparison. We discovered differences in the maximum force (11.1±6.4 to 100.9±9.4 N/cm), stiffness (0.3±0.1 to 4.6±0.5 N/mm), and breaking strain (150±6% to 340±20%) considering the direction of tension. Conclusions/Significance The measured stiffness and breaking strength vary widely among available mesh materials for hernia repair, and most of the materials show significant anisotropy in their mechanical behavior. Considering the forces present in the abdominal wall, our results suggest that some meshes should be implanted in an appropriate orientation, and that information regarding the directionality of their mechanical properties should be provided by the manufacturers. PMID:23071685

  6. Comparative analysis of histopathologic effects of synthetic meshes based on material, weight, and pore size in mice.

    PubMed

    Orenstein, Sean B; Saberski, Ean R; Kreutzer, Donald L; Novitsky, Yuri W

    2012-08-01

    While synthetic prosthetics have essentially become mandatory for hernia repair, mesh-induced chronic inflammation and scarring can lead to chronic pain and limited mobility. Mesh propensity to induce such adverse effects is likely related to the prosthetic's material, weight, and/or pore size. We aimed to compare histopathologic responses to various synthetic meshes after short- and long-term implantations in mice. Samples of macroporous polyester (Parietex [PX]), heavyweight microporous polypropylene (Trelex[TX]), midweight microporous polypropylene (ProLite[PL]), lightweight macroporous polypropylene (Ultrapro[UP]), and expanded polytetrafluoroethylene (DualMesh[DM]) were implanted subcutaneously in mice. Four and 12 wk post-implantation, meshes were assessed for inflammation, foreign body reaction (FBR), and fibrosis. All meshes induced varying levels of inflammatory responses. PX induced the greatest inflammatory response and marked FBR. DM induced moderate FBR and a strong fibrotic response with mesh encapsulation at 12 wk. UP and PL had the lowest FBR, however, UP induced a significant chronic inflammatory response. Although inflammation decreased slightly for TX, marked FBR was present throughout the study. Of the three polypropylene meshes, fibrosis was greatest for TX and slightly reduced for PL and UP. For UP and PL, there was limited fibrosis within each mesh pore. Polyester mesh induced the greatest FBR and lasting chronic inflammatory response. Likewise, marked fibrosis and encapsulation was seen surrounding ePTFE. Heavier polypropylene meshes displayed greater early and persistent fibrosis; the reduced-weight polypropylene meshes were associated with the least amount of fibrosis. Mesh pore size was inversely proportional to bridging fibrosis. Moreover, reduced-weight polypropylene meshes demonstrated the smallest FBR throughout the study. Overall, we demonstrated that macroporous, reduced-weight polypropylene mesh exhibited the highest degree of

  7. Initial experience of treating anal fistula with the Surgisis anal fistula plug.

    PubMed

    Chan, S; McCullough, J; Schizas, A; Vasas, P; Engledow, A; Windsor, A; Williams, A; Cohen, C R

    2012-06-01

    Complex anal fistulas remain a challenge for the colorectal surgeon. The anal fistula plug has been developed as a simple treatment for fistula-in-ano. We present and evaluate our experience with the Surgisis anal fistula plug from two centres. Data were prospectively collected and analysed from consecutive patients undergoing insertion of a fistula plug between January 2007 and October 2009. Fistula plugs were inserted according to a standard protocol. Data collected included patient demographics, fistula characteristics and postoperative outcome. Forty-four patients underwent insertion of 62 plugs (27 males, mean age 45.6 years), 25 of whom had prior fistula surgery. Mean follow-up was 10.5 months Twenty-two patients (50%) had successful healing following the insertion of plug with an overall success rate of 23 out of 62 plugs inserted (35%). Nineteen out of 29 patients healed following first-time plug placement, whereas repeated plug placement was successful in 3 out of 15 patients (20%; p = 0.0097). There was a statistically significant difference in the healing rate between patients who had one or less operations prior to plug insertion (i.e. simple fistulas) compared with patients who needed multiple operations (18 out of 24 patients vs. 4 out of 20 patients; p = 0.0007). Success of treatment with the Surgisis anal fistula plug relies on the eradication of sepsis prior to plug placement. Plugs inserted into simple tracts have a higher success rate, and recurrent insertion of plugs following previous plug failure is less likely to be successful. We suggest the fistula plug should remain a first-line treatment for primary surgery and simple tracts.

  8. A Predictive Model of Fragmentation using Adaptive Mesh Refinement and a Hierarchical Material Model

    SciTech Connect

    Koniges, A E; Masters, N D; Fisher, A C; Anderson, R W; Eder, D C; Benson, D; Kaiser, T B; Gunney, B T; Wang, P; Maddox, B R; Hansen, J F; Kalantar, D H; Dixit, P; Jarmakani, H; Meyers, M A

    2009-03-03

    Fragmentation is a fundamental material process that naturally spans spatial scales from microscopic to macroscopic. We developed a mathematical framework using an innovative combination of hierarchical material modeling (HMM) and adaptive mesh refinement (AMR) to connect the continuum to microstructural regimes. This framework has been implemented in a new multi-physics, multi-scale, 3D simulation code, NIF ALE-AMR. New multi-material volume fraction and interface reconstruction algorithms were developed for this new code, which is leading the world effort in hydrodynamic simulations that combine AMR with ALE (Arbitrary Lagrangian-Eulerian) techniques. The interface reconstruction algorithm is also used to produce fragments following material failure. In general, the material strength and failure models have history vector components that must be advected along with other properties of the mesh during remap stage of the ALE hydrodynamics. The fragmentation models are validated against an electromagnetically driven expanding ring experiment and dedicated laser-based fragmentation experiments conducted at the Jupiter Laser Facility. As part of the exit plan, the NIF ALE-AMR code was applied to a number of fragmentation problems of interest to the National Ignition Facility (NIF). One example shows the added benefit of multi-material ALE-AMR that relaxes the requirement that material boundaries must be along mesh boundaries.

  9. Histopathologic host response to polypropylene-based surgical mesh materials in a rat abdominal wall defect model.

    PubMed

    Huber, Alexander; Boruch, Alan V; Nieponice, Alejandro; Jiang, Hongbin; Medberry, Christopher; Badylak, Stephen F

    2012-04-01

    Composite polypropylene-based surgical mesh materials including various synthetic polymers and naturally occurring biomaterials have been developed to ameliorate device-associated inflammatory response and associated reduced compliance of pure polypropylene meshes. This study evaluated the histomorphologic response of three composite polypropylene-based surgical meshes, Revive™, a polycarbonate polyurethane reinforced monofilamentous polypropylene scaffold, Assure™, a polycarbonate polyurethane reinforced monofilamentous polypropylene scaffold with a resorbable anti-adhesion layer of lactide caprolactone copolymer, and Proceed™, a polypropylene mesh modified with oxidized cellulose, in a soft tissue repair model in the rat. The host inflammatory response and neotissue formation were evaluated by semiquantitative histologic scoring including the amount of cellular infiltration, angiogenesis, presence of multinucleate giant cells, fibrous connective tissue formation, and host neo-extracellular matrix deposition for up to 26 weeks. All three composite surgical mesh materials showed good integration with host tissue as indicated by rapid cellular infiltration, abundant neo-vascularization, minimal shrinkage, and the lack of visible mesh degradation. The devices elicited a similar inflammatory response and the presence of a mild foreign body response in spite of the different composition and morphology of these composite mesh materials. Copyright © 2011 Wiley Periodicals, Inc.

  10. Use of three types of synthetic mesh material in sling surgery: a prospective randomized clinical trial evaluating effectiveness and complications.

    PubMed

    Okulu, Emrah; Kayigil, Onder; Aldemir, Mustafa; Onen, Efe

    2013-06-01

    The aim of this study was to determine the surgical success and complication rates of mixed type of mesh materials compared with Prolene mesh in sling surgery over a 4-year follow-up period. Between 2005 and 2007, broad-based double-forced sling operations were performed in 144 women with stress incontinence using three different types of mesh material. Group I consisted of 48 patients in whom Vypro® mesh (Ethicon, USA) was used; group II of 48 patients in whom Ultrapro® mesh (Ethicon) and group III of 48 patients in whom Prolene® light mesh (Ethicon) was used. The patients' data and the success of the operation were evaluated based on the 24 h pad test, International Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF) scoring and Korman questionnaire analysis. The ICIQ-SF score, the number of pads used and the results of 24 h pad test were statistically lower in group II at postoperative month 48 (p < 0.05). The rate of postoperative complications was lower in Group II than in the other groups (p < 0.05). The continence rates of groups I, II and III were 84.7%, 91.6% and 85.1%, respectively, in the 48th postoperative month. Ultrapro mesh can be used in sling surgery owing to its higher success rates, and lower vaginal and urethral extrusion and de novo urgency rates, which have also been shown in clinical studies.

  11. Improvement in color properties of copper mesh electrodes via electrophoretic coating with nano-structured carbon materials

    NASA Astrophysics Data System (ADS)

    Hwang, Young-Jin; Kim, Bu-Jong; Park, Jin-Seok

    2017-03-01

    In this study, the effects of coating with nano-structured carbon materials, such as carbon nanotube (CNT) and graphene, on the characteristics of transparent conductive electrodes based on copper (Cu) meshes, particularly on the visibility related to their color properties, were examined. The electrical sheet resistance of the Cu meshes remained almost unchanged regardless of the coating with CNT and graphene. Through the electrophoretic deposition method, the CNT and graphene layers were selectively used to coat only the regions where Cu mesh patterns had been formed, which helped minimize the transmittance loss caused by the coating with CNT and graphene. The reflectance of the Cu mesh was substantially reduced by the coating with CNT and graphene, meaning that the CNT or graphene coating layer played the role of suppressing the visible light reflected from the Cu mesh. In addition, the reflectance reduction effect was greater when the Cu mesh was coated with CNT rather than with graphene, which was attributed to the difference in particle size between the CNT suspension and the graphene suspension. Furthermore, the chromatic parameters (e.g., redness, yellowness) of the Cu meshes approached almost zero as the thickness of the CNT or graphene coating layer increased, meaning that the Cu meshes became nearly colorless, while the primitive Cu mesh was tinged with a red-orange color. The experiment results presented in this study verified that the combined technology with CNT and graphene coating contributed to the amelioration of the poor visibility caused by the high reflectance and color-tinted nature of the conventional Cu mesh.

  12. High-Fidelity Geometric Modeling and Mesh Generation for Mechanics Characterization of Polycrystalline Materials

    DTIC Science & Technology

    2014-10-26

    from Cross Field. Workshop on Structured Meshing: Theory, Application and Evaluation, the 27th Conference on Computer Animation and Social Agents ( CASA ...Workshop on Structured Meshing: Theory, Application and Evaluation, the 27th Conference on Computer Animation and Social Agents ( CASA 2014). Houston, TX...Cross Field. Workshop on Structured Meshing: Theory, Application and Evaluation, the 27th Conference on Computer Animation and Social Agents ( CASA 2014

  13. Mesh implants: An overview of crucial mesh parameters

    PubMed Central

    Zhu, Lei-Ming; Schuster, Philipp; Klinge, Uwe

    2015-01-01

    Hernia repair is one of the most frequently performed surgical interventions that use mesh implants. This article evaluates crucial mesh parameters to facilitate selection of the most appropriate mesh implant, considering raw materials, mesh composition, structure parameters and mechanical parameters. A literature review was performed using the PubMed database. The most important mesh parameters in the selection of a mesh implant are the raw material, structural parameters and mechanical parameters, which should match the physiological conditions. The structural parameters, especially the porosity, are the most important predictors of the biocompatibility performance of synthetic meshes. Meshes with large pores exhibit less inflammatory infiltrate, connective tissue and scar bridging, which allows increased soft tissue ingrowth. The raw material and combination of raw materials of the used mesh, including potential coatings and textile design, strongly impact the inflammatory reaction to the mesh. Synthetic meshes made from innovative polymers combined with surface coating have been demonstrated to exhibit advantageous behavior in specialized fields. Monofilament, large-pore synthetic meshes exhibit advantages. The value of mesh classification based on mesh weight seems to be overestimated. Mechanical properties of meshes, such as anisotropy/isotropy, elasticity and tensile strength, are crucial parameters for predicting mesh performance after implantation. PMID:26523210

  14. Characterizing mesh size distributions (MSDs) in thermosetting materials using a high-pressure system.

    PubMed

    Larché, J-F; Seynaeve, J-M; Voyard, G; Bussière, P-O; Gardette, J-L

    2011-04-21

    The thermoporosimetry method was adapted to determine the mesh size distribution of an acrylate thermoset clearcoat. This goal was achieved by increasing the solvent rate transfer by increasing the pressure and temperature. A comparison of the results obtained using this approach with those obtained by DMA (dynamic mechanical analysis) underlined the accuracy of thermoporosimetry in characterizing the macromolecular architecture of thermosets. The thermoporosimetry method was also used to analyze the effects of photoaging on cross-linking, which result from the photodegradation of the acrylate thermoset. It was found that the formation of a three-dimensional network followed by densification generates a modification of the average mesh size that leads to a dramatic decrease of the meshes of the polymer.

  15. Carbon fiber/copper mesh reinforced carbon composite for sliding contact material

    NASA Astrophysics Data System (ADS)

    Deng, Chaoyong; Zhang, Hongbo; Yin, Jian; Xiong, Xiang; Wang, Pei; Sun, Miao

    2017-02-01

    A novel carbon fiber/copper mesh knitted fabric reinforced carbon (Cf/Cu/C) composite was fabricated by a CVI-I/C technique. The mechanical, electrical, arc discharge and tribological properties of the Cf/Cu/C composite were compared with those of a traditional C/Cu composite fabricated by powder metallurgy. The results show that the copper mesh distributes uniformly in the Cf/Cu/C composite, and it exhibits higher mechanical property and more excellent electrical resistivity than those of the C/Cu composite. Meanwhile, the arc resistance property of Cf/Cu/C composite is also better than the C/Cu composite under the same testing conditions. The wear rate is about 80% of the C/Cu composite.

  16. A peeling mesh.

    PubMed

    Bohmer, R D; Byrne, P D; Maddern, G J

    2002-07-01

    A number of different materials are available for incisional hernia repair. Benefits of the various types are controversial and are partly dependent on the anatomical placement of the mesh. Composite mesh has been introduced to provide tissue ingrowth for strength and a non-adherent side to protect the bowel, these layers being laminated together. This report is on the separation of layers in an infected mesh and adherence of the expanded polytetrafluoroethylene layer to the small bowel.

  17. A discontinuous Galerkin method on refined meshes for the two-dimensional time-harmonic Maxwell equations in composite materials

    NASA Astrophysics Data System (ADS)

    Lohrengel, Stephanie; Nicaise, Serge

    2007-09-01

    In this paper, a discontinuous Galerkin method for the two-dimensional time-harmonic Maxwell equations in composite materials is presented. The divergence constraint is taken into account by a regularized variational formulation and the tangential and normal jumps of the discrete solution at the element interfaces are penalized. Due to an appropriate mesh refinement near exterior and interior corners, the singular behaviour of the electromagnetic field is taken into account. Optimal error estimates in a discrete energy norm and in the L2-norm are proved in the case where the exact solution is singular.

  18. 50 CFR 300.110 - Mesh size.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... material and capable of retaining their shape. They may have either a series of parallel-edged sides... the resistance of the mesh. (3) Selection of meshes to be measured. (i) Meshes to be measured will...

  19. Magnetically tunable double-negative material composed of ferrite-dielectric and metallic mesh

    NASA Astrophysics Data System (ADS)

    He, Guanghua; Wu, Rui-xin; Poo, Yin; Chen, Ping

    2010-05-01

    We designed and studied a magnetic tunable metamaterial composed of ferrite-dielectric and metallic mesh. The retrieved electromagnetic parameters and the transmission characteristic showed the composite has a double-negative regime in magnetized state. Moreover, this regime is tunable in external magnetic fields. The composite has a lower loss with minimum about -0.3 dB/mm. The simulations of the wave propagation on the interface of the composite clearly display a negative refraction. The negative indexes calculated from Snell's law are in good agreement with the indexes retrieved from S parameters, quantitatively confirms the negative index of the composite.

  20. [Experience with titanium mesh as a temporary foreign material implant for the reconstruction of mandibular defects].

    PubMed

    Hauenstein, H; Steinhäuser, E W

    1977-07-01

    Restoration of a loadable mandible after extensive resections, defects or comminuted fractures, serious osteomyelitis and pseudarthrosis will be successful only if sufficiently stable fixation of the fragments and immobilization beyond the physiological period of bone healing are guaranteed. By means of various types of plates and extroral appliances for osteosynthesis the conventional methods have been improved, but failures and complications are still frequent. The treatment itself is a great strain for the patient. The titanium mesh implant system developed by Ph. Boyne and his group for reconstruction in mandibular defects means, in our opinion, an important therapeutical step forward. Its technical advantages and our own clinical experience advocate application of this system.

  1. Sexual function in women after vaginal surgery with synthetic mesh material.

    PubMed

    Rivière, J G L; Pruiksma, T R H; Jacquemyn, N; Jacquemyn, Y

    2014-01-01

    To prospectively assess the impact of surgery for stress urinary incontinence (SUI) and pelvic organ prolapse (POP) with vaginal synthetic mesh on female sexual function and satisfaction. Forty-four women treated by vaginal surgery for SUI and POP between October 2009 and October 2011 were asked to fill in questionnaires at baseline and at six months after surgery to determine the impact on their sexual function and satisfaction. The questionnaires used for assessment were the 19-item Female Sexual Function Index (FSFI) and the Dutch Seksueel Functioneren Algemeen (General sexual function) or SFA-questionnaire. The questionnaire was completed by 27 patients (61.4%) at baseline; Nineteen reported being sexually active and eight were not. At six months follow-up, the questionnaire was returned by eight patients. In the studied population, an overall improvement of sexual function at six months follow-up was found. All six FSFI-domains: desire, arousal, lubrication, orgasm, satisfaction, and pain seemed to slightly improve. The authors found that there was an overall improvement of sexual function after vaginal surgery with synthetic mesh for POP and SUI.

  2. Urogynecologic Surgical Mesh Implants

    MedlinePlus

    ... urogynecologic repair. Absorbable mesh will degrade and lose strength over time. It is not intended to provide long-term reinforcement to the repair site. As the material degrades, new tissue growth is intended to provide ...

  3. Assessment of the effect of mesh density on the material property discretisation within QCT based FE models: a practical example using the implanted proximal tibia.

    PubMed

    Perillo-Marcone, A; Alonso-Vazquez, A; Taylor, M

    2003-02-01

    A three-dimensional, quantitative computed tomography based finite element model of a proximal implanted tibia was analysed in order to assess the effect of mesh density on material property discretisation and the resulting influence on the predicted stress distribution. The mesh was refined on the contact surfaces (matched meshes) with element sizes of 3, 2, 1.4, 1 and 0.8 mm. The same loading conditions were used in all models (bi-condylar load: 60% medial, 40% lateral). Significant variations were observed in the modulus distributions between the coarsest and finest mesh densities. Poor discretisation of the material properties also resulted in poor correlations of the stresses and risk ratios between the coarsest and finest meshes. Little difference in Young's modulus, von Mises stress and risk ratio distributions were observed between the three finest models; hence, it was concluded that for this particular case an element size of 1.4 mm on the contact surfaces was enough to properly describe the stiffness, stress and risk ratio distributions within the bone. Poor convergence of the material property distribution occurred when the element size was significantly larger than the pixel size of the source CT data. It was concluded that unless there is convergence in the Young's modulus distribution, convergence of the stress field or of other parameters of interest will not occur either.

  4. Documentation for MeshKit - Reactor Geometry (&mesh) Generator

    SciTech Connect

    Jain, Rajeev; Mahadevan, Vijay

    2015-09-30

    This report gives documentation for using MeshKit’s Reactor Geometry (and mesh) Generator (RGG) GUI and also briefly documents other algorithms and tools available in MeshKit. RGG is a program designed to aid in modeling and meshing of complex/large hexagonal and rectilinear reactor cores. RGG uses Argonne’s SIGMA interfaces, Qt and VTK to produce an intuitive user interface. By integrating a 3D view of the reactor with the meshing tools and combining them into one user interface, RGG streamlines the task of preparing a simulation mesh and enables real-time feedback that reduces accidental scripting mistakes that could waste hours of meshing. RGG interfaces with MeshKit tools to consolidate the meshing process, meaning that going from model to mesh is as easy as a button click. This report is designed to explain RGG v 2.0 interface and provide users with the knowledge and skills to pilot RGG successfully. Brief documentation of MeshKit source code, tools and other algorithms available are also presented for developers to extend and add new algorithms to MeshKit. RGG tools work in serial and parallel and have been used to model complex reactor core models consisting of conical pins, load pads, several thousands of axially varying material properties of instrumentation pins and other interstices meshes.

  5. Prolene mesh mentoplasty.

    PubMed

    Ilhan, A Emre; Kayabasoglu, Gurkan; Kazikdas, K Cagdas; Goksel, Abdulkadir

    2011-04-01

    Augmentation mentoplasty is a cosmetic surgical procedure to correct chin retrusion or microgenia which usually requires placement of an alloplastic material over the pogonion, and which results in increased chin projection and a more aesthetically balanced facial profile. Polypropylene mesh is easy to purchase, widely available in a general hospital and most commonly used by general surgeons. In this series of 192 patients, we wanted to demonstrate our simple mentoplasty technique using prolene mesh that can easily be combined with a rhinoplasty procedure, with possible causes of infection and the rationale for using prolene mesh in such procedures.

  6. Finite Element Method Mesh Study for Efficient Modeling of Piezoelectric Material

    DTIC Science & Technology

    2013-01-01

    MATERIAL L. Reinhardt Dr. Aisha Haynes Dr. J. Cordes January 2013 Approved for public release; distribution...Dr. Aisha Haynes, and Dr. J. Cordes 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS

  7. Materials and noncoplanar mesh designs for integrated circuits with linear elastic responses to extreme mechanical deformations

    PubMed Central

    Kim, Dae-Hyeong; Song, Jizhou; Choi, Won Mook; Kim, Hoon-Sik; Kim, Rak-Hwan; Liu, Zhuangjian; Huang, Yonggang Y.; Hwang, Keh-Chih; Zhang, Yong-wei; Rogers, John A.

    2008-01-01

    Electronic systems that offer elastic mechanical responses to high-strain deformations are of growing interest because of their ability to enable new biomedical devices and other applications whose requirements are impossible to satisfy with conventional wafer-based technologies or even with those that offer simple bendability. This article introduces materials and mechanical design strategies for classes of electronic circuits that offer extremely high stretchability, enabling them to accommodate even demanding configurations such as corkscrew twists with tight pitch (e.g., 90° in ≈1 cm) and linear stretching to “rubber-band” levels of strain (e.g., up to ≈140%). The use of single crystalline silicon nanomaterials for the semiconductor provides performance in stretchable complementary metal-oxide-semiconductor (CMOS) integrated circuits approaching that of conventional devices with comparable feature sizes formed on silicon wafers. Comprehensive theoretical studies of the mechanics reveal the way in which the structural designs enable these extreme mechanical properties without fracturing the intrinsically brittle active materials or even inducing significant changes in their electrical properties. The results, as demonstrated through electrical measurements of arrays of transistors, CMOS inverters, ring oscillators, and differential amplifiers, suggest a valuable route to high-performance stretchable electronics. PMID:19015528

  8. Esophageal self-expandable stent material and mesh grid density are the major determining factors of external beam radiation dose perturbation: results from a phantom model.

    PubMed

    Abu Dayyeh, B K; Vandamme, J J; Miller, R C; Baron, T H

    2013-01-01

    Self-expandable esophageal stents are increasingly used for palliation or as an adjunct to chemoradiation for esophageal neoplasia. The optimal esophageal stent design and material to minimize dose perturbation with external beam radiation are unknown. We sought to quantify the deviation from intended radiation dose as a function of stent material and mesh density design. A laboratory dosimetric film model was used to quantify perturbation of intended radiation dose among 16 different esophageal stents with varying material and stent mesh density design. Radiation dose enhancement due to stent backscatter ranged from 0 % to 7.3 %, collectively representing a standard difference from the intended mean radiation dose of 1.9 (95 % confidence interval [CI] 1.5 - 2.2). This enhancement was negligible for polymer-based stents and approached 0 % for the biodegradable stents. In contrast, all metal alloy stents had significant radiation backscatter; this was largely determined by the density of mesh design and not by the type of alloy used. Stent characteristics should be considered when selecting the optimal stent for treatment and palliation of malignant esophageal strictures, especially when adjuvant or neo-adjuvant radiotherapy is planned. © Georg Thieme Verlag KG Stuttgart · New York.

  9. Mesh Optimization

    DTIC Science & Technology

    1994-01-01

    AD-A277 644 ARAI !: ’ Mesh Optimization Technical Report # 93-01-01 Hughes Hoppe, Tony DeRose, Tom Duchamp , John McDonald and Werner Stuetzle DTIC...SrECT3D I 94 i 31 108 Mesh Optimization Technical Report # 93-01-01 Hughes Hoppe, Tony DeRose, Tom Duchamp , John McDonald and Werner Stuetzle Department...1:1. Januairy 1991. [2] T. DeRose. 11. Hoppe, T. Duchamp . .1. McDonald. and NV. Stuetzle. Fitting of surfaces to scattered data. ,PIE, 1830:212-220

  10. Some New Verification Test Problems for Multimaterial Diffusion on Meshes that are Non-Aligned with Material Boundaries

    SciTech Connect

    Dawes, Alan Sidney; Malone, Christopher M.; Shashkov, Mikhail Jurievich

    2016-07-07

    In this report a number of new verification test problems for multimaterial diffusion will be shown. Using them we will show that homogenization of multimaterial cells in either Arbitrary Lagrangian Eulerian (ALE) or Eulerian simulations can lead to errors in the energy flow at the interfaces. Results will be presented that show that significant improvements and predictive capability can be gained by using either a surrogate supermesh, such as Thin Mesh in FLAG, or the emerging method based on Static Condensation.

  11. The role of TGF-beta1 as a determinant of foreign body reaction to alloplastic materials in rat fibroblast cultures: comparison of different commercially available polypropylene meshes for hernia repair.

    PubMed

    Weyhe, Dirk; Hoffmann, Peter; Belyaev, Orlin; Mros, Kirsten; Muller, Christophe; Uhl, Waldemar; Schmitz, Frank

    2007-01-10

    Animal experiments on hernia repair demonstrated better biocompatibility of light-weight polypropylene meshes. However, implanted medical devices trigger a variety of adverse tissue responses, such as inflammation, fibrosis, infection and thrombosis, but the mechanisms involved in such responses remain largely unknown. This study aimed to determine the effect of transforming growth factor beta1 (TGF-beta1) on host tolerance by quantification of foreign body reaction in cultured fibroblasts depending on the amount and composition of implanted material used for hernia repair. An NRK-49F fibroblast culture was incubated in the presence of 4 commercially available meshes approved for hernia repair. A mesh-free cell suspension served as a control group, in which the influence of TGF-beta1 on fibroblasts was evaluated. Levels of TGF-beta1 in the supernatant were dynamically measured in a time interval of 6 to 96 h and cell proliferation rates were assessed colorimetrically using MTT test. A dose-dependent suppression of fibroblasts proliferation by TGF-beta1 was observed. All meshes suppressed the secretion of TGF-beta1 and conversely increased significantly cell proliferation in comparison to the control group (p<0.01) in the first 24 to 48 h of incubation. That effect was more pronounced in meshes partially containing absorbable material when compared to samples of pure polypropylene meshes (p<0.05) and to the control group (p<0.001). Our experiment revealed that early biological reaction of connective tissue cells towards polypropylene meshes and their variants depended much more on the composition and type of the material than on its absolute amount. The assumption that material weight reduction alone might affect the foreign body reaction of mesh implants could not be confirmed by our in vitro study.

  12. Which mesh for hernia repair?

    PubMed Central

    Brown, CN; Finch, JG

    2010-01-01

    INTRODUCTION The concept of using a mesh to repair hernias was introduced over 50 years ago. Mesh repair is now standard in most countries and widely accepted as superior to primary suture repair. As a result, there has been a rapid growth in the variety of meshes available and choosing the appropriate one can be difficult. This article outlines the general properties of meshes and factors to be considered when selecting one. MATERIALS AND METHODS We performed a search of the medical literature from 1950 to 1 May 2009, as indexed by Medline, using the PubMed search engine (). To capture all potentially relevant articles with the highest degree of sensitivity, the search terms were intentionally broad. We used the following terms: ‘mesh, pore size, strength, recurrence, complications, lightweight, properties’. We also hand-searched the bibliographies of relevant articles and product literature to identify additional pertinent reports. RESULTS AND CONCLUSIONS The most important properties of meshes were found to be the type of filament, tensile strength and porosity. These determine the weight of the mesh and its biocompatibility. The tensile strength required is much less than originally presumed and light-weight meshes are thought to be superior due to their increased flexibility and reduction in discomfort. Large pores are also associated with a reduced risk of infection and shrinkage. For meshes placed in the peritoneal cavity, consideration should also be given to the risk of adhesion formation. A variety of composite meshes have been promoted to address this, but none appears superior to the others. Finally, biomaterials such as acellular dermis have a place for use in infected fields but have yet to prove their worth in routine hernia repair. PMID:20501011

  13. Spherical geodesic mesh generation

    SciTech Connect

    Fung, Jimmy; Kenamond, Mark Andrew; Burton, Donald E.; Shashkov, Mikhail Jurievich

    2015-02-27

    In ALE simulations with moving meshes, mesh topology has a direct influence on feature representation and code robustness. In three-dimensional simulations, modeling spherical volumes and features is particularly challenging for a hydrodynamics code. Calculations on traditional spherical meshes (such as spin meshes) often lead to errors and symmetry breaking. Although the underlying differencing scheme may be modified to rectify this, the differencing scheme may not be accessible. This work documents the use of spherical geodesic meshes to mitigate solution-mesh coupling. These meshes are generated notionally by connecting geodesic surface meshes to produce triangular-prismatic volume meshes. This mesh topology is fundamentally different from traditional mesh topologies and displays superior qualities such as topological symmetry. This work describes the geodesic mesh topology as well as motivating demonstrations with the FLAG hydrocode.

  14. Automatic Mesh Coarsening for Discrete Ordinates Codes

    SciTech Connect

    Turner, Scott A.

    1999-03-11

    This paper describes the use of a ''mesh potential'' function for automatic coarsening of meshes in discrete ordinates neutral particle transport codes. For many transport calculations, a user may find it helpful to have the code determine a ''good'' neutronics mesh. The complexity of a problem involving millions of mesh cells, dozens of materials, and many energy groups makes it difficult to determine an adequate level of mesh refinement with a minimum number of cells. A method has been implemented in PARTISN (Parallel Time-dependent SN) to calculate a ''mesh potential'' in each original cell of a problem, and use this information to determine the maximum coarseness allowed in the mesh while maintaining accuracy in the solution. Results are presented for a simple x-y-z fuel/control/reflector problem.

  15. Stretchable Mesh for Cavity Noise Reduction

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R. (Inventor)

    2017-01-01

    A stretchable mesh material extends across the opening of a cavity of the landing gear of an aircraft when the landing gear is in the deployed position. The mesh material alters the flow of air across the opening of the landing gear cavity and significantly reduces the amount of noise produced by the wheel well at low-to-mid frequencies.

  16. Mesh for prolapse surgery: Why the fuss?

    PubMed

    Rajshekhar, Smita; Mukhopadhyay, Sambit; Klinge, Uwe

    2015-06-01

    Pelvic organ prolapse is a common gynaecological problem. Surgical techniques to repair prolapse have been constantly evolving to reduce the recurrence of prolapse and need for reoperation. Grafts made of synthetic and biological materials became popular in the last decade as they were intended to provide extra support to native tissue repairs. However, serious complications related to use of synthetic meshes have been reported and there is increasing medico-legal concern about mesh use in prolapse surgery. Some mesh products already have been withdrawn from the market and the FDA has introduced stricter surveillance of new and existing products. Large randomized studies comparing mesh with non-mesh procedures are lacking which creates uncertainty for the surgeon and their patients.The small cohorts of the RCTs available with short follow-up periods just allow the conclusion that the mesh repair can be helpful in the short to medium term but unfortunately are not able to prove safety for all patients. In particular, current clinical reports cannot define for which indication what material may be superior compared to non-mesh repair.Quality control through long-term individual and national mesh registries is needed to keep a record of all surgeons using mesh and all devices being used, monitoring their effectiveness and safety data. Meshes with better biocompatibility designed specifically for use in vaginal surgery may provide superior clinical results, where the reduction of complications may allow a wider range of indications.

  17. Compact Mesh Generator

    SciTech Connect

    Grover, Benjamin T.; Nissen, III, Walter I.

    2007-02-02

    The CMG is a small, lightweight, structured mesh generation code. It features a simple text input parser that allows setup of various meshes via a small set of text commands. Mesh generation data can be output to text, the silo file format, or the API can be directly queried by applications. It can run serially or in parallel via MPI. The CMG includes the ability to specify varius initial conditions on a mesh via mesh tags.

  18. Porcine urinary bladder matrix-polypropylene mesh: a novel scaffold material reduces immunorejection in rat pelvic surgery.

    PubMed

    Liu, Lubin; Deng, Li; Wang, Yanzhou; Ge, Liangpeng; Chen, Yong; Liang, Zhiqing

    2012-09-01

    The present study set out to modify polypropylene vaginal surgical material using porcine urinary bladder matrix (UBM) in order to improve biocompatibility. The aim was to develop a compound scaffold that induced less vaginal erosion and to evaluate host immunoreactivity to this material in vivo. Forty-eight Sprague-Dawley rats were randomly divided into four equal groups. One group underwent a sham operation, and the other groups underwent vaginal implantation with different materials: UBM (U); UBM + polypropylene (UP); or polypropylene (P). The host tissue response was determined by macro-observation, and by histological and immunohistochemical methods at 7, 14, 21, or 28 days after surgery. The inflammation reaction was strongest throughout the entire observation time in Group P, but was weaker and had a tendency to decrease with time in Groups U and UP. The presence of the UBM material in the compound scaffold allowed the polypropylene to fuse with newly proliferating surrounding tissue and resulted in less rejection of the material by the host, as indicated by the reduced appearance of CD4-, and CD8-positive cells. Porcine UBM allowed mechanical isolation of polypropylene, and also reduced the immune reaction to polypropylene. This study suggests that the UBM + polypropylene compound scaffold may be a promising material for clinical use in pelvic reconstruction surgery.

  19. Hexahedral Mesh Untangling

    SciTech Connect

    KNUPP,PATRICK

    2000-12-13

    We investigate a well-motivated mesh untangling objective function whose optimization automatically produces non-inverted elements when possible. Examples show the procedure is highly effective on simplicial meshes and on non-simplicial (e.g., hexahedral) meshes constructed via mapping or sweeping algorithms. The current whisker-weaving (WW) algorithm in CUBIT usually produces hexahedral meshes that are unsuitable for analyses due to inverted elements. The majority of these meshes cannot be untangled using the new objective function. The most likely source of the difficulty is poor mesh topology.

  20. Comprehensive comparison of a new tin-coated copper mesh and a graphite plate electrode as an anode material in microbial fuel cell.

    PubMed

    Taskan, Ergin; Hasar, Halil

    2015-02-01

    This paper summarizes the comparison of a new tin-coated copper (t-coating Cu) mesh electrode with a graphite plate electrode for potential power generation and biocompatibility in a microbial fuel cell (MFC). The study, which used domestic wastewater, demonstrated that t-coating Cu mesh electrode produced a power density (271 mW/m(2)) approximately three times higher than that produced by a graphite electrode (87 mW/m(2)). Scanning electron microscopy (SEM) results revealed that bacterial morphology on the two electrodes significantly varied. The t-coating Cu mesh electrode surface had higher bacterial diversity because the open three-dimensional macro-mesh structure allowed an excellent electro-biofilm attachment. Kinetic performances evaluated using the Nernst-Monod equation demonstrated that the t-coating Cu mesh electrode had both higher power density and good biocompatibility in a large surface area, high chemical stability, and favorable metallic conductivity.

  1. [The "ideal" mesh--more than a mosquito net].

    PubMed

    Klinge, U; Klink, C D; Klosterhalfen, B

    2010-04-01

    Modern meshes permit a radical treatment of hernias, an expectation that Billroth articulated already more than 100 years ago. Because clinical trials are insufficient to evaluate the distinct effects of modified mesh materials in regard to tissue biocompatibility and functionality, a basic understanding of the physico-chemical properties is essential for a rational selection of the most appropriate device. Experimental data indicate that particularly the mesh's porosity is of outstanding importance, resulting from the demanded tensile strength as well as the employed fibre material. Considering that different operation techniques require different mesh materials, specific requirements are discussed using the example of intraabdominal meshes, of parastomal meshes, of meshes in areas with bacterial contamination and of meshes in the hiatus region. Considering the late manifestation of some complications even after many years, any thorough quality control should include an assessment of explanted implant failures in addition to clinical experience.

  2. Single port laparoscopic mesh rectopexy

    PubMed Central

    2016-01-01

    Introduction Traditionally, laparoscopic mesh rectopexy is performed with four ports, in an attempt to improve cosmetic results. Following laparoscopic mesh rectopexy there is a new operative technique called single-port laparoscopic mesh rectopexy. Aim To evaluate the single-port laparoscopic mesh rectopexy technique in control of rectal prolapse and the cosmesis and body image issues of this technique. Material and methods The study was conducted in El Fayoum University Hospital between July 2013 and November 2014 in elective surgery for symptomatic rectal prolapse with single-port laparoscopic mesh rectopexy on 10 patients. Results The study included 10 patients: 3 (30%) males and 7 (70%) females. Their ages ranged between 19 years and 60 years (mean: 40.3 ±6 years), and they all underwent laparoscopic mesh rectopexy. There were no conversions to open technique, nor injuries to the rectum or bowel, and there were no mortalities. Mean operative time was 120 min (range: 90–150 min), and mean hospital stay was 2 days (range: 1–3 days). Preoperatively, incontinence was seen in 5 (50%) patients and constipation in 4 (40%). Postoperatively, improvement in these symptoms was seen in 3 (60%) patients for incontinence and in 3 (75%) for constipation. Follow-up was done for 6 months and no recurrence was found with better cosmetic appearance for all patients. Conclusions Single-port laparoscopic mesh rectopexy is a safe procedure with good results as regards operative time, improvement in bowel function, morbidity, cost, and recurrence, and with better cosmetic appearance. PMID:27350840

  3. Mesh Size Control of Friction

    NASA Astrophysics Data System (ADS)

    Pitenis, Angela; Uruena, Juan Manuel; Schulze, Kyle D.; Cooper, Andrew C.; Angelini, Thomas E.; Sawyer, W. Gregory

    Soft, permeable sliding interfaces in aqueous environments are ubiquitous in nature but their ability to maintain high lubricity in a poor lubricant (water) has not been well understood. Hydrogels are excellent materials for fundamental soft matter and biotribology studies due to their high water content. While mesh size controls the material and transport properties of a hydrogel, its effects on friction were only recently explored. Polyacrylamide hydrogels slid in a Gemini (self-mated) interface produced low friction under low speeds, low pressures, macroscopic contact areas, and room temperature aqueous environments. The friction coefficients at these interfaces are lowest at low speeds and are speed-independent. This behavior is due to thermal fluctuations at the interface separating the surfaces, with water shearing in this region being the main source of dissipation. We found that mesh size had an inverse correlation with friction. We further investigated a transition from this behavior at higher speeds, and found that the transition speed correlated with the mesh size and relaxation time of the polymer network. Very soft and correspondingly large mesh size Gemini hydrogels show superlubricity under specific conditions with friction being less than 0.005.

  4. Invisible metallic mesh

    PubMed Central

    Ye, Dexin; Lu, Ling; Joannopoulos, John D.; Soljačić, Marin; Ran, Lixin

    2016-01-01

    A solid material possessing identical electromagnetic properties as air has yet to be found in nature. Such a medium of arbitrary shape would neither reflect nor refract light at any angle of incidence in free space. Here, we introduce nonscattering corrugated metallic wires to construct such a medium. This was accomplished by aligning the dark-state frequencies in multiple scattering channels of a single wire. Analytical solutions, full-wave simulations, and microwave measurement results on 3D printed samples show omnidirectional invisibility in any configuration. This invisible metallic mesh can improve mechanical stability, electrical conduction, and heat dissipation of a system, without disturbing the electromagnetic design. Our approach is simple, robust, and scalable to higher frequencies. PMID:26884208

  5. Invisible metallic mesh.

    PubMed

    Ye, Dexin; Lu, Ling; Joannopoulos, John D; Soljačić, Marin; Ran, Lixin

    2016-03-08

    A solid material possessing identical electromagnetic properties as air has yet to be found in nature. Such a medium of arbitrary shape would neither reflect nor refract light at any angle of incidence in free space. Here, we introduce nonscattering corrugated metallic wires to construct such a medium. This was accomplished by aligning the dark-state frequencies in multiple scattering channels of a single wire. Analytical solutions, full-wave simulations, and microwave measurement results on 3D printed samples show omnidirectional invisibility in any configuration. This invisible metallic mesh can improve mechanical stability, electrical conduction, and heat dissipation of a system, without disturbing the electromagnetic design. Our approach is simple, robust, and scalable to higher frequencies.

  6. Central mesh recurrence after incisional hernia repair with Marlex--are the meshes strong enough?

    PubMed

    Langer, C; Neufang, T; Kley, C; Liersch, T; Becker, H

    2001-09-01

    The use of biomaterial meshes in the repair of incisional abdominal wall hernias is now widely accepted internationally. The introduction of synthetic meshes to achieve tension-free repair has led to a satisfactory reduction in the recurrence rate to less than 10%. However, the use of such biomaterials can result in the occurrence of undesirable complications such as increased risk of infection, seromas, restriction of the abdominal wall and failure caused by mesh shrinkage. Additionally, at the time of writing there is much discussion concerning the potential risk of a persistent foreign body reaction directly associated with the meshes with regard to possible malignant transformation. As such, the trend seems to be toward the use of lighter meshes utilizing less non-absorbable material. One particular novel mesh theoretically capable of guaranteeing the necessary mechanical stability uses 70% less biomaterial. Against this background, we report a central mesh recurrence through the mesh following incisional hernia repair with a Marlex mesh. To our knowledge, this is the first description of a central mesh recurrence, and we discuss a possible mechanism with particular emphasis on the required abdominal wall forces both physiologically and after incisional hernia repair.

  7. A nanobursa mesh: a graded electrospun nanofiber mesh with metal nanoparticles on carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Senturk-Ozer, Semra; Chen, Tao; Degirmenbasi, Nebahat; Gevgilili, Halil; Podkolzin, Simon G.; Kalyon, Dilhan M.

    2014-07-01

    A new type of material, a ``nanobursa'' mesh (from ``bursa'' meaning ``sac or pouch''), is introduced. This material consists of sequential layers of porous polymeric nanofibers encapsulating carbon nanotubes, which are functionalized with different metal nanoparticles in each layer. The nanobursa mesh is fabricated via a novel combination of twin-screw extrusion and electrospinning. Use of this hybrid process at industrially-relevant rates is demonstrated by producing a nanobursa mesh with graded layers of Pd, Co, Ag, and Pt nanoparticles. The potential use of the fabricated nanobursa mesh is illustrated by modeling of catalytic hydrocarbon oxidation.A new type of material, a ``nanobursa'' mesh (from ``bursa'' meaning ``sac or pouch''), is introduced. This material consists of sequential layers of porous polymeric nanofibers encapsulating carbon nanotubes, which are functionalized with different metal nanoparticles in each layer. The nanobursa mesh is fabricated via a novel combination of twin-screw extrusion and electrospinning. Use of this hybrid process at industrially-relevant rates is demonstrated by producing a nanobursa mesh with graded layers of Pd, Co, Ag, and Pt nanoparticles. The potential use of the fabricated nanobursa mesh is illustrated by modeling of catalytic hydrocarbon oxidation. Electronic supplementary information (ESI) available: Experimental methods and computational details. See DOI: 10.1039/c4nr01145g

  8. Mesh Sutured Repairs of Abdominal Wall Defects

    PubMed Central

    Lanier, Steven T.; Jordan, Sumanas W.; Miller, Kyle R.; Ali, Nada A.; Stock, Stuart R.

    2016-01-01

    Background: A new closure technique is introduced, which uses strips of macroporous polypropylene mesh as a suture for closure of abdominal wall defects due to failures of standard sutures and difficulties with planar meshes. Methods: Strips of macroporous polypropylene mesh of 2 cm width were passed through the abdominal wall and tied as simple interrupted sutures. The surgical technique and surgical outcomes are presented. Results: One hundred and seven patients underwent a mesh sutured abdominal wall closure. Seventy-six patients had preoperative hernias, and the mean hernia width by CT scan for those with scans was 9.1 cm. Forty-nine surgical fields were clean-contaminated, contaminated, or dirty. Five patients had infections within the first 30 days. Only one knot was removed as an office procedure. Mean follow-up at 234 days revealed 4 recurrent hernias. Conclusions: Mesh sutured repairs reliably appose tissue under tension using concepts of force distribution and resistance to suture pull-through. The technique reduces the amount of foreign material required in comparison to sheet meshes, and avoids the shortcomings of monofilament sutures. Mesh sutured closures seem to be tolerant of bacterial contamination with low hernia recurrence rates and have replaced our routine use of mesh sheets and bioprosthetic grafts. PMID:27757361

  9. Conjugation of gold nanoparticles to polypropylene mesh for enhanced biocompatibility.

    PubMed

    Grant, D N; Benson, J; Cozad, M J; Whelove, O E; Bachman, S L; Ramshaw, B J; Grant, D A; Grant, S A

    2011-12-01

    Polypropylene mesh materials have been utilized in hernia surgery for over 40 years. However, they are prone to degradation due to the body's aggressive foreign body reaction, which may cause pain or complications, forcing mesh removal from the patient. To mitigate these complications, gold nanomaterials were attached to polypropylene mesh in order to improve cellular response. Pristine samples of polypropylene mesh were exposed to hydrogen peroxide/cobalt chloride solutions to induce formation of surface carboxyl functional groups. Gold nanoparticles were covalently linked to the mesh. Scanning electron microscopy confirmed the presence of gold nanoparticles. Differential scanning calorimetry and mechanical testing confirmed that the polypropylene did not undergo any significantly detrimental changes in physicochemical properties. A WST-1 cell culture study showed an increase in cellularity on the gold nanoparticle-polypropylene mesh as compared to pristine mesh. This study showed that biocompatibility of polypropylene mesh may be improved via the conjugation of gold nanoparticles.

  10. Engagement of Metal Debris into Gear Mesh

    NASA Technical Reports Server (NTRS)

    handschuh, Robert F.; Krantz, Timothy L.

    2010-01-01

    A series of bench-top experiments was conducted to determine the effects of metallic debris being dragged through meshing gear teeth. A test rig that is typically used to conduct contact fatigue experiments was used for these tests. Several sizes of drill material, shim stock and pieces of gear teeth were introduced and then driven through the meshing region. The level of torque required to drive the "chip" through the gear mesh was measured. From the data gathered, chip size sufficient to jam the mechanism can be determined.

  11. Past, Present and Future of Surgical Meshes: A Review.

    PubMed

    Baylón, Karen; Rodríguez-Camarillo, Perla; Elías-Zúñiga, Alex; Díaz-Elizondo, Jose Antonio; Gilkerson, Robert; Lozano, Karen

    2017-08-22

    Surgical meshes, in particular those used to repair hernias, have been in use since 1891. Since then, research in the area has expanded, given the vast number of post-surgery complications such as infection, fibrosis, adhesions, mesh rejection, and hernia recurrence. Researchers have focused on the analysis and implementation of a wide range of materials: meshes with different fiber size and porosity, a variety of manufacturing methods, and certainly a variety of surgical and implantation procedures. Currently, surface modification methods and development of nanofiber based systems are actively being explored as areas of opportunity to retain material strength and increase biocompatibility of available meshes. This review summarizes the history of surgical meshes and presents an overview of commercial surgical meshes, their properties, manufacturing methods, and observed biological response, as well as the requirements for an ideal surgical mesh and potential manufacturing methods.

  12. Functional impairment and complaints following incisional hernia repair with different polypropylene meshes.

    PubMed

    Welty, G; Klinge, U; Klosterhalfen, B; Kasperk, R; Schumpelick, V

    2001-09-01

    The influence of mesh material on the clinical outcome of hernia repair has often been neglected, although recent studies have clearly demonstrated the importance of mesh properties for integration in the abdominal wall. Of particular significance are the amount of mesh material and the pore size. In the following study, patients received different mesh types with distinct amounts of polypropylene and of various pore sizes for incisional hernia repair. We investigated whether the type of material influenced the clinical and functional outcomes. Between 1991 and 1999, 235 patients received polypropylene meshes in a sublay position for incisional hernia repair: 115 patients were implanted with a Marlex heavy-weight mesh (Mhw mesh), 37 patients with an Atrium heavy-weight mesh (Ahw mesh) and 83 with a Vypro low-weight mesh (Vlw mesh). The study protocol included ultrasound examination and 3D-stereography in all patients, with a total follow-up of 24 +/- 13 months (Mhw-mesh), 11 +/- 8 months (Ahw-mesh) and 8 +/- 7 months (Vlw-mesh). Our findings demonstrate that the side effects of mesh implantation, comprising paraesthesia and restriction of abdominal wall mobility, were significantly affected by the type of material implanted. Three-dimensional stereographic examinations were well in accordance with our clinical findings. Our data support the hypothesis that the use of low-weight large-pore meshes is advantageous for abdominal wall function.

  13. An Adaptive Mesh Algorithm: Mapping the Mesh Variables

    SciTech Connect

    Scannapieco, Anthony J.

    2016-07-25

    Both thermodynamic and kinematic variables must be mapped. The kinematic variables are defined on a separate kinematic mesh; it is the duel mesh to the thermodynamic mesh. The map of the kinematic variables is done by calculating the contributions of kinematic variables on the old thermodynamic mesh, mapping the kinematic variable contributions onto the new thermodynamic mesh and then synthesizing the mapped kinematic variables on the new kinematic mesh. In this document the map of the thermodynamic variables will be described.

  14. Optimized testing of meshes

    NASA Technical Reports Server (NTRS)

    Malek, Miroslaw; Ozden, Banu

    1990-01-01

    Efficient testing techniques for two-dimensional mesh interconnection networks are presented. The tests cover faults in the arbitration logic of the switches; this includes an examination of fault detection in the data paths, routing, and control circuitry, including the conflict resolution capabilities of mesh interconnection networks using topological test methods. The proposed methods are not implementation specific and can be applied to any design with a mesh topology. The topology and behavior of the network are described and definitions are presented. The fault model is defined and parallel testing methods for the entire network are given.

  15. Hernia Surgical Mesh Implants

    MedlinePlus

    ... The surgeon makes several small incisions in the abdomen that allow surgical tools into the openings to repair the hernia. Laparoscopic surgery can be performed with or without surgical mesh. Open Repair - The surgeon makes an incision near the ...

  16. Lattice Cleaving: A Multimaterial Tetrahedral Meshing Algorithm with Guarantees

    PubMed Central

    Bronson, Jonathan; Levine, Joshua A.; Whitaker, Ross

    2014-01-01

    We introduce a new algorithm for generating tetrahedral meshes that conform to physical boundaries in volumetric domains consisting of multiple materials. The proposed method allows for an arbitrary number of materials, produces high-quality tetrahedral meshes with upper and lower bounds on dihedral angles, and guarantees geometric fidelity. Moreover, the method is combinatoric so its implementation enables rapid mesh construction. These meshes are structured in a way that also allows grading, to reduce element counts in regions of homogeneity. Additionally, we provide proofs showing that both element quality and geometric fidelity are bounded using this approach. PMID:24356365

  17. Wireless Mesh Networks

    NASA Astrophysics Data System (ADS)

    Ishmael, Johnathan; Race, Nicholas

    Wireless Mesh Networks have emerged as an important technology in building next-generation networks. They are seen to have a range of benefits over traditional wired and wireless networks including low deployment costs, high scalability and resiliency to faults. Moreover, Wireless Mesh Networks (WMNs) are often described as being autonomic with self-* (healing and configuration) properties and their popularity has grown both as a research platform and as a commercially exploitable technology.

  18. 2D Mesh Manipulation

    DTIC Science & Technology

    2011-11-01

    PLATE A two-dimensional flat plate mesh was created using the Gridgen software package (Ref. 13). This mesh (shown in Fig. 10) closely resembled a...desired tolerance of the projection onto the surface. The geometry file on which the geometry surface is based can be easily generated using Gridgen ...by exporting a curve (or number of curves) under the INPUT/OUTPUT commands in the Gridgen interface (Ref. 13). Initially, the floating boundary

  19. [Tissue integration of various silicone-coated polypropylene surgical mesh].

    PubMed

    Takács, Ildikó; Horváth, Szabolcs; Balatonyi, Borbála; Jávor, Szaniszló; Molnár, Agnes; Gáspár, Sarolta; Hajós, Rebeka; Meczker, Agnes; Lantos, János; Roth, Erzsébet; Wéber, György

    2010-10-01

    Laparoscopic ventral hernia repair requires a surgical mesh implanted in intraperitoneal position. The combined, double layer meshes are promising in animal models as well as in human practice. The aim of this study was to compare the biological behaviour of two different textured silicone covered polypropylene mesh. 3 × 4 cm big full thickness defect of the abdominal wall was created in New Zealand White rabbits. The defect was covered in 20 animals with a polypropylene mesh with laminar silicone layer on the visceral surface (LSPP), while the remaining 20 cases the defects were covered with a macroporous textured silicone impregnated polypropylene mesh (MSPP). Intraperitoneal adhesion formation and tissue ingrowth in the meshes were investigated. Immunohistochemistry was used to detect proliferation activity (Ki-67), neovascularization (VEGF), and to visualize mesothelial layer (CK) over the mesh. Scanning electron microscopy was used to investigate the visceral surface of the meshes. While intraperitoneal adhesion formation showed no difference after 1 week, LSPP mesh induced significantly less adhesions after 21 days. The Ki-67 positivity was significantly lower and the number of the VEGF positive cells increased with time in the MSPP group, this was missing in the LSPP group. The thin neoperitoneum layer was detected over MSPP mesh only with CK antibody. The material and texture of the mesh are responsible for tissular incorporation which is in accordance with the generated foreign body reaction.

  20. Unstructured mesh generation and adaptivity

    NASA Technical Reports Server (NTRS)

    Mavriplis, D. J.

    1995-01-01

    An overview of current unstructured mesh generation and adaptivity techniques is given. Basic building blocks taken from the field of computational geometry are first described. Various practical mesh generation techniques based on these algorithms are then constructed and illustrated with examples. Issues of adaptive meshing and stretched mesh generation for anisotropic problems are treated in subsequent sections. The presentation is organized in an education manner, for readers familiar with computational fluid dynamics, wishing to learn more about current unstructured mesh techniques.

  1. Magnetic Resonance–Visible Meshes for Laparoscopic Ventral Hernia Repair

    PubMed Central

    Pallwein-Prettner, Leo; Koch, Oliver Owen; Luketina, Ruzica Rosalia; Lechner, Michael; Emmanuel, Klaus

    2015-01-01

    Background and Objectives: We aimed to evaluate the first human use of magnetic resonance–visible implants for intraperitoneal onlay repair of incisional hernias regarding magnetic resonance presentability. Methods: Ten patients were surgically treated with intraperitoneally positioned superparamagnetic flat meshes. A magnetic resonance investigation with a qualified protocol was performed on postoperative day 1 and at 3 months postoperatively to assess mesh appearance and demarcation. The total magnetic resonance–visible mesh surface area of each implant was calculated and compared with the original physical mesh size to evaluate potential reduction of the functional mesh surfaces. Results: We were able to show a precise mesh demarcation, as well as accurate assessment of the surrounding tissue, in all 10 cases. We documented a significant decrease in the magnetic resonance–visualized total mesh surface area after release of the pneumoperitoneum compared with the original mesh size (mean, 190 cm2 vs 225 cm2; mean reduction of mesh area, 35 cm2; P < .001). At 3 months postoperatively, a further reduction of the surface area due to significant mesh shrinkage could be observed (mean, 182 cm2 vs 190 cm2; mean reduction of mesh area, 8 cm2; P < .001). Conclusion: The new method of combining magnetic resonance imaging and meshes that provide enhanced signal capacity through direct integration of iron particles into the polyvinylidene fluoride base material allows for detailed mesh depiction and quantification of structural changes. In addition to a significant early postoperative decrease in effective mesh surface area, a further considerable reduction in size occurred within 3 months after implantation. PMID:25848195

  2. Adaptive Mesh Refinement for Microelectronic Device Design

    NASA Technical Reports Server (NTRS)

    Cwik, Tom; Lou, John; Norton, Charles

    1999-01-01

    Finite element and finite volume methods are used in a variety of design simulations when it is necessary to compute fields throughout regions that contain varying materials or geometry. Convergence of the simulation can be assessed by uniformly increasing the mesh density until an observable quantity stabilizes. Depending on the electrical size of the problem, uniform refinement of the mesh may be computationally infeasible due to memory limitations. Similarly, depending on the geometric complexity of the object being modeled, uniform refinement can be inefficient since regions that do not need refinement add to the computational expense. In either case, convergence to the correct (measured) solution is not guaranteed. Adaptive mesh refinement methods attempt to selectively refine the region of the mesh that is estimated to contain proportionally higher solution errors. The refinement may be obtained by decreasing the element size (h-refinement), by increasing the order of the element (p-refinement) or by a combination of the two (h-p refinement). A successful adaptive strategy refines the mesh to produce an accurate solution measured against the correct fields without undue computational expense. This is accomplished by the use of a) reliable a posteriori error estimates, b) hierarchal elements, and c) automatic adaptive mesh generation. Adaptive methods are also useful when problems with multi-scale field variations are encountered. These occur in active electronic devices that have thin doped layers and also when mixed physics is used in the calculation. The mesh needs to be fine at and near the thin layer to capture rapid field or charge variations, but can coarsen away from these layers where field variations smoothen and charge densities are uniform. This poster will present an adaptive mesh refinement package that runs on parallel computers and is applied to specific microelectronic device simulations. Passive sensors that operate in the infrared portion of

  3. Adaptive Mesh Refinement for Microelectronic Device Design

    NASA Technical Reports Server (NTRS)

    Cwik, Tom; Lou, John; Norton, Charles

    1999-01-01

    Finite element and finite volume methods are used in a variety of design simulations when it is necessary to compute fields throughout regions that contain varying materials or geometry. Convergence of the simulation can be assessed by uniformly increasing the mesh density until an observable quantity stabilizes. Depending on the electrical size of the problem, uniform refinement of the mesh may be computationally infeasible due to memory limitations. Similarly, depending on the geometric complexity of the object being modeled, uniform refinement can be inefficient since regions that do not need refinement add to the computational expense. In either case, convergence to the correct (measured) solution is not guaranteed. Adaptive mesh refinement methods attempt to selectively refine the region of the mesh that is estimated to contain proportionally higher solution errors. The refinement may be obtained by decreasing the element size (h-refinement), by increasing the order of the element (p-refinement) or by a combination of the two (h-p refinement). A successful adaptive strategy refines the mesh to produce an accurate solution measured against the correct fields without undue computational expense. This is accomplished by the use of a) reliable a posteriori error estimates, b) hierarchal elements, and c) automatic adaptive mesh generation. Adaptive methods are also useful when problems with multi-scale field variations are encountered. These occur in active electronic devices that have thin doped layers and also when mixed physics is used in the calculation. The mesh needs to be fine at and near the thin layer to capture rapid field or charge variations, but can coarsen away from these layers where field variations smoothen and charge densities are uniform. This poster will present an adaptive mesh refinement package that runs on parallel computers and is applied to specific microelectronic device simulations. Passive sensors that operate in the infrared portion of

  4. Algebraic mesh quality metrics

    SciTech Connect

    KNUPP,PATRICK

    2000-04-24

    Quality metrics for structured and unstructured mesh generation are placed within an algebraic framework to form a mathematical theory of mesh quality metrics. The theory, based on the Jacobian and related matrices, provides a means of constructing, classifying, and evaluating mesh quality metrics. The Jacobian matrix is factored into geometrically meaningful parts. A nodally-invariant Jacobian matrix can be defined for simplicial elements using a weight matrix derived from the Jacobian matrix of an ideal reference element. Scale and orientation-invariant algebraic mesh quality metrics are defined. the singular value decomposition is used to study relationships between metrics. Equivalence of the element condition number and mean ratio metrics is proved. Condition number is shown to measure the distance of an element to the set of degenerate elements. Algebraic measures for skew, length ratio, shape, volume, and orientation are defined abstractly, with specific examples given. Combined metrics for shape and volume, shape-volume-orientation are algebraically defined and examples of such metrics are given. Algebraic mesh quality metrics are extended to non-simplical elements. A series of numerical tests verify the theoretical properties of the metrics defined.

  5. A meta-analysis comparing lightweight meshes with heavyweight meshes in Lichtenstein inguinal hernia repair.

    PubMed

    Zhong, Chunlin; Wu, Bo; Yang, Zhili; Deng, Xianzhao; Kang, Jie; Guo, Bomin; Fan, Youben

    2013-02-01

    To evaluate the influence of lightweight and heavyweight mesh on postoperative recovery in Lichtenstein inguinal hernia repair. PubMed, EMBASE, and the Cochrane library were used to search for published clinical randomized controlled trials (RCTs), which compared lightweight meshes with heavyweight meshes in Lichtenstein inguinal hernia repair. Two independent reviewers assessed the trials for eligibility and quality, and all the related data matching our standards were abstracted for meta-analysis by RevMan 5.0 software. The evaluation criteria included recurrence, pain, seroma, hematoma, the sensation of a foreign body, wound infection, urine retention, and testicular atrophy. A total of 2231 hernias from 11 RCTs were included. Compared with a heavyweight polypropylene mesh, the lightweight mesh led to less postoperative chronic pain (odds ratio [OR] = 0.64, 95% confidence interval (CI) = 0.51-0.82; P < .05) and less sensation of a foreign body (OR = 0.56; 95% CI = 0.40-0.78; P < .05), regardless of whether the mesh was made of partially absorbable or nonabsorbable material. There was no significant difference in postoperative recurrence, seroma, hematoma, wound infection, urine retention, and testicular atrophy. Current evidence suggests that the use of a lightweight mesh is associated with less postoperative pain and less sensation of a foreign body, without increasing the incidence of recurrence. Further high-quality, long-term follow-up RCTs are needed to provide more reliable evidence.

  6. Cosmology on a Mesh

    NASA Astrophysics Data System (ADS)

    Gill, Stuart P. D.; Knebe, Alexander; Gibson, Brad K.; Flynn, Chris; Ibata, Rodrigo A.; Lewis, Geraint F.

    2003-04-01

    An adaptive multi grid approach to simulating the formation of structure from collisionless dark matter is described. MLAPM (Multi-Level Adaptive Particle Mesh) is one of the most efficient serial codes available on the cosmological "market" today. As part of Swinburne University's role in the development of the Square Kilometer Array, we are implementing hydrodynamics, feedback, and radiative transfer within the MLAPM adaptive mesh, in order to simulate baryonic processes relevant to the interstellar and intergalactic media at high redshift. We will outline our progress to date in applying the existing MLAPM to a study of the decay of satellite galaxies within massive host potentials.

  7. Lagrangian fluid dynamics using the Voronoi-Delauanay mesh

    SciTech Connect

    Dukowicz, J.K.

    1981-01-01

    A Lagrangian technique for numerical fluid dynamics is described. This technique makes use of the Voronoi mesh to efficiently locate new neighbors, and it uses the dual (Delaunay) triangulation to define computational cells. This removes all topological restrictions and facilitates the solution of problems containing interfaces and multiple materials. To improve computational accuracy a mesh smoothing procedure is employed.

  8. Curved mesh generation and mesh refinement using Lagrangian solid mechanics

    SciTech Connect

    Persson, P.-O.; Peraire, J.

    2008-12-31

    We propose a method for generating well-shaped curved unstructured meshes using a nonlinear elasticity analogy. The geometry of the domain to be meshed is represented as an elastic solid. The undeformed geometry is the initial mesh of linear triangular or tetrahedral elements. The external loading results from prescribing a boundary displacement to be that of the curved geometry, and the final configuration is determined by solving for the equilibrium configuration. The deformations are represented using piecewise polynomials within each element of the original mesh. When the mesh is sufficiently fine to resolve the solid deformation, this method guarantees non-intersecting elements even for highly distorted or anisotropic initial meshes. We describe the method and the solution procedures, and we show a number of examples of two and three dimensional simplex meshes with curved boundaries. We also demonstrate how to use the technique for local refinement of non-curved meshes in the presence of curved boundaries.

  9. Choice of mesh for laparoscopic ventral hernia repair.

    PubMed

    Eriksen, J R; Gögenur, I; Rosenberg, J

    2007-12-01

    Surgical treatment of ventral hernias has changed dramatically over the past decades by the introduction of laparoscopy and prosthetic biomaterials for reinforcement of the abdominal wall. There are many meshes available on the market for laparoscopic ventral hernia repair (LVHR), and new meshes are introduced regularly. Experimental and clinical documentation for safety and efficacy are, however, often not available for the clinician. The choice of mesh may therefore be difficult in clinical practice. We present a review of the current literature regarding safety measures such as adhesions, fistulas, and infections as well as the available data on pain, recurrence, mesh shrinkage, and seroma formation after LVHR. The literature was searched systematically using PubMed/MEDLINE and EMBASE for controlled studies, prospective descriptive series and retrospective case series. The literature clearly points in the direction of very few mesh-related complications after LVHR. Experimental studies and theoretical considerations may argue for using a covered mesh, i.e., a composite mesh, or ePTFE for LVHR in humans, although it is important to stress that there are no human data at the moment to support this. Concerns about using pure polypropylene mesh in the intraperitoneal position may be re-evaluated with the experience of lightweight macropore meshes from open surgery in mind. There is a tendency towards greater shrinkage in ePTFE-based meshes but no differences seems to exist between different mesh materials in other relevant outcome parameters from clinical series. The literature cannot give general recommendations for choice of mesh based on randomized controlled trials. The final choice of mesh for LVHR will therefore typically be based on surgeons' preference and cost while we await further data from randomized controlled clinical trials.

  10. MeshLab: 3D triangular meshes processing and editing

    NASA Astrophysics Data System (ADS)

    Cignoni, P.; Callieri, M.; Corsini, M.; Dellepiane, M.; Ganovelli, F.; Ranzuglia, G.

    2017-09-01

    MeshLab processes and edits 3D triangular meshes. It includes tools for editing, cleaning, healing, inspecting, rendering, texturing and converting meshes, and offers features for processing raw data produced by 3D digitization tools and devices and for preparing models for 3D printing.

  11. Advanced numerical methods in mesh generation and mesh adaptation

    SciTech Connect

    Lipnikov, Konstantine; Danilov, A; Vassilevski, Y; Agonzal, A

    2010-01-01

    Numerical solution of partial differential equations requires appropriate meshes, efficient solvers and robust and reliable error estimates. Generation of high-quality meshes for complex engineering models is a non-trivial task. This task is made more difficult when the mesh has to be adapted to a problem solution. This article is focused on a synergistic approach to the mesh generation and mesh adaptation, where best properties of various mesh generation methods are combined to build efficiently simplicial meshes. First, the advancing front technique (AFT) is combined with the incremental Delaunay triangulation (DT) to build an initial mesh. Second, the metric-based mesh adaptation (MBA) method is employed to improve quality of the generated mesh and/or to adapt it to a problem solution. We demonstrate with numerical experiments that combination of all three methods is required for robust meshing of complex engineering models. The key to successful mesh generation is the high-quality of the triangles in the initial front. We use a black-box technique to improve surface meshes exported from an unattainable CAD system. The initial surface mesh is refined into a shape-regular triangulation which approximates the boundary with the same accuracy as the CAD mesh. The DT method adds robustness to the AFT. The resulting mesh is topologically correct but may contain a few slivers. The MBA uses seven local operations to modify the mesh topology. It improves significantly the mesh quality. The MBA method is also used to adapt the mesh to a problem solution to minimize computational resources required for solving the problem. The MBA has a solid theoretical background. In the first two experiments, we consider the convection-diffusion and elasticity problems. We demonstrate the optimal reduction rate of the discretization error on a sequence of adaptive strongly anisotropic meshes. The key element of the MBA method is construction of a tensor metric from hierarchical edge

  12. Application of Quaternions for Mesh

    NASA Technical Reports Server (NTRS)

    Samareh, Jamshid A.

    2002-01-01

    A new three dimensional mesh deformation algorithm, based on quaternion algebra, is introduced. A brief overview of quaternion algebra is provided, along with some preliminary results for two-dimensional structured and unstructured viscous mesh deformation.

  13. Multigrid Methods for Mesh Relaxation

    SciTech Connect

    O'Brien, M J

    2006-06-12

    When generating a mesh for the initial conditions for a computer simulation, you want the mesh to be as smooth as possible. A common practice is to use equipotential mesh relaxation to smooth out a distorted computational mesh. Typically a Laplace-like equation is set up for the mesh coordinates and then one or more Jacobi iterations are performed to relax the mesh. As the zone count gets really large, the Jacobi iteration becomes less and less effective and we are stuck with our original unrelaxed mesh. This type of iteration can only damp high frequency errors and the smooth errors remain. When the zone count is large, almost everything looks smooth so relaxation cannot solve the problem. In this paper we examine a multigrid technique which effectively smooths out the mesh, independent of the number of zones.

  14. Toward An Unstructured Mesh Database

    NASA Astrophysics Data System (ADS)

    Rezaei Mahdiraji, Alireza; Baumann, Peter Peter

    2014-05-01

    Unstructured meshes are used in several application domains such as earth sciences (e.g., seismology), medicine, oceanography, cli- mate modeling, GIS as approximate representations of physical objects. Meshes subdivide a domain into smaller geometric elements (called cells) which are glued together by incidence relationships. The subdivision of a domain allows computational manipulation of complicated physical structures. For instance, seismologists model earthquakes using elastic wave propagation solvers on hexahedral meshes. The hexahedral con- tains several hundred millions of grid points and millions of hexahedral cells. Each vertex node in the hexahedrals stores a multitude of data fields. To run simulation on such meshes, one needs to iterate over all the cells, iterate over incident cells to a given cell, retrieve coordinates of cells, assign data values to cells, etc. Although meshes are used in many application domains, to the best of our knowledge there is no database vendor that support unstructured mesh features. Currently, the main tool for querying and manipulating unstructured meshes are mesh libraries, e.g., CGAL and GRAL. Mesh li- braries are dedicated libraries which includes mesh algorithms and can be run on mesh representations. The libraries do not scale with dataset size, do not have declarative query language, and need deep C++ knowledge for query implementations. Furthermore, due to high coupling between the implementations and input file structure, the implementations are less reusable and costly to maintain. A dedicated mesh database offers the following advantages: 1) declarative querying, 2) ease of maintenance, 3) hiding mesh storage structure from applications, and 4) transparent query optimization. To design a mesh database, the first challenge is to define a suitable generic data model for unstructured meshes. We proposed ImG-Complexes data model as a generic topological mesh data model which extends incidence graph model to multi

  15. Tangle-Free Finite Element Mesh Motion for Ablation Problems

    NASA Technical Reports Server (NTRS)

    Droba, Justin

    2016-01-01

    Mesh motion is the process by which a computational domain is updated in time to reflect physical changes in the material the domain represents. Such a technique is needed in the study of the thermal response of ablative materials, which erode when strong heating is applied to the boundary. Traditionally, the thermal solver is coupled with a linear elastic or biharmonic system whose sole purpose is to update mesh node locations in response to altering boundary heating. Simple mesh motion algorithms rely on boundary surface normals. In such schemes, evolution in time will eventually cause the mesh to intersect and "tangle" with itself, causing failure. Furthermore, such schemes are greatly limited in the problems geometries on which they will be successful. This paper presents a comprehensive and sophisticated scheme that tailors the directions of motion based on context. By choosing directions for each node smartly, the inevitable tangle can be completely avoided and mesh motion on complex geometries can be modeled accurately.

  16. Surgical mesh for ventral incisional hernia repairs: Understanding mesh design

    PubMed Central

    Rastegarpour, Ali; Cheung, Michael; Vardhan, Madhurima; Ibrahim, Mohamed M; Butler, Charles E; Levinson, Howard

    2016-01-01

    Surgical mesh has become an indispensable tool in hernia repair to improve outcomes and reduce costs; however, efforts are constantly being undertaken in mesh development to overcome postoperative complications. Common complications include infection, pain, adhesions, mesh extrusion and hernia recurrence. Reducing the complications of mesh implantation is of utmost importance given that hernias occur in hundreds of thousands of patients per year in the United States. In the present review, the authors present the different types of hernia meshes, discuss the key properties of mesh design, and demonstrate how each design element affects performance and complications. The present article will provide a basis for surgeons to understand which mesh to choose for patient care and why, and will explain the important technological aspects that will continue to evolve over the ensuing years. PMID:27054138

  17. Design of electrospinning mesh devices

    NASA Astrophysics Data System (ADS)

    Russo, Giuseppina; Peters, Gerrit W. M.; Solberg, Ramon H. M.; Vittoria, Vittoria

    2012-07-01

    This paper describes the features of new membranes that can act as local biomedical devices owing to their peculiar shape in the form of mesh structure. These materials are designed to provide significant effects to reduce local inflammations and improve the tissue regeneration. Lamellar Hydrotalcite loaded with Diclofenac Sodium (HTLc-DIK) was homogenously dispersed inside a polymeric matrix of Poly-caprolactone (PCL) to manufacture membranes by electrospinning technique. The experimental procedure and the criteria employed have shown to be extremely effective at increasing potentiality and related applications. The employed technique has proved to be very useful to manufacture polymeric fibers with diameters in the range of nano-micro scale. In this work a dedicated collector based on a proprietary technology of IME Technologies and Eindhoven University of Technology (TU/e) was used. It allowed to obtain devices with a macro shape of a 3D-mesh. Atomic Force Microscopy (AFM) highlights a very interesting texture of the electrospun fibers. They show a lamellar morphology that is only slightly modified by the inclusion of the interclay embedded in the devices to control the drug release phenomena.

  18. LaNi0.6Co0 4O3-δ dip-coated on Fe-Cr mesh as a composite cathode contact material on intermediate solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Morán-Ruiz, Aroa; Vidal, Karmele; Larrañaga, Aitor; Laguna-Bercero, Miguel Angel; Porras-Vázquez, Jose Manuel; Slater, Peter Raymond; Arriortua, María Isabel

    2014-12-01

    The feasibility of using Crofer22APU mesh dip coated with LaNi0.6Co0.4O3-δ (LNC) ceramic paste as a uniform contact layer on a Crofer22APU channeled interconnect was studied. The control of LNC dip coating thickness on Fe-Cr mesh was carried out by rheological measurements of the suspension. SEM cross-section of formed composite contact material showed good adherence between ceramic and metallic components. The measured area specific resistance (ASR) value at 800 °C was 0.46 ± 0.01 mΩ cm2, indicating low contact resistance itself. The long term stability of metallic/ceramic composite was also studied. The contact resistance, when composite contact material was adhered to channeled Crofer22APU interconnect, was 5.40 ± 0.01 mΩ cm2, which is a suitable value for the performance of IT-SOFC stack. The stability of the system after treating at 800 °C for 1000 h was characterized using X-ray Micro-Diffraction (XRMD), Scanning Electron Microscope equipped with an Energy Dispersive X-ray analyzer (SEM-EDX) and X-ray Photoelectron Spectroscopy (XPS) techniques. The oxidation rate of the alloy and Fe3O4 phase formation were enhanced on the channels of the interconnect. Thus, the formation of CrO3 (g) and CrO2(OH)2 (g) species was accelerated on the composite surface under the channel. Through XRMD and XPS analysis the coexistence of two perovskite phases (initial LNC and Cr-perovskite) was observed.

  19. SUPERIMPOSED MESH PLOTTING IN MCNP

    SciTech Connect

    J. HENDRICKS

    2001-02-01

    The capability to plot superimposed meshes has been added to MCNP{trademark}. MCNP4C featured a superimposed mesh weight window generator which enabled users to set up geometries without having to subdivide geometric cells for variance reduction. The variance reduction was performed with weight windows on a rectangular or cylindrical mesh superimposed over the physical geometry. Experience with the new capability was favorable but also indicated that a number of enhancements would be very beneficial, particularly a means of visualizing the mesh and its values. The mathematics for plotting the mesh and its values is described here along with a description of other upgrades.

  20. Particle-mesh techniques

    NASA Technical Reports Server (NTRS)

    Macneice, Peter

    1995-01-01

    This is an introduction to numerical Particle-Mesh techniques, which are commonly used to model plasmas, gravitational N-body systems, and both compressible and incompressible fluids. The theory behind this approach is presented, and its practical implementation, both for serial and parallel machines, is discussed. This document is based on a four-hour lecture course presented by the author at the NASA Summer School for High Performance Computational Physics, held at Goddard Space Flight Center.

  1. Parallel Adaptive Mesh Refinement

    SciTech Connect

    Diachin, L; Hornung, R; Plassmann, P; WIssink, A

    2005-03-04

    As large-scale, parallel computers have become more widely available and numerical models and algorithms have advanced, the range of physical phenomena that can be simulated has expanded dramatically. Many important science and engineering problems exhibit solutions with localized behavior where highly-detailed salient features or large gradients appear in certain regions which are separated by much larger regions where the solution is smooth. Examples include chemically-reacting flows with radiative heat transfer, high Reynolds number flows interacting with solid objects, and combustion problems where the flame front is essentially a two-dimensional sheet occupying a small part of a three-dimensional domain. Modeling such problems numerically requires approximating the governing partial differential equations on a discrete domain, or grid. Grid spacing is an important factor in determining the accuracy and cost of a computation. A fine grid may be needed to resolve key local features while a much coarser grid may suffice elsewhere. Employing a fine grid everywhere may be inefficient at best and, at worst, may make an adequately resolved simulation impractical. Moreover, the location and resolution of fine grid required for an accurate solution is a dynamic property of a problem's transient features and may not be known a priori. Adaptive mesh refinement (AMR) is a technique that can be used with both structured and unstructured meshes to adjust local grid spacing dynamically to capture solution features with an appropriate degree of resolution. Thus, computational resources can be focused where and when they are needed most to efficiently achieve an accurate solution without incurring the cost of a globally-fine grid. Figure 1.1 shows two example computations using AMR; on the left is a structured mesh calculation of a impulsively-sheared contact surface and on the right is the fuselage and volume discretization of an RAH-66 Comanche helicopter [35]. Note the

  2. The lightweight and large porous mesh concept for hernia repair.

    PubMed

    Klosterhalfen, Bernd; Junge, Karsten; Klinge, Uwe

    2005-01-01

    In modern hernia surgery, there are two competing mesh concepts which often lead to controversial discussions, on the one hand the heavyweight small porous model and on the other, the lightweight large porous hypothesis. The present review illustrates the rationale of both mesh concepts and compares experimental data with the first clinical data available. In summary, the lightweight large porous mesh philosophy takes into consideration all of the recent data regarding physiology and mechanics of the abdominal wall and inguinal region. Furthermore, the new mesh concept reveals an optimized foreign body reaction based on reduced amounts of mesh material and, in particular, a significantly decreased surface area in contact with the recipient host tissues by the large porous model. Finally, recent data demonstrate that alterations in the extracellular matrix of hernia patients play a crucial role in the development of hernia recurrence. In particular, long-term recurrences months or years after surgery and implantation of mesh can be explained by the extracellular matrix hypothesis. However, if the altered extracellular matrix proves to be the weak area, the decisive question is whether the amount of material as well as mechanical and tensile strength of the surgical mesh are really of significant importance for the development of recurrent hernia. All experimental evidence and first clinical data indicate the superiority of the lightweight large porous mesh concept with regard to a reduced number of long-term complications and particularly, increased comfort and quality of life after hernia repair.

  3. On Optimal Bilinear Quadrilateral Meshes

    SciTech Connect

    D'Azevedo, E

    2000-03-17

    The novelty of this work is in presenting interesting error properties of two types of asymptotically ''optimal'' quadrilateral meshes for bilinear approximation. The first type of mesh has an error equidistributing property where the maximum interpolation error is asymptotically the same over all elements. The second type has faster than expected ''super-convergence'' property for certain saddle-shaped data functions. The ''superconvergent'' mesh may be an order of magnitude more accurate than the error equidistributing mesh. Both types of mesh are generated by a coordinate transformation of a regular mesh of squares. The coordinate transformation is derived by interpreting the Hessian matrix of a data function as a metric tensor. The insights in this work may have application in mesh design near corner or point singularities.

  4. On Optimal Bilinear Quadrilateral Meshes

    SciTech Connect

    D'Azevedo, E.

    1998-10-26

    The novelty of this work is in presenting interesting error properties of two types of asymptotically optimal quadrilateral meshes for bilinear approximation. The first type of mesh has an error equidistributing property where the maximum interpolation error is asymptotically the same over all elements. The second type has faster than expected super-convergence property for certain saddle-shaped data functions. The super-convergent mesh may be an order of magnitude more accurate than the error equidistributing mesh. Both types of mesh are generated by a coordinate transformation of a regular mesh of squares. The coordinate transformation is derived by interpreting the Hessian matrix of a data function as a metric tensor. The insights in this work may have application in mesh design near known corner or point singularities.

  5. Mesh Algorithms for PDE with Sieve I: Mesh Distribution

    DOE PAGES

    Knepley, Matthew G.; Karpeev, Dmitry A.

    2009-01-01

    We have developed a new programming framework, called Sieve, to support parallel numerical partial differential equation(s) (PDE) algorithms operating over distributed meshes. We have also developed a reference implementation of Sieve in C++ as a library of generic algorithms operating on distributed containers conforming to the Sieve interface. Sieve makes instances of the incidence relation, or arrows, the conceptual first-class objects represented in the containers. Further, generic algorithms acting on this arrow container are systematically used to provide natural geometric operations on the topology and also, through duality, on the data. Finally, coverings and duality are used to encode notmore » only individual meshes, but all types of hierarchies underlying PDE data structures, including multigrid and mesh partitions. In order to demonstrate the usefulness of the framework, we show how the mesh partition data can be represented and manipulated using the same fundamental mechanisms used to represent meshes. We present the complete description of an algorithm to encode a mesh partition and then distribute a mesh, which is independent of the mesh dimension, element shape, or embedding. Moreover, data associated with the mesh can be similarly distributed with exactly the same algorithm. The use of a high level of abstraction within the Sieve leads to several benefits in terms of code reuse, simplicity, and extensibility. We discuss these benefits and compare our approach to other existing mesh libraries.« less

  6. Mesh Oriented datABase

    SciTech Connect

    Tautges, Timothy J.

    2004-04-01

    MOAB is a component for representing and evaluating mesh data. MOAB can store stuctured and unstructured mesh, consisting of elements in the finite element "zoo". The functional interface to MOAB is simple yet powerful, allowing the representation of many types of metadata commonly found on the mesh. MOAB is optimized for efficiency in space and time, based on access to mesh in chunks rather than through individual entities, while also versatile enough to support individual entity access. The MOAB data model consists of a mesh interface instance, mesh entities (vertices and elements), sets, and tags. Entities are addressed through handles rather than pointers, to allow the underlying representation of an entity to change without changing the handle to that entity. Sets are arbitrary groupings of mesh entities and other sets. Sets also support parent/child relationships as a relation distinct from sets containing other sets. The directed-graph provided by set parent/child relationships is useful for modeling topological relations from a geometric model or other metadata. Tags are named data which can be assigned to the mesh as a whole, individual entities, or sets. Tags are a mechanism for attaching data to individual entities and sets are a mechanism for describing relations between entities; the combination of these two mechanisms isa powerful yet simple interface for representing metadata or application-specific data. For example, sets and tags can be used together to describe geometric topology, boundary condition, and inter-processor interface groupings in a mesh. MOAB is used in several ways in various applications. MOAB serves as the underlying mesh data representation in the VERDE mesh verification code. MOAB can also be used as a mesh input mechanism, using mesh readers induded with MOAB, or as a t’anslator between mesh formats, using readers and writers included with MOAB.

  7. Developing metal coated mesh filters for mid-infrared astronomy

    NASA Astrophysics Data System (ADS)

    Sako, Shigeyuki; Miyata, Takashi; Kamizuka, Takafumi; Nakamura, Tomohiko; Asano, Kentaro; Uchiyama, Mizuho; Onaka, Takashi; Sakon, Itsuki; Wada, Takehiko

    2012-09-01

    A metal mesh filter is appropriate to a band-pass filter for astronomy in the long mid-infrared between 25 and 40 μm, where most of optical materials are opaque. The mesh filter does not require transparent dielectric materials unlike interference filters because the transmission characteristics bare determined by surface plasmon-polariton (SPP) resonances excited on a metal surface with a periodic structure. In this study, we have developed the mesh filters optimized to atmospheric windows at 31.8 and 37.5 μm accessible from the Chajnantor site of 5,640 m altitude. First, mesh filters made of a gold film of 2 μm thickness have been fabricated. Four identical film-type filters are stacked incoherently to suppress leakages at stop-bands. The transmissions of the stacked filters have been measured to be 0.8 at the peaks and below 1 x 10-3 at the stop-bands at 4 K. The ground-based mid-infrared camera MAX38 has been equipped with the stacked filters and successfully obtained diffraction-limited stellar images at the Chajnantor site. The film-type mesh filter does not have sufficient mechanical strength for a larger aperture and for use in space. We have developed mesh filters with higher strength by applying the membrane technology for x-ray optics. The membrane-type mesh filter is made of SiC and coated with a thin gold layer. The optical performance of the mesh filter is independent of internal materials in principle because the SPP resonances are excited only on the metal surface. The fabricated membrane-type mesh filter has been confirmed to provide comparable optical performance to the film-type mesh filter.

  8. [Treatment of large postoperative hernias using intraperitoneal meshes].

    PubMed

    Trojanowski, Piotr; Witczak, Witold; Najdecki, Marek; Stanowski, Edward

    2007-05-01

    Most common hernias among men and women are inguinal hernias (75-80%) and postoperative (incisional) hernias (8-10%). Management of large incisional hernias (hernia gate bigger than 10 cm) both primary and recurrent could be an encounter for a surgeon. In surgical repair of large hernia use of synthetic materials (mesh) is being prefered. Using mesh can significantly decrease recurrence rate (<10%), compare to operations without synthetic grafts where risk of recurrence can reach 50%. One of the methods of surgical treatment of large abdominal hernias is intraperitoneal placing of implants. For such purpose complex meshes (multi-layered) should be used to prevent adhesion of the mesh to the intestines and avoid dangerous complications such as migration of the mesh through the tissues, perforation of the urine bladder, small and large intestine, forming fistulas and blocking intestines. Presentation of own experience in dealing with patients with large postoperative abdominal hernias using composite meshes: Bard--Composix Mesh, Parietex--Composite Sofradim and Proceed Ethicon. Since 2003 to 2006 were performed 7 surgical repairs of large abdominal hernia via an open aproach. 3 male, 4 female, average age 47 years old. Every hernia gate was wider than 15 cm. Bard mesh was used three times, Sofradim and Ethicon two times. Mesh was implanted without tension with single sutures and overlap of more than 5 cm from the edge of the hernia gate. Mesh was separated from intestines with greater momentum if it was possible. Anticoagulant and antibiotic preventive therapies were applied as a rule. Average time of operation was 140 minutes; average time of postoperative hospitalization was 8 days. Only one case was complicated with seroma which was treated with transcutaneous punctures with good result. (1) Surgical treatment of large abdominal hernia using composite mesh (intraperitoneal). in selected cases has good results. (2) The limiting factor of using presented method is

  9. A lightweight polypropylene mesh (TiMesh) for laparoscopic intraperitoneal repair of abdominal wall hernias: comparison of biocompatibility with the DualMesh in an experimental study using the porcine model.

    PubMed

    Schug-Pass, C; Tamme, C; Tannapfel, A; Köckerling, F

    2006-03-01

    Despite numerous experimental studies, conducted most often with the open small-animal model, the ideal structure for a mesh with maximum biocompatibility in the intraabdominal region has yet to be found. To date, few experimental models have been concerned with the laparoscopic intraabdominal implantation of meshes. Numerous experimental and clinical studies appear to have identified expanded polytetrafluoroethylene (ePTFE), in the form of DualMesh, as the gold standard. Since publications have reported fistula formation and marked adhesions to be associated with the use of polypropylene meshes, only few studies have investigated meshes made of this material. It is known, however, that a reduction in the amount of material and an increase in pore size results in better mesh biocompatibility. Six pigs each underwent laparoscopic intraabdominal placement of either a TiMesh or a DualMesh, both of which were prepared for implantation in standardized fashion. After 87 +/- 2 days, the pigs were killed, and postmortem laparoscopy was performed, followed by the removal of the tissue embedding the mesh for assessment of adhesions and shrinkage, and for histologic workup. The specimens were processed both histologically and immunohistochemically. In all but one case, the greater omentum adhered, usually over discrete areas, to the mesh. In every case the omentum was separable from the mesh surface only by sharp dissection. With the titanium-coated polypropylene meshes, the average total adhesion area was only 0.085, as compared with 0.25 for the GoreTex meshes (p = 0.055). The GoreTex meshes showed an average shrinkage to almost half of the original surface area (median, 0.435). The average shrinkage of the TiMesh, was to 0.18 of the original area (p = 0.006), which thus was significantly smaller. Determination of the partial volume of the inflammatory cells showed significantly lower median figures for the TiMesh (p = 0.009). Measurements of the proliferation marker Ki67

  10. toolkit computational mesh conceptual model.

    SciTech Connect

    Baur, David G.; Edwards, Harold Carter; Cochran, William K.; Williams, Alan B.; Sjaardema, Gregory D.

    2010-03-01

    The Sierra Toolkit computational mesh is a software library intended to support massively parallel multi-physics computations on dynamically changing unstructured meshes. This domain of intended use is inherently complex due to distributed memory parallelism, parallel scalability, heterogeneity of physics, heterogeneous discretization of an unstructured mesh, and runtime adaptation of the mesh. Management of this inherent complexity begins with a conceptual analysis and modeling of this domain of intended use; i.e., development of a domain model. The Sierra Toolkit computational mesh software library is designed and implemented based upon this domain model. Software developers using, maintaining, or extending the Sierra Toolkit computational mesh library must be familiar with the concepts/domain model presented in this report.

  11. Streaming simplification of tetrahedral meshes.

    PubMed

    Vo, Huy T; Callahan, Steven P; Lindstrom, Peter; Pascucci, Valerio; Silva, Cláudio T

    2007-01-01

    Unstructured tetrahedral meshes are commonly used in scientific computing to represent scalar, vector, and tensor fields in three dimensions. Visualization of these meshes can be difficult to perform interactively due to their size and complexity. By reducing the size of the data, we can accomplish real-time visualization necessary for scientific analysis. We propose a two-step approach for streaming simplification of large tetrahedral meshes. Our algorithm arranges the data on disk in a streaming, I/O-efficient format that allows coherent access to the tetrahedral cells. A quadric-based simplification is sequentially performed on small portions of the mesh in-core. Our output is a coherent streaming mesh which facilitates future processing. Our technique is fast, produces high quality approximations, and operates out-of-core to process meshes too large for main memory.

  12. Consistent melting behavior induced by Joule heating between Ag microwire and nanowire meshes.

    PubMed

    Tsuchiya, Kaoru; Li, Yuan; Saka, Masumi

    2014-01-01

    The melting behavior of an Ag microwire mesh induced by Joule heating was numerically investigated and compared with that of the corresponding Ag nanowire mesh with the same structure but different geometrical and physical properties of the wire itself. According to the relationship of melting current and melting voltage during the melting process, a similar repetitive zigzag pattern in melting behavior was discovered in both meshes. On this basis, a dimensionless parameter defined as figure of merit was proposed to characterize the current-carrying ability of the mesh. The consistent feature of figure of merit in both meshes indicates that the melting behavior of the Ag nanowire mesh can be predicted from the present results of the corresponding Ag microwire mesh with the same structure but made from a different wire (e.g., different size, different material) through simple conversion. The present findings can provide fundamental insight into the reliability analysis on the metallic nanowire mesh-based transparent conductive electrode.

  13. An Adaptive Mesh Algorithm: Mesh Structure and Generation

    SciTech Connect

    Scannapieco, Anthony J.

    2016-06-21

    The purpose of Adaptive Mesh Refinement is to minimize spatial errors over the computational space not to minimize the number of computational elements. The additional result of the technique is that it may reduce the number of computational elements needed to retain a given level of spatial accuracy. Adaptive mesh refinement is a computational technique used to dynamically select, over a region of space, a set of computational elements designed to minimize spatial error in the computational model of a physical process. The fundamental idea is to increase the mesh resolution in regions where the physical variables are represented by a broad spectrum of modes in k-space, hence increasing the effective global spectral coverage of those physical variables. In addition, the selection of the spatially distributed elements is done dynamically by cyclically adjusting the mesh to follow the spectral evolution of the system. Over the years three types of AMR schemes have evolved; block, patch and locally refined AMR. In block and patch AMR logical blocks of various grid sizes are overlaid to span the physical space of interest, whereas in locally refined AMR no logical blocks are employed but locally nested mesh levels are used to span the physical space. The distinction between block and patch AMR is that in block AMR the original blocks refine and coarsen entirely in time, whereas in patch AMR the patches change location and zone size with time. The type of AMR described herein is a locally refi ned AMR. In the algorithm described, at any point in physical space only one zone exists at whatever level of mesh that is appropriate for that physical location. The dynamic creation of a locally refi ned computational mesh is made practical by a judicious selection of mesh rules. With these rules the mesh is evolved via a mesh potential designed to concentrate the nest mesh in regions where the physics is modally dense, and coarsen zones in regions where the physics is modally

  14. Multigrid techniques for unstructured meshes

    NASA Technical Reports Server (NTRS)

    Mavriplis, D. J.

    1995-01-01

    An overview of current multigrid techniques for unstructured meshes is given. The basic principles of the multigrid approach are first outlined. Application of these principles to unstructured mesh problems is then described, illustrating various different approaches, and giving examples of practical applications. Advanced multigrid topics, such as the use of algebraic multigrid methods, and the combination of multigrid techniques with adaptive meshing strategies are dealt with in subsequent sections. These represent current areas of research, and the unresolved issues are discussed. The presentation is organized in an educational manner, for readers familiar with computational fluid dynamics, wishing to learn more about current unstructured mesh techniques.

  15. Mechanical behaviour of knit synthetic mesh used in hernia surgery.

    PubMed

    Tomaszewska, Agnieszka

    2016-01-01

    There is a discussion in literature concerning mechanical properties and modelling of surgical meshes. An important feature of elastic modulus dependency on load history is taken into account in this paper, as implants are subjected to variable loading during human activity. The example of DynaMesh®-IPOM surgical implant is studied. The analysis is based on failure tension tests and cyclic loading and unloading tests performed for the material samples. Stiffness changes of the material samples within successive load cycles are noted. The values the elastic modulus of the material tend to during successive cycles determine the material stiffness in the preconditioned state. The analysis is performed for two axes of the mesh, as the material reveals orthotropic properties. For the initial displacements state of the material bilinear stiffness functions are determined for the two considered material axes. The functions for the preconditioned state are specified basing in the observed stiffness changes in subsequent loading cycles in experiments with different load (and strain) ranges. The identified elastic modulus values for different strain levels in the preconditioned state are then a basis for the nonlinear stiffness function formulation. The author concludes that two states of the considered mesh should be considered in calculations, initial and preconditioned ones. As the material stiffness in its preconditioned state is higher than in the initial one, omitting of the preconditioned state in calculation, e.g., considering fixation of the mesh, may lead to underestimation of necessary fixation strength.

  16. Host response to synthetic mesh in women with mesh complications

    PubMed Central

    Nolfi, Alexis L.; Brown, Bryan N.; Liang, Rui; Palcsey, Stacy L.; Bonidie, Michael J.; Abramowitch, Steven D.; Moalli, Pamela A.

    2016-01-01

    BACKGROUND Despite good anatomic and functional outcomes, urogynecologic polypropylene meshes that are used to treat pelvic organ prolapse and stress urinary incontinence are associated with significant complications, most commonly mesh exposure and pain. Few studies have been performed that specifically focus on the host response to urogynecologic meshes. The macrophage has long been known to be the key cell type that mediates the foreign body response. Conceptually, macrophages that respond to a foreign body can be dichotomized broadly into M1 proinflammatory and M2 proremodeling subtypes. A prolonged M1 response is thought to result in chronic inflammation and the formation of foreign body giant cells with potential for ongoing tissue damage and destruction. Although a limited M2 predominant response is favorable for tissue integration and ingrowth, excessive M2 activity can lead to accelerated fibrillar matrix deposition and result in fibrosis and encapsulation of the mesh. OBJECTIVE The purpose of this study was to define and compare the macrophage response in patients who undergo mesh excision surgery for the indication of pain vs a mesh exposure. STUDY DESIGN Patients who were scheduled to undergo a surgical excision of mesh for pain or exposure at Magee-Womens Hospital were offered enrollment. Twenty-seven mesh-vagina complexes that were removed for the primary complaint of a mesh exposure (n = 15) vs pain in the absence of an exposure (n = 12) were compared with 30 full-thickness vaginal biopsy specimens from women who underwent benign gynecologic surgery without mesh. Macrophage M1 proinflammatory vs M2 proremodeling phenotypes were examined via immunofluorescent labeling for cell surface markers CD86 (M1) vs CD206 (M2) and M1 vs M2 cytokines via enzyme-linked immunosorbent assay. The amount of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) proteolytic enzymes were quantified by zymography and substrate degradation assays, as an

  17. Engagement of Metal Debris into a Gear Mesh

    NASA Technical Reports Server (NTRS)

    Handschuh, Robert F.; Krantz, Timothy L.

    2010-01-01

    A series of bench top experiments was conducted to determine the effects of metallic debris being dragged through meshing gear teeth. A test rig that is typically used to conduct contact fatigue experiments was used for these tests. Several sizes of drill material, shim stock, and pieces of gear teeth were introduced and then driven through the meshing region. The level of torque required to drive the "chip" through the gear mesh was measured. From the data gathered, chip size sufficient to jam the mechanism can be determined.

  18. Prevention of Adhesion to Prosthetic Mesh

    PubMed Central

    van ’t Riet, Martijne; de Vos van Steenwijk, Peggy J.; Bonthuis, Fred; Marquet, Richard L.; Steyerberg, Ewout W.; Jeekel, Johannes; Bonjer, H. Jaap

    2003-01-01

    Objective To assess whether use of antiadhesive liquids or coatings could prevent adhesion formation to prosthetic mesh. Summary Background Data Incisional hernia repair frequently involves the use of prosthetic mesh. However, concern exists about development of adhesions between viscera and the mesh, predisposing to intestinal obstruction or enterocutaneous fistulas. Methods In 91 rats, a defect in the muscular abdominal wall was created, and mesh was fixed intraperitoneally to cover the defect. Rats were divided in five groups: polypropylene mesh only (control group), addition of Sepracoat or Icodextrin solution to polypropylene mesh, Sepramesh (polypropylene mesh with Seprafilm coating), and Parietex composite mesh (polyester mesh with collagen coating). Seven and 30 days postoperatively, adhesions were assessed and wound healing was studied by microscopy. Results Intraperitoneal placement of polypropylene mesh was followed by bowel adhesions to the mesh in 50% of the cases. A mean of 74% of the mesh surface was covered by adhesions after 7 days, and 48% after 30 days. Administration of Sepracoat or Icodextrin solution had no influence on adhesion formation. Coated meshes (Sepramesh and Parietex composite mesh) had no bowel adhesions. Sepramesh was associated with a significant reduction of the mesh surface covered by adhesions after 7 and 30 days. Infection was more prevalent with Parietex composite mesh, with concurrent increased mesh surface covered by adhesions after 30 days (78%). Conclusions Sepramesh significantly reduced mesh surface covered by adhesions and prevented bowel adhesion to the mesh. Parietex composite mesh prevented bowel adhesions as well but increased infection rates in the current model. PMID:12496539

  19. The effect of thymoquinone coating on adhesive properties of polypropylene mesh.

    PubMed

    Aydin, Oktay; Aydinuraz, Kuzey; Agalar, Fatih; Sahiner, I Tayfun; Agalar, Canan; Bayram, Cem; Denkbas, Emir Baki; Atasoy, Pinar

    2017-04-17

    An incisional hernia is a common complication following abdominal surgery. Polypropylene mesh is frequently used in the repair of such defects and has nearly become the standard surgical treatment modality. Though they are very effective in reducing recurrence, mesh materials exhibit a strong stimulating effect for intraabdominal adhesion. The thymoquinone (TQ) extracted from Nigella sativa seeds has potential medical properties. TQ has anti-inflammatory, antioxidant and antibacterial properties. The aim of this study is to coat polypropylene mesh with TQ in order to investigate the effect of surface modification on intraabdominal adhesions. TQ-coated polypropylene mesh material was tested for cytotoxicity, contact angle, surface spectroscopy, TQ content, sterility, and electron microscopic surface properties. An experimental incisional hernia model was created in study groups, each consisting of 12 female Wistar rats. The defect was closed with uncoated mesh in control group, with polylactic acid (PLA) coated mesh and PLA-TQ coated mesh in study groups. Adhesion scores and histopathologic properties were evaluated after sacrifice on postoperative 21th day. Granuloma formation, lymphocyte and polymorphonuclear leukocyte infiltration, histiocyte fibroblast and giant cell formation, capillary infiltration, collagen content were significantly reduced in the PLA-TQ coated mesh group (p < 0.05). Though not statistically significant, likely due to the limited number of study animals, adhesion formation was also reduced in the PLA-TQ coated mesh group (p: 0.067). TQ coated mesh is shown to reduce adhesion formation and TQ is a promising coating material for mesh surface modification.

  20. Risk Factors for Mesh Exposure after Transvaginal Mesh Surgery

    PubMed Central

    Niu, Ke; Lu, Yong-Xian; Shen, Wen-Jie; Zhang, Ying-Hui; Wang, Wen-Ying

    2016-01-01

    Background: Mesh exposure after surgery continues to be a clinical challenge for urogynecological surgeons. The purpose of this study was to explore the risk factors for polypropylene (PP) mesh exposure after transvaginal mesh (TVM) surgery. Methods: This study included 195 patients with advanced pelvic organ prolapse (POP), who underwent TVM from January 2004 to December 2012 at the First Affiliated Hospital of Chinese PLA General Hospital. Clinical data were evaluated including patient's demography, TVM type, concomitant procedures, operation time, blood loss, postoperative morbidity, and mesh exposure. Mesh exposure was identified through postoperative vaginal examination. Statistical analysis was performed to identify risk factors for mesh exposure. Results: Two-hundred and nine transvaginal PP meshes were placed, including 194 in the anterior wall and 15 in the posterior wall. Concomitant tension-free vaginal tape was performed in 61 cases. The mean follow-up time was 35.1 ± 23.6 months. PP mesh exposure was identified in 32 cases (16.4%), with 31 in the anterior wall and 1 in the posterior wall. Significant difference was found in operating time and concomitant procedures between exposed and nonexposed groups (F = 7.443, P = 0.007; F = 4.307, P = 0.039, respectively). Binary logistic regression revealed that the number of concomitant procedures and operation time were risk factors for mesh exposure (P = 0.001, P = 0.043). Conclusion: Concomitant procedures and increased operating time increase the risk for postoperative mesh exposure in patients undergoing TVM surgery for POP. PMID:27453227

  1. Colposacropexy with Prolene mesh.

    PubMed

    Baker, K R; Beresford, J M; Campbell, C

    1990-07-01

    A retrospective analysis of 59 patients who underwent colposacropexy (CSP) using Prolene (polypropylene) mesh is presented. Fifty-eight of the patients had undergone previous surgical treatment, including either vaginal or abdominal hysterectomy. Twenty-two patients underwent CSP alone, 24 had CSP and retropubic urethropexy (RPU), eight had CSP with anterior or posterior repair, or both, and five had CSP and RPU with anterior and posterior repair. The operations were associated with a minimum of intraoperative complications and acceptable postoperative problems. A postoperative questionnaire was sent to the patients with an 89 per cent response rate. None of the patients complained of protrusion from the vagina. It is concluded that, in the hands of experienced surgeons, CSP is a safe, efficacious operative procedure that should remain the procedure of choice for vaginal vault prolapse since it restores the normal vaginal axis, maintains existing vaginal length and provides permanent care.

  2. Quadrilateral finite element mesh coarsening

    SciTech Connect

    Staten, Matthew L; Dewey, Mark W; Benzley, Steven E

    2012-10-16

    Techniques for coarsening a quadrilateral mesh are described. These techniques include identifying a coarsening region within the quadrilateral mesh to be coarsened. Quadrilateral elements along a path through the coarsening region are removed. Node pairs along opposite sides of the path are identified. The node pairs along the path are then merged to collapse the path.

  3. ZnO nanorod array-coated mesh film for the separation of water and oil.

    PubMed

    Li, Hong; Li, Yushan; Liu, Qinzhuang

    2013-04-20

    Dense and vertically aligned ZnO nanorod arrays with a large area have been fabricated successfully on the stainless steel mesh by a simple chemical vapor deposition method. The coated mesh exhibited both superoleophilic and superhydrophobic properties, even if it was not modified by low surface energy materials. The separation efficiencies were more than 97% in the filtration of water and oil. Besides, the wettability of the coated mesh was still stable after it was soaked in the corrosive solutions for 1 h. A detailed investigation showed that the coated mesh has the best superhydrophobic property when the stainless steel mesh pore size was about 75 μm.

  4. ZnO nanorod array-coated mesh film for the separation of water and oil

    NASA Astrophysics Data System (ADS)

    Li, Hong; Li, Yushan; Liu, Qinzhuang

    2013-04-01

    Dense and vertically aligned ZnO nanorod arrays with a large area have been fabricated successfully on the stainless steel mesh by a simple chemical vapor deposition method. The coated mesh exhibited both superoleophilic and superhydrophobic properties, even if it was not modified by low surface energy materials. The separation efficiencies were more than 97% in the filtration of water and oil. Besides, the wettability of the coated mesh was still stable after it was soaked in the corrosive solutions for 1 h. A detailed investigation showed that the coated mesh has the best superhydrophobic property when the stainless steel mesh pore size was about 75 μm.

  5. Superhydrophobic hierarchical structure carbon mesh films for oil/water separation application

    NASA Astrophysics Data System (ADS)

    Lu, Zhaoxia; Huang, Xing; Wang, Lisheng

    2017-08-01

    In this study, we showed that a superoleophobic mesh with the self-cleaning ability could be readily prepared by a facile spray-coating method on stainless steel mesh. Poly(methyl methacrylate) was employed to provide a stable strength between carbon nanotubes and steel mesh surface. The effect of opening size of these steel meshes on surface wetting has been investigated. The dynamics of liquid droplets was investigated as well. The as-prepared meshes exhibited both superhydrophobicity and superoleophilicity and could effectively separate water from the oil and water mixture. The present study contributes to the development of oil and water separation materials for marine industrial application.

  6. Remodeling characteristics and collagen distribution in synthetic mesh materials explanted from human subjects after abdominal wall reconstruction: an analysis of remodeling characteristics by patient risk factors and surgical site classifications

    PubMed Central

    Cavallo, Jaime A.; Roma, Andres A.; Jasielec, Mateusz S.; Ousley, Jenny; Creamer, Jennifer; Pichert, Matthew D.; Baalman, Sara; Frisella, Margaret M.; Matthews, Brent D.

    2014-01-01

    Background The purpose of this study was to evaluate the associations between patient characteristics or surgical site classifications and the histologic remodeling scores of synthetic meshes biopsied from their abdominal wall repair sites in the first attempt to generate a multivariable risk prediction model of non-constructive remodeling. Methods Biopsies of the synthetic meshes were obtained from the abdominal wall repair sites of 51 patients during a subsequent abdominal re-exploration. Biopsies were stained with hematoxylin and eosin, and evaluated according to a semi-quantitative scoring system for remodeling characteristics (cell infiltration, cell types, extracellular matrix deposition, inflammation, fibrous encapsulation, and neovascularization) and a mean composite score (CR). Biopsies were also stained with Sirius Red and Fast Green, and analyzed to determine the collagen I:III ratio. Based on univariate analyses between subject clinical characteristics or surgical site classification and the histologic remodeling scores, cohort variables were selected for multivariable regression models using a threshold p value of ≤0.200. Results The model selection process for the extracellular matrix score yielded two variables: subject age at time of mesh implantation, and mesh classification (c-statistic = 0.842). For CR score, the model selection process yielded two variables: subject age at time of mesh implantation and mesh classification (r2 = 0.464). The model selection process for the collagen III area yielded a model with two variables: subject body mass index at time of mesh explantation and pack-year history (r2 = 0.244). Conclusion Host characteristics and surgical site assessments may predict degree of remodeling for synthetic meshes used to reinforce abdominal wall repair sites. These preliminary results constitute the first steps in generating a risk prediction model that predicts the patients and clinical circumstances for which non

  7. Tangle-Free Mesh Motion for Ablation Simulations

    NASA Technical Reports Server (NTRS)

    Droba, Justin

    2016-01-01

    Problems involving mesh motion-which should not be mistakenly associated with moving mesh methods, a class of adaptive mesh redistribution techniques-are of critical importance in numerical simulations of the thermal response of melting and ablative materials. Ablation is the process by which material vaporizes or otherwise erodes due to strong heating. Accurate modeling of such materials is of the utmost importance in design of passive thermal protection systems ("heatshields") for spacecraft, the layer of the vehicle that ensures survival of crew and craft during re-entry. In an explicit mesh motion approach, a complete thermal solve is first performed. Afterwards, the thermal response is used to determine surface recession rates. These values are then used to generate boundary conditions for an a posteriori correction designed to update the location of the mesh nodes. Most often, linear elastic or biharmonic equations are used to model this material response, traditionally in a finite element framework so that complex geometries can be simulated. A simple scheme for moving the boundary nodes involves receding along the surface normals. However, for all but the simplest problem geometries, evolution in time following such a scheme will eventually bring the mesh to intersect and "tangle" with itself, inducing failure. This presentation demonstrates a comprehensive and sophisticated scheme that analyzes the local geometry of each node with help from user-provided clues to eliminate the tangle and enable simulations on a wide-class of difficult problem geometries. The method developed is demonstrated for linear elastic equations but is general enough that it may be adapted to other modeling equations. The presentation will explicate the inner workings of the tangle-free mesh motion algorithm for both two and three-dimensional meshes. It will show abstract examples of the method's success, including a verification problem that demonstrates its accuracy and

  8. Mesh Copy/Move/Merge Tool for Reactor Simulation Applications

    SciTech Connect

    Tautges, Timothy J.; Jain, Rajeev

    2014-04-30

    Reactor core simulations require the construction and mesh generation for core models consisting of lattices of fuel and other rods grouped into assemblies, and lattices of assemblies of several types grouped into a core model. A set of tools has been described for generating assembly and core lattice models. Both rectangular and hexagonal lattices are supported. The tools operate in three stages. First, assembly models of various types can be generated by the AssyGen tool, based on input describing the content of unit cells, the arrangement of unit cells in the lattice, and the extent of the lattice and any surrounding material. After generating the assembly model, the model is meshed with the CUBIT mesh generation toolkit, optionally based on a journal file output by AssyGen. After one or more assembly model meshes have been constructed, they are arranged in a core model using the CoreGen tool. The input for CoreGen is similar to that of AssyGen, with assembly models substituted for unit cells. AssyGen and CoreGen also annotate the models with material and volume groupings necessary for specifying materials and boundary conditions required by the analysis. The AssyGen and CoreGen tools are packaged in the open-source MeshKit library for mesh generation; download and build instructions are included in this document.

  9. Drop impact on permeable meshes with yield-stress fluids

    NASA Astrophysics Data System (ADS)

    Ewoldt, Randy; Blackwell, Brendan; Nadhan, Athrey

    2015-11-01

    Yield-stress fluids, such as pastes and gels, can stick and accumulate where they impact. To understand coating of complex topography, we experimentally study the ability of drops to accumulate on permeable solid meshes (rigid surfaces with small, evenly spaced openings). Whereas Newtonian fluids can adhere on meshes with sufficiently small lengthscales due to surface tension, yield-stress fluids can adhere due to rheological properties and accumulate much larger volumes. When inertial stresses are sufficiently high compared to the yield stress, a drop can pass through a mesh, breaking into smaller fluid particles with varying shapes, sizes, and velocities in the process. In contrast, when inertial stresses are sufficiently low compared to the yield stress, a drop can stick to the open mesh as though it were an impermeable solid surface. Drop size, impact velocity, mesh geometry, and rheological material properties are varied. Layers of spaced meshes are also examined, demonstrating a range of behaviors and the ability to coat internal aspects of complex topography. Dimensional analysis is performed to characterize material transmittance, velocity variations, and material spreading as a function of the geometric, kinematic, and rheological parameters.

  10. Prosthetic Mesh Repair for Incarcerated Inguinal Hernia

    PubMed Central

    Tatar, Cihad; Tüzün, İshak Sefa; Karşıdağ, Tamer; Kızılkaya, Mehmet Celal; Yılmaz, Erdem

    2016-01-01

    Background: Incarcerated inguinal hernia is a commonly encountered urgent surgical condition, and tension-free repair is a well-established method for the treatment of non-complicated cases. However, due to the risk of prosthetic material-related infections, the use of mesh in the repair of strangulated or incarcerated hernia has often been subject to debate. Recent studies have demonstrated that biomaterials represent suitable materials for performing urgent hernia repair. Certain studies recommend mesh repair only for cases where no bowel resection is required; other studies, however, recommend mesh repair for patients requiring bowel resection as well. Aim: The aim of this study was to compare the outcomes of different surgical techniques performed for strangulated hernia, and to evaluate the effect of mesh use on postoperative complications. Study Design: Retrospective cross-sectional study. Methods: This retrospective study was performed with 151 patients who had been admitted to our hospital’s emergency department to undergo surgery for a diagnosis of incarcerated inguinal hernia. The patients were divided into two groups based on the applied surgical technique. Group 1 consisted of 112 patients treated with mesh-based repair techniques, while Group 2 consisted of 39 patients treated with tissue repair techniques. Patients in Group 1 were further divided into two sub-groups: one consisting of patients undergoing bowel resection (Group 3), and the other consisting of patients not undergoing bowel resection (Group 4). Results: In Group 1, it was observed that eight (7.14%) of the patients had wound infections, while two (1.78%) had hematomas, four (3.57%) had seromas, and one (0.89%) had relapse. In Group 2, one (2.56%) of the patients had a wound infection, while three (7.69%) had hematomas, one (2.56%) had seroma, and none had relapses. There were no statistically significant differences between the two groups with respect to wound infection, seroma

  11. Definitive Surgical Treatment of Infected or Exposed Ventral Hernia Mesh

    PubMed Central

    Szczerba, Steven R.; Dumanian, Gregory A.

    2003-01-01

    Objective To discuss the difficulties in dealing with infected or exposed ventral hernia mesh, and to illustrate one solution using an autogenous abdominal wall reconstruction technique. Summary Background Data The definitive treatment for any infected prosthetic material in the body is removal and substitution. When ventral hernia mesh becomes exposed or infected, its removal requires a solution to prevent a subsequent hernia or evisceration. Methods Eleven patients with ventral hernia mesh that was exposed, nonincorporated, with chronic drainage, or associated with a spontaneous enterocutaneous fistula were referred by their initial surgeons after failed local wound care for definitive management. The patients were treated with radical en bloc excision of mesh and scarred fascia followed by immediate abdominal wall reconstruction using bilateral sliding rectus abdominis myofascial advancement flaps. Results Four of the 11 patients treated for infected mesh additionally required a bowel resection. Transverse defect size ranged from 8 to 18 cm (average 13 cm). Average procedure duration was 3 hours without bowel repair and 5 hours with bowel repair. Postoperative length of stay was 5 to 7 days without bowel repair and 7 to 9 days with bowel repair. Complications included hernia recurrence in one case and stitch abscesses in two cases. Follow-up ranges from 6 to 54 months (average 24 months). Conclusions Removal of infected mesh and autogenous flap reconstruction is a safe, reliable, and one-step surgical solution to the problem of infected abdominal wall mesh. PMID:12616130

  12. Evaluation of Composite Mesh for Ventral Hernia Repair

    PubMed Central

    Byrd, Jim F.; Agee, Neal; Nguyen, Phuong H.; Heath, Jessica J.; Lau, Kwan N.; McKillop, Iain H.; Sindram, David; Martinie, John B.

    2011-01-01

    Introduction: Composite mesh prostheses incorporate the properties of multiple materials for ventral hernia repair. This study evaluated a polypropylene/ePTFE composite mesh with a novel internal polydioxanone (PDO) absorbable ring. Methods: Composite mesh was placed intraperitoneally in 16 pigs through an open laparotomy and explanted at 2, 4, 8, and 12 weeks. Intraabdominal adhesions were measured laparoscopically. Host tissue in-growth was assessed histologically and tensiometrically. Degradation of the internal PDO ring component was also measured tensiometrically. Appropriate statistical tests were used, and P≤.05 indicated significance. Results: No adhesions were formed in 50% of the grafts explanted at 8 weeks and 25% of grafts explanted at 12 weeks. There were significantly more vascular structures at 8 weeks, 73.5±28, compared with 2 weeks, 6.75±2 (P≤.01). The T-peel force at the mesh-host tissue interface was not significantly different among time points. The absorbable PDO ring underwent complete degradation by 12 weeks. Conclusions: This composite mesh was associated with minimal intraabdominal adhesions, progressive in-growth of host tissues, and complete degradation of a novel internal PDO ring that aided mesh positioning. This composite hernia mesh showed a favorable performance in a porcine model of open ventral hernia repair. PMID:21985713

  13. Wire mesh current collectors for passive direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Shrivastava, Naveen K.; Thombre, Shashikant B.; Motghare, Ramani V.

    2014-12-01

    This paper examines the feasibility of the stainless steel wire mesh as current collector in the passive direct methanol fuel cell (DMFCs-W). A novel single cell fixture is designed and fabricated. The cell performance is evaluated and compared with five different wire mesh current collectors. The supporting plates are optimized for every mesh. The performance of DMFCs-W is compared with the conventional passive DMFC which uses perforated metal plate as current collector (DMFC-P). The polarization tests and electrochemical impedance spectroscopy are performed to investigate the different aspects of the cell performance. The results reveal that the DMFCs-W yield better performance than the DMFC-P. Also, more uniform fuel distribution at catalyst layer and higher cell temperature is achieved with wire mesh current collectors. It is found that the wire mesh geometry has significant effect on the cell performance and the mesh made of relatively thick wires gives better cell performance. This study identifies the stainless steel wire mesh as promising material to be used as current collector and potential substitute to the perforated plate current collectors in the passive DMFC.

  14. 3-D Mesh Generation Nonlinear Systems

    SciTech Connect

    Christon, M. A.; Dovey, D.; Stillman, D. W.; Hallquist, J. O.; Rainsberger, R. B

    1994-04-07

    INGRID is a general-purpose, three-dimensional mesh generator developed for use with finite element, nonlinear, structural dynamics codes. INGRID generates the large and complex input data files for DYNA3D, NIKE3D, FACET, and TOPAZ3D. One of the greatest advantages of INGRID is that virtually any shape can be described without resorting to wedge elements, tetrahedrons, triangular elements or highly distorted quadrilateral or hexahedral elements. Other capabilities available are in the areas of geometry and graphics. Exact surface equations and surface intersections considerably improve the ability to deal with accurate models, and a hidden line graphics algorithm is included which is efficient on the most complicated meshes. The primary new capability is associated with the boundary conditions, loads, and material properties required by nonlinear mechanics programs. Commands have been designed for each case to minimize user effort. This is particularly important since special processing is almost always required for each load or boundary condition.

  15. Engagement of Metal Debris into a Gear Mesh

    NASA Technical Reports Server (NTRS)

    Handschuh, Robert F.; Krantz, Timothy L.

    2009-01-01

    A series of bench top experiments was conducted to determine the effects of metallic debris being dragged through meshing gear teeth. A test rig that is typically used to conduct contact fatigue experiments was used for these tests. Several sizes of drill material, shim stock, and pieces of gear teeth were introduced and then driven through the meshing region. The level of torque required to drive the "chip" through the gear mesh was measured. From the data gathered, chip size sufficient to jam the mechanism can be determined. INTRODUCTION In some space mechanisms the loading can be so high that there is some possibility that a gear chip might be liberated while in operation of the mechanism [1-5]. Also, due to the closely packed nature of some space mechanisms and the fact that a space grease is used for lubrication, chips that are released can then be introduced to other gear meshes within this mechanism. In this instance, it is desirable to know the consequences of a gear chip entering in between meshing gear teeth. To help provide some understanding, a series of bench-top experiments was conducted to engage chips of simulated and gear material fragments into a meshing gear pair. One purpose of the experiments was to determine the relationship of chip size to the torque required to rotate the gear set through the mesh cycle. The second purpose was to determine the condition of the gear chip material after engagement by the meshing gears, primarily to determine if the chip would break into pieces and to observe the motion of the chip as the engagement was completed. This document also presents preliminary testing done with metal debris other than chips from gears, namely steel shim stock and drill bits of various sizes and diameters.

  16. 21 CFR 878.3300 - Surgical mesh.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... GENERAL AND PLASTIC SURGERY DEVICES Prosthetic Devices § 878.3300 Surgical mesh. (a) Identification... acetabular and cement restrictor mesh used during orthopedic surgery. (b) Classification. Class II....

  17. 21 CFR 878.3300 - Surgical mesh.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... GENERAL AND PLASTIC SURGERY DEVICES Prosthetic Devices § 878.3300 Surgical mesh. (a) Identification... acetabular and cement restrictor mesh used during orthopedic surgery. (b) Classification. Class II....

  18. 21 CFR 878.3300 - Surgical mesh.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... GENERAL AND PLASTIC SURGERY DEVICES Prosthetic Devices § 878.3300 Surgical mesh. (a) Identification... acetabular and cement restrictor mesh used during orthopedic surgery. (b) Classification. Class II....

  19. 21 CFR 878.3300 - Surgical mesh.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... GENERAL AND PLASTIC SURGERY DEVICES Prosthetic Devices § 878.3300 Surgical mesh. (a) Identification... acetabular and cement restrictor mesh used during orthopedic surgery. (b) Classification. Class II. ...

  20. 21 CFR 878.3300 - Surgical mesh.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... GENERAL AND PLASTIC SURGERY DEVICES Prosthetic Devices § 878.3300 Surgical mesh. (a) Identification... acetabular and cement restrictor mesh used during orthopedic surgery. (b) Classification. Class II. ...

  1. Comparison of the fracture resistances of glass fiber mesh- and metal mesh-reinforced maxillary complete denture under dynamic fatigue loading

    PubMed Central

    2017-01-01

    PURPOSE The aim of this study was to investigate the effect of reinforcing materials on the fracture resistances of glass fiber mesh- and Cr–Co metal mesh-reinforced maxillary complete dentures under fatigue loading. MATERIALS AND METHODS Glass fiber mesh- and Cr–Co mesh-reinforced maxillary complete dentures were fabricated using silicone molds and acrylic resin. A control group was prepared with no reinforcement (n = 15 per group). After fatigue loading was applied using a chewing simulator, fracture resistance was measured by a universal testing machine. The fracture patterns were analyzed and the fractured surfaces were observed by scanning electron microscopy. RESULTS After cyclic loading, none of the dentures showed cracks or fractures. During fracture resistance testing, all unreinforced dentures experienced complete fracture. The mesh-reinforced dentures primarily showed posterior framework fracture. Deformation of the all-metal framework caused the metal mesh-reinforced denture to exhibit the highest fracture resistance, followed by the glass fiber mesh-reinforced denture (P<.05) and the control group (P<.05). The glass fiber mesh-reinforced denture primarily maintained its original shape with unbroken fibers. River line pattern of the control group, dimples and interdendritic fractures of the metal mesh group, and radial fracture lines of the glass fiber group were observed on the fractured surfaces. CONCLUSION The glass fiber mesh-reinforced denture exhibits a fracture resistance higher than that of the unreinforced denture, but lower than that of the metal mesh-reinforced denture because of the deformation of the metal mesh. The glass fiber mesh-reinforced denture maintains its shape even after fracture, indicating the possibility of easier repair. PMID:28243388

  2. Streaming Compression of Hexahedral Meshes

    SciTech Connect

    Isenburg, M; Courbet, C

    2010-02-03

    We describe a method for streaming compression of hexahedral meshes. Given an interleaved stream of vertices and hexahedral our coder incrementally compresses the mesh in the presented order. Our coder is extremely memory efficient when the input stream documents when vertices are referenced for the last time (i.e. when it contains topological finalization tags). Our coder then continuously releases and reuses data structures that no longer contribute to compressing the remainder of the stream. This means in practice that our coder has only a small fraction of the whole mesh in memory at any time. We can therefore compress very large meshes - even meshes that do not file in memory. Compared to traditional, non-streaming approaches that load the entire mesh and globally reorder it during compression, our algorithm trades a less compact compressed representation for significant gains in speed, memory, and I/O efficiency. For example, on the 456k hexahedra 'blade' mesh, our coder is twice as fast and uses 88 times less memory (only 3.1 MB) with the compressed file increasing about 3% in size. We also present the first scheme for predictive compression of properties associated with hexahedral cells.

  3. Nanowire mesh solar fuels generator

    DOEpatents

    Yang, Peidong; Chan, Candace; Sun, Jianwei; Liu, Bin

    2016-05-24

    This disclosure provides systems, methods, and apparatus related to a nanowire mesh solar fuels generator. In one aspect, a nanowire mesh solar fuels generator includes (1) a photoanode configured to perform water oxidation and (2) a photocathode configured to perform water reduction. The photocathode is in electrical contact with the photoanode. The photoanode may include a high surface area network of photoanode nanowires. The photocathode may include a high surface area network of photocathode nanowires. In some embodiments, the nanowire mesh solar fuels generator may include an ion conductive polymer infiltrating the photoanode and the photocathode in the region where the photocathode is in electrical contact with the photoanode.

  4. Altering surface characteristics of polypropylene mesh via sodium hydroxide treatment.

    PubMed

    Regis, Shawn; Jassal, Manisha; Mukherjee, Nilay; Bayon, Yves; Scarborough, Nelson; Bhowmick, Sankha

    2012-05-01

    Incisional hernias represent a serious and common complication following laparotomy. The use of synthetic (e.g. polypropylene) meshes to aid repair of these hernias has considerably reduced recurrence rates. While polypropylene is biocompatible and has a long successful clinical history in treating hernias and preventing reherniation, this material may suffer some limitations, particularly in challenging patients at risk of wound failure due to, for example, an exaggerated inflammation reaction, delayed wound healing, and infection. Surface modification of the polypropylene mesh without sacrificing its mechanical properties, critical for hernia repair, represents one way to begin to address these clinical complications. Our hypothesis is treatment of a proprietary polypropylene mesh with sodium hydroxide (NaOH) will increase in vitro NIH/3T3 cell attachment, predictive of earlier and improved cell colonization and tissue integration of polypropylene materials. Our goal is to achieve this altered surface functionality via enhanced removal of chemicals/oils used during material synthesis without compromising the mechanical properties of the mesh. We found that NaOH treatment does not appear to compromise the mechanical strength of the material, despite roughly a 10% decrease in fiber diameter. The treatment increases in vitro NIH/3T3 cell attachment within the first 72 h and this effect is sustained up to 7 days in vitro. This research demonstrates that sodium hydroxide treatment is an efficient way to modify the surface of polypropylene hernia meshes without losing the mechanical integrity of the material. This simple procedure could also allow the attachment of a variety of biomolecules to the polypropylene mesh that may aid in reducing the complications associated with polypropylene meshes today. Copyright © 2012 Wiley Periodicals, Inc.

  5. The Use of Biological Meshes in Diaphragmatic Defects - An Evidence-Based Review of the Literature.

    PubMed

    Antoniou, Stavros A; Pointner, Rudolph; Granderath, Frank-Alexander; Köckerling, Ferdinand

    2015-01-01

    The widespread use of meshes for hiatal hernia repair has emerged in the era of laparoscopic surgery, although sporadic cases of mesh augmentation of traumatic diaphragmatic rupture have been reported. The indications for biologic meshes in diaphragmatic repair are ill defined. This systematic review aims to investigate the available evidence on the role of biologic meshes in diaphragmatic rupture and hiatal hernia repair. Limited data from sporadic case reports and case series have demonstrated that repair of traumatic diaphragmatic rupture with biologic mesh is safe technique in both the acute or chronic setting. High level evidence demonstrates short-term benefits of biologic mesh augmentation in hiatal hernia repair over primary repair, although adequate long-term data are not currently available. Long-term follow-up data suggest no benefit of hiatal hernia repair using porcine small intestine submucosa over suture repair. The effectiveness of different biologic mesh materials on hernia recurrence requires further investigation.

  6. Adhesion prevention in ventral hernia repair: an experimental study comparing three lightweight porous meshes recommended for intraperitoneal use.

    PubMed

    D'Amore, L; Ceci, F; Mattia, S; Fabbi, M; Negro, P; Gossetti, F

    2017-02-01

    In ventral hernia repair, when prosthetic material is placed intraperitoneally, it may lead to an inflammatory reaction resulting in adhesions between the mesh and abdominal viscera. Several meshes have been developed to minimize this process. In this experimental study, the ability of different combined meshes to attenuate the adhesion formation was examined. Three commercially available lightweight porous combined meshes were placed intraperitoneally to repair an abdominal wall defect in rats: DynaMesh-IPOM (PVDF + PP), TiMesh (titanium-coated filament PP) and C-QUR/FX (omega-3 fatty acid-coated filament PP). The DynaMesh-CICAT (PVDF) was implanted in the control group. Adhesion formation was macroscopically evaluated and scored after 7 and 21 days. All animals except two presented intra-abdominal adhesions. None of the meshes examined in the study demonstrated to prevent adhesions. C-QUR/FX reduced adhesion formation at 7 days' follow-up compared with all other meshes but by 21 days this effect was diminished. Between 7 and 21 days adhesion extension significantly decreased for TiMesh. TAS did not show significant modifications between 7 and 21 days' follow-up for each mesh. The combined porous meshes tested in the present study demonstrated to reduce but not to prevent the adhesion formation, even if with some differences. Combined porous meshes could be chosen instead of simple meshes for retro-rectus preperitoneal prosthetic ventral hernia repair.

  7. Gradient scaling for nonuniform meshes

    SciTech Connect

    Margolin, L.G.; Ruppel, H.M.; Demuth, R.B.

    1985-01-01

    This paper is concerned with the effect of nonuniform meshes on the accuracy of finite-difference calculations of fluid flow. In particular, when a simple shock propagates through a nonuniform mesh, one may fail to model the jump conditions across the shock even when the equations are differenced in manifestly conservative fashion. We develop an approximate dispersion analysis of the numerical equations and identify the source of the mesh dependency with the form of the artificial viscosity. We then derive an algebraic correction to the numerical equations - a scaling factor for the pressure gradient - to essentially eliminate the mesh dependency. We present several calculations to illustrate our theory. We conclude with an alternate interpretation of our results. 14 refs., 5 figs.

  8. Parallel Adaptive Mesh Refinement Library

    NASA Technical Reports Server (NTRS)

    Mac-Neice, Peter; Olson, Kevin

    2005-01-01

    Parallel Adaptive Mesh Refinement Library (PARAMESH) is a package of Fortran 90 subroutines designed to provide a computer programmer with an easy route to extension of (1) a previously written serial code that uses a logically Cartesian structured mesh into (2) a parallel code with adaptive mesh refinement (AMR). Alternatively, in its simplest use, and with minimal effort, PARAMESH can operate as a domain-decomposition tool for users who want to parallelize their serial codes but who do not wish to utilize adaptivity. The package builds a hierarchy of sub-grids to cover the computational domain of a given application program, with spatial resolution varying to satisfy the demands of the application. The sub-grid blocks form the nodes of a tree data structure (a quad-tree in two or an oct-tree in three dimensions). Each grid block has a logically Cartesian mesh. The package supports one-, two- and three-dimensional models.

  9. Mersiline mesh in premaxillary augmentation.

    PubMed

    Foda, Hossam M T

    2005-01-01

    Premaxillary retrusion may distort the aesthetic appearance of the columella, lip, and nasal tip. This defect is characteristically seen in, but not limited to, patients with cleft lip nasal deformity. This study investigated 60 patients presenting with premaxillary deficiencies in which Mersiline mesh was used to augment the premaxilla. All the cases had surgery using the external rhinoplasty technique. Two methods of augmentation with Mersiline mesh were used: the Mersiline roll technique, for the cases with central symmetric deficiencies, and the Mersiline packing technique, for the cases with asymmetric deficiencies. Premaxillary augmentation with Mersiline mesh proved to be simple technically, easy to perform, and not associated with any complications. Periodic follow-up evaluation for a mean period of 32 months (range, 12-98 months) showed that an adequate degree of premaxillary augmentation was maintained with no clinically detectable resorption of the mesh implant.

  10. Unstructured mesh methods for CFD

    NASA Technical Reports Server (NTRS)

    Peraire, J.; Morgan, K.; Peiro, J.

    1990-01-01

    Mesh generation methods for Computational Fluid Dynamics (CFD) are outlined. Geometric modeling is discussed. An advancing front method is described. Flow past a two engine Falcon aeroplane is studied. An algorithm and associated data structure called the alternating digital tree, which efficiently solves the geometric searching problem is described. The computation of an initial approximation to the steady state solution of a given poblem is described. Mesh generation for transient flows is described.

  11. Image-driven mesh optimization

    SciTech Connect

    Lindstrom, P; Turk, G

    2001-01-05

    We describe a method of improving the appearance of a low vertex count mesh in a manner that is guided by rendered images of the original, detailed mesh. This approach is motivated by the fact that greedy simplification methods often yield meshes that are poorer than what can be represented with a given number of vertices. Our approach relies on edge swaps and vertex teleports to alter the mesh connectivity, and uses the downhill simplex method to simultaneously improve vertex positions and surface attributes. Note that this is not a simplification method--the vertex count remains the same throughout the optimization. At all stages of the optimization the changes are guided by a metric that measures the differences between rendered versions of the original model and the low vertex count mesh. This method creates meshes that are geometrically faithful to the original model. Moreover, the method takes into account more subtle aspects of a model such as surface shading or whether cracks are visible between two interpenetrating parts of the model.

  12. Comparison of the fracture resistances of glass fiber mesh- and metal mesh-reinforced maxillary complete denture under dynamic fatigue loading.

    PubMed

    Im, So-Min; Huh, Yoon-Hyuk; Cho, Lee-Ra; Park, Chan-Jin

    2017-02-01

    The aim of this study was to investigate the effect of reinforcing materials on the fracture resistances of glass fiber mesh- and Cr-Co metal mesh-reinforced maxillary complete dentures under fatigue loading. Glass fiber mesh- and Cr-Co mesh-reinforced maxillary complete dentures were fabricated using silicone molds and acrylic resin. A control group was prepared with no reinforcement (n = 15 per group). After fatigue loading was applied using a chewing simulator, fracture resistance was measured by a universal testing machine. The fracture patterns were analyzed and the fractured surfaces were observed by scanning electron microscopy. After cyclic loading, none of the dentures showed cracks or fractures. During fracture resistance testing, all unreinforced dentures experienced complete fracture. The mesh-reinforced dentures primarily showed posterior framework fracture. Deformation of the all-metal framework caused the metal mesh-reinforced denture to exhibit the highest fracture resistance, followed by the glass fiber mesh-reinforced denture (P<.05) and the control group (P<.05). The glass fiber mesh-reinforced denture primarily maintained its original shape with unbroken fibers. River line pattern of the control group, dimples and interdendritic fractures of the metal mesh group, and radial fracture lines of the glass fiber group were observed on the fractured surfaces. The glass fiber mesh-reinforced denture exhibits a fracture resistance higher than that of the unreinforced denture, but lower than that of the metal mesh-reinforced denture because of the deformation of the metal mesh. The glass fiber mesh-reinforced denture maintains its shape even after fracture, indicating the possibility of easier repair.

  13. Pathologic evaluation of explanted vaginal mesh: interdisciplinary experience from a referral center.

    PubMed

    Smith, Tovia M; Smith, Steven C; Delancey, John O; Fenner, Dee E; Schimpf, Megan O; Roh, Michael H; Morgan, Daniel M

    2013-01-01

    In light of vaginal mesh safety concerns, we reviewed our institutional experience with analytic processes and pathologic findings of explanted vaginal mesh to identify problems and opportunities to facilitate improved documentation and research. We reviewed gross and microscopic pathology reports and archival slides of explanted mesh specimens from January 2010 through February 2012. Specimen requisition clinical history, number of mesh specimens per case, and type of examination (gross or histologic) were abstracted from pathology records using the initial search word "mesh". One hundred two cases were reviewed. Explanted mesh specimens included tissue in 97%. Forty-eight percent of these cases were submitted for histopathologic evaluation (as opposed to gross examination only). Specimen requisitions listed clinical history as pain (28.4%), vaginal mesh erosion (24.5%), erosion (17.6%), urinary retention (5.9%), and infection (2.9%). When no history was provided (24.5%), the case was more frequently submitted for histologic examination (74% vs 41%, P = 0.05). In all but 2 cases, the mesh material was polypropylene; no requisition mentioned this information. Gross descriptions of mesh varied significantly; in 18% of the cases, mesh was inaccurately described as "metallic". No cases of neoplasm were diagnosed histologically; all tissue diagnoses described benign reactive processes. Our experience suggests that either gross or histopathologic examination is appropriate for mesh explants. Documentation of clinical history, mesh product, and material was frequently incomplete and associated with increased submission of tissue for histologic examination and inaccurate gross impression of material type. We recommend improved documentation to aid pathologic examination and enable future pathophysiologic study of mesh complications.

  14. An in vitro study assessing the effect of mesh morphology and suture fixation on bacterial adherence.

    PubMed

    Sanders, D; Lambie, J; Bond, P; Moate, R; Steer, J A

    2013-12-01

    Prosthetic infections, although relatively uncommon in hernia surgery, are a source of considerable morbidity and cost. The aims of this experimental study were to assess the influence of the morphological properties of the mesh on bacterial adherence in vitro. The morphological properties assessed were the polymer type, filament type, filament diameter, mesh weight, mean pore size, and the addition of silver chlorhexidine and titanium coatings. In addition, the study assessed the effect on bacterial adherence of adding a commonly used suture to the mesh and compared adherence rates to self-gripping mesh that does not require suture fixation. Eight commercially sourced flat hernia meshes with different material characteristics were included in the study. These were Prolene(®) (Ethicon(®)), DualMesh(®) (Gore(®)), DualMesh(®) Plus (Gore(®)), Parietex™ ProGrip (Covidien™), TiMesh(®) Light (GfE Medical), Bard(®) Soft Mesh (Bard(®)), Vypro(®) (Ethicon(®)), and Omyra(®) (Braun(®)). Individual meshes were inoculated with Staphylococcus epidermidis and Staphylococcus aureus with a bacterial inoculum of 10(2) bacteria. To assess the effect of suture material on bacterial adhesion, a sterile piece of commonly used monofilament suture material (2.0 Prolene(®), ZB370 Ethicon(®)) was sutured to selected meshes (chosen to represent different commonly used polymers and/or the presence of an antibacterial coating). Inoculated meshes were incubated for 18 h in tryptone soy broth and then analysed using scanning electron microscopy. A previously validated method for enumeration of bacteria using automated stage movement electron microscopy was used for direct bacterial counting. The final fraction of the bacteria adherent to the mesh was compared between the meshes and for each morphological variable. One-way analysis of variance (ANOVA) was performed on the bacterial counts. Tukey's test was used to determine the difference between the different biomaterials in

  15. Mesh Convergence Requirements for Composite Damage Models

    NASA Technical Reports Server (NTRS)

    Davila, Carlos G.

    2016-01-01

    The ability of the finite element method to accurately represent the response of objects with intricate geometry and loading renders the finite element method as an extremely versatile analysis technique for structural analysis. Finite element analysis is routinely used in industry to calculate deflections, stress concentrations, natural frequencies, buckling loads, and much more. The method works by discretizing complex problems into smaller, simpler approximations that are valid over small uniform domains. For common analyses, the maximum size of the elements that can be used is often be determined by experience. However, to verify the quality of a solution, analyses with several levels of mesh refinement should be performed to ensure that the solution has converged. In recent years, the finite element method has been used to calculate the resistance of structures, and in particular that of composite structures. A number of techniques such as cohesive zone modeling, the virtual crack closure technique, and continuum damage modeling have emerged that can be used to predict cracking, delaminations, fiber failure, and other composite damage modes that lead to structural collapse. However, damage models present mesh refinement requirements that are not well understood. In this presentation, we examine different mesh refinement issues related to the representation of damage in composite materials. Damage process zone sizes and their corresponding mesh requirements will be discussed. The difficulties of modeling discontinuities and the associated need for regularization techniques will be illustrated, and some unexpected element size constraints will be presented. Finally, some of the difficulties in constructing models of composite structures capable of predicting transverse matrix cracking will be discussed. It will be shown that to predict the initiation and propagation of transverse matrix cracks, their density, and their saturation may require models that are

  16. Method and system for mesh network embedded devices

    NASA Technical Reports Server (NTRS)

    Wang, Ray (Inventor)

    2009-01-01

    A method and system for managing mesh network devices. A mesh network device with integrated features creates an N-way mesh network with a full mesh network topology or a partial mesh network topology.

  17. User Manual for the PROTEUS Mesh Tools

    SciTech Connect

    Smith, Micheal A.; Shemon, Emily R.

    2015-06-01

    This report describes the various mesh tools that are provided with the PROTEUS code giving both descriptions of the input and output. In many cases the examples are provided with a regression test of the mesh tools. The most important mesh tools for any user to consider using are the MT_MeshToMesh.x and the MT_RadialLattice.x codes. The former allows the conversion between most mesh types handled by PROTEUS while the second allows the merging of multiple (assembly) meshes into a radial structured grid. Note that the mesh generation process is recursive in nature and that each input specific for a given mesh tool (such as .axial or .merge) can be used as “mesh” input for any of the mesh tools discussed in this manual.

  18. MRI is unable to illustrate the absorption time of the absorbable TIGR mesh in humans: a case report

    PubMed Central

    Öberg, Stina; Andresen, Kristoffer; Møller, Jakob M.; Rosenberg, Jacob

    2015-01-01

    A male patient had a bilateral laparoscopic inguinal hernia repair in 2012. The right-sided hernia was treated with a permanent mesh, and the left-sided hernia received an absorbable mesh. The absorbable TIGR mesh has been proved to be completely absorbed and replaced by new connective tissue after 3 years in sheep. The patient was therefore followed for 3 years by annual magnetic resonance imagings (MRIs) to illustrate the absorption time in humans. During follow-up, the thickness of the absorbable mesh slightly decreased, and at the last clinical examination, the patient was without a recurrence. However, MRI failed to illustrate absorption of the TIGR mesh, perhaps since new connective tissue and the mesh material had the same appearance on the images. In conclusion, MRI was unable to confirm an absorption time of 3 years for the TIGR mesh, and further studies are needed to investigate if the mesh also completely absorbs in humans. PMID:26581219

  19. Cache-oblivious mesh layouts

    SciTech Connect

    Yoon, Sung-Eui; Lindstrom, Peter; Pascucci, Valerio; Manocha, Dinesh

    2005-07-01

    We present a novel method for computing cache-oblivious layouts of large meshes that improve the performance of interactive visualization and geometric processing algorithms. Given that the mesh is accessed in a reasonably coherent manner, we assume no particular data access patterns or cache parameters of the memory hierarchy involved in the computation. Furthermore, our formulation extends directly to computing layouts of multi-resolution and bounding volume hierarchies of large meshes. We develop a simple and practical cache-oblivious metric for estimating cache misses. Computing a coherent mesh layout is reduced to a combinatorial optimization problem. We designed and implemented an out-of-core multilevel minimization algorithm and tested its performance on unstructured meshes composed of tens to hundreds of millions of triangles. Our layouts can significantly reduce the number of cache misses. We have observed 2-20 times speedups in view-dependent rendering, collision detection, and isocontour extraction without any modification of the algorithms or runtime applications.

  20. Multi-Block Enhancement for Lagrangian Dendritic Mesh setup in Altair5

    SciTech Connect

    Douglass, Rodney W

    2010-12-15

    Initial mesh setup for an ASC mUlti-physics code at LANL is done using Altair5. Altair5 assumes that the final mesh is composed of logical structured mesh blocks linked together at mesh boundaries to form, ultimately, an unstructured mesh. Within these blocks, meshes may have dendrites, that is, local regions where two zones share common edges (in two-dimensions, or faces in three-dimensions) with a single zone. In many cases, contiguous subsets of the initial set of blocks may have the same material assigned to them, but without smoothing the mesh would form a computationally challenging initial mesh. Some of these blocks may also have zones with nodes on domain boundaries. This paper reports on the implementation of multiblock smoothing in Altair5, which allows for dendrites and for moving boundary nodes. Dendritic nodes are constrained to be located at the average of their neighbor nodes while boundary nodes are constrained to move along the boundary geometry. Two fundamentally different smoothing methods were implemented. First, a variational principle is presented that balances zonal size and distortion via a user selected weighting with constraints imposed using penalty methods for dendritic nodes and Lagrange multipliers for boundary nodes. Second, the Laplace-Beltrami smoother is presented. This is a general elliptic smoother which can easily be modified to give Laplacian and Winslow-Crowley mesh smoothing. Results are shown for several test meshes of interest.

  1. A Mechanistic Study of Wetting Superhydrophobic Porous 3D Meshes.

    PubMed

    Yohe, Stefan T; Freedman, Jonathan D; Falde, Eric J; Colson, Yolonda L; Grinstaff, Mark W

    2013-08-07

    Superhydrophobic, porous, 3D materials composed of poly( ε -caprolactone) (PCL) and the hydrophobic polymer dopant poly(glycerol monostearate- co- ε -caprolactone) (PGC-C18) are fabricated using the electrospinning technique. These 3D materials are distinct from 2D superhydrophobic surfaces, with maintenance of air at the surface as well as within the bulk of the material. These superhydrophobic materials float in water, and when held underwater and pressed, an air bubble is released and will rise to the surface. By changing the PGC-C18 doping concentration in the meshes and/or the fiber size from the micro- to nanoscale, the long-term stability of the entrapped air layer is controlled. The rate of water infiltration into the meshes, and the resulting displacement of the entrapped air, is quantitatively measured using X-ray computed tomography. The properties of the meshes are further probed using surfactants and solvents of different surface tensions. Finally, the application of hydraulic pressure is used to quantify the breakthrough pressure to wet the meshes. The tools for fabrication and analysis of these superhydrophobic materials as well as the ability to control the robustness of the entrapped air layer are highly desirable for a number of existing and emerging applications.

  2. A Mechanistic Study of Wetting Superhydrophobic Porous 3D Meshes

    PubMed Central

    Yohe, Stefan T.; Freedman, Jonathan D.; Falde, Eric J.; Colson, Yolonda L.; Grinstaff, Mark W.

    2014-01-01

    Superhydrophobic, porous, 3D materials composed of poly( ε -caprolactone) (PCL) and the hydrophobic polymer dopant poly(glycerol monostearate-co- ε -caprolactone) (PGC-C18) are fabricated using the electrospinning technique. These 3D materials are distinct from 2D superhydrophobic surfaces, with maintenance of air at the surface as well as within the bulk of the material. These superhydrophobic materials float in water, and when held underwater and pressed, an air bubble is released and will rise to the surface. By changing the PGC-C18 doping concentration in the meshes and/or the fiber size from the micro- to nanoscale, the long-term stability of the entrapped air layer is controlled. The rate of water infiltration into the meshes, and the resulting displacement of the entrapped air, is quantitatively measured using X-ray computed tomography. The properties of the meshes are further probed using surfactants and solvents of different surface tensions. Finally, the application of hydraulic pressure is used to quantify the breakthrough pressure to wet the meshes. The tools for fabrication and analysis of these superhydrophobic materials as well as the ability to control the robustness of the entrapped air layer are highly desirable for a number of existing and emerging applications. PMID:25309305

  3. Omental Lipid-Coated Mesh

    DTIC Science & Technology

    2011-06-16

    infection. If benefit is proven, this method will be a cost- effective way to prepare biologic and possibly synthetic meshes for use in hernia repair...omental coating is encouraging. 10. ::’UD./CI.I I CI’IIVI::’ Omentum, Mesh , Hernia 𔃺. ::.CI.Utill , I.LA::’::’II"II.A IIUN UI": I-­ a -.-I’I-c­...-u...abdominal wall hernia repair. If cheap and effective promotion of neovascularization could be initiated, we might be able to improve upon current

  4. Imaging of slings and meshes

    PubMed Central

    Dietz, Hans Peter

    2015-01-01

    Abstract The popularity of imaging in pelvic floor medicine continues to increase. Among the various modalities, ultrasound is superior as it is cheap, safe, easily accesible and simple, resulting in high patient compliance. It is the only technique that allows imaging of modern wide‐weave polypropylene sling or mesh implants, and imaging of such implants is commonly required due to the popularity of surgical techniques that involve the placement of slings and meshes. This review article will discuss the role of translabial ultrasound in the evaluation of synthetic implants used in the treatment of urinary incontinence and pelvic organ prolapse. PMID:28191210

  5. Advances in the development of wire mesh reactor for coal gasification studies - article no. 084102

    SciTech Connect

    Zeng, C.; Chen, L.; Liu, G.; Li, W.H.; Huang, B.M.; Zhu, H.D.; Zhang, B.; Zamansky, V.

    2008-08-15

    In an effort to further understand the coal gasification behavior in entrained-flow gasifiers, a high pressure and high temperature wire mesh reactor with new features was recently built. An advanced LABVIEW-based temperature measurement and control system were adapted. Molybdenum wire mesh with aperture smaller than 70 {mu} m and type D thermocouple were used to enable high carbon conversion ({gt}90%) at temperatures {gt}1000 {sup o}C. Gaseous species from wire mesh reactor were quantified using a high sensitivity gas chromatography. The material balance of coal pyrolysis in wire mesh reactor was demonstrated for the first time by improving the volatile's quantification techniques.

  6. Advances in the development of wire mesh reactor for coal gasification studies.

    PubMed

    Zeng, Cai; Chen, Lei; Liu, Gang; Li, Wenhua; Huang, Baoming; Zhu, Hongdong; Zhang, Bing; Zamansky, Vladimir

    2008-08-01

    In an effort to further understand the coal gasification behavior in entrained-flow gasifiers, a high pressure and high temperature wire mesh reactor with new features was recently built. An advanced LABVIEW-based temperature measurement and control system were adapted. Molybdenum wire mesh with aperture smaller than 70 mum and type D thermocouple were used to enable high carbon conversion (>90%) at temperatures >1000 degrees C. Gaseous species from wire mesh reactor were quantified using a high sensitivity gas chromatography. The material balance of coal pyrolysis in wire mesh reactor was demonstrated for the first time by improving the volatile's quantification techniques.

  7. Content-Adaptive Finite Element Mesh Generation of 3-D Complex MR Volumes for Bioelectromagnetic Problems.

    PubMed

    Lee, W; Kim, T-S; Cho, M; Lee, S

    2005-01-01

    In studying bioelectromagnetic problems, finite element method offers several advantages over other conventional methods such as boundary element method. It allows truly volumetric analysis and incorporation of material properties such as anisotropy. Mesh generation is the first requirement in the finite element analysis and there are many different approaches in mesh generation. However conventional approaches offered by commercial packages and various algorithms do not generate content-adaptive meshes, resulting in numerous elements in the smaller volume regions, thereby increasing computational load and demand. In this work, we present an improved content-adaptive mesh generation scheme that is efficient and fast along with options to change the contents of meshes. For demonstration, mesh models of the head from a volume MRI are presented in 2-D and 3-D.

  8. Multiscale mesh generation on the sphere

    NASA Astrophysics Data System (ADS)

    Lambrechts, Jonathan; Comblen, Richard; Legat, Vincent; Geuzaine, Christophe; Remacle, Jean-François

    2008-12-01

    A method for generating computational meshes for applications in ocean modeling is presented. The method uses a standard engineering approach for describing the geometry of the domain that requires meshing. The underlying sphere is parametrized using stereographic coordinates. Then, coastlines are described with cubic splines drawn in the stereographic parametric space. The mesh generation algorithm builds the mesh in the parametric plane using available techniques. The method enables to import coastlines from different data sets and, consequently, to build meshes of domains with highly variable length scales. The results include meshes together with numerical simulations of various kinds.

  9. Latent Heat Thermal Energy Storage: Effect of Metallic Mesh Size on Storage Time and Capacity

    NASA Astrophysics Data System (ADS)

    Shuja, S. Z.; Yilbas, B. S.

    2015-11-01

    Use of metallic meshes in latent heat thermal storage system shortens the charging time (total melting of the phase change material), which is favorable in practical applications. In the present study, effect of metallic mesh size on the thermal characteristics of latent heat thermal storage system is investigated. Charging time is predicted for various mesh sizes, and the influence of the amount of mesh material on the charging capacity is examined. An experiment is carried out to validate the numerical predictions. It is found that predictions of the thermal characteristics of phase change material with presence of metallic meshes agree well with the experimental data. High conductivity of the metal meshes enables to transfer heat from the edges of the thermal system towards the phase change material while forming a conduction tree in the system. Increasing number of meshes in the thermal system reduces the charging time significantly due to increased rate of conduction heat transfer in the thermal storage system; however, increasing number of meshes lowers the latent heat storage capacity of the system.

  10. Effects of macroporous monofilament mesh on infection in a contaminated field.

    PubMed

    Bury, Kamil; Smietański, Maciej; Justyna, Bigda; Gumiela, Piotr; Smietańska, Anna Irmina; Owczuk, Radosław; Naumiuk, Lukasz; Samet, Alfred; Paradziej-Łukowicz, J

    2014-10-01

    The aim of this study was to evaluate whether the type of the mesh and proper surgical technique can influence the outcome of a tension-free hernia repair in a contaminated filed. This study was based on the model of bacterial peritonitis in rats induced with a mixture composed of Escherichia coli and Bacteroides fragilis. Two animals were used as a control group without induced peritonitis and 10 animals with mesh implanted inside of the peritoneal cavity. For the 20 animals in the studied group, bacterial fluid was applied into the abdominal cavity together with the mesh implantation. In 10 cases, the mesh was fixed flatly upon the surface of the peritoneum; in the other 10, the mesh was rolled and then fixed within the peritoneal cavity. After 5 weeks, the animals were operated on again, and the meshes, the peritoneal fluid and, if present, any granulomas were taken for bacterial cultivation. The results of the bacterial cultivation of the material from the control group (without mesh) and from the rats with flatly fixed mesh were almost completely negative (0/10 and 1/10, respectively). In 9 out of 10 rats that were exposed to the rolled mesh for 5 weeks, the colonisation of meshes with both B. fragilis and E. coli was found (p < 0.0198). When properly fixed, flat mesh, even in a contaminated field, may allow for a proper mesh healing and does not influence the ability to cure bacterial peritonitis in an animal model. A bad surgical technique, such as inadequately positioned or rolled mesh, may cause persistent peritoneal bacteraemia.

  11. An electrostatic Particle-In-Cell code on multi-block structured meshes

    DOE PAGES

    Meierbachtol, Collin S.; Svyatskiy, Daniil; Delzanno, Gian Luca; ...

    2017-09-14

    We present an electrostatic Particle-In-Cell (PIC) code on multi-block, locally structured, curvilinear meshes called Curvilinear PIC (CPIC). Multi-block meshes are essential to capture complex geometries accurately and with good mesh quality, something that would not be possible with single-block structured meshes that are often used in PIC and for which CPIC was initially developed. In spite of the structured nature of the individual blocks, multi-block meshes resemble unstructured meshes in a global sense and introduce several new challenges, such as the presence of discontinuities in the mesh properties and coordinate orientation changes across adjacent blocks, and polyjunction points where anmore » arbitrary number of blocks meet. In CPIC, these challenges have been met by an approach that features: (1) a curvilinear formulation of the PIC method: each mesh block is mapped from the physical space, where the mesh is curvilinear and arbitrarily distorted, to the logical space, where the mesh is uniform and Cartesian on the unit cube; (2) a mimetic discretization of Poisson's equation suitable for multi-block meshes; and (3) a hybrid (logical-space position/physical-space velocity), asynchronous particle mover that mitigates the performance degradation created by the necessity to track particles as they move across blocks. The numerical accuracy of CPIC was verified using two standard plasma–material interaction tests, which demonstrate good agreement with the corresponding analytic solutions. And compared to PIC codes on unstructured meshes, which have also been used for their flexibility in handling complex geometries but whose performance suffers from issues associated with data locality and indirect data access patterns, PIC codes on multi-block structured meshes may offer the best compromise for capturing complex geometries while also maintaining solution accuracy and computational efficiency.« less

  12. Hybrid mesh for nasal airflow studies.

    PubMed

    Zubair, Mohammed; Abdullah, Mohammed Zulkifly; Ahmad, Kamarul Arifin

    2013-01-01

    The accuracy of the numerical result is closely related to mesh density as well as its distribution. Mesh plays a very significant role in the outcome of numerical simulation. Many nasal airflow studies have employed unstructured mesh and more recently hybrid mesh scheme has been utilized considering the complexity of anatomical architecture. The objective of this study is to compare the results of hybrid mesh with unstructured mesh and study its effect on the flow parameters inside the nasal cavity. A three-dimensional nasal cavity model is reconstructed based on computed tomographic images of a healthy Malaysian adult nose. Navier-Stokes equation for steady airflow is solved numerically to examine inspiratory nasal flow. The pressure drop obtained using the unstructured computational grid is about 22.6 Pa for a flow rate of 20 L/min, whereas the hybrid mesh resulted in 17.8 Pa for the same flow rate. The maximum velocity obtained at the nasal valve using unstructured grid is 4.18 m/s and that with hybrid mesh is around 4.76 m/s. Hybrid mesh reported lower grid convergence index (GCI) than the unstructured mesh. Significant differences between unstructured mesh and hybrid mesh are determined highlighting the usefulness of hybrid mesh for nasal airflow studies.

  13. Hybrid Mesh for Nasal Airflow Studies

    PubMed Central

    Zubair, Mohammed; Abdullah, Mohammed Zulkifly; Ahmad, Kamarul Arifin

    2013-01-01

    The accuracy of the numerical result is closely related to mesh density as well as its distribution. Mesh plays a very significant role in the outcome of numerical simulation. Many nasal airflow studies have employed unstructured mesh and more recently hybrid mesh scheme has been utilized considering the complexity of anatomical architecture. The objective of this study is to compare the results of hybrid mesh with unstructured mesh and study its effect on the flow parameters inside the nasal cavity. A three-dimensional nasal cavity model is reconstructed based on computed tomographic images of a healthy Malaysian adult nose. Navier-Stokes equation for steady airflow is solved numerically to examine inspiratory nasal flow. The pressure drop obtained using the unstructured computational grid is about 22.6 Pa for a flow rate of 20 L/min, whereas the hybrid mesh resulted in 17.8 Pa for the same flow rate. The maximum velocity obtained at the nasal valve using unstructured grid is 4.18 m/s and that with hybrid mesh is around 4.76 m/s. Hybrid mesh reported lower grid convergence index (GCI) than the unstructured mesh. Significant differences between unstructured mesh and hybrid mesh are determined highlighting the usefulness of hybrid mesh for nasal airflow studies. PMID:23983811

  14. Does the additional application of a polylactide film (SurgiWrap) to a lightweight mesh (TiMesh) reduce adhesions after laparoscopic intraperitoneal implantation procedures? Experimental results obtained with the laparoscopic porcine model.

    PubMed

    Schug-Pass, Christine; Sommerer, Florian; Tannapfel, Andrea; Lippert, Hans; Köckerling, Ferdinand

    2008-11-01

    Intraperitoneal repair of incisional hernias using a mesh makes particular demands on the material used. In addition to good integration of the mesh on the parietal side, adhesions to the visceral peritoneum must be avoided. Large-pore, light-weight meshes induce fewer adhesions than heavy-weight polypropylene meshes. Although numerous adhesion-barrier substances for use in combination with a polypropylene mesh have been tested already, mostly in open small animal models, unequivocal benefits have been identified to date in only a few of the experiments. Using the laparoscopic intraperitoneal onlay mesh technique, six pigs were implanted with either a lightweight polypropylene mesh (TiMesh light) or TiMesh plus an adhesion-barrier film made of polylactide (SurgiWrap). After 3 months, the animals underwent a postmortem laparoscopy, and specimens were obtained for planimetric and histologic investigations. No adhesions to intestinal structures were found in any of the animals. Adhesions between the greater omentum and the mesh did not differ significantly between the TiMesh (32%) and SurgiWrap (33.5%) groups. The shrinkage of the mesh's surface area was comparable between the two groups (18% vs. 21%). Histology showed pronounced inflammatory reaction and bridging of scar tissue between the filaments with the use of SurgiWrap versus TiMesh light without film. However, immunohistochemical investigations examining the partial volume of the inflammatory cells, the proliferation marker Ki67, and the apoptotic index at the interface of the filaments all failed to show any significant differences. To avoid adhesions, it is essential that the acute and chronic inflammatory reaction to the implanted material be as small as possible. This requirement is met specifically by the lightweight polypropylene mesh TiMesh light. The additional application of a slowly absorbable adhesion-barrier film made of polylactide (SurgiWrap) does not appear to confer any further benefit.

  15. Multigrid for refined triangle meshes

    SciTech Connect

    Shapira, Yair

    1997-02-01

    A two-level preconditioning method for the solution of (locally) refined finite element schemes using triangle meshes is introduced. In the isotropic SPD case, it is shown that the condition number of the preconditioned stiffness matrix is bounded uniformly for all sufficiently regular triangulations. This is also verified numerically for an isotropic diffusion problem with highly discontinuous coefficients.

  16. High-Performance Heat Pipe With Screen Mesh

    NASA Technical Reports Server (NTRS)

    Alario, J. P.; Brown, R. F.; Kosson, R.

    1986-01-01

    Liquid distributed more evenly in evaporator section. Improved heat pipe contains an artery and wick rolled from stainless-steel screen of 180 mesh (openings about 80 micrometers). Screen material helps to prevent dryout in evaporator section by conducting liquid through hotspots and to vaporchannel wall. Insert reduces incidence of dryout at hotspots or during intervals of general thermal overload.

  17. Application of Quaternions for Mesh Deformation

    NASA Technical Reports Server (NTRS)

    Samareh, Jamshid A.

    2002-01-01

    A new three-dimensional mesh deformation algorithm, based on quaternion algebra, is introduced. A brief overview of quaternion algebra is provided, along with some preliminary results for two-dimensional structured and unstructured viscous mesh deformation.

  18. Bone Marrow–Derived Mesenchymal Stem Cells Enhance Bacterial Clearance and Preserve Bioprosthetic Integrity in a Model of Mesh Infection

    PubMed Central

    Criman, Erik T.; Kurata, Wendy E.; Matsumoto, Karen W.; Aubin, Harry T.; Campbell, Carmen E.

    2016-01-01

    Background: The reported incidence of mesh infection in contaminated operative fields is as high as 30% regardless of the material used. Recently, mesenchymal stem cells (MSCs) have been shown to possess favorable immunomodulatory properties and improve tissue incorporation when seeded onto bioprosthetics. The aim of this study was to evaluate whether seeding noncrosslinked bovine pericardium (Veritas Collagen Matrix) with allogeneic bone marrow–derived MSCs improves infection resistance in vivo after inoculation with Escherichia coli (E. coli). Methods: Rat bone marrow–derived MSCs at passage 3 were seeded onto bovine pericardium and cultured for 7 days before implantation. Additional rats (n = 24) were implanted subcutaneously with MSC-seeded or unseeded mesh and inoculated with 7 × 105 colony-forming units of E. coli or saline before wound closure (group 1, unseeded mesh/saline; group 2, unseeded mesh/E. coli; group 3, MSC-seeded mesh/E. coli; 8 rats per group). Meshes were explanted at 4 weeks and underwent microbiologic and histologic analyses. Results: MSC-seeded meshes inoculated with E. coli demonstrated superior bacterial clearance and preservation of mesh integrity compared with E. coli–inoculated unseeded meshes (87.5% versus 0% clearance; p = 0.001). Complete mesh degradation concurrent with abscess formation was observed in 100% of rats in the unseeded/E. coli group, which is in contrast to 12.5% of rats in the MSC-seeded/E. coli group. Histologic evaluation determined that remodeling characteristics of E. coli–inoculated MSC-seeded meshes were similar to those of uninfected meshes 4 weeks after implantation. Conclusions: Augmenting a bioprosthetic material with stem cells seems to markedly enhance resistance to bacterial infection in vivo and preserve mesh integrity. PMID:27482490

  19. Polypropylene surgical mesh coated with extracellular matrix mitigates the host foreign body response.

    PubMed

    Wolf, Matthew T; Carruthers, Christopher A; Dearth, Christopher L; Crapo, Peter M; Huber, Alexander; Burnsed, Olivia A; Londono, Ricardo; Johnson, Scott A; Daly, Kerry A; Stahl, Elizabeth C; Freund, John M; Medberry, Christopher J; Carey, Lisa E; Nieponice, Alejandro; Amoroso, Nicholas J; Badylak, Stephen F

    2014-01-01

    Surgical mesh devices composed of synthetic materials are commonly used for ventral hernia repair. These materials provide robust mechanical strength and are quickly incorporated into host tissue; factors that contribute to reduced hernia recurrence rates. However, such mesh devices cause a foreign body response with the associated complications of fibrosis and patient discomfort. In contrast, surgical mesh devices composed of naturally occurring extracellular matrix (ECM) are associated with constructive tissue remodeling, but lack the mechanical strength of synthetic materials. A method for applying a porcine dermal ECM hydrogel coating to a polypropylene mesh is described herein with the associated effects upon the host tissue response and biaxial mechanical behavior. Uncoated and ECM coated heavy-weight BARD™ Mesh were compared to the light-weight ULTRAPRO™ and BARD™ Soft Mesh devices in a rat partial thickness abdominal defect overlay model. The ECM coated mesh attenuated the pro-inflammatory response compared to all other devices, with a reduced cell accumulation and fewer foreign body giant cells. The ECM coating degraded by 35 days, and was replaced with loose connective tissue compared to the dense collagenous tissue associated with the uncoated polypropylene mesh device. Biaxial mechanical characterization showed that all of the mesh devices were of similar isotropic stiffness. Upon explanation, the light-weight mesh devices were more compliant than the coated or uncoated heavy-weight devices. This study shows that an ECM coating alters the default host response to a polypropylene mesh, but not the mechanical properties in an acute in vivo abdominal repair model. Copyright © 2013 Wiley Periodicals, Inc., a Wiley Company.

  20. Polypropylene Surgical Mesh Coated with Extracellular Matrix Mitigates the Host Foreign Body Response

    PubMed Central

    Wolf, Matthew T.; Carruthers, Christopher A.; Dearth, Christopher L.; Crapo, Peter M.; Huber, Alexander; Burnsed, Olivia A.; Londono, Ricardo; Johnson, Scott A.; Daly, Kerry A.; Stahl, Elizabeth C.; Freund, John M.; Medberry, Christopher J.; Carey, Lisa E.; Nieponice, Alejandro; Amoroso, Nicholas J.; Badylak, Stephen F.

    2013-01-01

    Surgical mesh devices composed of synthetic materials are commonly used for ventral hernia repair. These materials provide robust mechanical strength and are quickly incorporated into host tissue; factors which contribute to reduced hernia recurrence rates. However, such mesh devices cause a foreign body response with the associated complications of fibrosis and patient discomfort. In contrast, surgical mesh devices composed of naturally occurring extracellular matrix (ECM) are associated with constructive tissue remodeling, but lack the mechanical strength of synthetic materials. A method for applying a porcine dermal ECM hydrogel coating to a polypropylene mesh is described herein with the associated effects upon the host tissue response and biaxial mechanical behavior. Uncoated and ECM coated heavy-weight BARD™ Mesh were compared to the light-weight ULTRAPRO™ and BARD™ Soft Mesh devices in a rat partial thickness abdominal defect overlay model. The ECM coated mesh attenuated the pro-inflammatory response compared to all other devices, with a reduced cell accumulation and fewer foreign body giant cells. The ECM coating degraded by 35 days, and was replaced with loose connective tissue compared to the dense collagenous tissue associated with the uncoated polypropylene mesh device. Biaxial mechanical characterization showed that all of the mesh devices were of similar isotropic stiffness. Upon explantation, the light-weight mesh devices were more compliant than the coated or uncoated heavy-weight devices. The present study shows that an ECM coating alters the default host response to a polypropylene mesh, but not the mechanical properties in an acute in vivo abdominal repair model. PMID:23873846

  1. [Late vaginal mesh exposure after prolapse repair].

    PubMed

    Chanelles, O; Poncelet, C

    2010-12-01

    Mesh exposure is the major complication of vaginal prolapse repair. Incidence rates are variable according to the series. Mesh exposure usually occurs during the year following the intervention. We report here the first case of a patient with a late exposure of an anterior vaginal mesh 4 years after a surgical cystocele repair. The mesh has been easily removed at the operative theatre by vaginal approach.

  2. 6th International Meshing Roundtable '97

    SciTech Connect

    White, D.

    1997-09-01

    The goal of the 6th International Meshing Roundtable is to bring together researchers and developers from industry, academia, and government labs in a stimulating, open environment for the exchange of technical information related to the meshing process. In the pas~ the Roundtable has enjoyed significant participation born each of these groups from a wide variety of countries. The Roundtable will consist of technical presentations from contributed papers and abstracts, two invited speakers, and two invited panels of experts discussing topics related to the development and use of automatic mesh generation tools. In addition, this year we will feature a "Bring Your Best Mesh" competition and poster session to encourage discussion and participation from a wide variety of mesh generation tool users. The schedule and evening social events are designed to provide numerous opportunities for informal dialog. A proceedings will be published by Sandia National Laboratories and distributed at the Roundtable. In addition, papers of exceptionally high quaIity will be submitted to a special issue of the International Journal of Computational Geometry and Applications. Papers and one page abstracts were sought that present original results on the meshing process. Potential topics include but are got limited to: Unstructured triangular and tetrahedral mesh generation Unstructured quadrilateral and hexahedral mesh generation Automated blocking and structured mesh generation Mixed element meshing Surface mesh generation Geometry decomposition and clean-up techniques Geometry modification techniques related to meshing Adaptive mesh refinement and mesh quality control Mesh visualization Special purpose meshing algorithms for particular applications Theoretical or novel ideas with practical potential Technical presentations from industrial researchers.

  3. ECM hydrogel coating mitigates the chronic inflammatory response to polypropylene mesh.

    PubMed

    Faulk, Denver M; Londono, Ricardo; Wolf, Matthew T; Ranallo, Christian A; Carruthers, Christopher A; Wildemann, Justin D; Dearth, Christopher L; Badylak, Stephen F

    2014-10-01

    Polypropylene has been used as a surgical mesh material for several decades. This non-degradable synthetic polymer provides mechanical strength, a predictable host response, and its use has resulted in reduced recurrence rates for ventral hernia and pelvic organ prolapse. However, polypropylene and similar synthetic materials are associated with a chronic local tissue inflammatory response and dense fibrous tissue deposition. These outcomes have prompted variations in mesh design to minimize the surface area interface and increase integration with host tissue. In contrast, biologic scaffold materials composed of extracellular matrix (ECM) are rapidly degraded in-vivo and are associated with constructive tissue remodeling and minimal fibrosis. The objective of the present study was to assess the effects of an ECM hydrogel coating on the long-term host tissue response to polypropylene mesh in a rodent model of abdominal muscle injury. At 14 days post implantation, the ECM coated polypropylene mesh devices showed a decreased inflammatory response as characterized by the number and distribution of M1 macrophages (CD86+/CD68+) around mesh fibers when compared to the uncoated mesh devices. At 180 days the ECM coated polypropylene showed decreased density of collagen and amount of mature type I collagen deposited between mesh fibers when compared to the uncoated mesh devices. This study confirms and extends previous findings that an ECM coating mitigates the chronic inflammatory response and associated scar tissue deposition characteristic of polypropylene.

  4. Parallel Block Structured Adaptive Mesh Refinement on Graphics Processing Units

    SciTech Connect

    Beckingsale, D. A.; Gaudin, W. P.; Hornung, R. D.; Gunney, B. T.; Gamblin, T.; Herdman, J. A.; Jarvis, S. A.

    2014-11-17

    Block-structured adaptive mesh refinement is a technique that can be used when solving partial differential equations to reduce the number of zones necessary to achieve the required accuracy in areas of interest. These areas (shock fronts, material interfaces, etc.) are recursively covered with finer mesh patches that are grouped into a hierarchy of refinement levels. Despite the potential for large savings in computational requirements and memory usage without a corresponding reduction in accuracy, AMR adds overhead in managing the mesh hierarchy, adding complex communication and data movement requirements to a simulation. In this paper, we describe the design and implementation of a native GPU-based AMR library, including: the classes used to manage data on a mesh patch, the routines used for transferring data between GPUs on different nodes, and the data-parallel operators developed to coarsen and refine mesh data. We validate the performance and accuracy of our implementation using three test problems and two architectures: an eight-node cluster, and over four thousand nodes of Oak Ridge National Laboratory’s Titan supercomputer. Our GPU-based AMR hydrodynamics code performs up to 4.87× faster than the CPU-based implementation, and has been scaled to over four thousand GPUs using a combination of MPI and CUDA.

  5. Partial colpocleisis for the treatment of sacrocolpopexy mesh erosions.

    PubMed

    Quiroz, Lieschen H; Gutman, Robert E; Fagan, Matthew J; Cundiff, Geoffrey W

    2008-02-01

    The purpose of this study is to describe the outcomes of partial colpocleisis for mesh erosions after sacrocolpopexy. We retrospectively report our surgical management of mesh erosion after sacrocolpopexy. Between 1998 and 2006, we performed 499 sacral colpopexies and treated 21 patients for mesh erosion, including three referrals. Mean (range) time to diagnosis was 10.3 months (1-49). Grafts materials included: Mersilene (13), Prolene (7), and Pelvicol (1). Surgical outcomes were available for 19 patients. Ten (48%) patients were cured by the initial partial colpocleisis, while nine (45%) required a second or third (2, 10%) vaginal operation. All of the second and third vaginal excisions failed. Eight patients had an abdominal excision, and two patients required a second abdominal procedure. The success rate for the first and second abdominal resections was 38% (3/8) and 100% (2/2). Abdominal surgeries had higher blood loss (84 vs 378 cc, p = 0.012) longer hospitalization (outpatient vs 4.2 days p = 0.001), and additional morbidity (18.6%). Potential contributing factors to surgical failure were the presence of Actinomyces and current smoking. We recommend initial transvaginal mesh resection with partial colpocleisis for synthetic mesh erosions after sacrocolpopexy. Vaginal failures may be better served by an abdominal excision. Potential contributors to failure include current smoking and the presence of Actinomyces.

  6. Mesh Re-zoning In Multi-Stand Rolling

    SciTech Connect

    Subramanian, K.; Cherukuri, H. P.; Minisandram, R. S.

    2007-05-17

    A solution to mesh distortion and subsequent breakdown in solution procedure in the finite element analysis of multi-stand rolling is presented in this work. Simple cubic spline fits are applied on the deformed outer surface of the rolled material to smoothen the geometry due to distortion from the deformation in the previous stands. A mesh re-zoning algorithm found in the literature is applied while retaining the original number of elements in the new mesh. The appropriate boundary conditions are applied efficiently with the use of a linear interpolation. The approach is illustrated for the multi-stand rolling of a nickel-base super alloy bar of circular cross-section. An in-house finite element program for steady state rolling, based on ALE technique was employed for the current work. The results show that the mesh re-zoning algorithm eliminates the numerical issues associated with the mesh distortion. The predicted results for the final shape are also found to be in good agreement with the experimental data.

  7. Hybrid mesh generation using advancing reduction technique

    USDA-ARS?s Scientific Manuscript database

    This study presents an extension of the application of the advancing reduction technique to the hybrid mesh generation. The proposed algorithm is based on a pre-generated rectangle mesh (RM) with a certain orientation. The intersection points between the two sets of perpendicular mesh lines in RM an...

  8. Adhesions to Mesh after Ventral Hernia Mesh Repair Are Detected by MRI but Are Not a Cause of Long Term Chronic Abdominal Pain

    PubMed Central

    Langbach, Odd; Holmedal, Stein Harald; Grandal, Ole Jacob

    2016-01-01

    Aim. The aim of the present study was to perform MRI in patients after ventral hernia mesh repair, in order to evaluate MRI's ability to detect intra-abdominal adhesions. Materials and Methods. Single-center long term follow-up study of 155 patients operated for ventral hernia with laparoscopic (LVHR) or open mesh repair (OVHR), including analyzing medical records, clinical investigation with patient-reported pain (VAS-scale), and MRI. MRI was performed in 124 patients: 114 patients (74%) after follow-up, and 10 patients referred for late complaints after ventral mesh repair. To verify the MRI-diagnosis of adhesions, laparoscopy was performed after MRI in a cohort of 20 patients. Results. MRI detected adhesions between bowel and abdominal wall/mesh in 60% of the patients and mesh shrinkage in 20–50%. Adhesions were demonstrated to all types of meshes after both LVHR and OVHR with a sensitivity of 70%, specificity of 75%, positive predictive value of 78%, and negative predictive value of 67%. Independent predictors for formation of adhesions were mesh area as determined by MRI and Charlson index. The presence of adhesions was not associated with more pain. Conclusion. MRI can detect adhesions between bowel and abdominal wall in a fair reliable way. Adhesions are formed both after open and laparoscopic hernia mesh repair and are not associated with chronic pain. PMID:26819601

  9. User Manual for the PROTEUS Mesh Tools

    SciTech Connect

    Smith, Micheal A.; Shemon, Emily R

    2016-09-19

    PROTEUS is built around a finite element representation of the geometry for visualization. In addition, the PROTEUS-SN solver was built to solve the even-parity transport equation on a finite element mesh provided as input. Similarly, PROTEUS-MOC and PROTEUS-NEMO were built to apply the method of characteristics on unstructured finite element meshes. Given the complexity of real world problems, experience has shown that using commercial mesh generator to create rather simple input geometries is overly complex and slow. As a consequence, significant effort has been put into place to create multiple codes that help assist in the mesh generation and manipulation. There are three input means to create a mesh in PROTEUS: UFMESH, GRID, and NEMESH. At present, the UFMESH is a simple way to generate two-dimensional Cartesian and hexagonal fuel assembly geometries. The UFmesh input allows for simple assembly mesh generation while the GRID input allows the generation of Cartesian, hexagonal, and regular triangular structured grid geometry options. The NEMESH is a way for the user to create their own mesh or convert another mesh file format into a PROTEUS input format. Given that one has an input mesh format acceptable for PROTEUS, we have constructed several tools which allow further mesh and geometry construction (i.e. mesh extrusion and merging). This report describes the various mesh tools that are provided with the PROTEUS code giving both descriptions of the input and output. In many cases the examples are provided with a regression test of the mesh tools. The most important mesh tools for any user to consider using are the MT_MeshToMesh.x and the MT_RadialLattice.x codes. The former allows the conversion between most mesh types handled by PROTEUS while the second allows the merging of multiple (assembly) meshes into a radial structured grid. Note that the mesh generation process is recursive in nature and that each input specific for a given mesh tool (such as .axial

  10. Risk factors and management of vaginal mesh erosion after pelvic organ prolapse surgery.

    PubMed

    Cheng, Yung-Wen; Su, Tsung-Hsien; Wang, Hsuan; Huang, Wen-Chu; Lau, Hui-Hsuan

    2017-04-01

    Mesh erosion is a serious and not uncommon complication in women undergoing vaginal mesh repair. We hypothesized that mesh erosion is associated with the patient's comorbidities, surgical procedures, and mesh material. The aims of this study were to identify the risk factors and optimal management for mesh erosion. All women who underwent vaginal mesh repair from 2004 to 2014 were retrospectively reviewed. Data on patients' characteristics, presenting symptoms, treatment and outcomes were collected from their medical records. A total of 741 women underwent vaginal mesh repairs, of whom 47 had mesh erosion. The median follow-up period was 13 months (range 3-84 months). Another nine patients with mesh erosion were referred form other hospitals. Multivariate analysis revealed that concomitant hysterectomy (odds ratio 27.02, 95% confidence interval 12.35-58.82; p < 0.01) and hypertension (odds ratio 5.95, 95% confidence interval 2.43-14.49; p < 0.01) were independent risk factors for mesh erosion. Of these 56 women, 20 (36%) were successfully treated by conservative management, while 36 (64%) required subsequent surgical revision. Compared with surgery, conservative treatment was successful if the size of the erosion was smaller than 0.5 cm (p < 0.01). Six patients (17%) had recurrent erosions after primary revision, but all successfully healed after the second surgery. Concomitant hysterectomy and hypertension were associated with mesh erosion. In the management of mesh erosion, conservative treatment can be tried as the first-line treatment for smaller erosions, while surgical repair for larger erosions. Recurrent erosions could happen and requires repairs several times. Copyright © 2017. Published by Elsevier B.V.

  11. The Use of Biological Meshes in Diaphragmatic Defects – An Evidence-Based Review of the Literature

    PubMed Central

    Antoniou, Stavros A.; Pointner, Rudolph; Granderath, Frank-Alexander; Köckerling, Ferdinand

    2015-01-01

    The widespread use of meshes for hiatal hernia repair has emerged in the era of laparoscopic surgery, although sporadic cases of mesh augmentation of traumatic diaphragmatic rupture have been reported. The indications for biologic meshes in diaphragmatic repair are ill defined. This systematic review aims to investigate the available evidence on the role of biologic meshes in diaphragmatic rupture and hiatal hernia repair. Limited data from sporadic case reports and case series have demonstrated that repair of traumatic diaphragmatic rupture with biologic mesh is safe technique in both the acute or chronic setting. High level evidence demonstrates short-term benefits of biologic mesh augmentation in hiatal hernia repair over primary repair, although adequate long-term data are not currently available. Long-term follow-up data suggest no benefit of hiatal hernia repair using porcine small intestine submucosa over suture repair. The effectiveness of different biologic mesh materials on hernia recurrence requires further investigation. PMID:26539439

  12. EFFECTS OF ETHYLENE OXIDE RESTERILISATION AND IN-VITRO DEGRADATION ON MECHANICAL PROPERTIES OF PARTIALLY ABSORBABLE COMPOSITE HERNIA MESHES.

    PubMed

    Endogan, T; Ozyaylali, I; Kulacoglu, H; Serbetci, K; Kiyak, G; Hasirci, N

    2013-06-01

    Prosthetic mesh repair for abdominal wall hernias is widely used because of its technical simplicity and low hernia recurrence rates. The most commonly used material is pure polypropylene mesh, however newer composite materials are recommended by some centers because of their advantages. However, these meshes are more expensive than pure polypropylene meshes. Resterilisation of a pure polypropylene mesh has been shown to be quite safe, and many centers prefer slicing a large mesh into smaller pieces that suitable for hernia type or defect size. Nevertheless there is no data about the safety after resterilisation of the composite meshes. To search the effects of resterilisation and In vitro degradation in phosphate buffered saline solution on the physical structure and the mechanical properties of partially absorbable lightweigth meshes. Laboratory-based research. Two composite meshes were used in the study: One mesh is consisted of monofilament polypropylene and monofilament polyglecaprone--a copolymer of glycolide and epsilon (ε)-caprolactone--(Ultrapro®, 28 g/m2, Ethicon, Hamburg, Germany),andthe otherone consisted of multifilamentpolypropyleneandmultifilament polyglactine (Vypro II®, 30 g/m2,Ethicon, Hamburg, Germany). Two large meshes were cut into rectangular specimens sized 50x20 mm for mechanical testing and 20x20 mm for In vitro degradation experiments. Meshes were divided into control group with no resterilisation and gas resterilisation. Ethylene oxide gas sterilisation was performed at 55°C for 4.5 hours. In vitro degradation in 0.01 M phosphate buffered saline (PBS, pH 7.4) solution at 37 ± 1°C for 8 weeks was applied to one subgroup in each mesh group. Tensiometric measurements and scanning electron microscopyic evaluations were completed for control and resterilisation specimens. Regardless of resterilisation, when meshes were exposed to In vitro degradation, all mechanical parameters decreased significantly. Highest reduction in mechanical

  13. The moving mesh code SHADOWFAX

    NASA Astrophysics Data System (ADS)

    Vandenbroucke, B.; De Rijcke, S.

    2016-07-01

    We introduce the moving mesh code SHADOWFAX, which can be used to evolve a mixture of gas, subject to the laws of hydrodynamics and gravity, and any collisionless fluid only subject to gravity, such as cold dark matter or stars. The code is written in C++ and its source code is made available to the scientific community under the GNU Affero General Public Licence. We outline the algorithm and the design of our implementation, and demonstrate its validity through the results of a set of basic test problems, which are also part of the public version. We also compare SHADOWFAX with a number of other publicly available codes using different hydrodynamical integration schemes, illustrating the advantages and disadvantages of the moving mesh technique.

  14. Confined helium on Lagrange meshes.

    PubMed

    Baye, D; Dohet-Eraly, J

    2015-12-21

    The Lagrange-mesh method has the simplicity of a calculation on a mesh and can have the accuracy of a variational method. It is applied to the study of a confined helium atom. Two types of confinement are considered. Soft confinements by potentials are studied in perimetric coordinates. Hard confinement in impenetrable spherical cavities is studied in a system of rescaled perimetric coordinates varying in [0,1] intervals. Energies and mean values of the distances between electrons and between an electron and the helium nucleus are calculated. A high accuracy of 11 to 15 significant figures is obtained with small computing times. Pressures acting on the confined atom are also computed. For sphere radii smaller than 1, their relative accuracies are better than 10(-10). For larger radii up to 10, they progressively decrease to 10(-3), still improving the best literature results.

  15. Implicit solvers for unstructured meshes

    NASA Technical Reports Server (NTRS)

    Venkatakrishnan, V.; Mavriplis, Dimitri J.

    1991-01-01

    Implicit methods were developed and tested for unstructured mesh computations. The approximate system which arises from the Newton linearization of the nonlinear evolution operator is solved by using the preconditioned GMRES (Generalized Minimum Residual) technique. Three different preconditioners were studied, namely, the incomplete LU factorization (ILU), block diagonal factorization, and the symmetric successive over relaxation (SSOR). The preconditioners were optimized to have good vectorization properties. SSOR and ILU were also studied as iterative schemes. The various methods are compared over a wide range of problems. Ordering of the unknowns, which affects the convergence of these sparse matrix iterative methods, is also studied. Results are presented for inviscid and turbulent viscous calculations on single and multielement airfoil configurations using globally and adaptively generated meshes.

  16. Unstructured mesh algorithms for aerodynamic calculations

    NASA Technical Reports Server (NTRS)

    Mavriplis, D. J.

    1992-01-01

    The use of unstructured mesh techniques for solving complex aerodynamic flows is discussed. The principle advantages of unstructured mesh strategies, as they relate to complex geometries, adaptive meshing capabilities, and parallel processing are emphasized. The various aspects required for the efficient and accurate solution of aerodynamic flows are addressed. These include mesh generation, mesh adaptivity, solution algorithms, convergence acceleration, and turbulence modeling. Computations of viscous turbulent two-dimensional flows and inviscid three-dimensional flows about complex configurations are demonstrated. Remaining obstacles and directions for future research are also outlined.

  17. Translating MeSH concepts.

    PubMed

    Soualmia, Lina F; Letord, Catherine; Merabti, Tayeb; Griffon, Nicolas; Manel, Jacques; Darmoni, Stéfan J

    2013-01-01

    The concept-oriented structure of the MeSH® thesaurus is not yet in common use. Nevertheless, it has been shown that a concept-based querying of PubMed may be of interest. To take full advantage of the concept-oriented structure of MeSH in the information retrieval tool associated with the CISMeF catalogue, it was necessary to translate such concepts into French.

  18. Adaptive Mesh Refinement in CTH

    SciTech Connect

    Crawford, David

    1999-05-04

    This paper reports progress on implementing a new capability of adaptive mesh refinement into the Eulerian multimaterial shock- physics code CTH. The adaptivity is block-based with refinement and unrefinement occurring in an isotropic 2:1 manner. The code is designed to run on serial, multiprocessor and massive parallel platforms. An approximate factor of three in memory and performance improvements over comparable resolution non-adaptive calculations has-been demonstrated for a number of problems.

  19. Grating droplets with a mesh

    NASA Astrophysics Data System (ADS)

    Soto, Dan; Le Helloco, Antoine; Clanet, Cristophe; Quere, David; Varanasi, Kripa

    2016-11-01

    A drop thrown against a mesh can pass through its holes if impacting with enough inertia. As a result, although part of the droplet may remain on one side of the sieve, the rest will end up grated through the other side. This inexpensive method to break up millimetric droplets into micrometric ones may be of particular interest in a wide variety of applications: enhancing evaporation of droplets launched from the top of an evaporative cooling tower or preventing drift of pesticides sprayed above crops by increasing their initial size and atomizing them at the very last moment with a mesh. In order to understand how much liquid will be grated we propose in this presentation to start first by studying a simpler situation: a drop impacting a plate pierced with a single off centered hole. The study of the role of natural parameters such as the radius drop and speed or the hole position, size and thickness allows us to discuss then the more general situation of a plate pierced with multiple holes: the mesh.

  20. [Hernia surgery: minimization of complications by selection of the "correct mesh"].

    PubMed

    Klinge, U; Weyhe, D

    2014-02-01

    The risk for developing postoperative complications increases with the degree of surgical trauma, an altered wound healing capability of the patient due to comorbidities and environmental conditions and the selection of an inadequate implant material, the latter offering options for improvement at least in some patients. In general a mesh with large pores made of monofilaments provides a reduced surface area and causes less scarring and inflammation than those with small pores and thereby reduces the rate of scar contraction, pain and the challenge to explant a mesh from a scar bed. When placing the mesh in the abdominal cavity an additional surface coating of polypropylene should prevent the formation of a fistula between mesh and bowel. The risk of recurrence mainly depends on the extent of overlap; however, the flexibility of some meshes may increase the technical difficulties of some implants. In cases of bacterial contamination of the wound there is an increased risk for late onset mesh infection and monofilament meshes offer the best option for complete healing by conservative means. An impaired function of the spermatic cord because of the material, apart from the consequences of the surgical trauma, has not been confirmed in experimental and clinical studies. Revision of mesh sites always is a surgical challenge but could be much easier with implants which are visible in computed tomography (CT) or magnetic resonance imaging (MRI) scans.

  1. SHARP/PRONGHORN Interoperability: Mesh Generation

    SciTech Connect

    Avery Bingham; Javier Ortensi

    2012-09-01

    Progress toward collaboration between the SHARP and MOOSE computational frameworks has been demonstrated through sharing of mesh generation and ensuring mesh compatibility of both tools with MeshKit. MeshKit was used to build a three-dimensional, full-core very high temperature reactor (VHTR) reactor geometry with 120-degree symmetry, which was used to solve a neutron diffusion critical eigenvalue problem in PRONGHORN. PRONGHORN is an application of MOOSE that is capable of solving coupled neutron diffusion, heat conduction, and homogenized flow problems. The results were compared to a solution found on a 120-degree, reflected, three-dimensional VHTR mesh geometry generated by PRONGHORN. The ability to exchange compatible mesh geometries between the two codes is instrumental for future collaboration and interoperability. The results were found to be in good agreement between the two meshes, thus demonstrating the compatibility of the SHARP and MOOSE frameworks. This outcome makes future collaboration possible.

  2. Characterization of heavyweight and lightweight polypropylene prosthetic mesh explants from a single patient.

    PubMed

    Costello, C R; Bachman, S L; Grant, S A; Cleveland, D S; Loy, T S; Ramshaw, B J

    2007-09-01

    Although polypropylene has been used as a hernia repair material for nearly 50 years, very little science has been applied to studying the body's effect on this material. It is possible that oxidation of mesh occurs as a result of the chemical structure of polypropylene and the physiological conditions to which it is subjected; this leads to embrittlement of the material, impaired abdominal movement, and chronic pain. It is also possible that lightweight polypropylene meshes undergo less oxidation due to a reduced inflammatory reaction. The objective of this study was to characterize explanted hernia meshes using techniques such as scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and compliance testing to determine whether the mesh density of polypropylene affects the oxidative degradation of the material. The hypothesis was that heavyweight polypropylene would incite a more intense inflammatory response than lightweight polypropylene and thus undergo greater oxidative degradation. Overall, the results support this theory.

  3. The myth: in vivo degradation of polypropylene-based meshes.

    PubMed

    Thames, Shelby F; White, Joshua B; Ong, Kevin L

    2017-02-01

    Polypropylene is a base polymer used in biomaterial applications, including sutures and mesh products, for the treatment of pelvic organ prolapse, stress urinary incontinence, and hernia repairs. Previous studies have dismissed the value of formulation additives employed in polypropylene, and the importance and necessity of an effective mesh explant cleaning protocol when characterizing explanted devices. However, both are critical to understanding the alleged degradation of polypropylene-based meshes. An effective, nondestructive, hydrolytic cleaning process, supplemented with light microscopy (LM), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) data, was used to evaluate 78 explanted Prolene meshes (with duration of implantation ranging from 0.4 to 11.7 years). The cleaning process exposed clean, unoxidized, nondegraded Prolene fibers with smooth surfaces and with no visible evidence of gradient-type or ductile damage. LM showed identical translucent and sometimes clear, cracked/flaking material on both blue and clear fibers, instead of clear cracked/flaking material on the clear fibers and blue cracked/flaking material on the blue fibers. FTIR confirmed progressive protein removal and loss of protein absorption intensity after each cleaning step. Our effective cleaning of explanted Prolene meshes and subsequent analyses showed that they did not degrade in vivo, confirming the in vivo stability of properly formulated polypropylene. Instead, the cracked layer that some researchers have identified as degraded Prolene is an adsorbed protein-formaldehyde coating, resulting from the well-established formalin-protein fixation process, which occurs immediately upon placing an explant in formalin.

  4. Mesh-Based Fourier Imaging for Biological and Security Applications

    NASA Astrophysics Data System (ADS)

    Hayden, Danielle

    Traditional x-ray imaging provides only low contrast from low atomic number materials, like soft tissue, due to the small attenuation variations producing very small intensity changes. Higher contrast can be achieved through phase information. The phase change is obtained from the x-ray refracting in a sample, or phase object, due to the difference in refractive indexes. This causes a small angular deviation from the original path. Phase contrast imaging has not been realized in everyday practice due to the requirement for large spatial coherence width of the x-ray beam which typically requires sources on the order of 10-50 m, the use of a grating technique or synchrotron sources. The grating-based phase imaging method depends upon multiple fine-pitched, expensive gratings and extremely precise alignment. An alternative procedure based on a technique recently demonstrated by Bennett is mesh-based phase imaging that utilizes a single, inexpensive mesh with a coarse pitch. This considerably eases the small spot size source requirement, allowing the use of a 150 micron, micro-focus, tungsten anode source. The mesh-based phase imaging set up used to study biomedical and security screening applications consisted of a 123x123 m stainless steel mesh and a 1200x1600 CCD detector with a pixel size of 22 microns. This mesh based approach allows for near-real-time phase extraction of the first harmonics in the Fourier domain. With the phase information and absorption information (collected at the zeroth harmonic), edge enhanced images of a mouse's skull were optimized and several potentially dangerous liquids and powders were discriminated from water. The mesh-based phase set up resulted in high contrasts, signal-to-noise ratios and good resolution verifying the potential utility of this technique for future biomedical imaging and airport security screening.

  5. Synthetic Versus Biological Mesh-Related Erosion After Laparoscopic Ventral Mesh Rectopexy: A Systematic Review.

    PubMed

    Balla, Andrea; Quaresima, Silvia; Smolarek, Sebastian; Shalaby, Mostafa; Missori, Giulia; Sileri, Pierpaolo

    2017-04-01

    This review reports the incidence of mesh-related erosion after ventral mesh rectopexy to determine whether any difference exists in the erosion rate between synthetic and biological mesh. A systematic search of the MEDLINE and the Ovid databases was conducted to identify suitable articles published between 2004 and 2015. The search strategy capture terms were laparoscopic ventral mesh rectopexy, laparoscopic anterior rectopexy, robotic ventral rectopexy, and robotic anterior rectopexy. Eight studies (3,956 patients) were included in this review. Of those patients, 3,517 patients underwent laparoscopic ventral rectopexy (LVR) using synthetic mesh and 439 using biological mesh. Sixty-six erosions were observed with synthetic mesh (26 rectal, 32 vaginal, 8 recto-vaginal fistulae) and one (perineal erosion) with biological mesh. The synthetic and the biological mesh-related erosion rates were 1.87% and 0.22%, respectively. The time between rectopexy and diagnosis of mesh erosion ranged from 1.7 to 124 months. No mesh-related mortalities were reported. The incidence of mesh-related erosion after LVR is low and is more common after the placement of synthetic mesh. The use of biological mesh for LVR seems to be a safer option; however, large, multicenter, randomized, control trials with long follow-ups are required if a definitive answer is to be obtained.

  6. Effects of ethylene oxide resterilization and in-vitro degradation on mechanical properties of partially absorbable composite hernia meshes.

    PubMed

    Endogan, T; Ozyaylali, I; Kulacoglu, H; Serbetci, K; Kiyak, G; Hasirci, N

    2013-01-01

    Prosthetic mesh repair for abdominal wall hernias is widely used because of its technical simplicity and low hernia recurrence rates. The most commonly used material is pure polypropylene mesh, although newer composite materials are recommended by some centers due to their advantages.However, these meshes are more expensive than pure polypropylene meshes. Resterilization of a pure polypropylene mesh has been shown to be quite safe, and many centers prefer slicing a large mesh into smaller pieces, suitable for any hernia type or defect size. Nevertheless there is no data about the safety after resterilization of the composite meshes. The present study was carried out to investigate the effects of resterilization and in vitro degradation in phosphate buffered saline solution on the physical structure and the mechanical properties of partially absorbable lightweight meshes. Two composite meshes were used in the study: One mesh consists of monofilament polypropylene and monofilament polyglecaprone -a copolymer of glycolide and epsilon(ε)- caprolactone - (Ultrapro®, 28 g m2, Ethicon, Hamburg,Germany), and the other one consisted of multifilament polypropylene and multifilament polyglactine (Vypro II®, 30g m2, Ethicon, Hamburg, Germany). Two large meshes were cut into rectangular specimens sized 50 x 20 mm for mechanical testing and 20 x 20 mm for in vitro degradation experiments.Meshes were divided into control group with no resterilization and gas resterilization. Ethylene oxide gas sterilization was performed at 55°C for 4.5 hours. In vitro degradation in 0.01M phosphate buffered saline (PBS, pH 7.4) solution at 37 ± 1°C for 8 weeks was applied to one subgroup in each mesh group. Tensiometric measurements and scanning electronmicroscopic evaluations were completed for control and resterilization specimens. Regardless of resterilization, when the meshes were exposed to in vitro degradation, all mechanical parameters decreased significantly. Highest reduction in

  7. Postimplant behavior of lightweight polypropylene meshes in an experimental model of abdominal hernia.

    PubMed

    Bellon, Juan M; Rodriguez, Marta; Garcia-Honduvilla, Natalio; Gomez-Gil, Veronica; Pascual, Gemma; Bujan, Julia

    2008-01-01

    Over the years, reticular prostheses have undergone changes in their structure and composition to give rise to today's partially absorbable lightweight meshes. This study was designed to assess the biological and biomechanical behavior of these prostheses to establish whether they offer any advantages over nonabsorbable lightweight polypropylene prostheses. 7 x 5 cm defects were created in the anterior abdominal wall of New Zealand White rabbits and repaired by securing different prostheses to the edges of the defect with a running 4/0 polypropylene suture. The lightweight biomaterials compared were two nonabsorbable meshes: Parietene and Optilene elastic, and two partially absorbable prostheses: Vypro II and Ultrapro. At 14 and 90 days postimplant, tissue/prosthesis specimens were subjected to histological, immunohistochemical, shrinkage, and biomechanical analyses. Adhesion formation on the peritoneum-facing surface of the meshes was significantly less extensive in the meshes with absorbable components at 90 days postimplant. The newly formed tissue around the prosthetic filaments was comprised of collagen fibers, fibroblasts, blood vessels, and macrophages. The partially absorbable meshes showed higher macrophage proportions (due to remnants of absorbable material and their structure) than the nonabsorbable meshes at 90 days, although differences were not significant. At 90 days postimplant, similar tensile strengths were recorded for all the implants. All the prosthetic materials induced good host tissue ingrowth, with no significant differences in tensile strength observed. Our findings suggest that partially absorbable lightweight prostheses could offer advantages over nonabsorbable lightweight meshes since less foreign material persists in the recipient, improving abdominal wall compliance.

  8. Experimental study regarding the biocompatibility test of the Prolene (polypropylene abdominal mesh) product.

    PubMed

    Radu, Elena Violeta; Coman, IonuŢ Simion; David, Oana Ilona; Bedereag, Ştefan Iulian; Sinescu, Ruxandra Diana; Grigorean, Valentin Titus; Popescu, Mihai; Lupaşcu, Cristian Dumitru; Straja, Nicolae Dan; Florescu, Ioan Petre

    2016-01-01

    The polypropylene mesh, although is one of the most used prosthetic biomaterials for abdominal wall defects, proved not to be completely inert, generating from precocious foreign body inflammatory reactions (varying by individual reactivity, the amount of used material and its structure), to late complications such as chronic infections, stercoral fistulae or mesh migration. The present paper was aimed at studying the behavior of implants of this material in three different areas of the body of experimental animals, as follows: intramuscular, intraperitoneal and extraperitoneal. The observation time was 21 days and 90 days. We observed foreign body reactions induced locally by the mesh that remains temporary, generating a moderate number of macrophages and foreign body giant cells. The material did not systemically affect the healing and the scaring of the surgical wounds, but in all three implant areas, the polypropylene mesh generated locally a fibrous proliferation reaction of neoformation tissue, which wrapped and secured the implanted product on all surfaces.

  9. Fiber-mesh photonic molecule

    NASA Astrophysics Data System (ADS)

    Mishra, Subodha; Satpathy, Sashi

    2008-03-01

    Analogous to the photonic crystal, we introduce the concept of a fiber-mesh photonic molecule made up of optical fibers and study its transmission characteristics. We consider a specific example of a photonic molecule, inspired by the well-known C60 molecule, with the arms of the molecule formed out of single-moded optical fibers. The transmittance consists of sharp peaks determined by the pole structure of the scattering matrix in the complex energy plane. A molecule can be designed to control the positions and the widths of the transmission peaks, opening up the possibility of building new photonic devices such as high quality band-pass filters.

  10. A method to generate conformal finite-element meshes from 3D measurements of microstructurally small fatigue-crack propagation: 3D Meshes of Microstructurally Small Crack Growth

    DOE PAGES

    Spear, A. D.; Hochhalter, J. D.; Cerrone, A. R.; ...

    2016-04-27

    In an effort to reproduce computationally the observed evolution of microstructurally small fatigue cracks (MSFCs), a method is presented for generating conformal, finite-element (FE), volume meshes from 3D measurements of MSFC propagation. The resulting volume meshes contain traction-free surfaces that conform to incrementally measured 3D crack shapes. Grain morphologies measured using near-field high-energy X-ray diffraction microscopy are also represented within the FE volume meshes. Proof-of-concept simulations are performed to demonstrate the utility of the mesh-generation method. The proof-of-concept simulations employ a crystal-plasticity constitutive model and are performed using the conformal FE meshes corresponding to successive crack-growth increments. Although the simulationsmore » for each crack increment are currently independent of one another, they need not be, and transfer of material-state information among successive crack-increment meshes is discussed. The mesh-generation method was developed using post-mortem measurements, yet it is general enough that it can be applied to in-situ measurements of 3D MSFC propagation.« less

  11. Methods and evaluations of MRI content-adaptive finite element mesh generation for bioelectromagnetic problems.

    PubMed

    Lee, W H; Kim, T-S; Cho, M H; Ahn, Y B; Lee, S Y

    2006-12-07

    In studying bioelectromagnetic problems, finite element analysis (FEA) offers several advantages over conventional methods such as the boundary element method. It allows truly volumetric analysis and incorporation of material properties such as anisotropic conductivity. For FEA, mesh generation is the first critical requirement and there exist many different approaches. However, conventional approaches offered by commercial packages and various algorithms do not generate content-adaptive meshes (cMeshes), resulting in numerous nodes and elements in modelling the conducting domain, and thereby increasing computational load and demand. In this work, we present efficient content-adaptive mesh generation schemes for complex biological volumes of MR images. The presented methodology is fully automatic and generates FE meshes that are adaptive to the geometrical contents of MR images, allowing optimal representation of conducting domain for FEA. We have also evaluated the effect of cMeshes on FEA in three dimensions by comparing the forward solutions from various cMesh head models to the solutions from the reference FE head model in which fine and equidistant FEs constitute the model. The results show that there is a significant gain in computation time with minor loss in numerical accuracy. We believe that cMeshes should be useful in the FEA of bioelectromagnetic problems.

  12. Methods and evaluations of MRI content-adaptive finite element mesh generation for bioelectromagnetic problems

    NASA Astrophysics Data System (ADS)

    Lee, W. H.; Kim, T.-S.; Cho, M. H.; Ahn, Y. B.; Lee, S. Y.

    2006-12-01

    In studying bioelectromagnetic problems, finite element analysis (FEA) offers several advantages over conventional methods such as the boundary element method. It allows truly volumetric analysis and incorporation of material properties such as anisotropic conductivity. For FEA, mesh generation is the first critical requirement and there exist many different approaches. However, conventional approaches offered by commercial packages and various algorithms do not generate content-adaptive meshes (cMeshes), resulting in numerous nodes and elements in modelling the conducting domain, and thereby increasing computational load and demand. In this work, we present efficient content-adaptive mesh generation schemes for complex biological volumes of MR images. The presented methodology is fully automatic and generates FE meshes that are adaptive to the geometrical contents of MR images, allowing optimal representation of conducting domain for FEA. We have also evaluated the effect of cMeshes on FEA in three dimensions by comparing the forward solutions from various cMesh head models to the solutions from the reference FE head model in which fine and equidistant FEs constitute the model. The results show that there is a significant gain in computation time with minor loss in numerical accuracy. We believe that cMeshes should be useful in the FEA of bioelectromagnetic problems.

  13. Shrinkage evaluation of heavyweight and lightweight polypropylene meshes in inguinal hernia repair: a randomized controlled trial.

    PubMed

    Silvestre, A C; de Mathia, G B; Fagundes, D J; Medeiros, L R; Rosa, M I

    2011-12-01

    One of the current complications in inguinal repair is shrinkage following the use of mesh. The selected mesh material, heavyweight (HWM) mesh or lightweight (LWM) mesh, is associated with the frequency of shrinkage. The aim of this study was to investigate shrinkage of these two types of mesh in a controlled trial of male inguinal hernia repair. Thirty-two healthy men with primary unilateral inguinal hernias (Nyhus classification), who presented at São José Hospital of Criciúma, Brazil, underwent the Lichtenstein procedure. In total, 16 polypropylene HWM (105 g/m(2)) and 16 partially absorbable LWM (28 g/m(2)) were implanted into randomly selected patients. On post-operative days 1, 30, 60 and 90, the area of the mesh was evaluated by digital radiography. The study randomized 32 patients and analyzed 30 patients--15 for each type of mesh. At baseline, there were no differences between groups. There were significant differences between the two meshes when comparing the total area initially and on postoperative day 90 (P = 0.001). The HWM had significantly less area initial area, as compared with 90 days postoperatively (P = 0.04). Shrinkage was significantly higher for HWM, although the difference was not large.

  14. Consistent melting behavior induced by Joule heating between Ag microwire and nanowire meshes

    PubMed Central

    2014-01-01

    The melting behavior of an Ag microwire mesh induced by Joule heating was numerically investigated and compared with that of the corresponding Ag nanowire mesh with the same structure but different geometrical and physical properties of the wire itself. According to the relationship of melting current and melting voltage during the melting process, a similar repetitive zigzag pattern in melting behavior was discovered in both meshes. On this basis, a dimensionless parameter defined as figure of merit was proposed to characterize the current-carrying ability of the mesh. The consistent feature of figure of merit in both meshes indicates that the melting behavior of the Ag nanowire mesh can be predicted from the present results of the corresponding Ag microwire mesh with the same structure but made from a different wire (e.g., different size, different material) through simple conversion. The present findings can provide fundamental insight into the reliability analysis on the metallic nanowire mesh-based transparent conductive electrode. PMID:24910578

  15. High Performance Woven Mesh Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Wirtz, Richard A.; Li, Chen; Park, Ji-Wook; Xu, Jun

    2002-07-01

    Simple-to-fabricate woven mesh structures, consisting of bonded laminates of two-dimensional plain-weave conductive screens, or three-dimensional orthogonal weaves are described. Geometric equations show that these porous matrices can be fabricated to have a wide range of porosity and a highly anisotropic thermal conductivity vector. A mathematical model of the thermal performance of such a mesh, deployed as a heat exchange surface, is developed. Measurements of pressure drop and overall heat transfer rate are reported and used with the performance model to develop correlation equations of mesh friction factor and Colburn j-factor as a function of coolant properties, mesh characteristics and flow rate through the mesh. A heat exchanger performance analysis delineates conditions where the two mesh technologies offer superior performance.

  16. Bluetooth Low Energy Mesh Networks: A Survey.

    PubMed

    Darroudi, Seyed Mahdi; Gomez, Carles

    2017-06-22

    Bluetooth Low Energy (BLE) has gained significant momentum. However, the original design of BLE focused on star topology networking, which limits network coverage range and precludes end-to-end path diversity. In contrast, other competing technologies overcome such constraints by supporting the mesh network topology. For these reasons, academia, industry, and standards development organizations have been designing solutions to enable BLE mesh networks. Nevertheless, the literature lacks a consolidated view on this emerging area. This paper comprehensively surveys state of the art BLE mesh networking. We first provide a taxonomy of BLE mesh network solutions. We then review the solutions, describing the variety of approaches that leverage existing BLE functionality to enable BLE mesh networks. We identify crucial aspects of BLE mesh network solutions and discuss their advantages and drawbacks. Finally, we highlight currently open issues.

  17. Bluetooth Low Energy Mesh Networks: A Survey

    PubMed Central

    Darroudi, Seyed Mahdi; Gomez, Carles

    2017-01-01

    Bluetooth Low Energy (BLE) has gained significant momentum. However, the original design of BLE focused on star topology networking, which limits network coverage range and precludes end-to-end path diversity. In contrast, other competing technologies overcome such constraints by supporting the mesh network topology. For these reasons, academia, industry, and standards development organizations have been designing solutions to enable BLE mesh networks. Nevertheless, the literature lacks a consolidated view on this emerging area. This paper comprehensively surveys state of the art BLE mesh networking. We first provide a taxonomy of BLE mesh network solutions. We then review the solutions, describing the variety of approaches that leverage existing BLE functionality to enable BLE mesh networks. We identify crucial aspects of BLE mesh network solutions and discuss their advantages and drawbacks. Finally, we highlight currently open issues. PMID:28640183

  18. MPDATA error estimator for mesh adaptivity

    NASA Astrophysics Data System (ADS)

    Szmelter, Joanna; Smolarkiewicz, Piotr K.

    2006-04-01

    In multidimensional positive definite advection transport algorithm (MPDATA) the leading error as well as the first- and second-order solutions are known explicitly by design. This property is employed to construct refinement indicators for mesh adaptivity. Recent progress with the edge-based formulation of MPDATA facilitates the use of the method in an unstructured-mesh environment. In particular, the edge-based data structure allows for flow solvers to operate on arbitrary hybrid meshes, thereby lending itself to implementations of various mesh adaptivity techniques. A novel unstructured-mesh nonoscillatory forward-in-time (NFT) solver for compressible Euler equations is used to illustrate the benefits of adaptive remeshing as well as mesh movement and enrichment for the efficacy of MPDATA-based flow solvers. Validation against benchmark test cases demonstrates robustness and accuracy of the approach.

  19. Improved ALE mesh velocities for complex flows

    DOE PAGES

    Bakosi, Jozsef; Waltz, Jacob I.; Morgan, Nathaniel Ray

    2017-05-31

    A key choice in the development of arbitrary Lagrangian-Eulerian solution algorithms is how to move the computational mesh. The most common approaches are smoothing and relaxation techniques, or to compute a mesh velocity field that produces smooth mesh displacements. We present a method in which the mesh velocity is specified by the irrotational component of the fluid velocity as computed from a Helmholtz decomposition, and excess compression of mesh cells is treated through a noniterative, local spring-force model. This approach allows distinct and separate control over rotational and translational modes. In conclusion, the utility of the new mesh motion algorithmmore » is demonstrated on a number of 3D test problems, including problems that involve both shocks and significant amounts of vorticity.« less

  20. Mesh networking optimized for robotic teleoperation

    NASA Astrophysics Data System (ADS)

    Hart, Abraham; Pezeshkian, Narek; Nguyen, Hoa

    2012-06-01

    Mesh networks for robot teleoperation pose different challenges than those associated with traditional mesh networks. Unmanned ground vehicles (UGVs) are mobile and operate in constantly changing and uncontrollable environments. Building a mesh network to work well under these harsh conditions presents a unique challenge. The Manually Deployed Communication Relay (MDCR) mesh networking system extends the range of and provides non-line-of-sight (NLOS) communications for tactical and explosive ordnance disposal (EOD) robots currently in theater. It supports multiple mesh nodes, robots acting as nodes, and works with all Internet Protocol (IP)-based robotic systems. Under MDCR, the performance of different routing protocols and route selection metrics were compared resulting in a modified version of the Babel mesh networking protocol. This paper discusses this and other topics encountered during development and testing of the MDCR system.

  1. Floating shock fitting via Lagrangian adaptive meshes

    NASA Technical Reports Server (NTRS)

    Vanrosendale, John

    1995-01-01

    In recent work we have formulated a new approach to compressible flow simulation, combining the advantages of shock-fitting and shock-capturing. Using a cell-centered on Roe scheme discretization on unstructured meshes, we warp the mesh while marching to steady state, so that mesh edges align with shocks and other discontinuities. This new algorithm, the Shock-fitting Lagrangian Adaptive Method (SLAM), is, in effect, a reliable shock-capturing algorithm which yields shock-fitted accuracy at convergence.

  2. [Treatment of paracolostomic hernias using polypropylene mesh].

    PubMed

    Grigoriuk, A A; Ishchenko, V N; Matveev, A V; Kovalev, V A; Krasnobaev, A E; Stuzhin, S A

    2015-01-01

    It was analyzed the results of treatment of 23 patients with large paracolostomic hernias. Twenty patients underwent colostomy suturing and hernial ring Onlay-plasty with polypropylene mesh without tension. Onlay-plasty of hernial ring with own tissues and polypropylene mesh and colostomy reconstruction outside of implant were performed in 3 patients. Onlay-alloplasty with polypropylene mesh "PROLENE" is effective method of treatment of postoperative paracolostomic ventral hernias with colostomy closing as well as with its reconstruction outside of implant.

  3. Unstructured Polyhedral Mesh Thermal Radiation Diffusion

    SciTech Connect

    Palmer, T.S.; Zika, M.R.; Madsen, N.K.

    2000-07-27

    Unstructured mesh particle transport and diffusion methods are gaining wider acceptance as mesh generation, scientific visualization and linear solvers improve. This paper describes an algorithm that is currently being used in the KULL code at Lawrence Livermore National Laboratory to solve the radiative transfer equations. The algorithm employs a point-centered diffusion discretization on arbitrary polyhedral meshes in 3D. We present the results of a few test problems to illustrate the capabilities of the radiation diffusion module.

  4. Auto-adaptive finite element meshes

    NASA Technical Reports Server (NTRS)

    Richter, Roland; Leyland, Penelope

    1995-01-01

    Accurate capturing of discontinuities within compressible flow computations is achieved by coupling a suitable solver with an automatic adaptive mesh algorithm for unstructured triangular meshes. The mesh adaptation procedures developed rely on non-hierarchical dynamical local refinement/derefinement techniques, which hence enable structural optimization as well as geometrical optimization. The methods described are applied for a number of the ICASE test cases are particularly interesting for unsteady flow simulations.

  5. Are meshes with lightweight construction strong enough?

    PubMed

    Holste, Joerg L

    2005-01-01

    The use of mesh has become essential in the repair of abdominal wall incisional hernias. Suture techniques, reapplied after failure of a primary repair, are characterized by recurrence rates of up to 50 percent, whereas the reinforcement of the abdominal wall with surgical mesh has significantly decreased these rates to <10 percent. This article describes the background for the development of mesh with lightweight construction and physiological biomechanical performance.

  6. Delaunay triangulation and computational fluid dynamics meshes

    NASA Technical Reports Server (NTRS)

    Posenau, Mary-Anne K.; Mount, David M.

    1992-01-01

    In aerospace computational fluid dynamics (CFD) calculations, the Delaunay triangulation of suitable quadrilateral meshes can lead to unsuitable triangulated meshes. Here, we present case studies which illustrate the limitations of using structured grid generation methods which produce points in a curvilinear coordinate system for subsequent triangulations for CFD applications. We discuss conditions under which meshes of quadrilateral elements may not produce a Delaunay triangulation suitable for CFD calculations, particularly with regard to high aspect ratio, skewed quadrilateral elements.

  7. Implicit meshes for surface reconstruction.

    PubMed

    Ilic, Slobodan; Fua, Pascal

    2006-02-01

    Deformable 3D models can be represented either as traditional explicit surfaces, such as triangulated meshes, or as implicit surfaces. Explicit surfaces are widely accepted because they are simple to deform and render, but fitting them involves minimizing a nondifferentiable distance function. By contrast, implicit surfaces allow fitting by minimizing a differentiable algebraic distance, but are harder to meaningfully deform and render. Here, we propose a method that combines the strength of both approaches. It relies on a technique that can turn a completely arbitrary triangulated mesh, such as one taken from the Web, into an implicit surface that closely approximates it and can deform in tandem with it. This allows both automated algorithms to take advantage of the attractive properties of implicit surfaces for fitting purposes and people to use standard deformation tools they feel comfortable for interaction and animation purposes. We demonstrate the applicability of our technique to modeling the human upper-body, including face, neck, shoulders, and ears, from noisy stereo and silhouette data.

  8. Mesh infrastructure for coupled multiprocess geophysical simulations

    DOE PAGES

    Garimella, Rao V.; Perkins, William A.; Buksas, Mike W.; ...

    2014-01-01

    We have developed a sophisticated mesh infrastructure capability to support large scale multiphysics simulations such as subsurface flow and reactive contaminant transport at storage sites as well as the analysis of the effects of a warming climate on the terrestrial arctic. These simulations involve a wide range of coupled processes including overland flow, subsurface flow, freezing and thawing of ice rich soil, accumulation, redistribution and melting of snow, biogeochemical processes involving plant matter and finally, microtopography evolution due to melting and degradation of ice wedges below the surface. In addition to supporting the usual topological and geometric queries about themore » mesh, the mesh infrastructure adds capabilities such as identifying columnar structures in the mesh, enabling deforming of the mesh subject to constraints and enabling the simultaneous use of meshes of different dimensionality for subsurface and surface processes. The generic mesh interface is capable of using three different open source mesh frameworks (MSTK, MOAB and STKmesh) under the hood allowing the developers to directly compare them and choose one that is best suited for the application's needs. We demonstrate the results of some simulations using these capabilities as well as present a comparison of the performance of the different mesh frameworks.« less

  9. Mesh infrastructure for coupled multiprocess geophysical simulations

    SciTech Connect

    Garimella, Rao V.; Perkins, William A.; Buksas, Mike W.; Berndt, Markus; Lipnikov, Konstantin; Coon, Ethan; Moulton, John D.; Painter, Scott L.

    2014-01-01

    We have developed a sophisticated mesh infrastructure capability to support large scale multiphysics simulations such as subsurface flow and reactive contaminant transport at storage sites as well as the analysis of the effects of a warming climate on the terrestrial arctic. These simulations involve a wide range of coupled processes including overland flow, subsurface flow, freezing and thawing of ice rich soil, accumulation, redistribution and melting of snow, biogeochemical processes involving plant matter and finally, microtopography evolution due to melting and degradation of ice wedges below the surface. In addition to supporting the usual topological and geometric queries about the mesh, the mesh infrastructure adds capabilities such as identifying columnar structures in the mesh, enabling deforming of the mesh subject to constraints and enabling the simultaneous use of meshes of different dimensionality for subsurface and surface processes. The generic mesh interface is capable of using three different open source mesh frameworks (MSTK, MOAB and STKmesh) under the hood allowing the developers to directly compare them and choose one that is best suited for the application's needs. We demonstrate the results of some simulations using these capabilities as well as present a comparison of the performance of the different mesh frameworks.

  10. Conformal refinement of unstructured quadrilateral meshes

    SciTech Connect

    Garmella, Rao

    2009-01-01

    We present a multilevel adaptive refinement technique for unstructured quadrilateral meshes in which the mesh is kept conformal at all times. This means that the refined mesh, like the original, is formed of only quadrilateral elements that intersect strictly along edges or at vertices, i.e., vertices of one quadrilateral element do not lie in an edge of another quadrilateral. Elements are refined using templates based on 1:3 refinement of edges. We demonstrate that by careful design of the refinement and coarsening strategy, we can maintain high quality elements in the refined mesh. We demonstrate the method on a number of examples with dynamically changing refinement regions.

  11. Method of generating a surface mesh

    SciTech Connect

    Shepherd, Jason F.; Benzley, Steven; Grover, Benjamin T.

    2008-03-04

    A method and machine-readable medium provide a technique to generate and modify a quadrilateral finite element surface mesh using dual creation and modification. After generating a dual of a surface (mesh), a predetermined algorithm may be followed to generate and modify a surface mesh of quadrilateral elements. The predetermined algorithm may include the steps of generating two-dimensional cell regions in dual space, determining existing nodes in primal space, generating new nodes in the dual space, and connecting nodes to form the quadrilateral elements (faces) for the generated and modifiable surface mesh.

  12. Transrectal Mesh Erosion Requiring Bowel Resection.

    PubMed

    Kemp, Marta Maria; Slim, Karem; Rabischong, Benoît; Bourdel, Nicolas; Canis, Michel; Botchorishvili, Revaz

    To report a case of a transrectal mesh erosion as complication of laparoscopic promontofixation with mesh repair, necessitating bowel resection and subsequent surgical interventions. Sacrocolpopexy has become a standard procedure for vaginal vault prolapse [1], and the laparoscopic approach has gained popularity owing to more rapid recovery and less morbidity [2,3]. Mesh erosion is a well-known complication of surgical treatment for prolapse as reported in several negative evaluations, including a report from the US Food and Drug Administration in 2011 [4]. Mesh complications are more common after surgeries via the vaginal approach [5]; nonetheless, the incidence of vaginal mesh erosion after laparoscopic procedures is as high as 9% [6]. The incidence of transrectal mesh exposure after laparoscopic ventral rectopexy is roughly 1% [7]. The diagnosis may be delayed because of its rarity and variable presentation. In addition, polyester meshes, such as the mesh used in this case, carry a higher risk of exposure [8]. A 57-year-old woman experiencing genital prolapse, with the cervix classified as +3 according to the Pelvic Organ Prolapse Quantification system, underwent laparoscopic standard sacrocolpopexy using polyester mesh. Subtotal hysterectomy and bilateral adnexectomy were performed concomitantly. A 3-year follow-up consultation demonstrated no signs or symptoms of erosion of any type. At 7 years after the surgery, however, the patient presented with rectal discharge, diagnosed as infectious rectocolitis with the isolation of Clostridium difficile. She underwent a total of 5 repair surgeries in a period of 4 months, including transrectal resection of exposed mesh, laparoscopic ablation of mesh with digestive resection, exploratory laparoscopy with abscess drainage, and exploratory laparoscopy with ablation of residual mesh and transverse colostomy. She recovered well after the last intervention, exhibiting no signs of vaginal or rectal fistula and no recurrence

  13. MOAB : a mesh-oriented database.

    SciTech Connect

    Tautges, Timothy James; Ernst, Corey; Stimpson, Clint; Meyers, Ray J.; Merkley, Karl

    2004-04-01

    A finite element mesh is used to decompose a continuous domain into a discretized representation. The finite element method solves PDEs on this mesh by modeling complex functions as a set of simple basis functions with coefficients at mesh vertices and prescribed continuity between elements. The mesh is one of the fundamental types of data linking the various tools in the FEA process (mesh generation, analysis, visualization, etc.). Thus, the representation of mesh data and operations on those data play a very important role in FEA-based simulations. MOAB is a component for representing and evaluating mesh data. MOAB can store structured and unstructured mesh, consisting of elements in the finite element 'zoo'. The functional interface to MOAB is simple yet powerful, allowing the representation of many types of metadata commonly found on the mesh. MOAB is optimized for efficiency in space and time, based on access to mesh in chunks rather than through individual entities, while also versatile enough to support individual entity access. The MOAB data model consists of a mesh interface instance, mesh entities (vertices and elements), sets, and tags. Entities are addressed through handles rather than pointers, to allow the underlying representation of an entity to change without changing the handle to that entity. Sets are arbitrary groupings of mesh entities and other sets. Sets also support parent/child relationships as a relation distinct from sets containing other sets. The directed-graph provided by set parent/child relationships is useful for modeling topological relations from a geometric model or other metadata. Tags are named data which can be assigned to the mesh as a whole, individual entities, or sets. Tags are a mechanism for attaching data to individual entities and sets are a mechanism for describing relations between entities; the combination of these two mechanisms is a powerful yet simple interface for representing metadata or application

  14. Treatment of frontal sinus fracture using bioabsorbable mesh plates.

    PubMed

    Kim, Chung Hun; Kim, Dae Hee; Kim, Da Han; Song, Seung Yong

    2012-03-01

    Accurate reduction and stable fixation are important in the treatment of frontal sinus fracture. Usually, metal plates and screws were used because of easy handling and delicate fixation. However, palpability and possibility for secondary operation for plate removal were shortcomings. For improving these problems, we used absorbable mesh plate for fixation of reduced frontal bones.In this study, 14 patients with frontal sinus fracture were treated by open reduction and rigid fixation using absorbable mesh plates. Mean follow-up period was 17.6 months. Considering anterior and posterior table involvement, nasofrontal duct injury, and concomitant neurosurgical problems, additional surgical procedures including degloving sinus mucosa, cranialization, and obliteration of nasofrontal duct were also conducted.There was no remarkable early and late postoperative complication. Aesthetic results were also satisfactory. Absorbable mesh plates were easy to mold and convenient for screw fixation. Moreover, there was no necessity of secondary operation for removal of plates.We believe that absorbable mesh plates might be a useful material for fixation instead of metal plates and screws especially in mild to moderate degree of frontal bone fractures.

  15. Prevention of intraabdominal adhesions produced by polypropylene mesh.

    PubMed

    Besim, Hasan; Yalçin, Y; Hamamcí, O; Arslan, K; Soníşik, M; Korkmaz, A; Erdoğan, S

    2002-01-01

    Polypropylene mesh (PPM) is widely used in ventral hernia repair, however is also associated with visceral adhesions when the mesh is exposed to intraabdominal organs. In this study, a composite mesh [ePTFE (expanded polytetrafluoroehylene) + PPM] and sodium hyaluronate/carboxymethyl cellulose (NaHA/CMC) membrane laid under PPM are evaluated in terms of adhesion formation in a rat model of ventral hernia repair. In this experimental study, a 2 x 1 cm of peritoneum and underlying muscle defect was created at the right side of the anterior abdominal wall of 37 male Wistar albino rats. These defects were repaired with 2.5 x 2 cm PPM in group 1 (n = 13), with composite mesh in group 2 (n = 12) and with PPM+NaHA/CMC in group 3 (n = 12). Rats were sacrificed after 14 days and the prosthetic materials were examined for the calculation of surface area percentage covered by adhesions, for organ involvement in the adhesions and for histological evaluation. There was a reduction in the adhesion-covered area in group 2 and group 3. Organ involvement was predominantly seen in group 1. Neoperitoneum was perfect in group 2. Fibrosis and inflammation were higher in group 1. All groups showed adhesiogenic potential to some extent. This potential was maximum with PPM. Both ePTFE and NaHA/CMC displayed similar effects in preventing adhesion formation.

  16. Antibiotic Coating of Hernia Meshes: The Next Step Toward Preventing Mesh Infection.

    PubMed

    Majumder, Arnab; Neupane, Ruel; Novitsky, Yuri W

    2015-11-01

    Mesh bacterial colonization/infection remains a critical issue in complex ventral hernia repair. Despite the recent emergence of biologic meshes, current strategies to prevent and treat mesh infection are largely ineffective, often leading to device failure and subsequent explantation along with the associated costs and effect on patient welfare. Unacceptably high rates of morbidity and hernia recurrence following mesh infection highlight the need for innovation in the area of hernia repair for the complex patient. One recent strategy to address such shortcomings is local antibiosis in the form of polymer coatings applied to the mesh itself. Current literature regarding the use of antibiotic-coated hernia mesh is limited but does illustrate the ability of these devices to inhibit bacterial growth and prevent mesh infection in both in vitro and in vivo studies. Although there is a paucity of literature regarding long-term clinical efficacy, this provides opportunity for further inquiry into a promising new development to combat mesh infective complications.

  17. In vivo oxidative degradation of polypropylene pelvic mesh.

    PubMed

    Imel, Adam; Malmgren, Thomas; Dadmun, Mark; Gido, Samuel; Mays, Jimmy

    2015-12-01

    Commercial polypropylene pelvic mesh products were characterized in terms of their chemical compositions and molecular weight characteristics before and after implantation. These isotactic polypropylene mesh materials showed clear signs of oxidation by both Fourier-transform infrared spectroscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS). The oxidation was accompanied by a decrease in both weight-average and z-average molecular weights and narrowing of the polydispersity index relative to that of the non-implanted material. SEM revealed the formation of transverse cracking of the fibers which generally, but with some exceptions, increased with implantation time. Collectively these results, as well as the loss of flexibility and embrittlement of polypropylene upon implantation as reported by other workers, may only be explained by in vivo oxidative degradation of polypropylene. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Prospective repair of Ventral Hernia Working Group type 3 and 4 abdominal wall defects with condensed polytetrafluoroethylene (MotifMESH) mesh.

    PubMed

    Cheesborough, Jennifer E; Liu, Jing; Hsu, Derek; Dumanian, Gregory A

    2016-01-01

    Treatment of clean-contaminated and contaminated ventral hernia defects remains controversial. Newer prosthetic materials may play an important role in these patients. Ten patients with Ventral Hernia Working Group types 3 and 4 were prospectively enrolled and subsequently treated with direct supported repairs with condensed fenestrated polytetrafluoroethylene mesh. The primary outcome was hernia occurrence at 1 year after surgery. Secondary outcomes included surgical site infection, surgical site occurrence, medical complications, pain, and other patient-reported outcomes. There were no immediate postoperative infections and one minor postoperative hematoma treated in the office. One patient required delayed mesh removal 9 months after placement. Importantly, the mesh removal procedure was straightforward because of the material properties of the mesh. Of the 9 patients still with mesh, there were no hernia recurrences at the repair site with one full year of follow-up. Contaminated and clean-contaminated abdominal wall defects can be effectively and durably treated with condensed polytetrafluoroethylene mesh. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  19. Tensile Behaviour of Welded Wire Mesh and Hexagonal Metal Mesh for Ferrocement Application

    NASA Astrophysics Data System (ADS)

    Tanawade, A. G.; Modhera, C. D.

    2017-08-01

    Tension tests were conducted on welded mesh and hexagonal Metal mesh. Welded Mesh is available in the market in different sizes. The two types are analysed viz. Ø 2.3 mm and Ø 2.7 mm welded mesh, having opening size 31.75 mm × 31.75 mm and 25.4 mm × 25.4 mm respectively. Tensile strength test was performed on samples of welded mesh in three different orientations namely 0°, 30° and 45° degrees with the loading axis and hexagonal Metal mesh of Ø 0.7 mm, having opening 19.05 × 19.05 mm. Experimental tests were conducted on samples of these meshes. The objective of this study was to investigate the behaviour of the welded mesh and hexagonal Metal mesh. The result shows that the tension load carrying capacity of welded mesh of Ø 2.7 mm of 0° orientation is good as compared to Ø2.3 mm mesh and ductility of hexagonal Metal mesh is good in behaviour.

  20. Choosing corners of rectangles for mapped meshing

    SciTech Connect

    Mitchell, S.A.

    1996-12-16

    Consider mapping a regular i x j quadrilateral mesh of a rectangle onto a surface. The quality of the mapped mesh of the surface depends heavily on which vertices of the surface correspond to corners of the rectangle. The authors problem is, given an n-sided surface, chose as corners four vertices such that the surface resembles a rectangle with corners at those vertices. Note that n could be quite large, and the length and width of the rectangle, i and j, are not prespecified. In general, there is either a goal number or a prescribed number of mesh edges for each bounding curve of the surface. The goals affect the quality of the mesh, and the prescribed edges may make finding a feasible set of corners difficult. The algorithm need only work for surfaces that are roughly rectangular, particular those without large reflex angles, as otherwise an unstructured meshing algorithm is used instead. The authors report on the theory and implementation of algorithms for this problem. They also given an overview of a solution to a related problem called interval assignment: given a complex of surfaces sharing curves, globally assign the number of mesh edges or intervals for each curve such that it is possible to mesh each surface according to its prescribed quadrilateral meshing algorithm, and assigned and user-prescribed boundary mesh edges and corners. They also note a practical, constructive technique that relies on interval assignment that can generate a quadrilateral mesh of a complex of surfaces such that a compatible hexahedral mesh of the enclosed volume exists.

  1. A Nonlinear Dynamic Model and Free Vibration Analysis of Deployable Mesh Reflectors

    NASA Technical Reports Server (NTRS)

    Shi, H.; Yang, B.; Thomson, M.; Fang, H.

    2011-01-01

    This paper presents a dynamic model of deployable mesh reflectors, in which geometric and material nonlinearities of such a space structure are fully described. Then, by linearization around an equilibrium configuration of the reflector structure, a linearized model is obtained. With this linearized model, the natural frequencies and mode shapes of a reflector can be computed. The nonlinear dynamic model of deployable mesh reflectors is verified by using commercial finite element software in numerical simulation. As shall be seen, the proposed nonlinear model is useful for shape (surface) control of deployable mesh reflectors under thermal loads.

  2. An Engineering Solution for Using Coarse Meshes in the Simulation of Delamination with Cohesive Zone Models

    NASA Technical Reports Server (NTRS)

    Turon, Albert; Davila, Carlos G.; Camanho, Pedro P.; Costa, Josep

    2005-01-01

    This paper presents a methodology to determine the parameters used in the simulation of delamination in composite materials using decohesion finite elements. A closed-form expression is developed to define the stiffness of the cohesive layer. A novel procedure that allows the use of coarser meshes of decohesion elements in large-scale computations is proposed. The procedure ensures that the energy dissipated by the fracture process is correctly computed. It is shown that coarse-meshed models defined using the approach proposed here yield the same results as the models with finer meshes normally used in the simulation of fracture processes.

  3. Microstructure extraction and automatic quadrilateral mesh generation from rock images

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Xing, H.

    2011-12-01

    With the development of SEM and/or MRI based techniques, digital images are nowadays widely used to describe the complicated material structures. It is possible to automatically establish complex models in the format of images but such kind of digital models are very difficult and even impossible to use in the conventional numerical analysis, and thus an automatic quadrilateral mesh generator is developed. It has following steps: (1) Reading data from a image with material property/microstructure information and extracting points with the specified material property; (2) smoothing the extracted digital image (i.e. noise removal) for a better image according to the user's prescribed parameters/requirements for resolution; (3) extracting and generating boundaries to identify microstructures according to pixel colors; (4) fixing ambiguous connections; (5) smoothing the above boundaries and then discretising them into edges; (6) taking the generated edges as input line constraints for automatic quadrilateral mesh generation; (7) Output the mesh for the further numerical (e.g. FEM, FDM, FVM) analysis.

  4. Laparoscopic repair of incisional and ventral hernias with the new type of meshes: randomized control trial

    PubMed Central

    Grubnik, Aleksandra V.; Vorotyntseva, Kseniya O.

    2014-01-01

    Introduction Laparoscopic incisional and ventral hernia repair (LIVHR) was first reported by Le Blanc and Booth in 1993. Many studies are available in the literature that have shown that laparoscopic repair of incisional and ventral hernia is preferred over open repair because of lower recurrence rates (less than 10%), less wound morbidity, less pain, and early return to work. Aim To identify the long-term outcomes between the different types of meshes and two techniques of mesh fixation, i.e., tacks (method Double crown) and transfascial polypropylene sutures. Material and methods A total of 92 patients underwent LIVHR at our department between January 2009 and August 2012. The hernias were umbilical in 26 patients, paraumbilical in 15 patients and incisional in 51 patients. All patients admitted for LIVHR were randomized to either group I (tacker fixation of ePTFE meshes) or group II (suture fixation of meshes with nitinol frame) using computer-generated random numbers with block randomization and sealed envelopes for concealed allocation. Results The mean mesh fixation time was significantly higher in the tacker fixation group (117 ±15 min vs. 72 ±6 min, p < 0.01). There were no conversions in either group. The median postoperative hospital stay was 3.5 ±1.5 days. All patients were followed up at 1, 3, 6, 12 and every 6 months thereafter postoperatively. There were 5 recurrences in the study population. In group I there were 4 patients with recurrence, and only 1 patient in the group with meshes with a nitinol frame. Conclusions Meshes of the new generation with a nitinol framework can significantly improve laparoscopic ventral hernia repair. The fixation of these meshes is very simple using 3–4 transfascial sutures. The absence of shrinkage of these meshes makes the probability of recurrence minimal. Absence of tackers allows postoperative pain to be minimized. We consider that these new meshes can significantly improve laparoscopic ventral hernia repair

  5. Measured and predicted root-mean-square errors in square and triangular antenna mesh facets

    NASA Technical Reports Server (NTRS)

    Fichter, W. B.

    1989-01-01

    Deflection shapes of square and equilateral triangular facets of two tricot-knit, gold plated molybdenum wire mesh antenna materials were measured and compared, on the basis of root mean square (rms) differences, with deflection shapes predicted by linear membrane theory, for several cases of biaxial mesh tension. The two mesh materials contained approximately 10 and 16 holes per linear inch, measured diagonally with respect to the course and wale directions. The deflection measurement system employed a non-contact eddy current proximity probe and an electromagnetic distance sensing probe in conjunction with a precision optical level. Despite experimental uncertainties, rms differences between measured and predicted deflection shapes suggest the following conclusions: that replacing flat antenna facets with facets conforming to parabolically curved structural members yields smaller rms surface error; that potential accuracy gains are greater for equilateral triangular facets than for square facets; and that linear membrane theory can be a useful tool in the design of tricot knit wire mesh antennas.

  6. Elongated silica nanoparticles with a mesh phase mesopore structure by fluorosurfactant templating.

    PubMed

    Tan, Bing; Dozier, Alan; Lehmler, Hans-Joachim; Knutson, Barbara L; Rankin, Stephen E

    2004-08-17

    Mesoporous silica materials with pore structures such as 2D hexagonal close packed, bicontinuous cubic, lamellar, sponge, wormhole-like, and rectangular have been made by using surfactant templating sol-gel processes. However, there are still some "intermediate" phases, in particular mesh phases, that are formed by surfactants but which have not been made into analogous silica pore structures. Here, we describe the one-step synthesis of mesoporous silica with a mesh phase pore structure. The cationic fluorinated surfactant 1,1,2,2-tetrahydroperfluorodecylpyridinium chloride (HFDePC) is used as the template. Like many fluorinated surfactants, HFDePC forms intermediate phases in water (including a mesh phase) over a wider range of compositions than do hydrocarbon surfactants. The materials produced by this technique are novel elongated particles in which the layers of the mesh phase are oriented orthogonal to the main axis of the particles.

  7. Nanofibrous biomimetic mesh can be used for pelvic reconstructive surgery: A randomized study.

    PubMed

    Ding, Jing; Deng, Mou; Song, Xiao-Chen; Chen, Chun; Lai, Kui-Lin; Wang, Guo-Shuai; Yuan, Yu-Yu; Xu, Tao; Zhu, Lan

    2016-08-01

    Implantation of nonabsorbable polypropylene (PP) mesh in the vagina is the main surgical treatment for pelvic organ prolapse (POP); however, clinical outcomes remain controversial and far from satisfactory. In particular, reducing the exposure or erosion of vaginal implants to obtain improved functional reconstruction is challenging. There is an urgent need for the development of new materials and/or products for POP treatment. A nanofibrous biomimetic mesh was recently developed to address this issue. In this study, the basic properties of the newly developed mesh, including structural characteristics, mechanical properties, biological response of human umbilical cord mesenchymal stem cells in vitro, and tissue regeneration and biocompatibility in vivo, were evaluated and compared with those of Gynemesh™PS. Scanning electron microscopy and uniaxial tensile methods were used to evaluate microstructure and mechanical properties, respectively. Mesenchymal stem cell growth on the meshes was observed by fluorescence microscopy to visualize the expression of enhanced red fluorescent protein. Twenty-four mature female Sprague Dawley rats were randomly assigned to two groups: group 1 (nanofibrous biomimetic mesh, Medprin, Germany, n=12) and group 2 (Gynemesh(TM)PS, Ethicon, USA; n=12). The posterior vaginal wall was incised from the introitus, and the mesh was then implanted. Three implants of each type were tested for 1, 4, 8 and 12 weeks. Connective tissue organization, inflammation, vascularization, and regenerated tissue were histologically assessed. The nanofibrous biomimetic mesh is a relatively heavy material and exhibited lower porosity than Gynemesh(TM)PS. The new mesh was stiffer than Gynemesh(TM)PS (p<0.001) but supported human umbilical cord mesenchymal stem cell attachment. Erosion of the grafts did not occur in any animal. The nanofibrous biomimetic mesh was encapsulated by a thicker layer of connective tissue and was associated with significantly greater

  8. Adaptive mesh refinement in titanium

    SciTech Connect

    Colella, Phillip; Wen, Tong

    2005-01-21

    In this paper, we evaluate Titanium's usability as a high-level parallel programming language through a case study, where we implement a subset of Chombo's functionality in Titanium. Chombo is a software package applying the Adaptive Mesh Refinement methodology to numerical Partial Differential Equations at the production level. In Chombo, the library approach is used to parallel programming (C++ and Fortran, with MPI), whereas Titanium is a Java dialect designed for high-performance scientific computing. The performance of our implementation is studied and compared with that of Chombo in solving Poisson's equation based on two grid configurations from a real application. Also provided are the counts of lines of code from both sides.

  9. Deployable modular mesh antenna - Concept and feasibility

    NASA Astrophysics Data System (ADS)

    Mitsugi, Jin; Yasaka, Tetsuo

    The feasibility of a 10m aperture deployable modular mesh antenna is evaluated by integrating the results of a statistical surface accuracy estimation and of surface shape adjustment experiments. It has been clarified that by combining seven 4m aperture modules, a 10m aperture deployable modular mesh antenna can be constructed, preserving the surface accuracy that is applicable to C band mission.

  10. 7th International Meshing Roundtable '98

    SciTech Connect

    Eldred, T.J.

    1998-10-01

    The goal of the 7th International Meshing Roundtable is to bring together researchers and developers from industry, academia, and government labs in a stimulating, open environment for the exchange of technical information related to the meshing process. In the past, the Roundtable has enjoyed significant participation from each of these groups from a wide variety of countries.

  11. Structured mesh generation with smoothness controls

    USDA-ARS?s Scientific Manuscript database

    In geometrically complex domains, the RL (Ryskin and Leal) orthogonal mesh generation system may cause mesh distortion and overlapping problems when using the “weak constraint” method with specified boundary point distribution for all boundaries. To resolve these problems, an improved RL system with...

  12. Exploring the basic science of prolapse meshes

    PubMed Central

    Liang, Rui; Knight, Katrina; Abramowitch, Steve; Moalli, Pamela A.

    2016-01-01

    Purpose of review Polypropylene mesh has been widely used in the surgical repair of pelvic organ prolapse. However, low but persistent rates of complications related to mesh, most commonly mesh exposure and pain, have hampered its use. Complications are higher following transvaginal implantation prompting the Food and Drug Administration to release two public health notifications warning of complications associated with transvaginal mesh use (PHN 2008 and 2011) and to upclassify transvaginal prolapse meshes from Class II to Class III devices. Although there have been numerous studies to determine the incidence and management of mesh complications as well as impact on quality of life, few studies have focused on mechanisms. Recent findings In this review, we summarize the current understanding of how mesh textile properties and mechanical behavior impact vaginal structure and function, as well as the local immune response. We also discuss how mesh properties change in response to loading. Summary We highlight a few areas of current and future research to emphasize collaborative strategies that incorporate basic science research to improve patient outcomes. PMID:27517341

  13. Mesh refinement strategy for optimal control problems

    NASA Astrophysics Data System (ADS)

    Paiva, L. T.; Fontes, F. A. C. C.

    2013-10-01

    Direct methods are becoming the most used technique to solve nonlinear optimal control problems. Regular time meshes having equidistant spacing are frequently used. However, in some cases these meshes cannot cope accurately with nonlinear behavior. One way to improve the solution is to select a new mesh with a greater number of nodes. Another way, involves adaptive mesh refinement. In this case, the mesh nodes have non equidistant spacing which allow a non uniform nodes collocation. In the method presented in this paper, a time mesh refinement strategy based on the local error is developed. After computing a solution in a coarse mesh, the local error is evaluated, which gives information about the subintervals of time domain where refinement is needed. This procedure is repeated until the local error reaches a user-specified threshold. The technique is applied to solve the car-like vehicle problem aiming minimum consumption. The approach developed in this paper leads to results with greater accuracy and yet with lower overall computational time as compared to using a time meshes having equidistant spacing.

  14. Robust diamond meshes with unique wettability properties.

    PubMed

    Yang, Yizhou; Li, Hongdong; Cheng, Shaoheng; Zou, Guangtian; Wang, Chuanxi; Lin, Quan

    2014-03-18

    Robust diamond meshes with excellent superhydrophobic and superoleophilic properties have been fabricated. Superhydrophobicity is observed for water with varying pH from 1 to 14 with good recyclability. Reversible superhydrophobicity and hydrophilicity can be easily controlled. The diamond meshes show highly efficient water-oil separation and water pH droplet transference.

  15. Exploring the basic science of prolapse meshes.

    PubMed

    Liang, Rui; Knight, Katrina; Abramowitch, Steve; Moalli, Pamela A

    2016-10-01

    Polypropylene mesh has been widely used in the surgical repair of pelvic organ prolapse. However, low but persistent rates of complications related to mesh, most commonly mesh exposure and pain, have hampered its use. Complications are higher following transvaginal implantation prompting the Food and Drug Administration to release two public health notifications warning of complications associated with transvaginal mesh use (PHN 2008 and 2011) and to upclassify transvaginal prolapse meshes from Class II to Class III devices. Although there have been numerous studies to determine the incidence and management of mesh complications as well as impact on quality of life, few studies have focused on mechanisms. In this review, we summarize the current understanding of how mesh textile properties and mechanical behavior impact vaginal structure and function, as well as the local immune response. We also discuss how mesh properties change in response to loading. We highlight a few areas of current and future research to emphasize collaborative strategies that incorporate basic science research to improve patient outcomes.

  16. 50 CFR 300.110 - Mesh size.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... either with a manual force or using a weight or dynamometer, until it is stopped at the tapering edges by... without using a weight or dynamometer. The mesh size of the net will then be determined in accordance with... for the determination of the mesh size and the net will be remeasured. (A) A weight or dynamometer...

  17. Matrix computations on mesh arrays

    SciTech Connect

    Moreno, J.H.

    1989-01-01

    This dissertation addresses the systematic derivation of mesh arrays for matrix computations, in particular realizing the algorithm-specific arrays and mapping algorithms onto class-specific arrays. A data-dependency graph-based transformational method is proposed in a design frame work consisting of two stages, namely algorithm regularization and derivation of arrays. The first stage derives the fully-parallel data-dependency graph (FPG) of an algorithm and transforms this graph into a three-dimensional one with unidirectional nearest-neighbor dependencies (a multi-mesh graph MMG). The second stage transforms the MMG into a two-dimensional G-graph, which is realized as an algorithm-specific array or mapped onto a class-specific array. This stage allows the incorporation of implementation restrictions and the evaluation of tradeoffs in properties of cells, as well as the derivation of arrays for fixed-size data and partitioned problems, while performing optimization of specific performance/cost measures. The proposed method is formalized by presenting a sufficient set of transformations and demonstrating the equivalence of graphs obtained from those transformations. Moreover, it is demonstrated that the MMG representation is always possible, due to the characteristics of the operators. The method has been applied to a collection of matrix algorithms, including matrix multiplication, convolution, matrix decompositions, transitive closure, the Faddeev algorithm, and BBA{sup {minus}1}. The examples show that, in addition to the features listed earlier, this method is easy to apply. Moreover, the method is compared with other techniques, concluding that it is advantageous because it meets evaluation criteria and produces more efficient arrays.

  18. Laparoscopic Inguinal Hernia Repair With a Novel Hernia Mesh Incorporating a Nitinol Alloy Frame Compared With a Standard Lightweight Polypropylene Mesh.

    PubMed

    Bower, Curtis; Hazey, Jeffrey W; Jones, Edward L; Perry, Kyle A; Davenport, Daniel L; Roth, J Scott

    2015-10-01

    Numerous mesh materials are available for laparoscopic inguinal hernia repair. The role of fixation of mesh in laparoscopic inguinal hernia repair remains controversial. Mesh materials have been engineered to anatomically conform to the pelvis to potentially reduce or eliminate the need for fixation. This study evaluates the outcomes of laparoscopic inguinal hernia utilizing a device consisting of a lightweight polypropylene mesh with a nitinol frame (Rebound HRD) compared with repair with lightweight polypropylene mesh with permanent tack fixation. A prospective randomized trial evaluating the outcomes of laparoscopic inguinal hernia repair with a lightweight polypropylene mesh with a nitinol frame (N-LWM) compared with standard lightweight polypropylene mesh (LWM) was conducted. Randomization was performed at an N-LWM to LWM ratio of 2:1. Repairs were standardized to a laparoscopic extraperitoneal approach without fixation for N-LWM and titanium tack fixation for LWM repairs. Follow-up assessments were performed at 7 days, 6 months, and 1 year. Outcome measures include visual analog pain scale (VAS), Short Form 36 (SF-36), Carolinas Comfort Scale (CCS), operative details, complications, and recurrences. There were 47 patients that underwent laparoscopic inguinal hernia repair and adhered to study protocol (31 N-LWM, 16 LWM). The groups did not differ significantly in age, body mass index, ethnicity, or employment. The N-LWM group had bilateral mesh placed in 51.6% and LWM 43.8% (P = .76). Operative duration was similar, 59.6 ± 23.1 minutes for LWM and 62.4 ± 26.7 minutes for N-LWM (P = .705) as was mesh handling time was 5.4 ± 3.1 minutes LWM versus 7.3 ± 3.9 minutes N-LWM (P = .053). VAS, CCS, and SF-36 survey results were similar between groups. There was one recurrence (0.03%) in the N-LWM group. Nitinol-framed lightweight polypropylene mesh may be safely used during laparoscopic inguinal hernia repair with outcomes comparable to LWM at 1 year. N-LWM does

  19. Bonding bases coated with porous metal powder: a comparison with foil mesh.

    PubMed

    Hanson, G H; Gibbon, W M; Shimizu, H

    1983-01-01

    This study was undertaken to test the theory that a special porous metal powder coating can provide better mechanical keying than mesh by virtue of its greater surface area and intricate microscopic void network. Identical brackets were laser-welded to an equal number of conventional foil-mesh and powder-coated bases of identical shape and peripheral dimensions. The experimental base material was found to provide significantly greater tensile bond strength at the metal/adhesive interface.

  20. Mesh deformation based on artificial neural networks

    NASA Astrophysics Data System (ADS)

    Stadler, Domen; Kosel, Franc; Čelič, Damjan; Lipej, Andrej

    2011-09-01

    In the article a new mesh deformation algorithm based on artificial neural networks is introduced. This method is a point-to-point method, meaning that it does not use connectivity information for calculation of the mesh deformation. Two already known point-to-point methods, based on interpolation techniques, are also presented. In contrast to the two known interpolation methods, the new method does not require a summation over all boundary nodes for one displacement calculation. The consequence of this fact is a shorter computational time of mesh deformation, which is proven by different deformation tests. The quality of the deformed meshes with all three deformation methods was also compared. Finally, the generated and the deformed three-dimensional meshes were used in the computational fluid dynamics numerical analysis of a Francis water turbine. A comparison of the analysis results was made to prove the applicability of the new method in every day computation.

  1. A comparison of tetrahedral mesh improvement techniques

    SciTech Connect

    Freitag, L.A.; Ollivier-Gooch, C.

    1996-12-01

    Automatic mesh generation and adaptive refinement methods for complex three-dimensional domains have proven to be very successful tools for the efficient solution of complex applications problems. These methods can, however, produce poorly shaped elements that cause the numerical solution to be less accurate and more difficult to compute. Fortunately, the shape of the elements can be improved through several mechanisms, including face-swapping techniques that change local connectivity and optimization-based mesh smoothing methods that adjust grid point location. The authors consider several criteria for each of these two methods and compare the quality of several meshes obtained by using different combinations of swapping and smoothing. Computational experiments show that swapping is critical to the improvement of general mesh quality and that optimization-based smoothing is highly effective in eliminating very small and very large angles. The highest quality meshes are obtained by using a combination of swapping and smoothing techniques.

  2. Update on Development of Mesh Generation Algorithms in MeshKit

    SciTech Connect

    Jain, Rajeev; Vanderzee, Evan; Mahadevan, Vijay

    2015-09-30

    MeshKit uses a graph-based design for coding all its meshing algorithms, which includes the Reactor Geometry (and mesh) Generation (RGG) algorithms. This report highlights the developmental updates of all the algorithms, results and future work. Parallel versions of algorithms, documentation and performance results are reported. RGG GUI design was updated to incorporate new features requested by the users; boundary layer generation and parallel RGG support were added to the GUI. Key contributions to the release, upgrade and maintenance of other SIGMA1 libraries (CGM and MOAB) were made. Several fundamental meshing algorithms for creating a robust parallel meshing pipeline in MeshKit are under development. Results and current status of automated, open-source and high quality nuclear reactor assembly mesh generation algorithms such as trimesher, quadmesher, interval matching and multi-sweeper are reported.

  3. Automatic Mesh Generation of Hybrid Mesh on Valves in Multiple Positions in Feedline Systems

    NASA Technical Reports Server (NTRS)

    Ross, Douglass H.; Ito, Yasushi; Dorothy, Fredric W.; Shih, Alan M.; Peugeot, John

    2010-01-01

    Fluid flow simulations through a valve often require evaluation of the valve in multiple opening positions. A mesh has to be generated for the valve for each position and compounding. The problem is the fact that the valve is typically part of a larger feedline system. In this paper, we propose to develop a system to create meshes for feedline systems with parametrically controlled valve openings. Herein we outline two approaches to generate the meshes for a valve in a feedline system at multiple positions. There are two issues that must be addressed. The first is the creation of the mesh on the valve for multiple positions. The second is the generation of the mesh for the total feedline system including the valve. For generation of the mesh on the valve, we will describe the use of topology matching and mesh generation parameter transfer. For generation of the total feedline system, we will describe two solutions that we have implemented. In both cases the valve is treated as a component in the feedline system. In the first method the geometry of the valve in the feedline system is replaced with a valve at a different opening position. Geometry is created to connect the valve to the feedline system. Then topology for the valve is created and the portion of the topology for the valve is topology matched to the standard valve in a different position. The mesh generation parameters are transferred and then the volume mesh for the whole feedline system is generated. The second method enables the user to generate the volume mesh on the valve in multiple open positions external to the feedline system, to insert it into the volume mesh of the feedline system, and to reduce the amount of computer time required for mesh generation because only two small volume meshes connecting the valve to the feedline mesh need to be updated.

  4. Sonomorphological evaluation of polypropylene mesh implants after vaginal mesh repair in women with cystocele or rectocele.

    PubMed

    Tunn, R; Picot, A; Marschke, J; Gauruder-Burmester, A

    2007-04-01

    To investigate whether the sonographically measured size of the mesh implant in women who had undergone vaginal polypropylene mesh repair 6 weeks previously correlates with the original size of the mesh and whether the mesh ensures complete support of the anterior or posterior compartment. Forty postmenopausal women with anterior or posterior vaginal wall prolapse and sonographically proven cystocele (n = 20) or rectocele (n = 20) were evaluated preoperatively and 6 weeks after vaginal mesh repair. Introital ultrasound was performed to identify the polypropylene mesh and measure its distal to proximal length and configuration as well as its thickness. The initial mesh length was compared with that measured by ultrasound 6 weeks postoperatively. Vaginal length was measured pre- and postoperatively. The mean +/- SD age of the women was 68 +/- 7 years. The 20 women with cystocele underwent repair by means of anterior transobturator mesh implantation; the initial mesh length was 6.8 +/- 1.1 cm versus 2.9 +/- 0.6 cm postoperatively. The 20 women with rectocele underwent repair by posterior transischioanal mesh implantation; the initial mesh length was 9.9 +/- 0.8 cm versus 3.3 +/- 0.5 cm postoperatively. The mesh supported 43.4% of the length of the anterior vaginal wall and this value was 53.7% for the posterior wall (P = 0.016). Sonography is recommended for postoperative evaluation of the anterior and posterior mesh positions after prolapse surgery. There is a considerable discrepancy between the implanted mesh size and the length measured 6 weeks later by postoperative ultrasound. Published by John Wiley & Sons, Ltd. Copyright (c) 2007 ISUOG.

  5. Mesh-based phase contrast Fourier transform imaging

    NASA Astrophysics Data System (ADS)

    Tahir, Sajjad; Bashir, Sajid; MacDonald, C. A.; Petruccelli, Jonathan C.

    2017-04-01

    Traditional x-ray radiography is limited by low attenuation contrast in materials of low electron density. Phase contrast imaging offers the potential to improve the contrast between such materials, but due to the requirements on the spatial coherence of the x-ray beam, practical implementation of such systems with tabletop (i.e. non-synchrotron) sources has been limited. One phase imaging technique employs multiple fine-pitched gratings. However, the strict manufacturing tolerances and precise alignment requirements have limited the widespread adoption of grating-based techniques. In this work, we have investigated a recently developed technique that utilizes a single grid of much coarser pitch. Our system consisted of a low power 100 μm spot Mo source, a CCD with 22 μm pixel pitch, and either a focused mammography linear grid or a stainless steel woven mesh. Phase is extracted from a single image by windowing and comparing data localized about harmonics of the mesh in the Fourier domain. The effects on the diffraction phase contrast and scattering amplitude images of varying grid types and periods, and of varying the width of the window function used to separate the harmonics were investigated. Using the wire mesh, derivatives of the phase along two orthogonal directions were obtained and combined to form improved phase contrast images.

  6. MESH2D GRID GENERATOR DESIGN AND USE

    SciTech Connect

    Flach, G.; Smith, F.

    2012-01-20

    Mesh2d is a Fortran90 program designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j{sub 0}) coordinates along index i are permitted to undulate or otherwise vary. Mesh2d also assigns an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations. The overall mesh is constructed from grid zones that are typically then subdivided into a collection of smaller grid cells. The grid zones usually correspond to distinct materials or larger-scale geometric shapes. The structured grid zones are identified through uppercase indices (I,J). Subdivision of zonal regions into grid cells can be done uniformly, or nonuniformly using either a polynomial or geometric skewing algorithm. Grid cells may be concentrated backward, forward, or toward both ends. Figure 1 illustrates the above concepts in the context of a simple four zone grid.

  7. Non-conforming hybrid meshes for efficient 2-D wave propagation using the Discontinuous Galerkin Method

    NASA Astrophysics Data System (ADS)

    Hermann, Verena; Käser, Martin; Castro, Cristóbal E.

    2011-02-01

    We present a Discontinuous Galerkin finite element method using a high-order time integration technique for seismic wave propagation modelling on non-conforming hybrid meshes in two space dimensions. The scheme can be formulated to achieve the same approximation order in space and time and avoids numerical artefacts due to non-conforming mesh transitions or the change of the element type. A point-wise Gaussian integration along partially overlapping edges of adjacent elements is used to preserve the schemes accuracy while providing a higher flexibility in the problem-adapted mesh generation process. We describe the domain decomposition strategy of the parallel implementation and validate the performance of the new scheme by numerical convergence test and experiments with comparisons to independent reference solutions. The advantage of non-conforming hybrid meshes is the possibility to choose the mesh spacing proportional to the seismic velocity structure, which allows for simple refinement or coarsening methods even for regular quadrilateral meshes. For particular problems of strong material contrasts and geometrically thin structures, the scheme reduces the computational cost in the sense of memory and run-time requirements. The presented results promise to achieve a similar behaviour for an extension to three space dimensions where the coupling of tetrahedral and hexahedral elements necessitates non-conforming mesh transitions to avoid linking elements in form of pyramids.

  8. Applications of quadrilateral and quadrilateral-prism mesh generation in overland and subsurface simulations

    NASA Astrophysics Data System (ADS)

    Sun, Lu; Yeh, Gour-Tsyh; Zhao, Guoqun

    2017-05-01

    This paper developed an automatic mesh generator used for simulating real-world problems of hydrological cycles, fluid flow, salinity and thermal transport, sediment and water quality transport, etc. The 2-D overland area was discretized with quadrilaterals based on conformal mapping technique. A position-percent interpolation equation was established to determine nodal vertical-coordinates and match boundaries. For 3-D simulations of subsurface zones, an additional mesh generation method was proposed to create quadrilaterals for filling the empty regions along river reaches and around junctions with storage, ponds or lakes. In order to deal with special storage region with an odd number of boundary nodes, an additional triangle was inserted. Five topological optimization templates were proposed to improve the quality of degenerated elements. This paper proposed the basic algorithms to generate quadrilateral-prism meshes through stretching the quadrilateral mesh along vertical directions based on material domains. Aiming at four types of fractures, corresponding extraction methods were presented to preserve geometric features. In order to accommodate the need for overland and subsurface simulations, 1-D/2-D/3-D correspondence was established between rivers, junctions, ponds, lakes, control structures and finite element meshes. Finally, several realistic hydrologic and geologic examples for meshing multi-domain areas were provided to demonstrate the accuracy and effectiveness of the mesh generator developed in this paper.

  9. Constrained CVT Meshes and a Comparison of Triangular Mesh Generators

    SciTech Connect

    Nguyen, Hoa; Burkardt, John; Gunzburger, Max; Ju, Lili; Saka, Yuki

    2009-01-01

    Mesh generation in regions in Euclidean space is a central task in computational science, and especially for commonly used numerical methods for the solution of partial differential equations, e.g., finite element and finite volume methods. We focus on the uniform Delaunay triangulation of planar regions and, in particular, on how one selects the positions of the vertices of the triangulation. We discuss a recently developed method, based on the centroidal Voronoi tessellation (CVT) concept, for effecting such triangulations and present two algorithms, including one new one, for CVT-based grid generation. We also compare several methods, including CVT-based methods, for triangulating planar domains. To this end, we define several quantitative measures of the quality of uniform grids. We then generate triangulations of several planar regions, including some having complexities that are representative of what one may encounter in practice. We subject the resulting grids to visual and quantitative comparisons and conclude that all the methods considered produce high-quality uniform grids and that the CVT-based grids are at least as good as any of the others.

  10. Method of modifying a volume mesh using sheet extraction

    DOEpatents

    Borden, Michael J.; Shepherd, Jason F.

    2007-02-20

    A method and machine-readable medium provide a technique to modify a hexahedral finite element volume mesh using dual generation and sheet extraction. After generating a dual of a volume stack (mesh), a predetermined algorithm may be followed to modify the volume mesh of hexahedral elements. The predetermined algorithm may include the steps of determining a sheet of hexahedral mesh elements, generating nodes for merging, and merging the nodes to delete the sheet of hexahedral mesh elements and modify the volume mesh.

  11. Moderation and diffusion of positrons in tungsten meshes and foils

    NASA Astrophysics Data System (ADS)

    Williams, A. I.; Murtagh, D. J.; Fayer, S. E.; Andersen, S. L.; Chevallier, J.; Kövér, Á.; Van Reeth, P.; Humberston, J. W.; Laricchia, G.

    2015-09-01

    The efficiency of tungsten meshes and thin foils for moderation of fast positrons from 22Na has been investigated in transmission geometry and a fair agreement has been found with previous experimental results where directly comparable. For foils, the dependence on material thickness is found to be similar to the prediction of the Vehanen-Mäkinen diffusion model; however, the magnitude is 5-10 times lower. A broad consensus is observed between experiment and the results of a three-dimensional model developed in this work. For a given thickness, meshes are found to be generally better than foils by around a factor of 10 with a maximum efficiency ( ˜10-3) comparable to that achieved with thin single crystal foils, in accord with previous measurements and the results of the present model.

  12. Preclinical Bioassay of a Polypropylene Mesh for Hernia Repair Pretreated with Antibacterial Solutions of Chlorhexidine and Allicin: An In Vivo Study.

    PubMed

    Pérez-Köhler, Bárbara; García-Moreno, Francisca; Brune, Thierry; Pascual, Gemma; Bellón, Juan Manuel

    2015-01-01

    Prosthetic mesh infection constitutes one of the major complications following hernia repair. Antimicrobial, non-antibiotic biomaterials have the potential to reduce bacterial adhesion to the mesh surface and adjacent tissues while avoiding the development of novel antibiotic resistance. This study assesses the efficacy of presoaking reticular polypropylene meshes in chlorhexidine or a chlorhexidine and allicin combination (a natural antibacterial agent) for preventing bacterial infection in a short-time hernia-repair rabbit model. Partial hernia defects (5 x 2 cm) were created on the lateral right side of the abdominal wall of New Zealand White rabbits (n = 21). The defects were inoculated with 0.5 mL of a 106 CFU/mL Staphylococcus aureus ATCC25923 strain and repaired with a DualMesh Plus antimicrobial mesh or a Surgipro mesh presoaked in either chlorhexidine (0.05%) or allicin-chlorhexidine (900 μg/mL-0.05%). Fourteen days post-implant, mesh contraction was measured and tissue specimens were harvested to evaluate bacterial adhesion to the implant surface (via sonication, S. aureus immunolabeling), host-tissue incorporation (via staining, scanning electron microscopy) and macrophage response (via RAM-11 immunolabeling). The polypropylene mesh showed improved tissue integration relative to the DualMesh Plus. Both the DualMesh Plus and the chlorhexidine-soaked polypropylene meshes exhibited high bacterial clearance, with the latter material showing lower bacterial yields. The implants from the allicin-chlorhexidine group displayed a neoformed tissue containing differently sized abscesses and living bacteria, as well as a diminished macrophage response. The allicin-chlorhexidine coated implants exhibited the highest contraction. The presoaking of reticular polypropylene materials with a low concentration of chlorhexidine provides the mesh with antibacterial activity without disrupting tissue integration. Due to the similarities found with the antimicrobial DualMesh

  13. Mesh herniorrhaphy during elective colorectal surgery.

    PubMed

    Stringer, R A; Salameh, J R

    2005-03-01

    The management of large ventral hernias in patients undergoing elective colorectal surgery is controversial considering the reluctance to use a mesh during a clean-contaminated case. We retrospectively reviewed the charts of all patients having undergone at our institution any colorectal surgery along with ventral hernia repair with mesh as identified by the ICD-9 codes between 1997 and 2003. Three patients underwent incisional mesh herniorrhaphy along with elective colorectal surgery, including a right hemicolectomy, a colostomy closure, and a diverting colostomy. Hernia size varied between 330 and 1,243 cm(2). All hernias were repaired using polypropylene mesh in an onlay fashion. Average operative time was 199 min. Two patients developed postoperative wound infection, one of them requiring incision and drainage of a part of the wound. One patient developed skin necrosis of the lower aspect of his incision requiring skin excision and open wound. All open wounds granulated well and healed by secondary intention despite presence of exposed mesh. Therefore prosthetic ventral hernia repair using polypropylene mesh can be performed concomitant to elective colorectal operations, thus avoiding another laparotomy. The incidence of wound complications is, however, high but does not usually require mesh excision.

  14. Synthetic vaginal mesh for pelvic organ prolapse.

    PubMed

    Iglesia, Cheryl B

    2011-10-01

    The purpose of this review is to summarize recently published comparative trials on synthetic vaginal mesh versus traditional native tissue repairs for pelvic organ prolapse. Although studies suggest benefit from the use of synthetic vaginal mesh for anterior compartment prolapse, data are limited on the use of mesh for posterior and apical prolapse when compared with native tissue repair. The benefits of a more durable repair must be weighed against risks such as the development of de-novo stress incontinence, visceral injury, dyspareunia, pelvic pain and mesh contraction, exposure and extrusion requiring reoperation. Furthermore, the success rates of native tissue repairs are higher than previously considered using updated validated composite outcomes that incorporate both subjective relief of bulge and objective cure defined as prolapse above the hymenal ring. Surgeons placing synthetic mesh for pelvic organ prolapse should counsel patients regarding the potential benefits, risks, and alternatives including native tissue repairs. Level 1 evidence suggests anterior synthetic mesh may be superior to anterior repair. Expert opinion suggests potential benefit of vaginal mesh for recurrences, hysteropexy, and advanced prolapse in patients with medical co-morbidities precluding invasive open and endoscopic sacrocolpopexies; however, comparative clinical trials with long-term data are needed. (C) 2011 Lippincott Williams & Wilkins, Inc.

  15. Evolution of the mandibular mesh implant.

    PubMed

    Salyer, K E; Johns, D F; Holmes, R E; Layton, J G

    1977-07-01

    Between 1960 and 1972, the Dallas Veterans Administration Hospital Maxillofacial Research Laboratory developed and made over 150 cast-mesh implants. Successive designs were ovoid, circular, and double-lumened in cross section to improve implant strength, surface area for bioattachment, and adjustability. Sleeves, collars, and bows were employed in the assembly of these implants, with an acrylic condylar head attached when indicated. In 1972, our laboratory developed a mandibular mesh tray, cast in one piece on a single sprue, with preservation of the vertically adjustable ramus. Stainless steel replaced Vitallium because of its greater malleability. Essentially, a lost-wax technique is used to cast the mesh tray. The model of a mandibular segment is duplicated as a refractory model. Mesh wax, made in our own custom-made die, is adapted to the refractory model. The unit is then sprued and invested. The wax is fired our of the mold in a gas furnace. Casting is done by the transferral of molten stainless steel from the crucible to the mold by centrifugal force in an electro-induction casting machine. Other mesh implants that have been developed are made from wire mesh, Dacron mesh, cast Ticonium, and hydroformed titanium.

  16. Efficient texture mapping by adaptive mesh division in mesh-based computer generated hologram.

    PubMed

    Ji, Yeong-Min; Yeom, Hanju-; Park, Jae-Hyeung

    2016-11-28

    We propose a method that achieves efficient texture mapping in fully-analytic computer generated holograms based on triangular meshes. In computer graphics, the texture mapping is commonly used to represent the details of objects without increasing the number of the triangular meshes. In fully-analytic triangular-mesh-based computer generated holograms, however, those methods cannot be directly applied because each mesh cannot have arbitrary amplitude distribution inside the triangular mesh area in order to keep the analytic representation. In this paper, we propose an efficient texture mapping method for fully-analytic mesh-based computer generated hologram. The proposed method uses an adaptive triangular mesh division to minimize the increase of the number of the triangular meshes for the given texture image data. The geometrical similarity relationship between the original triangular mesh and the divided one is also exploited to obtain the angular spectrum of the divided mesh from pre-calculated data for the original one. As a result, the proposed method enables to obtain the computer generated hologram of high details with much smaller computation time in comparison with the brute-force approach. The feasibility of the proposed method is confirmed by simulations and optical experiments.

  17. Mesh optimization for microbial fuel cell cathodes constructed around stainless steel mesh current collectors

    NASA Astrophysics Data System (ADS)

    Zhang, Fang; Merrill, Matthew D.; Tokash, Justin C.; Saito, Tomonori; Cheng, Shaoan; Hickner, Michael A.; Logan, Bruce E.

    Mesh current collectors made of stainless steel (SS) can be integrated into microbial fuel cell (MFC) cathodes constructed of a reactive carbon black and Pt catalyst mixture and a poly(dimethylsiloxane) (PDMS) diffusion layer. It is shown here that the mesh properties of these cathodes can significantly affect performance. Cathodes made from the coarsest mesh (30-mesh) achieved the highest maximum power of 1616 ± 25 mW m -2 (normalized to cathode projected surface area; 47.1 ± 0.7 W m -3 based on liquid volume), while the finest mesh (120-mesh) had the lowest power density (599 ± 57 mW m -2). Electrochemical impedance spectroscopy showed that charge transfer and diffusion resistances decreased with increasing mesh opening size. In MFC tests, the cathode performance was primarily limited by reaction kinetics, and not mass transfer. Oxygen permeability increased with mesh opening size, accounting for the decreased diffusion resistance. At higher current densities, diffusion became a limiting factor, especially for fine mesh with low oxygen transfer coefficients. These results demonstrate the critical nature of the mesh size used for constructing MFC cathodes.

  18. Mixing materials within zone boundaries using shape overlays

    SciTech Connect

    Grandy, J.

    1997-04-22

    Shape overlays provide a means of statically imposing a physical region containing specified material properties onto a zoned mesh. In the most general case, material interface boundaries are unrelated to mesh zone boundaries, causing zones to contain a mixture of materials, and the mesh itself is not uniform in physical space. We develop and apply an algorithm for shape overlays on nonorthogonal, nonuniform meshes in two dimensions. Examples of shape generation in a multiblock uid dynamics code are shown.

  19. H(curl) Auxiliary Mesh Preconditioning

    SciTech Connect

    Kolev, T V; Pasciak, J E; Vassilevski, P S

    2006-08-31

    This paper analyzes a two-level preconditioning scheme for H(curl) bilinear forms. The scheme utilizes an auxiliary problem on a related mesh that is more amenable for constructing optimal order multigrid methods. More specifically, we analyze the case when the auxiliary mesh only approximately covers the original domain. The latter assumption is important since it allows for easy construction of nested multilevel spaces on regular auxiliary meshes. Numerical experiments in both two and three space dimensions illustrate the optimal performance of the method.

  20. Algebraic surface design and finite element meshes

    NASA Technical Reports Server (NTRS)

    Bajaj, Chandrajit L.

    1992-01-01

    Some of the techniques are summarized which are used in constructing C sup 0 and C sup 1 continuous meshes of low degree, implicitly defined, algebraic surface patches in three dimensional space. These meshes of low degree algebraic surface patches are used to construct accurate computer models of physical objects. These meshes are also used in the finite element simulation of physical phenomena (e.g., heat dissipation, stress/strain distributions, fluid flow characteristics) required in the computer prototyping of both the manufacturability and functionality of the geometric design.

  1. Composite mesh generator for CFD problems

    NASA Astrophysics Data System (ADS)

    Kalinin, E. I.; Mazo, A. B.; Isaev, S. A.

    2016-11-01

    In present paper a brief introduction of HybMesh grid generator which uses composite approach is given. The process of complicated area meshing using HybMesh generator consists of sequential building structured prototype grids in relatively simple geometry, mapping them to a non-regular domains and superposing to assemble resulting grid. Transitional areas between two superposed low level grids are filled with triangular cells. Currently only 2D algorithms of such approach are implemented; 3D grids can only be restored as a result of extrusion or revolution of 2D objects.

  2. Assessment of adhesion formation after laparoscopic intraperitoneal implantation of Dynamesh IPOM mesh

    PubMed Central

    Jałyński, Marek; Piskorz, Łukasz; Brocki, Marian

    2013-01-01

    Introduction Formation of adhesions after laparoscopic hernia repair using the intra-peritoneal onlay mesh (IPOM) procedure can lead to intestinal obstruction or mesh erosion into intestinal lumen. The aims of this study included: measurement of adhesion formation with Dynamesh IPOM after laparoscopic intraperitoneal implantation, and assessment of the occurrence of isolated adhesions at the fastening sites of slowly absorbable sutures. Material and methods Twelve healthy pigs underwent laparoscopic implantation of 2 Dynamesh IPOM mesh fragments each, one was fastened with PDSII, and the other with Maxon sutures. An assessment of adhesion formation was carried out after 6 weeks and included an evaluation of surface area, hardness according to the Zhulke scale, and index values. The occurrence of isolated adhesions at slowly absorbable suture fixation points was also analyzed. Results Adhesions were noted in 83.3% of Dynamesh IPOM meshes. Adhesions covered on average 37.7% of the mesh surface with mean hardness 1.46 and index value 78.8. In groups fixed with PDS in comparison to Maxon sutures adhesions covered mean 31.6% vs. 42.5% (p = 0.62) of the mesh surface, mean hardness was 1.67 vs.1.25 (p = 0.34) and index 85.42 vs. 72.02 (p = 0.95). Conclusions The Dynamesh IPOM mesh, in spite of its anti-adhesive layer of PVDF, does not prevent the formation of adhesions. Adhesion hardness, surface area, and index values of the Dynamesh IPOM mesh are close to the mean values of these parameters for other commercially available 2-layer meshes. Slowly absorbable sutures used for fastening did not increase the risk of adhesion formation. PMID:23847671

  3. Histologic and biomechanical evaluation of a novel macroporous polytetrafluoroethylene knit mesh compared to lightweight and heavyweight polypropylene mesh in a porcine model of ventral incisional hernia repair

    PubMed Central

    Melman, L.; Jenkins, E. D.; Hamilton, N. A.; Bender, L. C.; Brodt, M. D.; Deeken, C. R.; Greco, S. C.; Frisella, M. M.

    2013-01-01

    , over time, inflammation decreased significantly for all mesh types (P < 0.001) and tissue ingrowth reached a slight peak between 1 and 3 months (P = 0.001) but did not significantly change thereafter (P > 0.09). Conclusions The maximum tensile strength of mesh in the abdominal wall decreased over time for HWPP, LWPP, and mkPTFE mesh materials alike. This trend may actually reflect inability to adequately grip specimens at later time points rather than any mesh-specific trend. Histologically, inflammation decreased with time (P = 0.000), and tissue ingrowth increased (P = 0.019) for all meshes. No specific trends were observed between the polypropylene meshes and the monofilament knit PTFE, suggesting that this novel construction may be a suitable alternative to existing polypropylene meshes. PMID:21279663

  4. Time-engineeringed biphasic drug release by electrospun nanofiber meshes.

    PubMed

    Huang, Li-Ya; Branford-White, Christopher; Shen, Xia-Xia; Yu, Deng-Guang; Zhu, Li-Min

    2012-10-15

    A drug-loaded nanofiber mesh which could achieve time-engineeringed biphasic release was fabricated through sequential electrospinning. The drug to polymer ratio of each single mesh was allocated and designed before the tri-layered meshes were created. The resultant meshes had the following construction: (i) the first drug-loaded mesh (top side), (ii) the second drug-loaded mesh (second side), and (iii) the third drug-loaded mesh (bottom side). The drug release speed and duration were controlled by designing morphological features of the electrospun meshes such as the fiber diameter and mesh thickness. An in vitro release experiment revealed that the tri-layered construction with distinct morphological features of each component mesh can provide biphasic drug release. The time-engineeringed dual release system using the multilayered electrospun nanofiber meshes was proved to be a useful formulation when achieving controlled drug release at different times. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. Preparation of a small intestinal submucosa modified polypropylene hybrid mesh via a mussel-inspired polydopamine coating for pelvic reconstruction.

    PubMed

    Ge, Liangpeng; Liu, Lubin; Wei, Haoche; Du, Lei; Chen, Shixuan; Huang, Yong; Huang, Renshu

    2016-04-01

    Pelvic organ prolapse (POP) is a serious health issue that affects many adult women. Surgical treatments for POP patients comprise a common strategy in which scaffold materials are used to reconstruct the prolapsed pelvic. However, the existing materials for pelvic reconstruction cannot meet clinical requirements in terms of biocompatibility, mechanics and immunological rejection. To address these concerns, polypropylene (PP) mesh was selected because of its strong mechanical properties. Small intestinal submucosa (SIS) was used to modify the PP mesh via a mussel-inspired polydopamine coating to enhance its biocompatibility. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) results demonstrated that SIS was successfully conjugated on the surface of the PP mesh. Moreover, the cytotoxicity results indicated that the PP mesh and SIS-modified PP mesh were safe to use. Furthermore, in vivo tests demonstrated that the fibroplasia around the implanted site in the SIS-modified PP mesh group was significantly less than the fibroplasia around the PP mesh group. In addition, the immunohistochemistry staining results indicated that the expression of pro-inflammatory macrophages (M1) was substantially lower and that the expression of pro-healing macrophages (M2) was higher in the SIS-modified PP mesh group. Furthermore, ELISA detection indicated that the expression of IL-1β and IL-6 in the SIS-modified PP mesh group was reduced compared with the PP mesh group. These findings suggest that a SIS-modified polypropylene hybrid mesh via a mussel-inspired polydopamine coating is a promising approach in pelvic reconstruction. © The Author(s) 2016.

  6. Stable underwater superoleophobic and low adhesive polypyrrole nanowire mesh in highly corrosive environments.

    PubMed

    Teng, Chao; Wang, Shuangbao; Lu, Xianyong; Wang, Jianfeng; Ren, Guangyuan; Zhu, Ying; Jiang, Lei

    2015-06-07

    Underwater superoleophobic materials with low adhesion have been widely researched owing to their self-cleaning and anti-corrosive properties. In this study, polypyrrole (PPy) nanowire meshes have been successfully fabricated by in situ electrochemical polymerization on stainless steel mesh substrates in the presence of phosphate buffered saline as both an electrolyte and a dopant. PPy nanowire meshes have high oil contact angles (above 150°) and low sliding angles (less than 10°), and they show underwater superoleophobicity with an excellent self-cleaning performance, not only in pure water, but also in highly corrosive aqueous solutions, including salt solutions, strong acids or basic solutions. PPy nanowire meshes presented here show promise for potential applications in fields such as oil-water separation and marine oil spill clean-up.

  7. Mechanical properties of artificial tracheas composed of a mesh cylinder and a spiral stent.

    PubMed

    Kawaguchi, S; Nakamura, T; Shimizu, Y; Masuda, T; Takigawa, T; Liu, Y; Ueda, H; Sekine, T; Matsumoto, K

    2001-12-01

    Much work has been done on the materials used for mesh-type artificial tracheas, but a precise mechanical evaluation of these structures has not yet been performed. In the present study, we determined the mechanical properties of typical mesh-type artificial tracheas and compared them with those of native trachea. Four types of artificial trachea were made and used for the mechanical tests. The basic frame of all the specimens was composed of a mesh cylinder and a spiral stent. The specimen whose mesh was sealed with collagen sponge showed almost the same behavior in the force-strain curve under compression, suggesting that collagen sealing has little effect on mechanical properties. Agreement between measured and estimated mechanical properties was good, especially in the low strain region, suggesting that artificial tracheas can be designed in terms of mechanical properties by mainly considering the basic frame structure.

  8. Hiatal hernia repair with the use of biologic meshes: a literature review.

    PubMed

    Antoniou, Stavros A; Pointner, Rudolph; Granderath, Frank A

    2011-02-01

    During the past few years, biologic meshes, primarily evolved for routine and complex cases of abdominal wall reconstruction, have been evaluated in clinical cases and experimental models. Although there is published experience on the use of small intestine submucosa and human cadaveric dermis in hiatal hernia repair with encouraging results, porcine dermal collagen (PDC) matrix has not been subject of study to date in this patient population. A systematic review of the literature was conducted, aiming at evaluating the biomechanical characteristics of cross-linked PDC in comparison to synthetic and biologic meshes. Evidence shows that cross-linked PDC is superior to synthetic meshes in terms of incorporation, adhesion formation, and mesh fibrosis; their biodynamic and biotechnical characteristics do not seem to be superior to other bioprosthetic materials according to current data. The clinical and experimental results of cross-linked PDC implants justify their pilot clinical evaluation in hiatal hernia patients.

  9. Label-free THz sensing of living body-related molecular binding using a metallic mesh.

    PubMed

    Hasebe, Takayuki; Yamada, Yuki; Tabata, Hitoshi

    2011-10-14

    We have demonstrated label-free THz sensing of living body-related molecular binding using a thin metallic mesh and a polyvinylidene difluoride (PVDF) membrane. Metallic meshes in the THz region are designed for anomalous transmission phenomena derived from a resonant excitation of surface waves. Additionally, they are designed to have a sharp dip in transmittance. The metallic mesh is very sensitive to a change of the refractive index of materials attached to the metallic mesh. In this paper, we report sensing of interactions between lectin and sugar using this technique. We found that the dip frequency shift, transmittance attenuation of the dip frequency, and peak shift of the derivative spectrum of the phase shift depend on the bonding amount of lectin-sugar interactions. We also applied this technique to detect avidin-biotin interactions, leading to the detection of a small amount of biotin (0.17 pg/mm(2)).

  10. Biocompatibility, cell growth and clinical relevance of synthetic meshes and biological matrixes for internal support in implant-based breast reconstruction.

    PubMed

    Dieterich, Max; Stubert, Johannes; Gerber, Bernd; Reimer, Toralf; Richter, Dagmar-Ulrike

    2015-06-01

    Biological matrixes and synthetic meshes are increasingly used in implant-based breast reconstruction (IBBR). The objective was to test different materials used for internal support in IBBR in regards to biocompatibility and discuss possible limitations in a clinical context. In vitro investigations were performed on four relevant cell lines: Normal Human Dermal Fibroblasts (NHDF), Human White Preadipocytes (HWP), Endothelial cells (HDMEC) and Skeletal muscle cells (SkMC). A titanium-coated polypropylene mesh (TiLOOP Bra), a partially resorbable mesh (SERAGYN BR) and a porcine derived biologic matrix (Strattice) were investigated. Test of cytotoxicity, cell proliferation and oxidative stress was performed. Real-time cell analysis was used to determine adhesion rate. Light- and scanning electron microscopy investigated cell migration. No relevant cytotoxicity was detected for any mesh or matrix. Good cell proliferation was observed in all materials with best results for NHDF and SkMC. For HWP and HDMEC decreased proliferation and adherence to the synthetic meshes and biologic matrix were observed. Real-time cell analysis of fibroblasts incubated with the corresponding material, showed increased impedance for the synthetic meshes. A morphologic cell change was observed within all materials. Scanning electron microscopy showed good cell penetration into the meshes and matrix. The material compositions did not seem to influence the clinical outcome, although the biological matrix was much thicker compared to the synthetic meshes. Biochemical examination showed good biocompatibility for the investigated meshes and matrix. All products seem to have their value in IBBR and can be recommended for IBBR.

  11. 50 CFR 300.110 - Mesh size.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... will be stretched in the direction of the long diagonal of the meshes. (ii) A gauge as described in.... This distance will be measured perpendicular to the lacings, ropes or codline with the net stretched...

  12. LR: Compact connectivity representation for triangle meshes

    SciTech Connect

    Gurung, T; Luffel, M; Lindstrom, P; Rossignac, J

    2011-01-28

    We propose LR (Laced Ring) - a simple data structure for representing the connectivity of manifold triangle meshes. LR provides the option to store on average either 1.08 references per triangle or 26.2 bits per triangle. Its construction, from an input mesh that supports constant-time adjacency queries, has linear space and time complexity, and involves ordering most vertices along a nearly-Hamiltonian cycle. LR is best suited for applications that process meshes with fixed connectivity, as any changes to the connectivity require the data structure to be rebuilt. We provide an implementation of the set of standard random-access, constant-time operators for traversing a mesh, and show that LR often saves both space and traversal time over competing representations.

  13. Lithium-6 coated wire mesh neutron detector

    SciTech Connect

    Young, C.A.; Geelhood, B.D.

    1984-11-06

    A neutron detection apparatus is provided which includes a selected number of surfaces of Lithium-6 coated wire mesh and which further includes a gas mixture in contact with each sheet of Lithium-6 coated wire mesh for selectively reacting to charged particles emitted or radiated by the Lithium-6 coated mesh. A container is provided to seal the Lithium-6 coated mesh and the gas mixture in a volume from which water vapor and atmospheric gases are excluded, the container having one or more walls which are transmissive to neutrons. Monitoring equipment in contact with the gas mixture detects the generation of charged particles in the gas mixture and, in response to such charged particles, provides an indication of the flux of neutrons passing through the volume of the detector.

  14. Grid adaptation using Chimera composite overlapping meshes

    NASA Technical Reports Server (NTRS)

    Kao, Kai-Hsiung; Liou, Meng-Sing; Chow, Chuen-Yen

    1993-01-01

    The objective of this paper is to perform grid adaptation using composite over-lapping meshes in regions of large gradient to capture the salient features accurately during computation. The Chimera grid scheme, a multiple overset mesh technique, is used in combination with a Navier-Stokes solver. The numerical solution is first converged to a steady state based on an initial coarse mesh. Solution-adaptive enhancement is then performed by using a secondary fine grid system which oversets on top of the base grid in the high-gradient region, but without requiring the mesh boundaries to join in any special way. Communications through boundary interfaces between those separated grids are carried out using tri-linear interpolation. Applications to the Euler equations for shock reflections and to a shock wave/boundary layer interaction problem are tested. With the present method, the salient features are well resolved.

  15. Grid adaptation using chimera composite overlapping meshes

    NASA Technical Reports Server (NTRS)

    Kao, Kai-Hsiung; Liou, Meng-Sing; Chow, Chuen-Yen

    1994-01-01

    The objective of this paper is to perform grid adaptation using composite overlapping meshes in regions of large gradient to accurately capture the salient features during computation. The chimera grid scheme, a multiple overset mesh technique, is used in combination with a Navier-Stokes solver. The numerical solution is first converged to a steady state based on an initial coarse mesh. Solution-adaptive enhancement is then performed by using a secondary fine grid system which oversets on top of the base grid in the high-gradient region, but without requiring the mesh boundaries to join in any special way. Communications through boundary interfaces between those separated grids are carried out using trilinear interpolation. Application to the Euler equations for shock reflections and to shock wave/boundary layer interaction problem are tested. With the present method, the salient features are well-resolved.

  16. Grid adaption using Chimera composite overlapping meshes

    NASA Technical Reports Server (NTRS)

    Kao, Kai-Hsiung; Liou, Meng-Sing; Chow, Chuen-Yen

    1993-01-01

    The objective of this paper is to perform grid adaptation using composite over-lapping meshes in regions of large gradient to capture the salient features accurately during computation. The Chimera grid scheme, a multiple overset mesh technique, is used in combination with a Navier-Stokes solver. The numerical solution is first converged to a steady state based on an initial coarse mesh. Solution-adaptive enhancement is then performed by using a secondary fine grid system which oversets on top of the base grid in the high-gradient region, but without requiring the mesh boundaries to join in any special way. Communications through boundary interfaces between those separated grids are carried out using tri-linear interpolation. Applications to the Euler equations for shock reflections and to a shock wave/boundary layer interaction problem are tested. With the present method, the salient features are well resolved.

  17. Lagrange-mesh calculations in momentum space.

    PubMed

    Lacroix, Gwendolyn; Semay, Claude; Buisseret, Fabien

    2012-08-01

    The Lagrange-mesh method is a powerful method to solve eigenequations written in configuration space. It is very easy to implement and very accurate. Using a Gauss quadrature rule, the method requires only the evaluation of the potential at some mesh points. The eigenfunctions are expanded in terms of regularized Lagrange functions which vanish at all mesh points except one. It is shown that this method can be adapted to solve eigenequations written in momentum space, keeping the convenience and the accuracy of the original technique. In particular, the kinetic operator is a diagonal matrix. Observables and wave functions in both configuration space and momentum space can also be easily computed with good accuracy using only eigenfunctions computed in the momentum space. The method is tested with Gaussian and Yukawa potentials, requiring, respectively, a small and a large mesh to reach convergence. Corresponding wave functions in both spaces are compared with each other using the Fourier transform.

  18. Efficiently Sorting Zoo-Mesh Data Sets

    SciTech Connect

    Cook, R; Max, N; Silva, C; Williams, P

    2001-03-26

    The authors describe the SXMPVO algorithm for performing a visibility ordering zoo-meshed polyhedra. The algorithm runs in practice in linear time and the visibility ordering which it produces is exact.

  19. A mesh gradient technique for numerical optimization

    NASA Technical Reports Server (NTRS)

    Willis, E. A., Jr.

    1973-01-01

    A class of successive-improvement optimization methods in which directions of descent are defined in the state space along each trial trajectory are considered. The given problem is first decomposed into two discrete levels by imposing mesh points. Level 1 consists of running optimal subarcs between each successive pair of mesh points. For normal systems, these optimal two-point boundary value problems can be solved by following a routine prescription if the mesh spacing is sufficiently close. A spacing criterion is given. Under appropriate conditions, the criterion value depends only on the coordinates of the mesh points, and its gradient with respect to those coordinates may be defined by interpreting the adjoint variables as partial derivatives of the criterion value function. In level 2, the gradient data is used to generate improvement steps or search directions in the state space which satisfy the boundary values and constraints of the given problem.

  20. Pectus excavatum repair using Prolene polypropylene mesh.

    PubMed

    Rasihashemi, Seyed Ziaeddin; Ramouz, Ali

    2016-02-01

    We aimed to assess the clinical outcomes of our surgical technique for repair of pectus excavatum using Prolene polypropylene mesh. Among 29 patients with pectus excavatum, the major complaint was cosmetic dissatisfaction, and the main symptom was exercise dyspnea in 15 patients. The Haller index used to assess pectus excavatum severity; it was significant in 22 patients. In all patients, a 2-layer sheet of Prolene polypropylene mesh was placed behind the sternum. No serious complication was observed postoperatively, and all patients were satisfied with the cosmetic result. Mitral valve prolapse improved in all cases after 3 months. Spirometry revealed improved pulmonary function after surgery. With due attention to the advantages of Prolene polypropylene mesh, such as remaining permanently in place, adapting to various stresses encountered in the body, resisting degradation by tissue enzymes, and trimming without unraveling, we concluded that this mesh is suitable for use as posterior sternal support in pectus excavatum patients. © The Author(s) 2016.

  1. Some mesh generation requirements and methods

    NASA Technical Reports Server (NTRS)

    Dickson, L. J.

    1978-01-01

    Discretized solution algorithms, which find solutions of field equations in a two or three dimensional field, generally use meshes which are fitted to the field boundary to allow convenient formulation of boundary conditions there. A mesh is defined to be the image of a rectangular grid in computational space under a mesh mapping which maps computational space into physical space. It is not necessary that all of computational space be mapped onto the region of interest in physical space. Parts of it can be excised to give a better fit to the boundary. Many different excisions can be made to fit a single boundary; the choice depends on the mesh arrangement desired in the field.

  2. 50 CFR 300.110 - Mesh size.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... will be stretched in the direction of the long diagonal of the meshes. (ii) A gauge as described in.... This distance will be measured perpendicular to the lacings, ropes or codline with the net stretched in...

  3. 50 CFR 300.110 - Mesh size.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... will be stretched in the direction of the long diagonal of the meshes. (ii) A gauge as described in.... This distance will be measured perpendicular to the lacings, ropes or codline with the net stretched in...

  4. Surface Generation and Cartesian Mesh Support

    NASA Technical Reports Server (NTRS)

    Haimes, Robert

    2004-01-01

    This document serves as the final report for the grant titled Surface Generation and Cartesian Mesh Support . This completed work was in algorithmic research into automatically generating surface triangulations from CAD geometries. NASA's OVERFLOW and Cart3D simulation packages use surface triangulations as an underlying geometry description and the ability to automatically generate these from CAD files (without translation) substantially reduces both the wall-clock time and expertise required to get geometry out of CAD and into mesh generation. This surface meshing was exercised greatly during the Shuttle investigation during the last year with success. The secondary efforts performed in this grant involve work on a visualization system cut-cell handling for Cartesian Meshes with embedded boundaries.

  5. Quadrilateral/hexahedral finite element mesh coarsening

    DOEpatents

    Staten, Matthew L; Dewey, Mark W; Scott, Michael A; Benzley, Steven E

    2012-10-16

    A technique for coarsening a finite element mesh ("FEM") is described. This technique includes identifying a coarsening region within the FEM to be coarsened. Perimeter chords running along perimeter boundaries of the coarsening region are identified. The perimeter chords are redirected to create an adaptive chord separating the coarsening region from a remainder of the FEM. The adaptive chord runs through mesh elements residing along the perimeter boundaries of the coarsening region. The adaptive chord is then extracted to coarsen the FEM.

  6. MHD simulations on an unstructured mesh

    SciTech Connect

    Strauss, H.R.; Park, W.; Belova, E.; Fu, G.Y.; Longcope, D.W.; Sugiyama, L.E.

    1998-12-31

    Two reasons for using an unstructured computational mesh are adaptivity, and alignment with arbitrarily shaped boundaries. Two codes which use finite element discretization on an unstructured mesh are described. FEM3D solves 2D and 3D RMHD using an adaptive grid. MH3D++, which incorporates methods of FEM3D into the MH3D generalized MHD code, can be used with shaped boundaries, which might be 3D.

  7. 3D-Meshes aus medizinischen Volumendaten

    NASA Astrophysics Data System (ADS)

    Zelzer, Sascha; Meinzer, Hans-Peter

    Diese Arbeit beschreibt eine template-basierte Methode zur Erzeugung von adaptiven Hexaeder-Meshes aus Volumendaten, welche komplizierte konkave Strukturen aufweisen können. Es wird ein vollständiger Satz von Templates generiert der es erlaubt, die Ränder konkaver Regionen feiner zu zerlegen als angrenzende Bereiche und somit die Gesamtzahl an Hexaeder verringert. Der Algorithmus arbeitet mit beliebigen gelabelten Volumendaten und erzeugt ein adaptives, konformes, reines Hexaeder-Mesh.

  8. Airplane Mesh Development with Grid Density Studies

    NASA Technical Reports Server (NTRS)

    Cliff, Susan E.; Baker, Timothy J.; Thomas, Scott D.; Lawrence, Scott L.; Rimlinger, Mark J.

    1999-01-01

    Automatic Grid Generation Wish List Geometry handling, including CAD clean up and mesh generation, remains a major bottleneck in the application of CFD methods. There is a pressing need for greater automation in several aspects of the geometry preparation in order to reduce set up time and eliminate user intervention as much as possible. Starting from the CAD representation of a configuration, there may be holes or overlapping surfaces which require an intensive effort to establish cleanly abutting surface patches, and collections of many patches may need to be combined for more efficient use of the geometrical representation. Obtaining an accurate and suitable body conforming grid with an adequate distribution of points throughout the flow-field, for the flow conditions of interest, is often the most time consuming task for complex CFD applications. There is a need for a clean unambiguous definition of the CAD geometry. Ideally this would be carried out automatically by smart CAD clean up software. One could also define a standard piece-wise smooth surface representation suitable for use by computational methods and then create software to translate between the various CAD descriptions and the standard representation. Surface meshing remains a time consuming, user intensive procedure. There is a need for automated surface meshing, requiring only minimal user intervention to define the overall density of mesh points. The surface mesher should produce well shaped elements (triangles or quadrilaterals) whose size is determined initially according to the surface curvature with a minimum size for flat pieces, and later refined by the user in other regions if necessary. Present techniques for volume meshing all require some degree of user intervention. There is a need for fully automated and reliable volume mesh generation. In addition, it should be possible to create both surface and volume meshes that meet guaranteed measures of mesh quality (e.g. minimum and maximum

  9. Gear Mesh Loss-of-Lubrication Experiments and Analytical Simulation

    NASA Technical Reports Server (NTRS)

    Handschuh, Robert F.; Polly, Joseph; Morales, Wilfredo

    2011-01-01

    An experimental program to determine the loss-of-lubrication (LOL) characteristics of spur gears in an aerospace simulation test facility has been completed. Tests were conducted using two different emergency lubricant types: (1) an oil mist system (two different misted lubricants) and (2) a grease injection system (two different grease types). Tests were conducted using a NASA Glenn test facility normally used for conducting contact fatigue. Tests were run at rotational speeds up to 10000 rpm using two different gear designs and two different gear materials. For the tests conducted using an air-oil misting system, a minimum lubricant injection rate was determined to permit the gear mesh to operate without failure for at least 1 hr. The tests allowed an elevated steady state temperature to be established. A basic 2-D heat transfer simulation has been developed to investigate temperatures of a simulated gear as a function of frictional behavior. The friction (heat generation source) between the meshing surfaces is related to the position in the meshing cycle, the load applied, and the amount of lubricant in the contact. Experimental conditions will be compared to those from the 2-D simulation.

  10. The argument for lightweight polypropylene mesh in hernia repair.

    PubMed

    Cobb, William S; Kercher, Kent W; Heniford, B Todd

    2005-03-01

    The development of polypropylene prosthetics revolutionized surgery for the repair of abdominal wall hernias. A tension-free mesh technique has drastically reduced recurrence rates for all hernias compared to tissue repairs and has made it possible to reconstruct large ventral defects that were previously irreparable. The repair of abdominal wall defects is one of the most commonly performed general surgical procedures, with over 1 million polypropylene implants inserted each year. Surprisingly, little research has been performed to investigate the interaction of abdominal wall forces on a ventral hernia repair or the required amount or strength of the foreign-body material necessary for an adequate hernia repair. The long-term consequences of implantable polypropylene prosthetics are not without concern. The body generates an intense inflammatory response to the prosthetic that results in scar plate formation, increased stiffness of the abdominal wall, and shrinkage of the biomaterial. Reducing the density of polypropylene and creating a ''light weight'' mesh theoretically induces less foreign-body response, results in improved abdominal wall compliance, causes less contraction or shrinkage of the mesh, and allows for better tissue incorporation. A review of the laboratory data and short-term clinical follow-up is reviewed to provide a strong basis or argument for the use of ''light weight'' prosthetics in hernia surgery.

  11. Poly(ε-caprolactone) Microfiber Meshes for Repeated Oil Retrieval

    PubMed Central

    Hersey, J. S.; Yohe, S. T.; Grinstaff, M. W.

    2016-01-01

    Electrospun non-woven poly(ε-caprolactone) (PCL) microfiber meshes are described as biodegradable, mechanically robust, and reusable polymeric oil sorbents capable of selectively retrieving oil from simulated oil spills in both fresh and seawater scenarios. Hydrophobic PCL meshes have >99.5% (oil over water) oil selectivity and oil absorption capacities of ~10 grams of oil per gram of sorbent material, which is shown to be a volumetrically driven process. Both the oil selectivity and absorption capacity remained constant over several oil absorption and vacuum assisted retrieval cycles when removing crude oil or mechanical pump oil from deionized water or simulated seawater mixtures. Finally, when challenged with surfactant stabilized water-in-oil emulsions, the PCL meshes continued to show selective oil absorption. These studies add to the knowledge base of synthetic oil sorbents highlighting a need for biodegradable synthetic oil sorbents which balance porosity and mechanical integrity enabling reuse, allowing for the efficient recovery of oil after an accidental oil spill. PMID:26989490

  12. TVD differencing on three-dimensional unstructured meshes with monotonicity-preserving correction of mesh skewness

    NASA Astrophysics Data System (ADS)

    Denner, Fabian; van Wachem, Berend G. M.

    2015-10-01

    Total variation diminishing (TVD) schemes are a widely applied group of monotonicity-preserving advection differencing schemes for partial differential equations in numerical heat transfer and computational fluid dynamics. These schemes are typically designed for one-dimensional problems or multidimensional problems on structured equidistant quadrilateral meshes. Practical applications, however, often involve complex geometries that cannot be represented by Cartesian meshes and, therefore, necessitate the application of unstructured meshes, which require a more sophisticated discretisation to account for their additional topological complexity. In principle, TVD schemes are applicable to unstructured meshes, however, not all the data required for TVD differencing is readily available on unstructured meshes, and the solution suffers from considerable numerical diffusion as a result of mesh skewness. In this article we analyse TVD differencing on unstructured three-dimensional meshes, focusing on the non-linearity of TVD differencing and the extrapolation of the virtual upwind node. Furthermore, we propose a novel monotonicity-preserving correction method for TVD schemes that significantly reduces numerical diffusion caused by mesh skewness. The presented numerical experiments demonstrate the importance of accounting for the non-linearity introduced by TVD differencing and of imposing carefully chosen limits on the extrapolated virtual upwind node, as well as the efficacy of the proposed method to correct mesh skewness.

  13. Robust moving mesh algorithms for hybrid stretched meshes: Application to moving boundaries problems

    NASA Astrophysics Data System (ADS)

    Landry, Jonathan; Soulaïmani, Azzeddine; Luke, Edward; Ben Haj Ali, Amine

    2016-12-01

    A robust Mesh-Mover Algorithm (MMA) approach is designed to adapt meshes of moving boundaries problems. A new methodology is developed from the best combination of well-known algorithms in order to preserve the quality of initial meshes. In most situations, MMAs distribute mesh deformation while preserving a good mesh quality. However, invalid meshes are generated when the motion is complex and/or involves multiple bodies. After studying a few MMA limitations, we propose the following approach: use the Inverse Distance Weighting (IDW) function to produce the displacement field, then apply the Geometric Element Transformation Method (GETMe) smoothing algorithms to improve the resulting mesh quality, and use an untangler to revert negative elements. The proposed approach has been proven efficient to adapt meshes for various realistic aerodynamic motions: a symmetric wing that has suffered large tip bending and twisting and the high-lift components of a swept wing that has moved to different flight stages. Finally, the fluid flow problem has been solved on meshes that have moved and they have produced results close to experimental ones. However, for situations where moving boundaries are too close to each other, more improvements need to be made or other approaches should be taken, such as an overset grid method.

  14. Adaptive Meshing Techniques for Viscous Flow Calculations on Mixed Element Unstructured Meshes

    NASA Technical Reports Server (NTRS)

    Mavriplis, D. J.

    1997-01-01

    An adaptive refinement strategy based on hierarchical element subdivision is formulated and implemented for meshes containing arbitrary mixtures of tetrahendra, hexahendra, prisms and pyramids. Special attention is given to keeping memory overheads as low as possible. This procedure is coupled with an algebraic multigrid flow solver which operates on mixed-element meshes. Inviscid flows as well as viscous flows are computed an adaptively refined tetrahedral, hexahedral, and hybrid meshes. The efficiency of the method is demonstrated by generating an adapted hexahedral mesh containing 3 million vertices on a relatively inexpensive workstation.

  15. Mesh-type acoustic vector sensor

    NASA Astrophysics Data System (ADS)

    Zalalutdinov, M. K.; Photiadis, D. M.; Szymczak, W. G.; McMahon, J. W.; Bucaro, J. A.; Houston, B. H.

    2017-07-01

    Motivated by the predictions of a theoretical model developed to describe the acoustic flow force exerted on closely spaced nano-fibers in a viscous medium, we have demonstrated a novel concept for a particle velocity-based directional acoustic sensor. The central element of the concept exploits the acoustically induced normal displacement of a fine mesh as a measure of the collinear projection of the particle velocity in the sound wave. The key observations are (i) the acoustically induced flow force on an individual fiber within the mesh is nearly independent of the fiber diameter and (ii) the mesh-flow interaction can be well-described theoretically by a nearest neighbor coupling approximation. Scaling arguments based on these two observations indicate that the refinement of the mesh down to the nanoscale leads to significant improvements in performance. The combination of the two dimensional nature of the mesh together with the nanoscale dimensions provides a dramatic gain in the total length of fiber exposed to the flow, leading to a sensitivity enhancement by orders of magnitude. We describe the fabrication of a prototype mesh sensor equipped with optical readout. Preliminary measurements carried out over a considerable bandwidth together with the results of numerical simulations are in good agreement with the theory, thus providing a proof of concept.

  16. Automatic scheme selection for toolkit hex meshing

    SciTech Connect

    WHITE,DAVID R.; TAUTGES,TIMOTHY J.

    2000-02-17

    Current hexahedral mesh generation techniques rely on a set of meshing tools, which when combined with geometry decomposition leads to an adequate mesh generation process. Of these tools, sweeping tends to be the workhorse algorithm, accounting for at least 50% of most meshing applications. Constraints which must be met for a volume to be sweepable are derived, and it is proven that these constraints are necessary but not sufficient conditions for sweepability. This paper also describes a new algorithm for detecting extruded or sweepable geometries. This algorithm, based on these constraints, uses topological and local geometric information, and is more robust than feature recognition-based algorithms. A method for computing sweep dependencies in volume assemblies is also given. The auto sweep detect and sweep grouping algorithms have been used to reduce interactive user time required to generate all-hexahedral meshes by filtering out non-sweepable volumes needing further decomposition and by allowing concurrent meshing of independent sweep groups. Parts of the auto sweep detect algorithm have also been used to identify independent sweep paths, for use in volume-based interval assignment.

  17. Hybrid Surface Mesh Adaptation for Climate Modeling

    SciTech Connect

    Ahmed Khamayseh; Valmor de Almeida; Glen Hansen

    2008-10-01

    Solution-driven mesh adaptation is becoming quite popular for spatial error control in the numerical simulation of complex computational physics applications, such as climate modeling. Typically, spatial adaptation is achieved by element subdivision (h adaptation) with a primary goal of resolving the local length scales of interest. A second, less-popular method of spatial adaptivity is called “mesh motion” (r adaptation); the smooth repositioning of mesh node points aimed at resizing existing elements to capture the local length scales. This paper proposes an adaptation method based on a combination of both element subdivision and node point repositioning (rh adaptation). By combining these two methods using the notion of a mobility function, the proposed approach seeks to increase the flexibility and extensibility of mesh motion algorithms while providing a somewhat smoother transition between refined regions than is produced by element subdivision alone. Further, in an attempt to support the requirements of a very general class of climate simulation applications, the proposed method is designed to accommodate unstructured, polygonal mesh topologies in addition to the most popular mesh types.

  18. Large area nanoscale metal meshes for use as transparent conductive layers

    NASA Astrophysics Data System (ADS)

    Jin, Yuanhao; Li, Qunqing; Chen, Mo; Li, Guanhong; Zhao, Yudan; Xiao, Xiaoyang; Wang, Jiaping; Jiang, Kaili; Fan, Shoushan

    2015-10-01

    We report on the experimental realization of using super-aligned carbon nanotubes (SACNTs) as etching masks for the fabrication of large area nanoscale metal meshes. This method can easily be extended to different metals on both rigid and flexible substrates. The as-fabricated metal meshes, including the ones made of gold, copper, and aluminum, are suitable for use as transparent conductive layers (TCLs). The metal meshes, which are similar to the SACNT networks in their dimensional features of tens of nanometers, exhibit compatible performance in terms of optical transmittance and sheet resistance. Moreover, because the metal meshes are fabricated as an integrated material, there is no junction resistance between the interconnected metal nanostructures, which markedly lowers their sheet resistance at high temperatures. The fabrication of such an effective etching mask involves a simple drawing process of the SACNT networks prepared and a common deposition process. This approach should be easy to extend to various research fields and has broad prospects in commercial applications.We report on the experimental realization of using super-aligned carbon nanotubes (SACNTs) as etching masks for the fabrication of large area nanoscale metal meshes. This method can easily be extended to different metals on both rigid and flexible substrates. The as-fabricated metal meshes, including the ones made of gold, copper, and aluminum, are suitable for use as transparent conductive layers (TCLs). The metal meshes, which are similar to the SACNT networks in their dimensional features of tens of nanometers, exhibit compatible performance in terms of optical transmittance and sheet resistance. Moreover, because the metal meshes are fabricated as an integrated material, there is no junction resistance between the interconnected metal nanostructures, which markedly lowers their sheet resistance at high temperatures. The fabrication of such an effective etching mask involves a simple

  19. The 2D and 3D hypersonic flows with unstructured meshes

    NASA Technical Reports Server (NTRS)

    Thareja, Rajiv

    1993-01-01

    Viewgraphs on 2D and 3D hypersonic flows with unstructured meshes are presented. Topics covered include: mesh generation, mesh refinement, shock-shock interaction, velocity contours, mesh movement, vehicle bottom surface, and adapted meshes.

  20. Adhesion Prevention Efficacy of Composite Meshes Parietex(®), Proceed(®) and 4DryField(®) PH Covered Polypropylene Meshes in an IPOM Rat Model.

    PubMed

    Winny, Markus; Maegel, Lavinia; Grethe, Leonie; Lippmann, Torsten; Jonigk, Danny; Schrem, Harald; Kaltenborn, Alexander; Klempnauer, Juergen; Poehnert, Daniel

    2016-01-01

    Background: Adhesions to intraperitoneally implanted meshes (IPOM) are a common problem following hernia surgery and may cause severe complications. Recently, we showed that missing peritoneal coverage of the intestine is a decisive factor for adhesion formation and 4DryField(®) PH (4DF) gel significantly prevents intestine-to-mesh adhesions even with use of uncoated Ultrapro(®) polypropylene mesh (UPM). The present study investigates adhesion prevention capability of coated Parietex(®) mesh (PTM) and Proceed(®) mesh (PCM) in comparison to 4DF treated UPM. Methods: 20 rats were randomized into two groups. A 1.5 x 2 cm patch of PTM or PCM was attached to the abdominal wall and the cecum was depleted from peritoneum by abrasion. After seven days incidence of intestine-to-mesh adhesions was evaluated using Lauder and Hoffmann adhesion scores. Histological specimens were evaluated; statistics were performed using student's t-test. The data were compared with recently published data of 4DF treated uncoated UPM. Results: Use of PTM or PCM did not significantly diminish development of intestine-to-mesh adhesions (adhesion reduction rate PTM: 29%, p = 0.069 and PCM: 25%, p = 0.078). Histological results confirmed macroscopic finding of agglutination of intestine and abdominal wall with the mesh in between. Compared to these data, the use of UPM combined with 4DF gel reveals significantly better adhesion prevention capability (p < 0.0001) as shown in earlier studies. However, in clinical situation interindividual differences in adhesion induction mechanisms cannot be excluded by this experimental approach as healing responses towards the different materials might vary. Conclusion: This study shows that in case of impaired intestinal peritoneum coated PTM and PCM do not provide significant adhesion prevention. In contrast, use of UPM combined with 4DF gel achieved a significant reduction of adhesions. Hence, in case of injury of the visceral peritoneum, application of a

  1. Adhesion Prevention Efficacy of Composite Meshes Parietex®, Proceed® and 4DryField® PH Covered Polypropylene Meshes in an IPOM Rat Model

    PubMed Central

    Winny, Markus; Maegel, Lavinia; Grethe, Leonie; Lippmann, Torsten; Jonigk, Danny; Schrem, Harald; Kaltenborn, Alexander; Klempnauer, Juergen; Poehnert, Daniel

    2016-01-01

    Background: Adhesions to intraperitoneally implanted meshes (IPOM) are a common problem following hernia surgery and may cause severe complications. Recently, we showed that missing peritoneal coverage of the intestine is a decisive factor for adhesion formation and 4DryField® PH (4DF) gel significantly prevents intestine-to-mesh adhesions even with use of uncoated Ultrapro® polypropylene mesh (UPM). The present study investigates adhesion prevention capability of coated Parietex® mesh (PTM) and Proceed® mesh (PCM) in comparison to 4DF treated UPM. Methods: 20 rats were randomized into two groups. A 1.5 x 2 cm patch of PTM or PCM was attached to the abdominal wall and the cecum was depleted from peritoneum by abrasion. After seven days incidence of intestine-to-mesh adhesions was evaluated using Lauder and Hoffmann adhesion scores. Histological specimens were evaluated; statistics were performed using student's t-test. The data were compared with recently published data of 4DF treated uncoated UPM. Results: Use of PTM or PCM did not significantly diminish development of intestine-to-mesh adhesions (adhesion reduction rate PTM: 29%, p = 0.069 and PCM: 25%, p = 0.078). Histological results confirmed macroscopic finding of agglutination of intestine and abdominal wall with the mesh in between. Compared to these data, the use of UPM combined with 4DF gel reveals significantly better adhesion prevention capability (p < 0.0001) as shown in earlier studies. However, in clinical situation interindividual differences in adhesion induction mechanisms cannot be excluded by this experimental approach as healing responses towards the different materials might vary. Conclusion: This study shows that in case of impaired intestinal peritoneum coated PTM and PCM do not provide significant adhesion prevention. In contrast, use of UPM combined with 4DF gel achieved a significant reduction of adhesions. Hence, in case of injury of the visceral peritoneum, application of a

  2. Method of modifying a volume mesh using sheet insertion

    DOEpatents

    Borden, Michael J.; Shepherd, Jason F.

    2006-08-29

    A method and machine-readable medium provide a technique to modify a hexahedral finite element volume mesh using dual generation and sheet insertion. After generating a dual of a volume stack (mesh), a predetermined algorithm may be followed to modify (refine) the volume mesh of hexahedral elements. The predetermined algorithm may include the steps of locating a sheet of hexahedral mesh elements, determining a plurality of hexahedral elements within the sheet to refine, shrinking the plurality of elements, and inserting a new sheet of hexahedral elements adjacently to modify the volume mesh. Additionally, another predetermined algorithm using mesh cutting may be followed to modify a volume mesh.

  3. Polyglactine/Polypropylene Mesh vs. Propylene Mesh: Is There a Need for Newer Prosthesis in Inguinal Hernia?

    PubMed Central

    Khan, Nadim; Bangash, Adil; Sadiq, Muzaffaruddin; Ul Hadi, Ain; Hamid, Haris

    2010-01-01

    Background/Aim: To compare outcomes of light and heavy weight mesh for repair of inguinal hernia. Materials and Methods: This study was conducted at the Department of Surgery; Lady Reading Hospital, Peshawar from January 1, 2007 to December 31, 2008. Patients were divided into two groups based on the type of mesh implanted for inguinal hernia repair. Group 1 included patients in whom light weight composite (VyproII®) mesh is implanted: Group 2 included patients in whom polypropylene (ProleneR) mesh is implanted. Data concerning the complications and post operative pain in the perioperative and postoperative period were collected and analyzed. Categorical data were presented as percentages with 95% confidence intervals and compared using a χ2test and P<0.05 were considered significant. Results: Following allocation and exclusion of violating cases, 111 patients in group 1 and 138 patients in group 2 were analyzed. The mean age in group 1 was 38.20 ± 13.34 years and in group 2 was 39.55 ± 13.70 (P = 0.434). In group 1, hematoma formation was observed in four cases (3.6%), while it was observed in six cases (4.2%) in group 2 (P = 0.766). During the entire study, ten patients in all developed urinary retention, three of which required transient catheterization. One year post operation, there was a recurrence in only five cases overall, while only two patients complained of pain (P = 0.826). Conclusion: The frequency of postoperative pain and complications in patients was similar in both groups. PMID:20065567

  4. Long-term results following reconstruction of craniofacial defects with titanium micro-mesh systems.

    PubMed

    Kuttenberger, Johannes J.; Hardt, Nicolas

    2001-04-01

    Introduction: Reconstruction of craniofacial defects can be carried out with autogenous tissue (calvarium, rib, iliac crest), allogeneic implants (AAA-bone, lyophilized cartilage) or alloplastic material (methacrylate, hydroxyapatite, titanium implants and mesh systems). Selection of the implant material used for reconstruction is still controversial. Material and Methods: At the Department of Oral and Maxillofacial Surgery, Kantonsspital Luzern, 20 patients with defects in the craniofacial and/or orbito-ethmoidal region have been treated using titanium micro-mesh between 1991 and 1998. Two different mesh systems, micro-titanium augmentation mesh and dynamic mesh, have been used for bony reconstruction in non load-bearing areas. The defects were caused by acute trauma, osteomyelitis of the frontal bone and previous operations. The titanium micro-mesh was used with the following indications: (1) immediate reconstruction in the primary treatment of comminuted fractures with bone loss in non load-bearing areas, (2) treatment of contour irregularities (possibly in combination with bone or cartilage grafts). All patients were followed up clinically and radiographically at quarterly intervals for a year. Results: No wound infections, exposures or loss of the mesh have been observed. Long-term stability of the reconstructions was excellent. When walls of the paranasal sinuses were reconstructed complete repneumatisation took place. Conclusions: Advantages of this reconstructive technique are: (1) universal applicability (craniofacial, orbital, sinus defects, comminuted fractures); (2) stable 3-D reconstruction of complex anatomic structures were easily performed; (3) immediate availability with no donor site morbidity as bone or cartilage grafts were not necessary; (4) combination with bone or cartilage grafts is possible; and (5) very low susceptibility to infection. Copyright 2001 European Association for Cranio-Maxillofacial Surgery.

  5. Adaptive superposition of finite element meshes in linear and nonlinear dynamic analysis

    NASA Astrophysics Data System (ADS)

    Yue, Zhihua

    2005-11-01

    The numerical analysis of transient phenomena in solids, for instance, wave propagation and structural dynamics, is a very important and active area of study in engineering. Despite the current evolutionary state of modern computer hardware, practical analysis of large scale, nonlinear transient problems requires the use of adaptive methods where computational resources are locally allocated according to the interpolation requirements of the solution form. Adaptive analysis of transient problems involves obtaining solutions at many different time steps, each of which requires a sequence of adaptive meshes. Therefore, the execution speed of the adaptive algorithm is of paramount importance. In addition, transient problems require that the solution must be passed from one adaptive mesh to the next adaptive mesh with a bare minimum of solution-transfer error since this form of error compromises the initial conditions used for the next time step. A new adaptive finite element procedure (s-adaptive) is developed in this study for modeling transient phenomena in both linear elastic solids and nonlinear elastic solids caused by progressive damage. The adaptive procedure automatically updates the time step size and the spatial mesh discretization in transient analysis, achieving the accuracy and the efficiency requirements simultaneously. The novel feature of the s-adaptive procedure is the original use of finite element mesh superposition to produce spatial refinement in transient problems. The use of mesh superposition enables the s-adaptive procedure to completely avoid the need for cumbersome multipoint constraint algorithms and mesh generators, which makes the s-adaptive procedure extremely fast. Moreover, the use of mesh superposition enables the s-adaptive procedure to minimize the solution-transfer error. In a series of different solid mechanics problem types including 2-D and 3-D linear elastic quasi-static problems, 2-D material nonlinear quasi-static problems

  6. Single-Institution Financial Analysis of Biologic Versus Synthetic Mesh Hernia Repair: A Retrospective Analysis of Patients Readmitted for Hernia Repair.

    PubMed

    Otake, Leo R; Satterwhite, Thomas; Echo, Anthony; Chiou, Grace; Lee, Gordon K

    2013-07-11

    The advent and proliferation of commercially available biologic mesh material has expanded the repertoire of hernia repair materials available to the surgeon. Given the higher initial cost of these mesh materials relative to synthetic materials such as polypropylene, there has been debate regarding the purported benefit of the use of biologic mesh. This study is a single-institution review of complex hernia repairs using both biologic and synthetic mesh materials. The patients included in the analyses were admitted to the institution at least twice for management of hernia; this permitted specific evaluation of a given diagnosis, hernia, in the same patient, but at different points in time. In a subset of patients, hernia repair was performed upon the second admission with conversion from biologic or synthetic mesh, which had been placed at the initial repair. The objective of this study was to evaluate the financial implications of mesh choice. Specific parameters reviewed included type of mesh used, total costs of hospitalization, direct cost associated with the hernia repair, total collections, and percentage of collections relative to total charges. Through such analysis, our aim was to determine whether there were any variances in revenue and costs associated with the application of either mesh material or the associated clinical scenarios.

  7. A moving mesh finite difference method for equilibrium radiation diffusion equations

    SciTech Connect

    Yang, Xiaobo; Huang, Weizhang; Qiu, Jianxian

    2015-10-01

    An efficient moving mesh finite difference method is developed for the numerical solution of equilibrium radiation diffusion equations in two dimensions. The method is based on the moving mesh partial differential equation approach and moves the mesh continuously in time using a system of meshing partial differential equations. The mesh adaptation is controlled through a Hessian-based monitor function and the so-called equidistribution and alignment principles. Several challenging issues in the numerical solution are addressed. Particularly, the radiation diffusion coefficient depends on the energy density highly nonlinearly. This nonlinearity is treated using a predictor–corrector and lagged diffusion strategy. Moreover, the nonnegativity of the energy density is maintained using a cutoff method which has been known in literature to retain the accuracy and convergence order of finite difference approximation for parabolic equations. Numerical examples with multi-material, multiple spot concentration situations are presented. Numerical results show that the method works well for radiation diffusion equations and can produce numerical solutions of good accuracy. It is also shown that a two-level mesh movement strategy can significantly improve the efficiency of the computation.

  8. Fibroblast attachment onto novel titanium mesh membranes for guided bone regeneration.

    PubMed

    Rakhmatia, Yunia Dwi; Ayukawa, Yasunori; Atsuta, Ikiru; Furuhashi, Akihiro; Koyano, Kiyoshi

    2015-05-01

    Titanium mesh is used in orthopedic surgery as a barrier membrane, as it offers suitable characteristics, which allow mechanical support during the formation of new bone. An ideal membrane would facilitate cell attachment onto its surface, thereby helping to stabilize the blood clot and integrate the membrane into the tissue. However, currently available titanium mesh has millimeter-level pore sizes, which lead to soft tissue ingrowth through the pores. Therefore, the aim of this study was to investigate the fibroblast attachment and migration on different designs of novel titanium mesh with micrometer pore size for guided bone regeneration treatment. Six types of novel titanium mesh membrane and three groups of commercially available membranes were used in this study. Fibroblasts were isolated from 4-day-old green fluorescence protein rats and seeded onto membrane surfaces. At 24 h, the cells attached to the membrane surfaces were fixed and stained with DAPI. The blue-stained nuclei on membrane surfaces, and both upper and lower sides were counted. It was shown that different membrane materials, structure and design differ considerably in their capacity for cell attachment to the membrane surface. The novel membranes, especially mesh with 12 pores compared with mesh with multi-pores, allowed the fibroblast attachment on the membrane surface, but hindered the fibroblast migration through the pores into the lower side of the membrane, which is associated with the defect area in the clinical condition.

  9. Non-woven PGA/PVA fibrous mesh as an appropriate scaffold for chondrocyte proliferation.

    PubMed

    Rampichová, M; Koštáková, E; Filová, E; Prosecká, E; Plencner, M; Ocheretná, L; Lytvynets, A; Lukáš, D; Amler, E

    2010-01-01

    Non-woven textile mesh from polyglycolic acid (PGA) was found as a proper material for chondrocyte adhesion but worse for their proliferation. Neither hyaluronic acid nor chitosan nor polyvinyl alcohol (PVA) increased chondrocyte adhesion. However, chondrocyte proliferation suffered from acidic byproducts of PGA degradation. However, the addition of PVA and/or chitosan into a wet-laid non-woven textile mesh from PGA improved chondrocyte proliferation seeded in vitro on the PGA-based composite scaffold namely due to a diminished acidification of their microenvironment. This PVA/PGA composite mesh used in combination with a proper hydrogel minimized the negative effect of PGA degradation without dropping positive parameters of the PGA wet-laid non-woven textile mesh. In fact, presence of PVA and/or chitosan in the PGA-based wet-laid non-woven textile mesh even advanced the PGA-based wet-laid non-woven textile mesh for chondrocyte seeding and artificial cartilage production due to a positive effect of PVA in such a scaffold on chondrocyte proliferation.

  10. Maintaining tetrahedral mesh quality in response to time-dependent topological and geometrical deformation

    SciTech Connect

    Kuprat, A.; George, D.

    1998-12-01

    When modeling deformation of geometrically complex regions, unstructured tetrahedral meshes provide the flexibility necessary to track interfaces as they change geometrically and topologically. In the class of time-dependent simulations considered in this paper, multimaterial interfaces are represented by sets of triangular facets, and motion of the interfaces is controlled by physical considerations. The motion of interior points in the conforming tetrahedral mesh (i.e., points not on interfaces) is arbitrary and may be chosen to produce good element shapes. In the context of specified boundary motion driven by physical considerations, they have found that a rather large glossary of mesh changes is required to allow the simulation to survive all the transitions of interface geometry and topology that occur during time evolution. This paper will describe mesh changes required to maintain good element quality as the geometry evolves, as well as mesh changes required to capture changes i n topology that occur when material regions collapse or pinch off. This paper will present a detailed description of mesh changes necessary for capturing the aforementioned geometrical and topological changes, as implemented in the code GRAIN3D, and will provide examples from a metallic grain growth simulation in which the normal velocity of the grain boundary is proportional to mean curvature.

  11. The “Pelvic Harness”: a skeletonized mesh implant for safe pelvic floor reconstruction

    PubMed Central

    Natalia, Sumerova; Menahem, Neuman; Haim, Krissi; Dmitri, Pushkar

    2016-01-01

    ABSTRACT Objectives To evaluate the feasibility, safety and surgical results of skeletonized mesh implants to form a pelvic harness for pelvic floor reconstruction surgery. Study design Patients with advanced pelvic floor prolapse were enrolled to this study. Study model was a kit mesh, reduced to 75% of the original surface area by cutting out mesh material from the central mesh body. Patients were evaluated at the end of the 1st and 6th post-operative months and interviewed at the study conclusion. Results Ninety-five women with advanced pelvic floor prolapse had this implant. Mean follow-up duration was 9 months (6-12 months). The POP-Q point’s measurements showed marked and statistically significant improvements. Bladder over-activity symptoms, fecal incontinence, pelvic pain and constipation rates were all reduced as well. No adverse effects related to the dissection or mesh implantation were marked. The first and sixth post-operative month follow-up records as well as the study conclusion interview findings were satisfactory in terms of subjective and objective cure and adverse effects occurrence. Conclusion This study data proposes that skeletonizing meshes might be safely and successfully implanted for potentially improved pelvic floor reconstruction. PMID:27286114

  12. A Numerical Study of Mesh Adaptivity in Multiphase Flows with Non-Newtonian Fluids

    NASA Astrophysics Data System (ADS)

    Percival, James; Pavlidis, Dimitrios; Xie, Zhihua; Alberini, Federico; Simmons, Mark; Pain, Christopher; Matar, Omar

    2014-11-01

    We present an investigation into the computational efficiency benefits of dynamic mesh adaptivity in the numerical simulation of transient multiphase fluid flow problems involving Non-Newtonian fluids. Such fluids appear in a range of industrial applications, from printing inks to toothpastes and introduce new challenges for mesh adaptivity due to the additional ``memory'' of viscoelastic fluids. Nevertheless, the multiscale nature of these flows implies huge potential benefits for a successful implementation. The study is performed using the open source package Fluidity, which couples an unstructured mesh control volume finite element solver for the multiphase Navier-Stokes equations to a dynamic anisotropic mesh adaptivity algorithm, based on estimated solution interpolation error criteria, and conservative mesh-to-mesh interpolation routine. The code is applied to problems involving rheologies ranging from simple Newtonian to shear-thinning to viscoelastic materials and verified against experimental data for various industrial and microfluidic flows. This work was undertaken as part of the EPSRC MEMPHIS programme grant EP/K003976/1.

  13. Positive Contrast MRI Techniques for Visualization of Iron-Loaded Hernia Mesh Implants in Patients

    PubMed Central

    Ciritsis, Alexander; Truhn, Daniel; Hansen, Nienke L.; Otto, Jens; Kuhl, Christiane K.; Kraemer, Nils A.

    2016-01-01

    Object In MRI, implants and devices can be delineated via susceptibility artefacts. To discriminate susceptibility voids from proton-free structures, different positive contrast techniques were implemented. The purpose of this study was to evaluate a pulse sequence-based positive contrast technique (PCSI) and a post-processing susceptibility gradient mapping algorithm (SGM) for visualization of iron loaded mesh implants in patients. Material and Methods Five patients with iron-loaded MR-visible inguinal hernia mesh implants were examined at 1.5 Tesla. A gradient echo sequence (GRE; parameters: TR: 8.3ms; TE: 4.3ms; NSA:2; FA:20°; FOV:350mm²) and a PCSI sequence (parameters: TR: 25ms; TE: 4.6ms; NSA:4; FA:20°; FOV:350mm²) with on-resonant proton suppression were performed. SGM maps were calculated using two algorithms. Image quality and mesh delineation were independently evaluated by three radiologists. Results On GRE, the iron-loaded meshes generated distinct susceptibility-induced signal voids. PCSI exhibited susceptibility differences including the meshes as hyperintense signals. SGM exhibited susceptibility differences with positive contrast. Visually, the different algorithms presented no significant differences. Overall, the diagnostic value was rated best in GRE whereas PCSI and SGM were barely “sufficient”. Conclusion Both “positive contrast” techniques depicted implanted meshes with hyperintense signal. SGM comes without additional acquisition time and can therefore be utilized in every patient. PMID:27192201

  14. [Osteosynthesis treatment of periorbital fractures with the mandibular mesh system].

    PubMed

    Kurzeja, A

    1984-10-01

    We report about 11 patients with periorbital fracture. Blow-out fracture and patients with fracture of the anterior wall of the frontal sinus. Treatment was operative osteosynthesis. We used for that the Mandibular Mesh System of 3M Company, Germany. We usually observed the patients for one year and got a firm unification of the fragments, as well a good cosmetic success from the beginning. We had not seen any complications caused by the osteosynthesis material. The author consider the most important advantages of this system to be the considerably smaller measurements, the possibility to form the osteosynthetical sheets out of a lattice, the higher solidity of Titanium and the good formability.

  15. Array-based, parallel hierarchical mesh refinement algorithms for unstructured meshes

    DOE PAGES

    Ray, Navamita; Grindeanu, Iulian; Zhao, Xinglin; ...

    2016-08-18

    In this paper, we describe an array-based hierarchical mesh refinement capability through uniform refinement of unstructured meshes for efficient solution of PDE's using finite element methods and multigrid solvers. A multi-degree, multi-dimensional and multi-level framework is designed to generate the nested hierarchies from an initial coarse mesh that can be used for a variety of purposes such as in multigrid solvers/preconditioners, to do solution convergence and verification studies and to improve overall parallel efficiency by decreasing I/O bandwidth requirements (by loading smaller meshes and in memory refinement). We also describe a high-order boundary reconstruction capability that can be used tomore » project the new points after refinement using high-order approximations instead of linear projection in order to minimize and provide more control on geometrical errors introduced by curved boundaries.The capability is developed under the parallel unstructured mesh framework "Mesh Oriented dAtaBase" (MOAB Tautges et al. (2004)). We describe the underlying data structures and algorithms to generate such hierarchies in parallel and present numerical results for computational efficiency and effect on mesh quality. Furthermore, we also present results to demonstrate the applicability of the developed capability to study convergence properties of different point projection schemes for various mesh hierarchies and to a multigrid finite-element solver for elliptic problems.« less

  16. Automatic finite-element mesh generation using artificial neural networks. Part 1: Prediction of mesh density

    SciTech Connect

    Chedid, R.; Najjar, N.

    1996-09-01

    One of the inconveniences associated with the existing finite-element packages is the need for an educated user to develop a correct mesh at the preprocessing level. Procedures which start with a coarse mesh and attempt serious refinements, as is the case in most adaptive finite-element packages, are time consuming and costly. Hence, it is very important to develop a tool that can provide a mesh that either leads immediately to an acceptable solution, or would require fewer correcting steps to achieve better results. In this paper, the authors present a technique for automatic mesh generation based on artificial neural networks (ANN). The essence of this technique is to predict the mesh density distribution of a given model, and then supply this information to a Kohonen neural network which provides the final mesh. Prediction of mesh density is accomplished by a simple feedforward neural network which has the ability to learn the relationship between mesh density and model geometric features. It will be shown that ANN are able to recognize delicate areas where a sharp variation of the magnetic field is expected. Examples of 2-D models are provided to illustrate the usefulness of the proposed technique.

  17. Array-based, parallel hierarchical mesh refinement algorithms for unstructured meshes

    SciTech Connect

    Ray, Navamita; Grindeanu, Iulian; Zhao, Xinglin; Mahadevan, Vijay; Jiao, Xiangmin

    2016-08-18

    In this paper, we describe an array-based hierarchical mesh refinement capability through uniform refinement of unstructured meshes for efficient solution of PDE's using finite element methods and multigrid solvers. A multi-degree, multi-dimensional and multi-level framework is designed to generate the nested hierarchies from an initial coarse mesh that can be used for a variety of purposes such as in multigrid solvers/preconditioners, to do solution convergence and verification studies and to improve overall parallel efficiency by decreasing I/O bandwidth requirements (by loading smaller meshes and in memory refinement). We also describe a high-order boundary reconstruction capability that can be used to project the new points after refinement using high-order approximations instead of linear projection in order to minimize and provide more control on geometrical errors introduced by curved boundaries.The capability is developed under the parallel unstructured mesh framework "Mesh Oriented dAtaBase" (MOAB Tautges et al. (2004)). We describe the underlying data structures and algorithms to generate such hierarchies in parallel and present numerical results for computational efficiency and effect on mesh quality. Furthermore, we also present results to demonstrate the applicability of the developed capability to study convergence properties of different point projection schemes for various mesh hierarchies and to a multigrid finite-element solver for elliptic problems.

  18. Formation of a chronic pain syndrome due to mesh shrinkage after laparoscopic intraperitoneal onlay mesh (IPOM).

    PubMed

    Klein, Fritz; Ospina, Carlos; Rudolph, Birgit; Wüstefeld, Joost; Denecke, Timm; Neuhaus, Peter; Schmidt, Sven-Christian

    2012-10-01

    The case of a 58-year-old male patient who developed a chronic pain syndrome after laparoscopic intraperitoneal onlay mesh for treatment of a large symptomatic umbilical hernia combined with rectus diastasis is reported. Twelve months after an uncomplicated initial surgery, the patient presented with progressive signs of a foreign body sensation and pain in the anterior abdominal wall. Computed tomography examination revealed no pathologic findings but a marked shrinkage of the mesh implant. Because of further progressive symptoms, explorative laparotomy was performed. Mesh shrinkage and adhesions with a surrounding chronic tissue reaction were found as the cause of the pain syndrome. This case demonstrates a case of a chronic pain syndrome due to mesh shrinkage 12 months after initial ventral hernia repair. Mesh shrinkage should therefore be taken into consideration in patients with progressive pain chronic syndromes after laparoscopic ventral hernia repair.

  19. Floating shock fitting via Lagrangian adaptive meshes

    NASA Technical Reports Server (NTRS)

    Vanrosendale, John

    1994-01-01

    In recent works we have formulated a new approach to compressible flow simulation, combining the advantages of shock-fitting and shock-capturing. Using a cell-centered Roe scheme discretization on unstructured meshes, we warp the mesh while marching to steady state, so that mesh edges align with shocks and other discontinuities. This new algorithm, the Shock-fitting Lagrangian Adaptive Method (SLAM) is, in effect, a reliable shock-capturing algorithm which yields shock-fitted accuracy at convergence. Shock-capturing algorithms like this, which warp the mesh to yield shock-fitted accuracy, are new and relatively untried. However, their potential is clear. In the context of sonic booms, accurate calculation of near-field sonic boom signatures is critical to the design of the High Speed Civil Transport (HSCT). SLAM should allow computation of accurate N-wave pressure signatures on comparatively coarse meshes, significantly enhancing our ability to design low-boom configurations for high-speed aircraft.

  20. Hydrophobic meshes for oil spill recovery devices.

    PubMed

    Deng, Da; Prendergast, Daniel P; MacFarlane, John; Bagatin, Roberto; Stellacci, Francesco; Gschwend, Philip M

    2013-02-01

    Widespread use of petrochemicals often leads to accidental releases in aquatic environments, occasionally with disastrous results. We have developed a hydrophobic and oleophilic mesh that separates oil from water continuously in situ via capillary action, providing a means of recovering spilt oil from surface waters. Steel mesh is dip-coated in a xylene solution of low-density polyethylene, creating a hydrophobic surface with tunable roughness and opening size. The hydrophobic mesh allows oil to pass through the openings while preventing the concomitant passage of water. A bench-top prototype demonstrated the efficacy of such an oil recovery device and allowed us to quantify the factors governing the ability of the mesh to separate oil and water. Preliminary data analysis suggested that the oleophilic openings behave somewhat like capillary tubes: the oil flux is inversely proportional to oil viscosity, and directly proportional to the size of the mesh openings. An unpinned meniscus model was found to predict the water intrusion pressure successfully, which increased as the opening size decreased. The trade-off between water intrusion and oil flow rate suggests an optimal pore size for given oil properties and sea conditions.

  1. Drag reduction properties of superhydrophobic mesh pipes

    NASA Astrophysics Data System (ADS)

    Geraldi, Nicasio R.; Dodd, Linzi E.; Xu, Ben B.; Wells, Gary G.; Wood, David; Newton, Michael I.; McHale, Glen

    2017-09-01

    Even with the recent extensive study into superhydrophobic surfaces, the fabrication of such surfaces on the inside walls of a pipe remains challenging. In this work we report a convenient bi-layered pipe design using a thin superhydrophobic metallic mesh formed into a tube, supported inside another pipe. A flow system was constructed to test the fabricated bi-layer pipeline, which allowed for different constant flow rates of water to be passed through the pipe, whilst the differential pressure was measured, from which the drag coefficient (ƒ) and Reynolds numbers (Re) were calculated. Expected values of ƒ were found for smooth glass pipes for the Reynolds number (Re) range 750-10 000, in both the laminar and part of the turbulent regimes. Flow through plain meshes without the superhydrophobic coating were also measured over a similar range (750  <  Re  <  14 000). After applying the superhydrophobic coating, ƒ was found for 4000  <  Re  <  14 000 and was found to be less than that of an uncoated mesh, but greater than that of a smooth glass pipe of the same diameter. This demonstrates that a superhydrophobic mesh can support a plastron and provide a drag reduction compared to a plain mesh, however, the plastron is progressively destroyed with use and in particular at higher flow rates.

  2. 2D nearly orthogonal mesh generation

    NASA Astrophysics Data System (ADS)

    Zhang, Yaoxin; Jia, Yafei; Wang, Sam S. Y.

    2004-11-01

    The Ryskin and Leal (RL) system is the most widely used mesh generation system for the orthogonal mapping. However, when this system is used in domains with complex geometry, particularly in those with sharp corners and strong curvatures, serious distortion or overlapping of mesh lines may occur and an acceptable solution may not be possible. In the present study, two methods are proposed to generate nearly orthogonal meshes with the smoothness control. In the first method, the original RL system is modified by introducing smoothness control functions, which are formulated through the blending of the conformal mapping and the orthogonal mapping; while in the second method, the RL system is modified by introducing the contribution factors. A hybrid system of both methods is also developed. The proposed methods are illustrated by several test examples. Applications of these methods in a natural river channel are demonstrated. It is shown that the modified RL systems are capable of producing meshes with an adequate balance between the orthogonality and the smoothness for complex computational domains without mesh distortions and overlapping.

  3. Multislope MUSCL method for general unstructured meshes

    NASA Astrophysics Data System (ADS)

    Le Touze, C.; Murrone, A.; Guillard, H.

    2015-03-01

    The multislope concept has been recently introduced in the literature to deal with MUSCL reconstructions on triangular and tetrahedral unstructured meshes in the finite volume cell-centered context. Dedicated scalar slopes are used to compute the interpolations on each face of a given element, in opposition to the monoslope methods in which a unique limited gradient is used. The multislope approach reveals less expensive and potentially more accurate than the classical gradient techniques. Besides, it may also help the robustness when dealing with hyperbolic systems involving complex solutions, with large discontinuities and high density ratios. However some important limitations on the mesh topology still have to be overcome with the initial multislope formalism. In this paper, a generalized multislope MUSCL method is introduced for cell-centered finite volume discretizations. The method is freed from constraints on the mesh topology, thereby operating on completely general unstructured meshes. Moreover optimal second-order accuracy is reached at the faces centroids. The scheme can be written with nonnegative coefficients, which makes it L∞-stable. Special attention has also been paid to equip the reconstruction procedure with well-adapted dedicated limiters, potentially CFL-dependent. Numerical tests are provided to prove the ability of the method to deal with completely general meshes, while exhibiting second-order accuracy.

  4. Conservative interpolation between general spherical meshes

    NASA Astrophysics Data System (ADS)

    Kritsikis, Evaggelos; Aechtner, Matthias; Meurdesoif, Yann; Dubos, Thomas

    2017-01-01

    An efficient, local, explicit, second-order, conservative interpolation algorithm between spherical meshes is presented. The cells composing the source and target meshes may be either spherical polygons or latitude-longitude quadrilaterals. Second-order accuracy is obtained by piece-wise linear finite-volume reconstruction over the source mesh. Global conservation is achieved through the introduction of a supermesh, whose cells are all possible intersections of source and target cells. Areas and intersections are computed exactly to yield a geometrically exact method. The main efficiency bottleneck caused by the construction of the supermesh is overcome by adopting tree-based data structures and algorithms, from which the mesh connectivity can also be deduced efficiently.The theoretical second-order accuracy is verified using a smooth test function and pairs of meshes commonly used for atmospheric modelling. Experiments confirm that the most expensive operations, especially the supermesh construction, have O(NlogN) computational cost. The method presented is meant to be incorporated in pre- or post-processing atmospheric modelling pipelines, or directly into models for flexible input/output. It could also serve as a basis for conservative coupling between model components, e.g., atmosphere and ocean.

  5. Laparoscopic-assisted Ventral Hernia Repair: Primary Fascial Repair with Polyester Mesh versus Polyester Mesh Alone.

    PubMed

    Karipineni, Farah; Joshi, Priya; Parsikia, Afshin; Dhir, Teena; Joshi, Amit R T

    2016-03-01

    Laparoscopic-assisted ventral hernia repair (LAVHR) with mesh is well established as the preferred technique for hernia repair. We sought to determine whether primary fascial closure and/or overlap of the mesh reduced recurrence and/or complications. We conducted a retrospective review on 57 LAVHR patients using polyester composite mesh between August 2010 and July 2013. They were divided into mesh-only (nonclosure) and primary fascial closure with mesh (closure) groups. Patient demographics, prior surgical history, mesh overlap, complications, and recurrence rates were compared. Thirty-nine (68%) of 57 patients were in the closure group and 18 (32%) in the nonclosure group. Mean defect sizes were 15.5 and 22.5 cm(2), respectively. Participants were followed for a mean of 1.3 years [standard deviation (SD) = 0.7]. Recurrence rates were 2/39 (5.1%) in the closure group and 1/18 (5.6%) in the nonclosure group (P = 0.947). There were no major postoperative complications in the nonclosure group. The closure group experienced four (10.3%) complications. This was not a statistically significant difference (P = 0.159). The median mesh-to-hernia ratio for all repairs was 15.2 (surface area) and 3.9 (diameter). Median length of stay was 14.5 hours (1.7-99.3) for patients with nonclosure and 11.9 hours (6.9-90.3 hours) for patients with closure (P = 0.625). In conclusion, this is one of the largest series of LAVHR exclusively using polyester dual-sided mesh. Our recurrence rate was about 5 per cent. Significant mesh overlap is needed to achieve such low recurrence rates. Primary closure of hernias seems less important than adequate mesh overlap in preventing recurrence after LAVHR.

  6. [Synthetic meshes for transvaginal surgical cure of genital prolapse: evaluation in 2005].

    PubMed

    Debodinance, P; Cosson, M; Collinet, P; Boukerrou, M; Lucot, J-P; Madi, N

    2006-09-01

    Since 1996, prosthetic meshes have become increasingly popular for transvaginal surgical cure of genital prolapse. In light of the growing number of proposed techniques and materials we reviewed the experience of the pioneers in order to provide surgeons with the most objective information available. We reviewed the literature indexed in Meline/PubMed and Current Contents retaining all work concerning resorbable and non-resorbable meshes. For the larger class of non-resorbable meshes we also reviewed articles by category of material, each type of mesh being carefully defined: different compositions of polypropylene, polyester, composite meshes and also insertion kits. Resorbable meshes were evaluated in two randomized studies which did not demonstrate better results than with simple folding known to have a high rate of recurrence. For polypropylene meshes, Marlex was studied in six trials which demonstrated a high rate of cure at one year but also a high rate of erosion which reached 25%. Use of Atrium was mentioned in three studies with a 6 to 12% recurrence rate and an erosion rate nearly reaching 20%. The majority of studies used Prolene and Gynemesh. Seventeen authors reported their experience, generally reviewing retrospective series, with recurrence rates of less than 10% for follow-up periods rarely greater than two years. A large variety of forms and sizes have been used, hindering comparisons. The rate of erosion was also quite variable, as high as 45%, demonstrating the need for a precise definition of erosion. Only recently have authors shown interest in the impact of prosthetic meshes on quality of life and sexual activity. An improvement is generally noted for defecation but the rate of dyspareunia has reached as high as 60%. Here again grades of prosthetic retraction should be better defined. Proposed to improve these phenomena, soft Prolene recently used by several authors does not appear to fulfil expectations. Since 2005, several precut

  7. Evaluation of various seeding techniques for culturing osteogenic cells on titanium fiber mesh.

    PubMed

    van den Dolder, Juliette; Spauwen, Paul H M; Jansen, John A

    2003-04-01

    The objective of the present study was to learn more about the effect of seeding and loading techniques on the osteogenic differentiation in vitro of rat bone marrow cells into titanium fiber mesh. This material was used as received or subjected to glow discharge treatment (RFGD). The seeding methods that were used included a so-called droplet, cell suspension (high and low cell density), and rotating plate method. Osteogenic cells were cultured for 4, 8, and 16 days into titanium fiber mesh. DNA, osteocalcin, scanning electron microscopy (SEM) analysis, and calcium measurements were used to determine cellular proliferation and differentiation. DNA analysis of the differently seeded specimens showed that proliferation proceeded faster in the first versus second run for droplet and cell suspension samples. No clear and distinct additional effect was found when RFGD treatment was used. Statistical analyses revealed that high cell density and low rotational speed resulted always in a significantly higher DNA content. Calcium measurements and osteocalcin analysis showed that using high cell densities during inoculation of the scaffolds prevented the occurrence of differences between experimental runs. SEM examination showed that for droplet and cell suspension samples cells were present at only one side of the mesh. The mesh side where the cell sheet was observed depended on the additional use of glow discharge treatment. On these materials, the cells had penetrated through the meshes and formed a cell sheet at the bottom side. When rotation was used, no cell sheet was formed and cells had invaded the meshes and were growing around the titanium fibers. On the basis of our results, we conclude that (1). titanium fiber mesh is indeed suitable to support the osteogenic expression of bone marrow cells, and (2). changing the initial cell density as well as the use of dynamic seeding methods can influence the osteogenic capacity of the scaffold.

  8. Management of strangulated abdominal wall hernias with mesh; early results

    PubMed Central

    Ozbagriacik, Mustafa; Bas, Gurhan; Basak, Fatih; Sisik, Abdullah; Acar, Aylin; Kudas, Ilyas; Yucel, Metin; Ozpek, Adnan; Alimoglu, Orhan

    2015-01-01

    OBJECTIVE: Surgery for abdominal wall hernias is a common procedure in general surgery practice. The main causes of delay for the operation are comorbid problems and patient unwillingness, which eventually, means that some patients are admitted to emergency clinics with strangulated hernias. In this report, patients who admitted to the emergency department with strangulated adominal wall hernias are presented together with their clinical management. METHODS: Patients who admitted to our clinic between January 2009 and November 2011 and underwent emergency operation were included in the study retrospectively. Demographic characteristics, hernia type, length of hospital stay, surgical treatment and complications were assessed. RESULTS: A total 81 patients (37 female, 44 male) with a mean age of 52.1±17.64 years were included in the study. Inguinal, femoral, umbilical and incisional hernias were detected in 40, 26, 9 and 6 patients respectively. Polypropylene mesh was used in 75 patients for repair. Primary repair without mesh was used in six patients. Small bowel (n=10; 12.34%), omentum (n=19; 23.45%), appendix (n=1; 1.2%) and Meckel’s diverticulum (n=1; 1.2%) were resected. Median length of hospital stay was 2 (1–7) days. Surgical site infection was detected in five (6.2%) patients. No significant difference was detected for length of hospital stay and surgical site infection in patients who had mesh repair (p=0.232 and 0.326 respectively). CONCLUSION: The need for bowel resection is common in strangulated abdominal wall hernias which undergo emergency operation. In the present study, an increase of morbidity was seen in patients who underwent bowel resection. No morbidity was detected related to the usage of prosthetic materials in repair of hernias. Hence, we believe that prosthetic materials can be used safely in emergency cases. PMID:28058336

  9. Mesh saliency with adaptive local patches

    NASA Astrophysics Data System (ADS)

    Nouri, Anass; Charrier, Christophe; Lézoray, Olivier

    2015-03-01

    3D object shapes (represented by meshes) include both areas that attract the visual attention of human observers and others less or not attractive at all. This visual attention depends on the degree of saliency exposed by these areas. In this paper, we propose a technique for detecting salient regions in meshes. To do so, we define a local surface descriptor based on local patches of adaptive size and filled with a local height field. The saliency of mesh vertices is then defined as its degree measure with edges weights computed from adaptive patch similarities. Our approach is compared to the state-of-the-art and presents competitive results. A study evaluating the influence of the parameters establishing this approach is also carried out. The strength and the stability of our approach with respect to noise and simplification are also studied.

  10. GRChombo: Numerical relativity with adaptive mesh refinement

    NASA Astrophysics Data System (ADS)

    Clough, Katy; Figueras, Pau; Finkel, Hal; Kunesch, Markus; Lim, Eugene A.; Tunyasuvunakool, Saran

    2015-12-01

    In this work, we introduce {\\mathtt{GRChombo}}: a new numerical relativity code which incorporates full adaptive mesh refinement (AMR) using block structured Berger-Rigoutsos grid generation. The code supports non-trivial ‘many-boxes-in-many-boxes’ mesh hierarchies and massive parallelism through the message passing interface. {\\mathtt{GRChombo}} evolves the Einstein equation using the standard BSSN formalism, with an option to turn on CCZ4 constraint damping if required. The AMR capability permits the study of a range of new physics which has previously been computationally infeasible in a full 3 + 1 setting, while also significantly simplifying the process of setting up the mesh for these problems. We show that {\\mathtt{GRChombo}} can stably and accurately evolve standard spacetimes such as binary black hole mergers and scalar collapses into black holes, demonstrate the performance characteristics of our code, and discuss various physics problems which stand to benefit from the AMR technique.

  11. GRChombo : Numerical Relativity with Adaptive Mesh Refinement

    SciTech Connect

    Clough, Katy; Figueras, Pau; Finkel, Hal; Kunesch, Markus; Lim, Eugene A.; Tunyasuvunakool, Saran

    2015-12-24

    In this work, we introduce GRChombo: a new numerical relativity code which incorporates full adaptive mesh refinement (AMR) using block structured Berger-Rigoutsos grid generation. The code supports non-trivial 'many-boxes-in-many-boxes' mesh hierarchies and massive parallelism through the message passing interface. GRChombo evolves the Einstein equation using the standard BSSN formalism, with an option to turn on CCZ4 constraint damping if required. The AMR capability permits the study of a range of new physics which has previously been computationally infeasible in a full 3 + 1 setting, while also significantly simplifying the process of setting up the mesh for these problems. We show that GRChombo can stably and accurately evolve standard spacetimes such as binary black hole mergers and scalar collapses into black holes, demonstrate the performance characteristics of our code, and discuss various physics problems which stand to benefit from the AMR technique.

  12. The generation of hexahedral meshes for assembly geometries: A survey

    SciTech Connect

    TAUTGES,TIMOTHY J.

    2000-02-14

    The finite element method is being used today to model component assemblies in a wide variety of application areas, including structural mechanics, fluid simulations, and others. Generating hexahedral meshes for these assemblies usually requires the use of geometry decomposition, with different meshing algorithms applied to different regions. While the primary motivation for this approach remains the lack of an automatic, reliable all-hexahedral meshing algorithm, requirements in mesh quality and mesh configuration for typical analyses are also factors. For these reasons, this approach is also sometimes required when producing other types of unstructured meshes. This paper will review progress to date in automating many parts of the hex meshing process, which has halved the time to produce all-hex meshes for large assemblies. Particular issues which have been exposed due to this progress will also be discussed, along with their applicability to the general unstructured meshing problem.

  13. Titanium Mesh Nasal Repair without Nasal Lining.

    PubMed

    Zenga, Joseph; Kao, Katherine; Chen, Collin; Gross, Jennifer; Hahn, Samuel; Chi, John J; Branham, Gregory H

    2017-02-01

    The objective of this study was to describe outcomes for patients who underwent titanium mesh reconstruction of full-thickness nasal defects without internal lining repair. This is a retrospective cohort study. Patients with through-and-through nasal defects were identified at a single academic institution between 2008 and 2016. Nasal reconstruction was performed with either titanium mesh and external skin reconstruction without repair of the intranasal lining or traditional three-layer closure. Five patients underwent titanium mesh reconstruction and 11 underwent traditional three-layer repair. Median follow-up was 11 months (range, 2-66 months). The only significant difference between groups was older age in patients undergoing titanium reconstruction (mean, 81 vs. 63 years; difference of 18; 95% confidence interval [CI], 4-32 years). Defect extent including overall size and structures removed was similar between groups (p > 0.05). Paramedian forehead flap was the most common external reconstruction in both groups (100% for titanium mesh and 73% for three-layer closure). Time under anesthesia was significantly shorter for titanium mesh reconstruction (median, 119 vs. 314 minutes; difference of 195; 95% CI, 45-237). Estimated blood loss and length of hospital stay were similar between groups (p > 0.05). Complication rates were substantial although not significantly different, 40 and 36% in titanium and three-layer reconstruction, respectively (p > 0.05). All patients with complications after titanium reconstruction had prior or postoperative radiotherapy. Titanium mesh reconstruction of through-and-through nasal defects can successfully be performed without reconstruction of the intranasal lining, significantly decreasing operative times. This reconstructive technique may not be suitable for patients who undergo radiotherapy.

  14. Degradation of polypropylene in vivo: A microscopic analysis of meshes explanted from patients.

    PubMed

    Iakovlev, Vladimir V; Guelcher, Scott A; Bendavid, Robert

    2017-02-01

    Polypropylene meshes, originally introduced for hernia repair, are presently utilized in several anatomical sites. Several million are implanted annually worldwide. Depending on the device, up to 10% will be excised to treat complications. The excised meshes can provide material to study the complications, however, they have remained underutilized over the last decades and the mechanisms of complications continue to be incompletely understood. The fundamental question as to whether polypropylene degrades in vivo is still debated. We have examined 164 excised meshes using conventional microscopy to search for features of polypropylene degradation. Four specimens were also examined by transmission electron microscopy. The degraded material, detected by its ability to absorb dyes in the degradation nanopores, formed a continuous layer at the surface of the mesh fibers. It retained birefringence, inclusions of non-degraded polypropylene, and showed ability to meld with the non-degraded fiber core when heated by the surgical cautery. Several features indicated that the degradation layer formed in vivo: inflammatory cells trapped within fissures, melting caused by cautery of excision surgery, and gradual but progressive growth of the degradation layer while in the body. Cracking of the degraded material indicated a contribution to clinically important mesh stiffening and deformation. Chemical products of degradation need to be analyzed and studied for their role in the mesh-body interactions. The described methods can also be used to study degradation of other materials. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 237-248, 2017. © 2015 Wiley Periodicals, Inc.

  15. Development of modular cable mesh deployable antenna

    NASA Astrophysics Data System (ADS)

    Meguro, Akira; Mitsugi, Jin; Andou, Kazuhide

    1993-03-01

    This report describes a concept and key technologies for the modular mesh deployable antenna. The antenna reflector composed of independently manufactured and tested modules is presented. Each module consists of a mesh surface, a cable network, and a deployable truss structure. The cable network comprises three kinds of cables, surface, tie, and back cables. Adjustment of tie cable lengths improves the surface accuracy. Synchronous deployment truss structures are considered as a supporting structure. Their design method, BBM's (Bread Board Model) and deployment analysis are also explained.

  16. Shuffle-exchanges on augmented meshes

    NASA Technical Reports Server (NTRS)

    Bokhari, S. H.

    1984-01-01

    A mesh connected array of size N = two to the Kth power, K an integer, can be augmented by adding at most one edge per node such that it can perform a shuffle-exchange of size N/2 in constant time. A shuffle-exchange of size N is performed on this augmented array in constant time. This is done by combining the available perfect shuffle of size N/2 with the existing nearest neighbor connections of the mesh. By carefully scheduling the different permutations that are composed in order to achieve the shuffle, the time required is reduced to 5 steps, which is optimal for this network.

  17. Multigrid solution strategies for adaptive meshing problems

    NASA Technical Reports Server (NTRS)

    Mavriplis, Dimitri J.

    1995-01-01

    This paper discusses the issues which arise when combining multigrid strategies with adaptive meshing techniques for solving steady-state problems on unstructured meshes. A basic strategy is described, and demonstrated by solving several inviscid and viscous flow cases. Potential inefficiencies in this basic strategy are exposed, and various alternate approaches are discussed, some of which are demonstrated with an example. Although each particular approach exhibits certain advantages, all methods have particular drawbacks, and the formulation of a completely optimal strategy is considered to be an open problem.

  18. Adaptive mesh refinement for storm surge

    NASA Astrophysics Data System (ADS)

    Mandli, Kyle T.; Dawson, Clint N.

    2014-03-01

    An approach to utilizing adaptive mesh refinement algorithms for storm surge modeling is proposed. Currently numerical models exist that can resolve the details of coastal regions but are often too costly to be run in an ensemble forecasting framework without significant computing resources. The application of adaptive mesh refinement algorithms substantially lowers the computational cost of a storm surge model run while retaining much of the desired coastal resolution. The approach presented is implemented in the GEOCLAW framework and compared to ADCIRC for Hurricane Ike along with observed tide gauge data and the computational cost of each model run.

  19. Stochastic diffusion processes on Cartesian meshes

    PubMed Central

    Meinecke, Lina; Lötstedt, Per

    2015-01-01

    Diffusion of molecules is simulated stochastically by letting them jump between voxels in a Cartesian mesh. The jump coefficients are first derived using finite difference, finite element, and finite volume approximations of the Laplacian on the mesh. An alternative is to let the first exit time for a molecule in random walk in a voxel define the jump coefficient. Such coefficients have the advantage of always being non-negative. These four different ways of obtaining the diffusion propensities are compared theoretically and in numerical experiments. A finite difference and a finite volume approximation generate the most accurate coefficients. PMID:26594087

  20. Unstructured Adaptive Meshes: Bad for Your Memory?

    NASA Technical Reports Server (NTRS)

    Biswas, Rupak; Feng, Hui-Yu; VanderWijngaart, Rob

    2003-01-01

    This viewgraph presentation explores the need for a NASA Advanced Supercomputing (NAS) parallel benchmark for problems with irregular dynamical memory access. This benchmark is important and necessary because: 1) Problems with localized error source benefit from adaptive nonuniform meshes; 2) Certain machines perform poorly on such problems; 3) Parallel implementation may provide further performance improvement but is difficult. Some examples of problems which use irregular dynamical memory access include: 1) Heat transfer problem; 2) Heat source term; 3) Spectral element method; 4) Base functions; 5) Elemental discrete equations; 6) Global discrete equations. Nonconforming Mesh and Mortar Element Method are covered in greater detail in this presentation.

  1. Intra Peritoneal Polypropylene Mesh and Newer Meshes in Ventral Hernia Repair: What EBM Says?

    PubMed

    Ramakrishna, H K; Lakshman, K

    2013-10-01

    Incisional hernias and other ventral hernias are common surgical problems. It is estimated that incisional hernia complicates about 2 % to 10 % of laparotomies. Ventral and incisional hernia repairs are among the common surgeries done by a general surgeon. It is proven beyond any doubt that suture repair of these hernias should not be done as recurrence rates are unacceptably high, some series reporting as high as 54 % on long-term follow-up. A prosthetic mesh should always be used in ventral hernia repair (VHR). Now, the polypropylene mesh (PPM) has become the prosthetic mesh of choice in the repair of hernias, including inguinal hernia. However, with the advent of laparoscopic repair where the mesh is placed intraperitoneally, concerns regarding safety of PPM are raised. Newer meshes are introduced, claiming lesser complication rate. Many types of newer meshes are available now. Newer meshes are invariably costlier than PPM by 15-20 times. Is this extra cost worth? We looked in to available literature for an answer.

  2. Rarefield gas flows through meshes and implications for atmospheric measurements

    NASA Astrophysics Data System (ADS)

    Gumbel, J.

    2001-05-01

    Meshes are commonly used as part of instruments for in situ atmospheric measurements. This study analyses the aerodynamic effect of meshes by means of wind tunnel experiments and numerical simulations. Based on the Direct Simulation Monte Carlo method, a simple mesh parameterisation is described and applied to a number of representative flow conditions. For open meshes freely exposed to the flow, substantial compression effects are found both upstream and downstream of the mesh. Meshes attached to close instrument structures, on the other hand, cause only minor flow disturbances. In an accompanying paper, the approach developed here is applied to the quantitative analysis of rocket-borne density measurements in the middle atmosphere.

  3. Oestradiol-releasing Biodegradable Mesh Stimulates Collagen Production and Angiogenesis: An Approach to Improving Biomaterial Integration in Pelvic Floor Repair.

    PubMed

    Mangır, Naşide; Hillary, Christopher J; Chapple, Christopher R; MacNeil, Sheila

    2017-06-03

    Polypropylene meshes cause severe complications in some patients. Materials that are biomechanically compatible and can better integrate into host tissues are urgently needed. To design an oestradiol-releasing electrospun poly-l-lactic acid (PLA) mesh and evaluate its ability to stimulate new extracellular matrix and new blood vessel formation. Human adipose derived mesenchymal cells (ADMSC) were isolated from fat. PLA meshes with micro- to nano-sized fibres containing 1%, 5%, and 10% oestradiol were constructed and used for in vitro and in vivo experiments. The angiogenic potential of the fibrous meshes was evaluated using an in vivo chorioallantoic membrane and an in vitro chick aortic arch assays. Oestradiol release was measured fluorometrically. The effect of fibrous meshes on proliferation and extracellular matrix (ECM) production of ADMSC was assessed using immunohistology. Mechanical properties were tested using a tensiometer. The ultrastructure of the mesh was not affected by the inclusion of oestradiol and mechanical properties were only slightly modified. Oestradiol was released from PLA meshes over a 5-mo period. ADMSCs cultured on oestradiol-releasing PLA meshes produced more ECM involving collagen I, collagen III, and elastin. Oestradiol-releasing meshes doubled new blood vessel formation in the chorioallantoic membrane assay (p=0.001) and outgrowth of pro-angiogenic cells in the aortic arch assay (p=0.001). Further studies in longer-term animal models are required to confirm these results. Oestradiol-releasing PLA meshes increase ECM production and stimulate angiogenesis. As such, they are promising candidate materials to be used in pelvic floor repair and to improve the initial healing phase of a repair material following implantation. In this study, we designed a tissue engineered material to be used to support weakened pelvic floor tissues in women to avoid the complications associated with current surgical mesh. Our results showed that this

  4. Sharpening diffuse interfaces with compressible fluids on unstructured meshes

    NASA Astrophysics Data System (ADS)

    Chiapolino, Alexandre; Saurel, Richard; Nkonga, Boniface

    2017-07-01

    Diffuse interface methods with compressible fluids, considered through hyperbolic multiphase flow models, have demonstrated their capability to solve a wide range of complex flow situations in severe conditions (both high and low speeds). These formulations can deal with the presence of shock waves, chemical and physical transformations, such as cavitation and detonation. Compared to existing approaches able to consider compressible materials and interfaces, these methods are conservative with respect to mixture mass, momentum, energy and are entropy preserving. Thanks to these properties they are very robust. However, in many situations, typically in low transient conditions, numerical diffusion at material interfaces is excessive. Several approaches have been developed to lower this weakness. In the present contribution, a specific flux limiter is proposed and inserted into conventional MUSCL type schemes, in the frame of the diffuse interface formulation of Saurel et al. (2009). With this limiter, interfaces are captured with 3 ± 1 mesh points depending on the test problem, showing significant improvement in interface representation compared to conventional limiters, such as for example Superbee. The method works on both structured and unstructured meshes and its implementation in existing codes is simple. Computational examples showing method capabilities and accuracy are presented.

  5. Materialism.

    PubMed

    Melnyk, Andrew

    2012-05-01

    Materialism is nearly universally assumed by cognitive scientists. Intuitively, materialism says that a person's mental states are nothing over and above his or her material states, while dualism denies this. Philosophers have introduced concepts (e.g., realization and supervenience) to assist in formulating the theses of materialism and dualism with more precision, and distinguished among importantly different versions of each view (e.g., eliminative materialism, substance dualism, and emergentism). They have also clarified the logic of arguments that use empirical findings to support materialism. Finally, they have devised various objections to materialism, objections that therefore serve also as arguments for dualism. These objections typically center around two features of mental states that materialism has had trouble in accommodating. The first feature is intentionality, the property of representing, or being about, objects, properties, and states of affairs external to the mental states. The second feature is phenomenal consciousness, the property possessed by many mental states of there being something it is like for the subject of the mental state to be in that mental state. WIREs Cogn Sci 2012, 3:281-292. doi: 10.1002/wcs.1174 For further resources related to this article, please visit the WIREs website.

  6. MeshEZW: an image coder using mesh and finite elements

    NASA Astrophysics Data System (ADS)

    Landais, Thomas; Bonnaud, Laurent; Chassery, Jean-Marc

    2003-08-01

    In this paper, we present a new method to compress the information in an image, called MeshEZW. The proposed approach is based on the finite elements method, a mesh construction and a zerotree method. The zerotree method is an adaptive of the EZW algorithm with two new symbols for increasing the performance. These steps allow a progressive representation of the image by the automatic construction of a bitstream. The mesh structure is adapted to the image compression domain and is defined to allow video comrpession. The coder is described and some preliminary results are discussed.

  7. Highly Symmetric and Congruently Tiled Meshes for Shells and Domes

    PubMed Central

    Rasheed, Muhibur; Bajaj, Chandrajit

    2016-01-01

    We describe the generation of all possible shell and dome shapes that can be uniquely meshed (tiled) using a single type of mesh face (tile), and following a single meshing (tiling) rule that governs the mesh (tile) arrangement with maximal vertex, edge and face symmetries. Such tiling arrangements or congruently tiled meshed shapes, are frequently found in chemical forms (fullerenes or Bucky balls, crystals, quasi-crystals, virus nano shells or capsids), and synthetic shapes (cages, sports domes, modern architectural facades). Congruently tiled meshes are both aesthetic and complete, as they support maximal mesh symmetries with minimal complexity and possess simple generation rules. Here, we generate congruent tilings and meshed shape layouts that satisfy these optimality conditions. Further, the congruent meshes are uniquely mappable to an almost regular 3D polyhedron (or its dual polyhedron) and which exhibits face-transitive (and edge-transitive) congruency with at most two types of vertices (each type transitive to the other). The family of all such congruently meshed polyhedra create a new class of meshed shapes, beyond the well-studied regular, semi-regular and quasi-regular classes, and their duals (platonic, Catalan and Johnson). While our new mesh class is infinite, we prove that there exists a unique mesh parametrization, where each member of the class can be represented by two integer lattice variables, and moreover efficiently constructable. PMID:27563368

  8. Particle Collection Efficiency for Nylon Mesh Screens

    PubMed Central

    Cena, Lorenzo G.; Ku, Bon-Ki; Peters, Thomas M.

    2015-01-01

    Mesh screens composed of nylon fibers leave minimal residual ash and produce no significant spectral interference when ashed for spectrometric examination. These characteristics make nylon mesh screens attractive as a collection substrate for nanoparticles. A theoretical single-fiber efficiency expression developed for wire-mesh screens was evaluated for estimating the collection efficiency of submicrometer particles for nylon mesh screens. Pressure drop across the screens, the effect of particle morphology (spherical and highly fractal) on collection efficiency and single-fiber efficiency were evaluated experimentally for three pore sizes (60, 100 and 180 μm) at three flow rates (2.5, 4 and 6 Lpm). The pressure drop across the screens was found to increase linearly with superficial velocity. The collection efficiency of the screens was found to vary by less than 4% regardless of particle morphology. Single-fiber efficiency calculated from experimental data was in good agreement with that estimated from theory for particles between 40 and 150 nm but deviated from theory for particles outside this size range. New coefficients for the single-fiber efficiency model were identified that minimized the sum of square error (SSE) between the values estimated with the model and those determined experimentally. Compared to the original theory, the SSE calculated using the modified theory was at least one order of magnitude lower for all screens and flow rates with the exception of the 60-μm pore screens at 2.5 Lpm, where the decrease was threefold. PMID:26692631

  9. Details of tetrahedral anisotropic mesh adaptation

    NASA Astrophysics Data System (ADS)

    Jensen, Kristian Ejlebjerg; Gorman, Gerard

    2016-04-01

    We have implemented tetrahedral anisotropic mesh adaptation using the local operations of coarsening, swapping, refinement and smoothing in MATLAB without the use of any for- N loops, i.e. the script is fully vectorised. In the process of doing so, we have made three observations related to details of the implementation: 1. restricting refinement to a single edge split per element not only simplifies the code, it also improves mesh quality, 2. face to edge swapping is unnecessary, and 3. optimising for the Vassilevski functional tends to give a little higher value for the mean condition number functional than optimising for the condition number functional directly. These observations have been made for a uniform and a radial shock metric field, both starting from a structured mesh in a cube. Finally, we compare two coarsening techniques and demonstrate the importance of applying smoothing in the mesh adaptation loop. The results pertain to a unit cube geometry, but we also show the effect of corners and edges by applying the implementation in a spherical geometry.

  10. Constrained and joint inversion on unstructured meshes

    NASA Astrophysics Data System (ADS)

    Doetsch, J.; Jordi, C.; Rieckh, V.; Guenther, T.; Schmelzbach, C.

    2015-12-01

    Unstructured meshes allow for inclusion of arbitrary surface topography, complex acquisition geometry and undulating geological interfaces in the inversion of geophysical data. This flexibility opens new opportunities for coupling different geophysical and hydrological data sets in constrained and joint inversions. For example, incorporating geological interfaces that have been derived from high-resolution geophysical data (e.g., ground penetrating radar) can add geological constraints to inversions of electrical resistivity data. These constraints can be critical for a hydrogeological interpretation of the inversion results. For time-lapse inversions of geophysical data, constraints can be derived from hydrological point measurements in boreholes, but it is difficult to include these hard constraints in the inversion of electrical resistivity monitoring data. Especially mesh density and the regularization footprint around the hydrological point measurements are important for an improved inversion compared to the unconstrained case. With the help of synthetic and field examples, we analyze how regularization and coupling operators should be chosen for time-lapse inversions constrained by point measurements and for joint inversions of geophysical data in order to take full advantage of the flexibility of unstructured meshes. For the case of constraining to point measurements, it is important to choose a regularization operator that extends beyond the neighboring cells and the uncertainty in the point measurements needs to be accounted for. For joint inversion, the choice of the regularization depends on the expected subsurface heterogeneity and the cell size of the parameter mesh.

  11. Functionalized Nanofiber Meshes Enhance Immunosorbent Assays.

    PubMed

    Hersey, Joseph S; Meller, Amit; Grinstaff, Mark W

    2015-12-01

    Three-dimensional substrates with high surface-to-volume ratios and subsequently large protein binding capacities are of interest for advanced immunosorbent assays utilizing integrated microfluidics and nanosensing elements. A library of bioactive and antifouling electrospun nanofiber substrates, which are composed of high-molecular-weight poly(oxanorbornene) derivatives, is described. Specifically, a set of copolymers are synthesized from three 7-oxanorbornene monomers to create a set of water insoluble copolymers with both biotin (bioactive) and triethylene glycol (TEG) (antifouling) functionality. Porous three-dimensional nanofiber meshes are electrospun from these copolymers with the ability to specifically bind streptavidin while minimizing the nonspecific binding of other proteins. Fluorescently labeled streptavidin is used to quantify the streptavidin binding capacity of each mesh type through confocal microscopy. A simplified enzyme-linked immunosorbent assay (ELISA) is presented to assess the protein binding capabilities and detection limits of these nanofiber meshes under both static conditions (26 h) and flow conditions (1 h) for a model target protein (i.e., mouse IgG) using a horseradish peroxidase (HRP) colorimetric assay. Bioactive and antifouling nanofiber meshes outperform traditional streptavidin-coated polystyrene plates under flow, validating their use in future advanced immunosorbent assays and their compatibility with microfluidic-based biosensors.

  12. Hash functions and triangular mesh reconstruction*1

    NASA Astrophysics Data System (ADS)

    Hrádek, Jan; Kuchař, Martin; Skala, Václav

    2003-07-01

    Some applications use data formats (e.g. STL file format), where a set of triangles is used to represent the surface of a 3D object and it is necessary to reconstruct the triangular mesh with adjacency information. It is a lengthy process for large data sets as the time complexity of this process is O( N log N), where N is number of triangles. Triangular mesh reconstruction is a general problem and relevant algorithms can be used in GIS and DTM systems as well as in CAD/CAM systems. Many algorithms rely on space subdivision techniques while hash functions offer a more effective solution to the reconstruction problem. Hash data structures are widely used throughout the field of computer science. The hash table can be used to speed up the process of triangular mesh reconstruction but the speed strongly depends on hash function properties. Nevertheless the design or selection of the hash function for data sets with unknown properties is a serious problem. This paper describes a new hash function, presents the properties obtained for large data sets, and discusses validity of the reconstructed surface. Experimental results proved theoretical considerations and advantages of hash function use for mesh reconstruction.

  13. Polypropylene mesh: evidence for lack of carcinogenicity

    PubMed Central

    Moalli, Pamela; Brown, Bryan; Reitman, Maureen T. F.

    2016-01-01

    Tumors related to the implantation of surgical grade polypropylene in humans have never been reported. In this commentary we present a balanced review of the information on what is known regarding the host response to polypropylene and provide data as to why the potential for carcinogenicity of polypropylene mesh is exceedingly small. PMID:24614956

  14. The Factory Approach to Creating TSTT Meshes

    SciTech Connect

    Epperly, T

    2003-10-21

    The factory approach (a.k.a. virtual constructor) hides the details of the class implementing the TSTT from TSTT users. In version 0.5 of TSTT.sidl, the client hard codes the name of the implementing class into their code. The client is forced to choose from the small set of possible concrete classes defined in TSTT.sidl. This approach makes it impossible to support multiple implementations of the TSTT in a single process because each implementation has to implement the same class. The factory approach hides the details of mesh creation from the client. The client does not need to know the name of the implementing class, and the client can dynamically determine which interfaces are supported by the new mesh. A factory can support multiple TSTT implementation because each implementation defines its own concrete classes to implement. The factory approach does require the TSTT compliant mesh packages to implement a MeshFactory interface, and everyone needs to link against an implementation of the Registry. The Registry only has 7 methods that are fairly easy to implement, and everyone can share one implementation of the Registry.

  15. Stainless steel mesh-acrylic cranioplasty.

    PubMed

    Tysvaer, A T; Hovind, K H

    1977-03-01

    Twenty-four steel mesh-acrylic plates have been used for repair of skull defects in 1970-73. Three plates had to be removed due to complications, two due to infection and one due to an allergic reaction. The plate is easy to mould, strong, and light. The cosmetic results are excellent.

  16. Particle Collection Efficiency for Nylon Mesh Screens.

    PubMed

    Cena, Lorenzo G; Ku, Bon-Ki; Peters, Thomas M

    Mesh screens composed of nylon fibers leave minimal residual ash and produce no significant spectral interference when ashed for spectrometric examination. These characteristics make nylon mesh screens attractive as a collection substrate for nanoparticles. A theoretical single-fiber efficiency expression developed for wire-mesh screens was evaluated for estimating the collection efficiency of submicrometer particles for nylon mesh screens. Pressure drop across the screens, the effect of particle morphology (spherical and highly fractal) on collection efficiency and single-fiber efficiency were evaluated experimentally for three pore sizes (60, 100 and 180 μm) at three flow rates (2.5, 4 and 6 Lpm). The pressure drop across the screens was found to increase linearly with superficial velocity. The collection efficiency of the screens was found to vary by less than 4% regardless of particle morphology. Single-fiber efficiency calculated from experimental data was in good agreement with that estimated from theory for particles between 40 and 150 nm but deviated from theory for particles outside this size range. New coefficients for the single-fiber efficiency model were identified that minimized the sum of square error (SSE) between the values estimated with the model and those determined experimentally. Compared to the original theory, the SSE calculated using the modified theory was at least one order of magnitude lower for all screens and flow rates with the exception of the 60-μm pore screens at 2.5 Lpm, where the decrease was threefold.

  17. The accuracy of treatment planning system dose modelling in the presence of brass mesh bolus.

    PubMed

    Richmond, Neil

    2017-01-01

    This work assesses the dosimetric accuracy of three commercial treatment planning system (TPS) photon dose calculation algorithms in the presence of brass mesh used as a bolus. Bolus material is used in radiotherapy to provide dose build-up where superficial tissues require irradiation. They are generally water equivalent but high density materials can also be used. Dose calculations were performed on Monaco and Masterplan TPS (Elekta AB, Sweden) using phantoms defined by the three DICOM CT image sets of water equivalent blocks (no bolus, 1 layer and 2 layers of brass mesh) exported from the CT scanner. The effect of the mesh on monitor units, build-up dose, phantom exit dose and beam penumbra were compared to measured data. Dose calculations for 6 and 15 MV photon beams on plain water equivalent phantoms were seen to agree well with measurement validating the basic planning system algorithms and models. Dose in the build-up region, phantom exit dose and beam penumbra were poorly modelled in the presence of the brass mesh. The beam attenuation created by the bolus material was overestimated by all three calculation algorithms, at both photon energies, e.g. 1.6% for one layer and up to 3.1% for two layers at 6 MV. The poor modelling of the physical situation in the build-up region is in part a consequence of the high HU artefact caused by the mesh in the CT image. CT imaging is not recommended with the brass mesh bolus in situ due to the poor accuracy of the subsequent TPS modelling.

  18. Chest Wall Reconstruction Using a Methyl Methacrylate Neo-Rib and Mesh.

    PubMed

    Suzuki, Kei; Park, Bernard J; Adusumilli, Prasad S; Rizk, Nabil P; Huang, James; Jones, David R; Bains, Manjit S

    2015-08-01

    Prosthetic reconstruction of the chest wall after oncologic resection is performed by means of various techniques using different materials. We describe a new technique of chest wall reconstruction that includes the use of Marlex mesh and the creation of a neo-rib from a Steinmann pin and methyl methacrylate.

  19. A biocompatible polysaccharide hydrogel-embedded polypropylene mesh for enhanced tissue integration in rats.

    PubMed

    Abed, Aicha; Deval, Bruno; Assoul, Nabila; Bataille, Isabelle; Portes, Patrick; Louedec, Liliane; Henin, Dominique; Letourneur, Didier; Meddahi-Pellé, Anne

    2008-04-01

    Prosthetic materials are largely used in surgery and tissue engineering. However, many postoperative complications are due to poor integration of the materials, which delays the healing process. The objective of our study was to develop a synthetic scaffold that, according to histopathological and biomechanical criteria, would achieve both tolerance and efficiency. In this study, we evaluated the effect of intramuscular and subcutaneous implantation of a new hybrid mesh (HM) in rats. This HM was composed of clinical grade polypropylene mesh embedded in a polysaccharide hydrogel. Histological and biomechanical studies on the polysaccharide gel alone and on HM were performed 15 and 30 days after implantation, and then compared with two clinically used materials, porcine decellularized small intestinal submucosa and a polypropylene mesh. Results showed that the incorporation of a polypropylene mesh within the polysaccharide hydrogel led to the absence of adverse effects and better tissue organization. Thus, this new synthetic biocompatible HM with suitable properties for tissue repair appears to be a promising material for clinical applications.

  20. Accurate, finite-volume methods for 3D MHD on unstructured Lagrangian meshes

    SciTech Connect

    Barnes, D.C.; Rousculp, C.L.

    1998-10-01

    Previous 2D methods for magnetohydrodynamics (MHD) have contributed both to development of core code capability and to physics applications relevant to AGEX pulsed-power experiments. This strategy is being extended to 3D by development of a modular extension of an ASCI code. Extension to 3D not only increases complexity by problem size, but also introduces new physics, such as magnetic helicity transport. The authors have developed a method which incorporates all known conservation properties into the difference scheme on a Lagrangian unstructured mesh. Because the method does not depend on the mesh structure, mesh refinement is possible during a calculation to prevent the well known problem of mesh tangling. Arbitrary polyhedral cells are decomposed into tetrahedrons. The action of the magnetic vector potential, A {center_dot} {delta}l, is centered on the edges of this extended mesh. For ideal flow, this maintains {del} {center_dot} B = 0 to round-off error. Vertex forces are derived by the variation of magnetic energy with respect to vertex positions, F = {minus}{partial_derivative}W{sub B}/{partial_derivative}r. This assures symmetry as well as magnetic flux, momentum, and energy conservation. The method is local so that parallelization by domain decomposition is natural for large meshes. In addition, a simple, ideal-gas, finite pressure term has been included. The resistive diffusion part is calculated using the support operator method, to obtain an energy conservative, symmetric method on an arbitrary mesh. Implicit time difference equations are solved by preconditioned, conjugate gradient methods. Results of convergence tests are presented. Initial results of an annular Z-pinch implosion problem illustrate the application of these methods to multi-material problems.

  1. A systematic review and meta-analysis of the post-operative adverse effects associated with mosquito net mesh in comparison to commercial hernia mesh for inguinal hernia repair in low income countries.

    PubMed

    Patterson, T; Currie, P; Patterson, S; Patterson, P; Meek, C; McMaster, R

    2017-06-01

    Abdominal wall hernia is a common surgical condition, with more than 20 million estimated to be repaired each year. Mesh repair is the standard for most repairs; however, the mesh material itself may be a barrier to care, the cost prohibitively high for some populations and healthcare systems. The aim of this systematic review and meta-analysis was to produce a pooled comparison between the adverse event rate associated with mosquito net mesh and commercial hernia mesh. A systematic review was carried out in accordance with PRISMA guidelines. PubMed, Ovid Embase/Medline, SCOPUS, Web of Science and the Cochrane library were searched. In addition, the ISRCTN register, ClinicalTrials.gov, ICTR Platform and EU Clinical Trials Register were searched. Five randomised controlled trials (RCTs) were identified. The RCTs were deemed to have similar sample populations after inspection of their sample parameters. Therefore, the adverse effects were compared individually (reoccurrence, haematoma, seroma, infection, and serous discharge) and pooled. A total of 313 mosquito net meshes were included in the study, there was no significant difference between the intervention and control groups for pooled adverse effects or individually. There is not a significant difference between the commercial mesh group and the mosquito net mesh group for pooled [odds ratio 0.93 (0.63, 1.35)] and individual adverse event rates. However, the 95% confidence intervals of these results are still wide. To reduce this uncertainty sample sizes must increase in future studies.

  2. Oxidation and degradation of polypropylene transvaginal mesh.

    PubMed

    Talley, Anne D; Rogers, Bridget R; Iakovlev, Vladimir; Dunn, Russell F; Guelcher, Scott A

    2017-04-01

    Polypropylene (PP) transvaginal mesh (TVM) repair for stress urinary incontinence (SUI) has shown promising short-term objective cure rates. However, life-altering complications have been associated with the placement of PP mesh for SUI repair. PP degradation as a result of the foreign body reaction (FBR) has been proposed as a contributing factor to mesh complications. We hypothesized that PP oxidizes under in vitro conditions simulating the FBR, resulting in degradation of the PP. Three PP mid-urethral slings from two commercial manufacturers were evaluated. Test specimens (n = 6) were incubated in oxidative medium for up to 5 weeks. Oxidation was assessed by Fourier Transform Infrared Spectroscopy (FTIR), and degradation was evaluated by scanning electron microscopy (SEM). FTIR spectra of the slings revealed evidence of carbonyl and hydroxyl peaks after 5 weeks of incubation time, providing evidence of oxidation of PP. SEM images at 5 weeks showed evidence of surface degradation, including pitting and flaking. Thus, oxidation and degradation of PP pelvic mesh were evidenced by chemical and physical changes under simulated in vivo conditions. To assess changes in PP surface chemistry in vivo, fibers were recovered from PP mesh explanted from a single patient without formalin fixation, untreated (n = 5) or scraped (n = 5) to remove tissue, and analyzed by X-ray photoelectron spectroscopy. Mechanical scraping removed adherent tissue, revealing an underlying layer of oxidized PP. These findings underscore the need for further research into the relative contribution of oxidative degradation to complications associated with PP-based TVM devices in larger cohorts of patients.

  3. Shear Alignment of Diblock Copolymers for Patterning Nanowire Meshes

    SciTech Connect

    Gustafson, Kyle T.

    2016-09-08

    Metallic nanowire meshes are useful as cheap, flexible alternatives to indium tin oxide – an expensive, brittle material used in transparent conductive electrodes. We have fabricated nanowire meshes over areas up to 2.5 cm2 by: 1) mechanically aligning parallel rows of diblock copolymer (diBCP) microdomains; 2) selectively infiltrating those domains with metallic ions; 3) etching away the diBCP template; 4) sintering to reduce ions to metal nanowires; and, 5) repeating steps 1 – 4 on the same sample at a 90° offset. We aligned parallel rows of polystyrene-b-poly(2-vinylpyridine) [PS(48.5 kDa)-b-P2VP(14.5 kDa)] microdomains by heating above its glass transition temperature (Tg ≈ 100°C), applying mechanical shear pressure (33 kPa) and normal force (13.7 N), and cooling below Tg. DiBCP samples were submerged in aqueous solutions of metallic ions (15 – 40 mM ions; 0.1 – 0.5 M HCl) for 30 – 90 minutes, which coordinate to nitrogen in P2VP. Subsequent ozone-etching and sintering steps yielded parallel nanowires. We aimed to optimize alignment parameters (e.g. shear and normal pressures, alignment duration, and PDMS thickness) to improve the quality, reproducibility, and scalability of meshes. We also investigated metals other than Pt and Au that may be patterned using this technique (Cu, Ag).

  4. Cartesian-cell based grid generation and adaptive mesh refinement

    NASA Technical Reports Server (NTRS)

    Coirier, William J.; Powell, Kenneth G.

    1993-01-01

    Viewgraphs on Cartesian-cell based grid generation and adaptive mesh refinement are presented. Topics covered include: grid generation; cell cutting; data structures; flow solver formulation; adaptive mesh refinement; and viscous flow.

  5. CUBIT mesh generation environment. Volume 1: Users manual

    SciTech Connect

    Blacker, T.D.; Bohnhoff, W.J.; Edwards, T.L.

    1994-05-01

    The CUBIT mesh generation environment is a two- and three-dimensional finite element mesh generation tool which is being developed to pursue the goal of robust and unattended mesh generation--effectively automating the generation of quadrilateral and hexahedral elements. It is a solid-modeler based preprocessor that meshes volume and surface solid models for finite element analysis. A combination of techniques including paving, mapping, sweeping, and various other algorithms being developed are available for discretizing the geometry into a finite element mesh. CUBIT also features boundary layer meshing specifically designed for fluid flow problems. Boundary conditions can be applied to the mesh through the geometry and appropriate files for analysis generated. CUBIT is specifically designed to reduce the time required to create all-quadrilateral and all-hexahedral meshes. This manual is designed to serve as a reference and guide to creating finite element models in the CUBIT environment.

  6. On Adaptive Mesh Generation in Two-Dimensions

    SciTech Connect

    D'Azevedo, E.

    1999-10-11

    This work considers the effectiveness of using anisotropic coordinate transformation in adaptive mesh generation. The anisotropic coordinate transformation is derived by interpreting the Hessian matrix of the data function as a metric tensor that measures the local approximation error. The Hessian matrix contains information about the local curvature of the surface and gives guidance in the aspect ratio and orientation for mesh generation. Since theoretically, an asymptotically optimally efficient mesh can be produced by transforming a regular mesh of optimal shape elements, it would be interesting to compare this approach with existing techniques in solution adaptive meshes. PLTMG , a general elliptic solver, is used to generate solution adapted triangular meshes for comparison. The solver has the capability of performing a posteriori error estimates in performing longest edge refinement, vertex unrefinement and mesh smoothing. Numerical experiments on three simple problems suggest the methodology employed in PLTMG is effective in generating near optimally efficient meshes.

  7. Vein, silastic, and polyglycolic acid fine mesh: a comparative study in peripheral nerve repair.

    PubMed

    Lolley, R D; Bose, W J; Bastian, F; Bassam, B; Meyer, F N; Anderson, L D

    1995-09-01

    We investigated three sheathing materials (autogenous vein, silastic, and polyglycolic acid fine mesh) using the rat model. Forty rats were divided into five groups of eight animals each. Group A animals underwent transection of the sciatic nerve but had no repair. In Group B, a standard epineural repair was performed. In Groups C, D, and E, the nerve was repaired as in Group B with the addition of autogenous vein, Silastic, and polyglycolic acid fine mesh sheaths, respectively. Nerve regeneration and function were assessed using sciatic functional index, nerve conduction studies, and light microscopy. Sheathing methods showed no statistically significant advantage to standard epineural repair without a sheath.

  8. Contact stresses in meshing spur gear teeth: Use of an incremental finite element procedure

    NASA Technical Reports Server (NTRS)

    Hsieh, Chih-Ming; Huston, Ronald L.; Oswald, Fred B.

    1992-01-01

    Contact stresses in meshing spur gear teeth are examined. The analysis is based upon an incremental finite element procedure that simultaneously determines the stresses in the contact region between the meshing teeth. The teeth themselves are modeled by two dimensional plain strain elements. Friction effects are included, with the friction forces assumed to obey Coulomb's law. The analysis assumes that the displacements are small and that the tooth materials are linearly elastic. The analysis procedure is validated by comparing its results with those for the classical two contacting semicylinders obtained from the Hertz method. Agreement is excellent.

  9. To mesh or not to mesh: a review of pelvic organ reconstructive surgery

    PubMed Central

    Dällenbach, Patrick

    2015-01-01

    Pelvic organ prolapse (POP) is a major health issue with a lifetime risk of undergoing at least one surgical intervention estimated at close to 10%. In the 1990s, the risk of reoperation after primary standard vaginal procedure was estimated to be as high as 30% to 50%. In order to reduce the risk of relapse, gynecological surgeons started to use mesh implants in pelvic organ reconstructive surgery with the emergence of new complications. Recent studies have nevertheless shown that the risk of POP recurrence requiring reoperation is lower than previously estimated, being closer to 10% rather than 30%. The development of mesh surgery – actively promoted by the marketing industry – was tremendous during the past decade, and preceded any studies supporting its benefit for our patients. Randomized trials comparing the use of mesh to native tissue repair in POP surgery have now shown better anatomical but similar functional outcomes, and meshes are associated with more complications, in particular for transvaginal mesh implants. POP is not a life-threatening condition, but a functional problem that impairs quality of life for women. The old adage “primum non nocere” is particularly appropriate when dealing with this condition which requires no treatment when asymptomatic. It is currently admitted that a certain degree of POP is physiological with aging when situated above the landmark of the hymen. Treatment should be individualized and the use of mesh needs to be selective and appropriate. Mesh implants are probably an important tool in pelvic reconstructive surgery, but the ideal implant has yet to be found. The indications for its use still require caution and discernment. This review explores the reasons behind the introduction of mesh augmentation in POP surgery, and aims to clarify the risks, benefits, and the recognized indications for its use. PMID:25848324

  10. Mesh quality control for multiply-refined tetrahedral grids

    NASA Technical Reports Server (NTRS)

    Biswas, Rupak; Strawn, Roger

    1994-01-01

    A new algorithm for controlling the quality of multiply-refined tetrahedral meshes is presented in this paper. The basic dynamic mesh adaption procedure allows localized grid refinement and coarsening to efficiently capture aerodynamic flow features in computational fluid dynamics problems; however, repeated application of the procedure may significantly deteriorate the quality of the mesh. Results presented show the effectiveness of this mesh quality algorithm and its potential in the area of helicopter aerodynamics and acoustics.

  11. Numerical evaluation of moiré pattern in touch sensor module with electrode mesh structure in oblique view

    NASA Astrophysics Data System (ADS)

    Pournoury, M.; Zamiri, A.; Kim, T. Y.; Yurlov, V.; Oh, K.

    2016-03-01

    Capacitive touch sensor screen with the metal materials has recently become qualified for substitution of ITO; however several obstacles still have to be solved. One of the most important issues is moiré phenomenon. The visibility problem of the metal-mesh, in touch sensor module (TSM) is numerically considered in this paper. Based on human eye contract sensitivity function (CSF), moiré pattern of TSM electrode mesh structure is simulated with MATLAB software for 8 inch screen display in oblique view. Standard deviation of the generated moiré by the superposition of electrode mesh and screen image is calculated to find the optimal parameters which provide the minimum moiré visibility. To create the screen pixel array and mesh electrode, rectangular function is used. The filtered image, in frequency domain, is obtained by multiplication of Fourier transform of the finite mesh pattern (product of screen pixel and mesh electrode) with the calculated CSF function for three different observer distances (L=200, 300 and 400 mm). It is observed that the discrepancy between analytical and numerical results is less than 0.6% for 400 mm viewer distance. Moreover, in the case of oblique view due to considering the thickness of the finite film between mesh electrodes and screen, different points of minimum standard deviation of moiré pattern are predicted compared to normal view.

  12. Copper Mesh Templated by Breath-Figure Polymer Films as Flexible Transparent Electrodes for Organic Photovoltaic Devices.

    PubMed

    Zhou, Weixin; Chen, Jun; Li, Yi; Wang, Danbei; Chen, Jianyu; Feng, Xiaomiao; Huang, Zhendong; Liu, Ruiqing; Lin, Xiujing; Zhang, Hongmei; Mi, Baoxiu; Ma, Yanwen

    2016-05-04

    Metal mesh is a significant candidate of flexible transparent electrodes to substitute the current state-of-the-art material indium tin oxide (ITO) for future flexible electronics. However, there remains a challenge to fabricate metal mesh with order patterns by a bottom-up approach. In this work, high-quality Cu mesh transparent electrodes with ordered pore arrays are prepared by using breath-figure polymer films as template. The optimal Cu mesh films present a sheet resistance of 28.7 Ω·sq(-1) at a transparency of 83.5%. The work function of Cu mesh electrode is tuned from 4.6 to 5.1 eV by Ag deposition and the following short-time UV-ozone treatment, matching well with the PSS (5.2 eV) hole extraction layer. The modified Cu mesh electrodes show remarkable potential as a substitute of ITO/PET in the flexible OPV and OLED devices. The OPV cells constructed on our Cu mesh electrodes present a similar power conversion efficiency of 2.04% as those on ITO/PET electrodes. The flexible OLED prototype devices can achieve a brightness of 10 000 cd at an operation voltage of 8 V.

  13. Comparing the behavior of different polypropylene meshes (heavy and lightweight) in an experimental model of ventral hernia repair.

    PubMed

    Bellón, J M; Rodríguez, M; García-Honduvilla, N; Gómez-Gil, V; Pascual, G; Buján, J

    2009-05-01

    New generation prosthetic biomaterials for abdominal wall repair have been designed to be less dense, by having larger pores than that of the standard polypropylene meshes, to improve abdominal wall compliance. The aim of the present study was to analyze the functional and morphologic properties of these new meshes. For this purpose, 7 x 5 cm(2) defects were created in the anterior abdominal wall of 36 male New Zealand White rabbits and repaired using different polypropylene meshes: a heavyweight mesh (HW), Surgipro, and two lightweight meshes (LW), Parietene and Optilene. Six animals each implanted with biomaterial were sacrificed on postoperative days 14 and 90. Histological and morphometric analysis, adhesion assessment, and biomechanical resistance tests were performed. Similar behavior was shown by the LW and HW meshes in terms of the adhesions and macrophage response induced. After 14 days, the tensile strength of Optilene was greater than the strengths recorded for the other two biomaterials, probably because of its high elasticity. By 90 days, however, the tensile strengths of the three biomaterials were comparable. In conclusion, despite an initial tensile strength advantage shown by the mesh with larger pores, at 90 days postimplant, tensile strengths were similar. Compared with HW, LW prostheses have the benefit that less foreign material was implanted, preserving the elasticity of the recipient host tissue. (c) 2008 Wiley Periodicals, Inc.

  14. On Reducing Delay in Mesh-Based P2P Streaming: A Mesh-Push Approach

    NASA Astrophysics Data System (ADS)

    Liu, Zheng; Xue, Kaiping; Hong, Peilin

    The peer-assisted streaming paradigm has been widely employed to distribute live video data on the internet recently. In general, the mesh-based pull approach is more robust and efficient than the tree-based push approach. However, pull protocol brings about longer streaming delay, which is caused by the handshaking process of advertising buffer map message, sending request message and scheduling of the data block. In this paper, we propose a new approach, mesh-push, to address this issue. Different from the traditional pull approach, mesh-push implements block scheduling algorithm at sender side, where the block transmission is initiated by the sender rather than by the receiver. We first formulate the optimal upload bandwidth utilization problem, then present the mesh-push approach, in which a token protocol is designed to avoid block redundancy; a min-cost flow model is employed to derive the optimal scheduling for the push peer; and a push peer selection algorithm is introduced to reduce control overhead. Finally, we evaluate mesh-push through simulation, the results of which show mesh-push outperforms the pull scheduling in streaming delay, and achieves comparable delivery ratio at the same time.

  15. Development of Au-Ag nanowire mesh fabrication by UV-induced approach

    SciTech Connect

    Saggar, Siddhartha; Predeep, Padmanabhan

    2014-10-15

    In an attempt to overcome the limitations of the presently prevailing transparent conducting electrode (TCE) - indium tin oxide (ITO) - many materials have been considered for replacing ITO. Recently, a novel method has been reported for the synthesis of Au-Ag nanowire (NW) mesh, and tested successfully for organic-light-emitting-diodes (OLEDs). It employs UV-induced reduction of gold- and silver- precursors to form Au-Ag NW mesh. In this report, Au-Ag NW mesh thin films are synthesized on glass substrates with an objective for use as facing-electrode for Organic Photovoltaics. Various issues and factors affecting the fabrication-process have been improved, and are also discussed here. The electrode showed good transmitivity, of around 95% (excluding that of glass substrate). The advantage of the technique is its simple processing method and cost-effectiveness.

  16. Selective separation of oil and water with mesh membranes by capillarity.

    PubMed

    Yu, Yuanlie; Chen, Hua; Liu, Yun; Craig, Vincent S J; Lai, Zhiping

    2016-09-01

    The separation of oil and water from wastewater generated in the oil-production industries, as well as in frequent oil spillage events, is important in mitigating severe environmental and ecological damage. Additionally, a wide arrange of industrial processes require oils or fats to be removed from aqueous systems. The immiscibility of oil and water allows for the wettability of solid surfaces to be engineered to achieve the separation of oil and water through capillarity. Mesh membranes with extreme, selective wettability can efficiently remove oil or water from oil/water mixtures through a simple filtration process using gravity. A wide range of different types of mesh membranes have been successfully rendered with extreme wettability and applied to oil/water separation in the laboratory. These mesh materials have typically shown good durability, stability as well as reusability, which makes them promising candidates for an ever widening range of practical applications.

  17. Tungsten mesh as positron transmission moderator in a monoenergetic positron beam

    NASA Astrophysics Data System (ADS)

    Weng, H. M.; Ling, C. C.; Beling, C. D.; Fung, S.; Cheung, C. K.; Kwan, P. Y.; Hui, I. P.

    2004-09-01

    The slow positron yield has been measured for various tungsten (W) moderator samples from a 22Na radioactive source. Multi-folded W mesh, W(1 0 0) single crystal foil and W polycrystalline foil samples have been investigated. It is found that the fast to slow conversion efficiency of the W mesh moderator depends on: (1) the annealing pretreatments, (2) the chemical etching duration and (3) the number of the folding layers. With the raw W mesh material having a wire diameter of 20 μm and transmission efficiency of 92.5%, an optimal efficiency of 1.2 × 10 -3 was achieved with 5 min etching duration and a folding number of 12 layers.

  18. A new anisotropic mesh adaptation method based upon hierarchical a posteriori error estimates

    NASA Astrophysics Data System (ADS)

    Huang, Weizhang; Kamenski, Lennard; Lang, Jens

    2010-03-01

    A new anisotropic mesh adaptation strategy for finite element solution of elliptic differential equations is presented. It generates anisotropic adaptive meshes as quasi-uniform ones in some metric space, with the metric tensor being computed based on hierarchical a posteriori error estimates. A global hierarchical error estimate is employed in this study to obtain reliable directional information of the solution. Instead of solving the global error problem exactly, which is costly in general, we solve it iteratively using the symmetric Gauß-Seidel method. Numerical results show that a few GS iterations are sufficient for obtaining a reasonably good approximation to the error for use in anisotropic mesh adaptation. The new method is compared with several strategies using local error estimators or recovered Hessians. Numerical results are presented for a selection of test examples and a mathematical model for heat conduction in a thermal battery with large orthotropic jumps in the material coefficients.

  19. Cell adhesion on NiTi thin film sputter-deposited meshes.

    PubMed

    Loger, K; Engel, A; Haupt, J; Li, Q; Lima de Miranda, R; Quandt, E; Lutter, G; Selhuber-Unkel, C

    2016-02-01

    Scaffolds for tissue engineering enable the possibility to fabricate and form biomedical implants in vitro, which fulfill special functionality in vivo. In this study, free-standing Nickel–Titanium(NiTi) thin film mesheswere produced by means of magnetron sputter deposition.Meshes contained precisely defined rhombic holes in the size of 440 to 1309 μm2 and a strut width ranging from 5.3 to 9.2 μm. The effective mechanical properties of the microstructured superelastic NiTi thin film were examined by tensile testing. These results will be adapted for the design of the holes in the film. The influence of hole and strut dimensions on the adhesion of sheep autologous cells (CD133+) was studied after 24 h and after seven days of incubation. Optical analysis using fluorescence microscopy and scanning electron microscopy showed that cell adhesion depends on the structural parameters of the mesh. After 7 days in cell culture a large part of the mesh was covered with aligned fibrous material. Cell adhesion is particularly facilitated on meshes with small rhombic holes of 440 μm2 and a strut width of 5.3 μm. Our results demonstrate that free-standing NiTi thin film meshes have a promising potential for applicationsin cardiovascular tissue engineering, particularly for the fabrication of heart valves.

  20. Highly purified collagen coating enhances tissue adherence and integration properties of monofilament polypropylene meshes.

    PubMed

    Siniscalchi, Rodrigo Teixeira; Melo, Marli; Palma, Paulo César Rodrigues; Dal Fabbro, Inácio Maria; Vidal, Benedicto de Campos; Riccetto, Cassio Luiz Zanettini

    2013-10-01

    Complications related to tissue integration of polypropylene implants used in the treatment of pelvic organ prolapse are relatively prevalent. Collagen, a biocompatible, less immunogenic material with modulating properties on the inflammatory process, may improve polypropylene integration. The objective was to study biomechanical and histological effects of monofilament polypropylene mesh coated with purified collagen gel. Forty rats were implanted with two fragments of polypropylene mesh in their abdominal walls (one on each side of the linea alba). One of the fragments had a collagen gel coating (group I) while the other one did not (group II). The animals were euthanized at 7, 14, 90, and 180 days after implantation and their abdominal walls were excised for analysis. The biomechanical study showed that mesh adherence to neighboring tissue increased significantly in group II (p < 0.05). Acute (p < 0.001) and chronic (p = 0.004) inflammatory responses as well as granulation tissue formation (p = 0.001) were less intense in group II at 7 and 14 days. Granulomatous inflammation and foreign body reaction was less significant at 7 days in group II (p = 0.029 and p < 0.001). The birefringence analysis showed higher mean brightness density in the late phase of implantation in group II meshes (p = 0.000). Polypropylene mesh coated with purified collagen gel increases adherence to tissue, promotes a less intense and lasting inflammatory response and triggers a greater organization and packing arrangement of collagen fibers in the late phase of implantation.

  1. Development of silver nanoparticle loaded antibacterial polymer mesh using plasma polymerization process.

    PubMed

    Kumar, Virendra; Jolivalt, Claude; Pulpytel, Jerome; Jafari, Reza; Arefi-Khonsari, Farzaneh

    2013-04-01

    Plasma polymerized polyacrylic acid (PPAA) was deposited on a polymer substrate, namely polyethylene terephthalate (PET) mesh, for entrapment of silver nanoparticle (Ag-NP) in order to achieve antibacterial property to the material. Carboxylic groups of PPAA act as anchor as well as capping and stabilizing agents for Ag-NPs synthesized by chemical reduction method using NaBH(4) as a reducing agent. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), and water contact angle analysis were used to characterize the PPAA coatings. The Ag-NPs loaded polymer samples were characterized by UV-visible spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray, and XPS techniques. XPS analysis showed ~1.0 at.% loading of Ag-NPs on to the PPAA-PET-mesh, which was composed of 79% zero-valent (Ag°) and 21% oxidized nano-Ag (Ag(+) ). The plasma processed PET meshes samples were tested for antibacterial activity against two bacterial strains, namely Staphylococcus aureus (Gram positive) and Escherichia coli (Gram negative). Qualitative and quantitative tests showed that silver containing PPAA-PET meshes exhibit excellent antibacterial property against the tested bacteria with percent reduction of bacterial concentration >99%, compared to the untreated PET mesh.

  2. Optically transparent superhydrophobic surfaces with enhanced mechanical abrasion resistance enabled by mesh structure.

    PubMed

    Yokoi, Naoyuki; Manabe, Kengo; Tenjimbayashi, Mizuki; Shiratori, Seimei

    2015-03-04

    Inspired by naturally occurring superhydrophobic surfaces such as "lotus leaves", a number of approaches have been attempted to create specific surfaces having nano/microscale rough structures and a low surface free energy. Most importantly, much attention has been paid in recent years to the improvement of the durability of highly transparent superhydrophobic surfaces. In this report, superhydrophobic surfaces are fabricated using three steps. First, chemical and morphological changes are generated in the polyester mesh by alkaline treatment of NaOH. Second, alkaline treatment causes hydrophobic molecules of 1H,1H,2H,2H-perfluorodecyltrichlorosilane to react with the hydroxyl groups on the fiber surfaces forming covalent bonds by using the chemical vapor deposition method. Third, hydrophobicity is enhanced by treating the mesh with SiO2 nanoparticles modified with 1H,1H,2H,2H-perfluorooctyltriethoxysilane using a spray method. The transmittance of the fabricated superhydrophobic mesh is approximately 80% in the spectral range of 400-1000 nm. The water contact angle and the water sliding angle remain greater than 150° and lower than 25°, respectively, and the transmittance remains approximately 79% after 100 cycles of abrasion under approximately 10 kPa of pressure. The mesh surface exhibits a good resistance to acidic and basic solutions over a wide range of pH values (pH 2-14), and the surface can also be used as an oil/water separation material because of its mesh structure.

  3. 21 CFR 870.3650 - Pacemaker polymeric mesh bag.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Pacemaker polymeric mesh bag. 870.3650 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is an implanted device used to hold...

  4. 21 CFR 870.3650 - Pacemaker polymeric mesh bag.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Pacemaker polymeric mesh bag. 870.3650 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is an implanted device used to hold...

  5. 21 CFR 870.3650 - Pacemaker polymeric mesh bag.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Pacemaker polymeric mesh bag. 870.3650 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is an implanted device used to hold...

  6. 21 CFR 870.3650 - Pacemaker polymeric mesh bag.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Pacemaker polymeric mesh bag. 870.3650 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is an implanted device used to hold...

  7. 21 CFR 870.3650 - Pacemaker polymeric mesh bag.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Pacemaker polymeric mesh bag. 870.3650 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is an implanted device used to hold...

  8. 50 CFR 622.302 - Minimum mesh size.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 12 2014-10-01 2014-10-01 false Minimum mesh size. 622.302 Section 622.302 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC... Sargassum Habitat of the South Atlantic Region § 622.302 Minimum mesh size. (a) The minimum allowable mesh...

  9. 50 CFR 622.302 - Minimum mesh size.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 12 2013-10-01 2013-10-01 false Minimum mesh size. 622.302 Section 622.302 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC... Sargassum Habitat of the South Atlantic Region § 622.302 Minimum mesh size. (a) The minimum allowable mesh...

  10. A density driven mesh generator guided by a neural network

    SciTech Connect

    Lowther, D.A.; Dyck, D.N. )

    1993-03-01

    A neural network guided mesh generator is described. The mesh generator used density information provided by the neural network to determine the size and placement of elements. This system is coupled with an adaptive meshing and solving process and is shown to have major computational benefits compared with adaptation alone.

  11. Cubit Mesh Generation Toolkit V11.1

    SciTech Connect

    HANKS, BYRON; KERR, ROBERT; KNUPP, PATRICK; MAEZ, JONATHAN; WHITE, DAVID; MITCHELL, SCOTT; OWEN, STEVEN; SHEPHERD, JASON; TAUTGES, TIMOTHY; MELANDER, DARRYL; BLACKER, TEDDY; BORDEN, MICHAEL; BREWER, MICHAEL; CLARK, BRETT; FORTIER, LESLIE; KALLAHER, JENNA; PEBAY, PHILIPPE; STATEN, MATTHEW; VINEYARD, CRAIG; GROVER, BENJAMIN; BENZLEY, STEVEN; SIMPSON, CLINTON; NIELSON, ERIC; KOPP, JOEL; STORM, STEVE; NUGENT, MARK; WALTON, KIRK; BORDEN, MIKE; ERNST, CORY; FOWLER, JOHN; KRAFTCHECL, JASON; STEPHNSON, MIKE; YEOU, RAMMAGAY; MERKLEY, KARL; METERS, RAY; DEWET, MARK; RICHARDS, SARA; PENDLEY, KEVIN; MORRIS, RANDY; RICHARDSON, MARK; VYAS, VED; SHOWMAN, SAM; HAYS, ALEX; TIDWELL, BOYD; MILLAR, ALEX

    2009-03-25

    CUBIT prepares models to be used in computer-based simulation of real-world events. CUBIT is a full-featured software toolkit for robust generation of two- and three-dimensional finite element meshes (grids) and geometry preparation. Its main goal is to reduce the time to generate meshes, particularly large hex meshes of complicated, interlocking assemblies.

  12. A method to generate conformal finite-element meshes from 3D measurements of microstructurally small fatigue-crack propagation [A method to generate conformal finite-element meshes from 3D measurements of microstructurally small fatigue-crack propagation: 3D Meshes of Microstructurally Small Crack Growth

    SciTech Connect

    Spear, Ashley D.; Hochhalter, Jacob D.; Cerrone, Albert R.; Li, Shiu Fai; Lind, Jonathan F.; Suter, Robert M.; Ingraffea, Anthony R.

    2016-04-27

    In an effort to reproduce computationally the observed evolution of microstructurally small fatigue cracks (MSFCs), a method is presented for generating conformal, finite-element (FE), volume meshes from 3D measurements of MSFC propagation. The resulting volume meshes contain traction-free surfaces that conform to incrementally measured 3D crack shapes. Grain morphologies measured using near-field high-energy X-ray diffraction microscopy are also represented within the FE volume meshes. Proof-of-concept simulations are performed to demonstrate the utility of the mesh-generation method. The proof-of-concept simulations employ a crystal-plasticity constitutive model and are performed using the conformal FE meshes corresponding to successive crack-growth increments. Although the simulations for each crack increment are currently independent of one another, they need not be, and transfer of material-state information among successive crack-increment meshes is discussed. The mesh-generation method was developed using post-mortem measurements, yet it is general enough that it can be applied to in-situ measurements of 3D MSFC propagation.

  13. A method to generate conformal finite-element meshes from 3D measurements of microstructurally small fatigue-crack propagation [A method to generate conformal finite-element meshes from 3D measurements of microstructurally small fatigue-crack propagation: 3D Meshes of Microstructurally Small Crack Growth

    DOE PAGES

    Spear, Ashley D.; Hochhalter, Jacob D.; Cerrone, Albert R.; ...

    2016-04-27

    In an effort to reproduce computationally the observed evolution of microstructurally small fatigue cracks (MSFCs), a method is presented for generating conformal, finite-element (FE), volume meshes from 3D measurements of MSFC propagation. The resulting volume meshes contain traction-free surfaces that conform to incrementally measured 3D crack shapes. Grain morphologies measured using near-field high-energy X-ray diffraction microscopy are also represented within the FE volume meshes. Proof-of-concept simulations are performed to demonstrate the utility of the mesh-generation method. The proof-of-concept simulations employ a crystal-plasticity constitutive model and are performed using the conformal FE meshes corresponding to successive crack-growth increments. Although the simulationsmore » for each crack increment are currently independent of one another, they need not be, and transfer of material-state information among successive crack-increment meshes is discussed. The mesh-generation method was developed using post-mortem measurements, yet it is general enough that it can be applied to in-situ measurements of 3D MSFC propagation.« less

  14. Use of Mesh in Laparoscopic Paraesophageal Hernia Repair: A Meta-Analysis and Risk-Benefit Analysis

    PubMed Central

    Gondan, Matthias; Stock, Christian; Linke, Georg R.; Fritz, Franziska; Nickel, Felix; Diener, Markus K.; Gutt, Carsten N.; Wente, Moritz; Büchler, Markus W.; Fischer, Lars

    2015-01-01

    Introduction Mesh augmentation seems to reduce recurrences following laparoscopic paraesophageal hernia repair (LPHR). However, there is an uncertain risk of mesh-associated complications. Risk-benefit analysis might solve the dilemma. Materials and Methods A systematic literature search was performed to identify randomized controlled trials (RCTs) and observational clinical studies (OCSs) comparing laparoscopic mesh-augmented hiatoplasty (LMAH) with laparoscopic mesh-free hiatoplasty (LH) with regard to recurrences and complications. Random effects meta-analyses were performed to determine potential benefits of LMAH. All data regarding LMAH were used to estimate risk of mesh-associated complications. Risk-benefit analysis was performed using a Markov Monte Carlo decision-analytic model. Results Meta-analysis of 3 RCTs and 9 OCSs including 915 patients revealed a significantly lower recurrence rate for LMAH compared to LH (pooled proportions, 12.1% vs. 20.5%; odds ratio (OR), 0.55; 95% confidence interval (CI), 0.34 to 0.89; p = 0.04). Complication rates were comparable in both groups (pooled proportions, 15.3% vs. 14.2%; OR, 1.02; 95% CI, 0.63 to 1.65; p = 0.94). The systematic review of LMAH data yielded a mesh-associated complication rate of 1.9% (41/2121; 95% CI, 1.3% to 2.5%) for those series reporting at least one mesh-associated complication. The Markov Monte Carlo decision-analytic model revealed a procedure-related mortality rate of 1.6% for LMAH and 1.8% for LH. Conclusions Mesh application should be considered for LPHR because it reduces recurrences at least in the mid-term. Overall procedure-related complications and mortality seem to not be increased despite of potential mesh-associated complications. PMID:26469286

  15. Laparoscopic Total Extraperitoneal (TEP) Inguinal Hernia Repair Using 3-dimensional Mesh Without Mesh Fixation.

    PubMed

    Aliyazicioglu, Tolga; Yalti, Tunc; Kabaoglu, Burcak

    2017-08-01

    Approximately one fifth of patients suffer from inguinal pain after laparoscopic total extraperitoneal (TEP) inguinal hernia repair. There is existing literature suggesting that the staples used to fix the mesh can cause postoperative inguinal pain. In this study, we describe our experience with laparoscopic TEP inguinal hernia surgery using 3-dimensional mesh without mesh fixation, in our institution. A total of 300 patients who had undergone laparoscopic TEP inguinal hernia repair with 3-dimensional mesh in VKV American Hospital, Istanbul from November 2006 to November 2015 were studied retrospectively. Using the hospital's electronic archive, we studied patients' selected parameters, which are demographic features (age, sex), body mass index, hernia locations and types, duration of operations, preoperative and postoperative complications, duration of hospital stays, cost of surgery, need for analgesics, time elapsed until returning to daily activities and work. A total of 300 patients underwent laparoscopic TEP hernia repair of 437 inguinal hernias from November 2006 to November 2015. Of the 185 patients, 140 were symptomatic. Mean duration of follow-up was 48 months (range, 6 to 104 mo). The mean duration of surgery was 55 minutes for bilateral hernia repair, and 38 minutes for unilateral hernia repair. The mean duration of hospital stay was 0.9 day. There was no conversion to open surgery. In none of the cases the mesh was fixated with either staples or fibrin glue. Six patients (2%) developed seroma that were treated conservatively. One patient had inguinal hernia recurrence. One patient had preperitoneal hematoma. One patient operated due to indirect right-sided hernia developed right-sided hydrocele. One patient had wound dehiscence at the umbilical port entry site. Chronic pain developed postoperatively in 1 patient. Ileus developed in 1 patient. Laparoscopic TEP inguinal repair with 3-dimensional mesh without mesh fixation can be performed as safe as

  16. A 3-D adaptive mesh refinement algorithm for multimaterial gas dynamics

    SciTech Connect

    Puckett, E.G. ); Saltzman, J.S. )

    1991-08-12

    Adaptive Mesh Refinement (AMR) in conjunction with high order upwind finite difference methods has been used effectively on a variety of problems. In this paper we discuss an implementation of an AMR finite difference method that solves the equations of gas dynamics with two material species in three dimensions. An equation for the evolution of volume fractions augments the gas dynamics system. The material interface is preserved and tracked from the volume fractions using a piecewise linear reconstruction technique. 14 refs., 4 figs.

  17. Vertical-Axis Wind Turbine Mesh Generator

    SciTech Connect

    2014-01-24

    VAWTGen is a mesh generator for creating a finite element beam mesh of arbitrary vertical-axis wind turbines (VAWT). The software accepts input files specifying tower and blade structural and aerodynamic descriptions and constructs a VAWT using a minimal set of inputs. VAWTs with an arbitrary number of blades can be constructed with or without a central tower. Strut connections between the tower and blades can be specified in an arbitrary manner. The software also facilitates specifying arbitrary joints between structural components and concentrated structural tenns (mass and stiffness). The output files which describe the VAWT configuration are intended to be used with the Offshore Wind ENergy Simulation (OWENS) Toolkit software for structural dynamics analysis of VAWTs. Furthermore, VAWTGen is useful for visualizing output from the OWENS analysis software.

  18. Nondispersive optical activity of meshed helical metamaterials.

    PubMed

    Park, Hyun Sung; Kim, Teun-Teun; Kim, Hyeon-Don; Kim, Kyungjin; Min, Bumki

    2014-11-17

    Extreme optical properties can be realized by the strong resonant response of metamaterials consisting of subwavelength-scale metallic resonators. However, highly dispersive optical properties resulting from strong resonances have impeded the broadband operation required for frequency-independent optical components or devices. Here we demonstrate that strong, flat broadband optical activity with high transparency can be obtained with meshed helical metamaterials in which metallic helical structures are networked and arranged to have fourfold rotational symmetry around the propagation axis. This nondispersive optical activity originates from the Drude-like response as well as the fourfold rotational symmetry of the meshed helical metamaterials. The theoretical concept is validated in a microwave experiment in which flat broadband optical activity with a designed magnitude of 45° per layer of metamaterial is measured. The broadband capabilities of chiral metamaterials may provide opportunities in the design of various broadband optical systems and applications.

  19. Adaptive upscaling with the dual mesh method

    SciTech Connect

    Guerillot, D.; Verdiere, S.

    1997-08-01

    The objective of this paper is to demonstrate that upscaling should be calculated during the flow simulation instead of trying to enhance the a priori upscaling methods. Hence, counter-examples are given to motivate our approach, the so-called Dual Mesh Method. The main steps of this numerical algorithm are recalled. Applications illustrate the necessity to consider different average relative permeability values depending on the direction in space. Moreover, these values could be different for the same average saturation. This proves that an a priori upscaling cannot be the answer even in homogeneous cases because of the {open_quotes}dynamical heterogeneity{close_quotes} created by the saturation profile. Other examples show the efficiency of the Dual Mesh Method applied to heterogeneous medium and to an actual field case in South America.

  20. Isomorphic routing on a toroidal mesh

    NASA Technical Reports Server (NTRS)

    Mao, Weizhen; Nicol, David M.

    1993-01-01

    We study a routing problem that arises on SIMD parallel architectures whose communication network forms a toroidal mesh. We assume there exists a set of k message descriptors (xi, yi), where (xi, yi) indicates that the ith message's recipient is offset from its sender by xi hops in one mesh dimension, and yi hops in the other. Every processor has k messages to send, and all processors use the same set of message routing descriptors. The SIMD constraint implies that at any routing step, every processor is actively routing messages with the same descriptors as any other processor. We call this isomorphic routing. Our objective is to find the isomorphic routing schedule with least makespan. We consider a number of variations on the problem, yielding complexity results from O(k) to NP-complete. Most of our results follow after we transform the problem into a scheduling problem, where it is related to other well-known scheduling problems.

  1. Structured mesh generation with smoothness controls

    NASA Astrophysics Data System (ADS)

    Zhang, Yaoxin; Jia, Yafei; Wang, Sam S. Y.

    2006-08-01

    In geometrically complex domains, the Ryskin and Leal (RL) orthogonal mesh generation system may cause mesh distortion and overlapping problems when using the weak constraint method with specified boundary point distribution for all boundaries. To resolve these problems, an improved RL system with automatic smoothness control is proposed. In this improved RL system, the automatic smoothness control mechanism is based on five types of smoothness conditions and includes the self-adjustment mechanism and the auto-evaluation mechanism for an empirical parameter. The proposed system is illustrated using several test examples. Several applications to natural domains are also demonstrated. It is shown that the improved RL system is capable of resolving the above problems at little cost of orthogonality.

  2. Mesh convergence study for hydraulic turbine draft-tube

    NASA Astrophysics Data System (ADS)

    Devals, C.; Vu, T. C.; Zhang, Y.; Dompierre, J.; Guibault, F.

    2016-11-01

    Computational flow analysis is an essential tool for hydraulic turbine designers. Grid generation is the first step in the flow analysis process. Grid quality and solution accuracy are strongly linked. Even though many studies have addressed the issue of mesh independence, there is still no definitive consensus on mesh best practices, and research on that topic is still needed. This paper presents a mesh convergence study for turbulence flow in hydraulic turbine draft- tubes which represents the most challenging turbine component for CFD predictions. The findings from this parametric study will be incorporated as mesh control rules in an in-house automatic mesh generator for turbine components.

  3. Analysis automation with paving: A new quadrilateral meshing technique

    SciTech Connect

    Blacker, T.D. ); Stephenson, M.B.; Canann, S. )

    1990-01-01

    This paper describes the impact of paving, a new automatic mesh generation algorithm, on the analysis portion of the design process. Paving generates an all-quadrilateral mesh in arbitrary 2D geometries. The paving technique significantly impacts the analysis process by drastically reducing the time and expertise requirements of traditional mesh generation. Paving produces a high quality mesh based on geometric boundary definitions and user specified element sizing constraints. In this paper we describe the paving algorithm, discuss varying aspects of the impact of the technique on design automation, and elaborate on current research into 3D all-hexahedral mesh generation. 11 refs., 10 figs.

  4. Parallel adaptive mesh refinement within the PUMAA3D Project

    NASA Technical Reports Server (NTRS)

    Freitag, Lori; Jones, Mark; Plassmann, Paul

    1995-01-01

    To enable the solution of large-scale applications on distributed memory architectures, we are designing and implementing parallel algorithms for the fundamental tasks of unstructured mesh computation. In this paper, we discuss efficient algorithms developed for two of these tasks: parallel adaptive mesh refinement and mesh partitioning. The algorithms are discussed in the context of two-dimensional finite element solution on triangular meshes, but are suitable for use with a variety of element types and with h- or p-refinement. Results demonstrating the scalability and efficiency of the refinement algorithm and the quality of the mesh partitioning are presented for several test problems on the Intel DELTA.

  5. Diffusive mesh relaxation in ALE finite element numerical simulations

    SciTech Connect

    Dube, E.I.

    1996-06-01

    The theory for a diffusive mesh relaxation algorithm is developed for use in three-dimensional Arbitary Lagrange/Eulerian (ALE) finite element simulation techniques. This mesh relaxer is derived by a variational principle for an unstructured 3D grid using finite elements, and incorporates hourglass controls in the numerical implementation. The diffusive coefficients are based on the geometric properties of the existing mesh, and are chosen so as to allow for a smooth grid that retains the general shape of the original mesh. The diffusive mesh relaxation algorithm is then applied to an ALE code system, and results from several test cases are discussed.

  6. A Method for Combining Thin and Thick Malleable Titanium Mesh in the Repair of Cranial Defects

    PubMed Central

    McDermott, Michael W

    2015-01-01

    Introduction: Cranial defects following the removal of tumor involved bone require repair and reconstruction for brain protection and cosmesis. A variety of autologous bone substrates and synthetic materials can be employed, alone or in combination. In this article, we describe the use of dual thin and thick titanium mesh, connected together using plate hardware, to repair a right frontotemporal sphenoidal bone defect following resection of a hyperostosing sphenoid wing meningioma. Methods: Reconstruction of the pterion was done with a dual mesh cranioplasty. After replacement of the native orbitozygomatic and frontotemporal bone pieces, a piece of thinner mesh was molded to the pterional defect connecting the two bone pieces and re-creating the concave shape of the pterion below the superior temporal line. The circular area of the bony defect overlying the frontal and temporal lobes was supplemented by cutting and molding an additional piece of thicker mesh which was secured to the thinner mesh with burr hole cover sectors using rescue screws. Results: A 30-year-old woman presented with painless proptosis and was found to have a hyperostosing right sphenoid wing meningioma. The patient underwent a frontotemporal orbitozygomatic craniotomy for tumor resection and extensive bony osteotomy. Repair and reconstruction of the cranial defect in the region were accomplished at the time of open operation using two thicknesses of mesh connected one to another with titanium plate pieces and rescue screws. The patient underwent gross total resection of the meningioma and near total resection of the soft tissue and bony components (Simpson Grade II). The external cosmetic results following the orbital-cranial reconstruction with the dual mesh technique was deemed “very good” by the surgeon and patient. Postoperative CT imaging demonstrated symmetric re-approximation of the shape of the pterion as compared to the opposite side. Conclusions: We present a method for

  7. Computation of a finite element-conformal tetrahedral mesh approximation for simulated soft tissue deformation using a deformable surface model.

    PubMed

    Weichert, Frank; Schröder, Andreas; Landes, Constantin; Shamaa, Ali; Awad, Said Kamel; Walczak, Lars; Müller, Heinrich; Wagner, Mathias

    2010-06-01

    In this article, we present a new method for the generation of surface meshes of biological soft tissue. The method is based on the deformable surface model technique and is extended to histological data sets. It relies on an iterative adjustment towards polygonal segments describing the histological structures of the soft tissue. The generated surface meshes allow for the construction of volumetric meshes through a standard constrained Delaunay approach and, thus, for the application in finite element methods. The geometric properties of volumetric meshes have an immediate influence on the numerical conditioning and, therewith, on the stability of the finite element method and the convergence of iterative solvers. In this article, the influence of the surface meshes on the quality of the volumetric meshes is analysed in terms of the spectral condition number of the stiffness matrices, which are assembled within Newton's method. The non-linear material behavior of biological soft tissue is modeled by the Mooney-Rivlin material law. The subject is motivated by the requirements of virtual surgery.

  8. Coating of Mesh Grafts for Prolapse and Urinary Incontinence Repair with Autologous Plasma: Exploration Stage of a Surgical Innovation

    PubMed Central

    Bär, Andreas; Lammers, Bernhard; Ramon, Albert; Ysebaert, Dirk; Klosterhalfen, Bernd; Boros, Mihaly; Otto, Thomas

    2014-01-01

    Purpose. Optimized biocompatibility is a major requirement for alloplastic materials currently applied for stress urinary incontinence (SUI) and pelvic organ prolapse (POP) repair. In the preliminary studies the mesh modification by coating with autologous plasma resulted in the increased adherence score in vitro and improved biocompatibility in an animal model. The first use of plasma coated meshes in human is presented. Materials and Methods. Between 04/2013 and 05/2014, 20 patients with the indication for SUI and POP repair were selected in a single institution. The applied meshes were modified by autologous plasma coating prior to implantation. A retrospective chart review for peri- and early postoperative complications was performed. Functional outcome and QoL were evaluated pre- and postoperatively. Results. The functional outcome and QoL improved significantly in all groups. Two reoperations (Grade IIIB) with the release of TVT-mesh in anesthesia due to the obstruction were needed. No other severe complications were registered. Conclusion. For the first time we applied a mesh modification in a human setting according to IDEAL criteria of surgical innovations. The procedure of mesh coating with autologous plasma is safe and a prospective randomized trial proving a positive effect of plasma coating on the biocompatibility and morbidity outcome with long-term registry is planned. PMID:25313358

  9. Structured Adaptive Mesh Refinement Application Infrastructure

    SciTech Connect

    2010-07-15

    SAMRAI is an object-oriented support library for structured adaptice mesh refinement (SAMR) simulation of computational science problems, modeled by systems of partial differential equations (PDEs). SAMRAI is developed and maintained in the Center for Applied Scientific Computing (CASC) under ASCI ITS and PSE support. SAMRAI is used in a variety of application research efforts at LLNL and in academia. These applications are developed in collaboration with SAMRAI development team members.

  10. Adaption of unstructured meshes using node movement

    SciTech Connect

    Carpenter, J.G.; McRae, V.D.S.

    1996-12-31

    The adaption algorithm of Benson and McRae is modified for application to unstructured grids. The weight function generation was modified for application to unstructured grids and movement was limited to prevent cross over. A NACA 0012 airfoil is used as a test case to evaluate the modified algorithm when applied to unstructured grids and compared to results obtained by Warren. An adaptive mesh solution for the Sudhoo and Hall four element airfoil is included as a demonstration case.

  11. Optimal eigenvalue computation on a mesh multiprocessor

    SciTech Connect

    Crivelli, S.; Jessup, E. R.

    1993-01-01

    In this paper, we compare the costs of computing a single eigenvalue of a symmetric tridiagonal matrix by serial bisection and by parallel multisection on a mesh multiprocessor. We show how the optimal method for computing one eigenvalue depends on such variables as the matrix order and parameters of the multiprocessor used. We present the results of experiments on the 520-processor Intel Touchstone Delta to support our analysis.

  12. Mesh Networking Optimized for Robotic Teleoperation

    DTIC Science & Technology

    2012-04-01

    the performance of different routing protocols and route selection metrics were compared resulting in a modified version of the Babel mesh networking... Babel , robot, teleoperation, VPN, communication, relay, ad hoc, routing protocol. 1. BACKGROUND The Manually Deployed Communication Relay (MDCR...Optimized Link-State Routing Protocol (OLSR) 3 , the Better Approach To Mobile Ad hoc Networking (B.A.T.M.A.N.) 4 , and Babel 5 . Abolhasan, Hagelstein, and

  13. Wireless experiments on a Motorola mesh testbed.

    SciTech Connect

    Riblett, Loren E., Jr.; Wiseman, James M.; Witzke, Edward L.

    2010-06-01

    Motomesh is a Motorola product that performs mesh networking at both the client and access point levels and allows broadband mobile data connections with or between clients moving at vehicular speeds. Sandia National aboratories has extensive experience with this product and its predecessors in infrastructure-less mobile environments. This report documents experiments, which characterize certain aspects of how the Motomesh network performs when obile units are added to a fixed network infrastructure.

  14. Mesh deployable antenna mechanics testing method

    NASA Astrophysics Data System (ADS)

    Jiang, Li

    Rapid development in spatial technologies and continuous expansion of astronautics applications require stricter and stricter standards in spatial structure. Deployable space structure as a newly invented structural form is being extensively adopted because of its characteristic (i.e. deployability). Deployable mesh reflector antenna is a kind of common deployable antennas. Its reflector consists in a kind of metal mesh. Its electrical properties are highly dependent on its mechanics parameters (including surface accuracy, angle, and position). Therefore, these mechanics parameters have to be calibrated. This paper presents a mesh antenna mechanics testing method that employs both an electronic theodolite and a laser tracker. The laser tracker is firstly used to measure the shape of radial rib deployable antenna. The measurement data are then fitted to a paraboloid by means of error compensation. Accordingly, the focus and the focal axis of the paraboloid are obtained. The following step is to synchronize the coordinate systems of the electronic theodolite and the measured antenna. Finally, in a microwave anechoic chamber environment, the electromechanical axis is calibrated. Testing results verify the effectiveness of the presented method.

  15. Cu Mesh for Flexible Transparent Conductive Electrodes

    PubMed Central

    Kim, Won-Kyung; Lee, Seunghun; Hee Lee, Duck; Hee Park, In; Seong Bae, Jong; Woo Lee, Tae; Kim, Ji-Young; Hun Park, Ji; Chan Cho, Yong; Ryong Cho, Chae; Jeong, Se-Young

    2015-01-01

    Copper electrodes with a micromesh/nanomesh structure were fabricated on a polyimide substrate using UV lithography and wet etching to produce flexible transparent conducting electrodes (TCEs). Well-defined mesh electrodes were realized through the use of high-quality Cu thin films. The films were fabricated using radio-frequency (RF) sputtering with a single-crystal Cu target—a simple but innovative approach that overcame the low oxidation resistance of ordinary Cu. Hybrid Cu mesh electrodes were fabricated by adding a capping layer of either ZnO or Al-doped ZnO. The sheet resistance and the transmittance of the electrode with an Al-doped ZnO capping layer were 6.197 ohm/sq and 90.657%, respectively, and the figure of merit was 60.502 × 10–3/ohm, which remained relatively unchanged after thermal annealing at 200 °C and 1,000 cycles of bending. This fabrication technique enables the mass production of large-area flexible TCEs, and the stability and high performance of Cu mesh hybrid electrodes in harsh environments suggests they have strong potential for application in smart displays and solar cells. PMID:26039977

  16. Constant-mesh, multiple-shaft transmission

    SciTech Connect

    Rea, J.E.; Mills, D.D.; Sewell, J.S.

    1992-04-21

    This patent describes a multiple-shaft, constant-mesh transmission adapted to establish selectively a reverse torque delivery path and a forward drive torque delivery path and having a torque input means including a torque input shaft, a mainshaft aligned with the input shaft, a countershaft geared to the input shaft in spaced, parallel relationship with respect to the mainshaft, a torque output shaft joined to the mainshaft; multiple mainshaft gear elements journalled on the main airshaft, multiple cluster gear elements carried by the countershaft in meshing engagement with the mainshaft gear elements, one of the cluster gear elements being rotatably journalled on the countershaft; a reverse idle gear, a reverse gear journalled on the countershaft, the reverse idler gear being in constant mesh with the reverse gear and one of the mainshaft gear elements; first clutch means for connecting selectively the reverse gear and the countershaft; second synchronizer clutch means for connecting selectively the one of the mainshaft gear elements to the mainshaft; and third synchronizer clutch means for selectively connecting another of the mainshaft gear elements to the mainshaft; the first clutch means being a double-acting clutch with a first common axially movable clutch element adapted upon movement in one axial direction to drivably connected the reverse gear to the countershaft and adapted upon movement in the opposite axial direction to connect the one cluster gear element to the countershaft.

  17. Software for Automated Generation of Cartesian Meshes

    NASA Technical Reports Server (NTRS)

    Aftosmis, Michael J.; Melton, John E.; Berger, Marshal J.

    2006-01-01

    Cart3D is a collection of computer programs for generating Cartesian meshes [for computational fluid dynamics (CFD) and other applications] in volumes bounded by solid objects. Aspects of Cart3D at earlier stages of development were reported in "Robust and Efficient Generation of Cartesian Meshes for CFD" (ARC-14275), NASA Tech Briefs, Vol. 23, No. 8 (August 1999), page 30. The geometric input to Cart3D comprises surface triangulations like those commonly generated by computer-aided-design programs. Complexly shaped objects can be represented as assemblies of simpler ones. Cart3D deletes all portions of such an assembled object that are not on the exterior surface. Intersections between components are preserved in the resulting triangulation. A tie-breaking routine unambiguously resolves geometric degeneracies. Then taking the intersected surface triangulation as input, the volume mesh is generated through division of cells of an initially coarse hexahedral grid. Cells are subdivided to refine the grid in regions of increased surface curvature and/or increased flow gradients. Cells that become split into multiple unconnected regions by thin pieces of surface are identified.

  18. Particle Mesh Hydrodynamics for Astrophysics Simulations

    NASA Astrophysics Data System (ADS)

    Chatelain, Philippe; Cottet, Georges-Henri; Koumoutsakos, Petros

    We present a particle method for the simulation of three dimensional compressible hydrodynamics based on a hybrid Particle-Mesh discretization of the governing equations. The method is rooted on the regularization of particle locations as in remeshed Smoothed Particle Hydrodynamics (rSPH). The rSPH method was recently introduced to remedy problems associated with the distortion of computational elements in SPH, by periodically re-initializing the particle positions and by using high order interpolation kernels. In the PMH formulation, the particles solely handle the convective part of the compressible Euler equations. The particle quantities are then interpolated onto a mesh, where the pressure terms are computed. PMH, like SPH, is free of the convection CFL condition while at the same time it is more efficient as derivatives are computed on a mesh rather than particle-particle interactions. PMH does not detract from the adaptive character of SPH and allows for control of its accuracy. We present simulations of a benchmark astrophysics problem demonstrating the capabilities of this approach.

  19. Retrieval study at 623 human mesh explants made of polypropylene--impact of mesh class and indication for mesh removal on tissue reaction.

    PubMed

    Klosterhalfen, B; Klinge, U

    2013-11-01

    Textile meshes frequently are implanted in the abdominal wall to reinforce a hernia repair. However, revisions for mesh associated complications confirm that these devices are not completely free of risk. Explanted devices offer an opportunity to define the impact of mesh structure on tissue response. This retrieval study analyses the tissue reaction to 623 polypropylene mesh samples (170 class 1 with large pores, and 453 class 2 with small pores) explanted for pain, infection, or recurrence. Histopathological assessment included morphometry of inflammatory infiltrate (IF) and connective tissue (CT), and of collagen 1/3 ratio. Half of the meshes were removed after more than 23 month. Despite large inter-individual differences removal for infection showed more IF than for pain or recurrence with significant correlation of IF with CT. Class 1 meshes with large pores showed less IF, CT, fistula formation, calcification, and bridging than class 2 meshes with small pores. Meshes removed for recurrence showed a lowered collagen 1/3 ratio in 70%. Large pore class 1 meshes showed an improved tissue response and may be considered as favorable to prevent inflammatory side effects. The presence of lowered collagen 1/3 ratio in most of the samples with recurrences stresses the relevance of an intact healing process. Late manifestation of complications demands long-lasting follow-up.

  20. Retrieval study at 623 human mesh explants made of polypropylene - impact of mesh class and indication for mesh removal on tissue reaction.

    PubMed

    Klosterhalfen, B; Klinge, U

    2013-05-19

    Textile meshes frequently are implanted in the abdominal wall to reinforce a hernia repair. However, revisions for mesh associated complications confirm that these devices are not completely free of risk. Explanted devices offer an opportunity to define the impact of mesh structure on tissue response. This retrieval study analyses the tissue reaction to 623 polypropylene mesh samples (170 class 1 with large pores, and 453 class 2 with small pores) explanted for pain, infection, or recurrence. Histopathological assessment included morphometry of inflammatory infiltrate (IF) and connective tissue (CT), and of collagen 1/3 ratio. Half of the meshes were removed after more than 23 month. Despite large inter-individual differences removal for infection showed more IF than for pain or recurrence with significant correlation of IF with CT. Class 1 meshes with large pores showed less IF, CT, fistula formation, calcification, and bridging than class 2 meshes with small pores. Meshes removed for recurrence showed a lowered collagen 1/3 ratio in 70%. Large pore class 1 meshes showed an improved tissue response and may be considered as favorable to prevent inflammatory side effects. The presence of lowered collagen 1/3 ratio in most of the samples with recurrences stresses the relevance of an intact healing process. Late manifestation of complications demands long-lasting follow-up. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2013.

  1. MeSH Now: automatic MeSH indexing at PubMed scale via learning to rank.

    PubMed

    Mao, Yuqing; Lu, Zhiyong

    2017-04-17

    MeSH indexing is the task of assigning relevant MeSH terms based on a manual reading of scholarly publications by human indexers. The task is highly important for improving literature retrieval and many other scientific investigations in biomedical research. Unfortunately, given its manual nature, the process of MeSH indexing is both time-consuming (new articles are not immediately indexed until 2 or 3 months later) and costly (approximately ten dollars per article). In response, automatic indexing by computers has been previously proposed and attempted but remains challenging. In order to advance the state of the art in automatic MeSH indexing, a community-wide shared task called BioASQ was recently organized. We propose MeSH Now, an integrated approach that first uses multiple strategies to generate a combined list of candidate MeSH terms for a target article. Through a novel learning-to-rank framework, MeSH Now then ranks the list of candidate terms based on their relevance to the target article. Finally, MeSH Now selects the highest-ranked MeSH terms via a post-processing module. We assessed MeSH Now on two separate benchmarking datasets using traditional precision, recall and F1-score metrics. In both evaluations, MeSH Now consistently achieved over 0.60 in F-score, ranging from 0.610 to 0.612. Furthermore, additional experiments show that MeSH Now can be optimized by parallel computing in order to process MEDLINE documents on a large scale. We conclude that MeSH Now is a robust approach with state-of-the-art performance for automatic MeSH indexing and that MeSH Now is capable of processing PubMed scale documents within a reasonable time frame. http://www.ncbi.nlm.nih.gov/CBBresearch/Lu/Demo/MeSHNow/ .

  2. Antibacterial mesh: a novel technique involving naturally occurring cellular proteins.

    PubMed

    Yurko, Yuliya; McDeavitt, Kathleen; Kumar, Rohan Satish; Martin, Terri; Prabhu, Ajita; Lincourt, Amy E; Vertegel, Alexey; Heniford, B Todd

    2012-03-01

    Naturally occurring antimicrobial peptides are possibly the "next frontier" in infection prevention. Binding them to mesh could reduce the rate of mesh infections. This study identifies an antimicrobial agent capable of significant antibacterial activity when bound to mesh. Lysozyme, human beta defensin (HBD-3), human cathelicidin (LL-37), and lysostaphin were adsorbed to polypropylene mesh at various concentrations. Treated meshes were placed in a suspension of 1 × 10(6) Staphylococcus aureus. Antibacterial action was monitored by turbidimetric assay, fluorescent imaging, and a colony counting method. A very high rate of lysis of S aureus cells was observed in the lysostaphin-treated group as measured by optical density; none survived as seen on colony count assays. Optical density for mesh coated with lysozyme, HBD-3, and LL-37 did not differ from untreated controls, with 100% survival rates by colony counts. Lysostaphin had superior antibacterial activity following adsorption to mesh.

  3. Automated hexahedral meshing of anatomic structures using deformable registration.

    PubMed

    Grosland, Nicole M; Bafna, Ritesh; Magnotta, Vincent A

    2009-02-01

    This work introduces a novel method of automating the process of patient-specific finite element (FE) model development using a mapped mesh technique. The objective is to map a predefined mesh (template) of high quality directly onto a new bony surface (target) definition, thereby yielding a similar mesh with minimal user interaction. To bring the template mesh into correspondence with the target surface, a deformable registration technique based on the FE method has been adopted. The procedure has been made hierarchical allowing several levels of mesh refinement to be used, thus reducing the time required to achieve a solution. Our initial efforts have focused on the phalanx bones of the human hand. Mesh quality metrics, such as element volume and distortion were evaluated. Furthermore, the distance between the target surface and the final mapped mesh were measured. The results have satisfactorily proven the applicability of the proposed method.

  4. Array-based Hierarchical Mesh Generation in Parallel

    DOE PAGES

    Ray, Navamita; Grindeanu, Iulian; Zhao, Xinglin; ...

    2015-11-03

    In this paper, we describe an array-based hierarchical mesh generation capability through uniform refinement of unstructured meshes for efficient solution of PDE's using finite element methods and multigrid solvers. A multi-degree, multi-dimensional and multi-level framework is designed to generate the nested hierarchies from an initial mesh that can be used for a number of purposes such as multi-level methods to generating large meshes. The capability is developed under the parallel mesh framework “Mesh Oriented dAtaBase” a.k.a MOAB. We describe the underlying data structures and algorithms to generate such hierarchies and present numerical results for computational efficiency and mesh quality. Inmore » conclusion, we also present results to demonstrate the applicability of the developed capability to a multigrid finite-element solver.« less

  5. Array-based Hierarchical Mesh Generation in Parallel

    SciTech Connect

    Ray, Navamita; Grindeanu, Iulian; Zhao, Xinglin; Mahadevan, Vijay; Jiao, Xiangmin

    2015-11-03

    In this paper, we describe an array-based hierarchical mesh generation capability through uniform refinement of unstructured meshes for efficient solution of PDE's using finite element methods and multigrid solvers. A multi-degree, multi-dimensional and multi-level framework is designed to generate the nested hierarchies from an initial mesh that can be used for a number of purposes such as multi-level methods to generating large meshes. The capability is developed under the parallel mesh framework “Mesh Oriented dAtaBase” a.k.a MOAB. We describe the underlying data structures and algorithms to generate such hierarchies and present numerical results for computational efficiency and mesh quality. In conclusion, we also present results to demonstrate the applicability of the developed capability to a multigrid finite-element solver.

  6. A Triangle Mesh Standardization Method Based on Particle Swarm Optimization

    PubMed Central

    Duan, Liming; Bai, Yang; Wang, Haoyu; Shao, Hui; Zhong, Siyang

    2016-01-01

    To enhance the triangle quality of a reconstructed triangle mesh, a novel triangle mesh standardization method based on particle swarm optimization (PSO) is proposed. First, each vertex of the mesh and its first order vertices are fitted to a cubic curve surface by using least square method. Additionally, based on the condition that the local fitted surface is the searching region of PSO and the best average quality of the local triangles is the goal, the vertex position of the mesh is regulated. Finally, the threshold of the normal angle between the original vertex and regulated vertex is used to determine whether the vertex needs to be adjusted to preserve the detailed features of the mesh. Compared with existing methods, experimental results show that the proposed method can effectively improve the triangle quality of the mesh while preserving the geometric features and details of the original mesh. PMID:27509129

  7. Tomographic mesh generation for OSEM reconstruction of SPECT images

    NASA Astrophysics Data System (ADS)

    Lu, Yao; Yu, Bo; Vogelsang, Levon; Krol, Andrzej; Xu, Yuesheng; Hu, Xiaofei; Feiglin, David

    2009-02-01

    To improve quality of OSEM SPECT reconstruction in the mesh domain, we implemented an adaptive mesh generation method that produces tomographic mesh consisting of triangular elements with size and density commensurate with geometric detail of the objects. Node density and element size change smoothly as a function of distance from the edges and edge curvature without creation of 'bad' elements. Tomographic performance of mesh-based OSEM reconstruction is controlled by the tomographic mesh structure, i.e. node density distribution, which in turn is ruled by the number of key points on the boundaries. A greedy algorithm is used to influence the distribution of nodes on the boundaries. The relationship between tomographic mesh properties and OSEM reconstruction quality has been investigated. We conclude that by selecting adequate number of key points, one can produce a tomographic mesh with lowest number of nodes that is sufficient to provide desired quality of reconstructed images, appropriate for the imaging system properties.

  8. Data-Parallel Mesh Connected Components Labeling and Analysis

    SciTech Connect

    Harrison, Cyrus; Childs, Hank; Gaither, Kelly

    2011-04-10

    We present a data-parallel algorithm for identifying and labeling the connected sub-meshes within a domain-decomposed 3D mesh. The identification task is challenging in a distributed-memory parallel setting because connectivity is transitive and the cells composing each sub-mesh may span many or all processors. Our algorithm employs a multi-stage application of the Union-find algorithm and a spatial partitioning scheme to efficiently merge information across processors and produce a global labeling of connected sub-meshes. Marking each vertex with its corresponding sub-mesh label allows us to isolate mesh features based on topology, enabling new analysis capabilities. We briefly discuss two specific applications of the algorithm and present results from a weak scaling study. We demonstrate the algorithm at concurrency levels up to 2197 cores and analyze meshes containing up to 68 billion cells.

  9. Biaxial Mechanical Evaluation of Absorbable and Nonabsorbable Synthetic Surgical Meshes Used for Hernia Repair: Physiological Loads Modify Anisotropy Response.

    PubMed

    Cordero, A; Hernández-Gascón, B; Pascual, G; Bellón, J M; Calvo, B; Peña, E

    2016-07-01

    The aim of this study was to obtain information about the mechanical properties of six meshes commonly used for hernia repair (Surgipro(®), Optilene(®), Infinit(®), DynaMesh(®), Ultrapro™ and TIGR(®)) by planar biaxial tests. Stress-stretch behavior and equibiaxial stiffness were evaluated, and the anisotropy was determined by testing. In particular, equibiaxial test (equal simultaneous loading in both directions) and biaxial test (half of the load in one direction following the Laplace law) were selected as a representation of physiologically relevant loads. The majority of the meshes displayed values in the range of 8 and 18 (N/mm) in each direction for equibiaxial stiffness (tangent modulus under equibiaxial load state in both directions), while a few achieved 28 and 50 (N/mm) (Infinit (®) and TIGR (®)). Only the Surgipro (®) mesh exhibited planar isotropy, with similar mechanical properties regardless of the direction of loading, and an anisotropy ratio of 1.18. Optilene (®), DynaMesh (®), Ultrapro (®) and TIGR (®) exhibited moderate anisotropy with ratios of 1.82, 1.84, 2.17 and 1.47, respectively. The Infinit (®) scaffold exhibited very high anisotropy with a ratio of 3.37. These trends in material anisotropic response changed during the physiological state in the human abdominal wall, i.e. T:0.5T test, which the meshes were loaded in one direction with half the load used in the other direction. The Surgipro (®) mesh increased its anisotropic response (Anis[Formula: see text] = 0.478) and the materials that demonstrated moderate and high anisotropic responses during multiaxial testing presented a quasi-isotropic response, especially the Infinit(®) mesh that decreased its anisotropic response from 3.369 to 1.292.

  10. A Mesh Refinement Study on the Impact Response of a Shuttle Leading-Edge Panel Finite Element Simulation

    NASA Technical Reports Server (NTRS)

    Fasanella, Edwin L.; Jackson, Karen E.; Lyle, Karen H.; Spellman, Regina L.

    2006-01-01

    A study was performed to examine the influence of varying mesh density on an LS-DYNA simulation of a rectangular-shaped foam projectile impacting the space shuttle leading edge Panel 6. The shuttle leading-edge panels are fabricated of reinforced carbon-carbon (RCC) material. During the study, nine cases were executed with all possible combinations of coarse, baseline, and fine meshes of the foam and panel. For each simulation, the same material properties and impact conditions were specified and only the mesh density was varied. In the baseline model, the shell elements representing the RCC panel are approximately 0.2-in. on edge, whereas the foam elements are about 0.5-in. on edge. The element nominal edge-length for the baseline panel was halved to create a fine panel (0.1-in. edge length) mesh and doubled to create a coarse panel (0.4-in. edge length) mesh. In addition, the element nominal edge-length of the baseline foam projectile was halved (0.25-in. edge length) to create a fine foam mesh and doubled (1.0-in. edge length) to create a coarse foam mesh. The initial impact velocity of the foam was 775 ft/s. The simulations were executed in LS-DYNA for 6 ms of simulation time. Contour plots of resultant panel displacement and effective stress in the foam were compared at four discrete time intervals. Also, time-history responses of internal and kinetic energy of the panel, kinetic and hourglass energy of the foam, and resultant contact force were plotted to determine the influence of mesh density.

  11. Totally extraperitoneal inguinal hernioplasty with titanium-coated lightweight polypropylene mesh: early results.

    PubMed

    Tamme, C; Garde, N; Klingler, A; Hampe, C; Wunder, R; Köckerling, F

    2005-08-01

    This prospective study of a new titanium-coated low-weight polypropylene (PP) mesh (16 g PP/m2) was designed to investigate the clinical efficacy and safety of totally extraperitoneal endoscopic hernioplasty (TEP). In this study, 400 patients (average age, 53.5 years; range, 19-80 years) with a total of 588 inguinal hernias underwent surgery with the TEP technique between September 2002 and October 2003. Of these patients, 12.4% had experienced recurrent hernias after open suture herniotomy. In 92% of the cases (368 patients with 540 hernias), a lightweight (16 g PP/m2) titanium-coated polypropylene mesh was implanted without fixation, and in 8% (32 patients with 48 hernias) an identical medium-weight (35 g PP/m2) mesh was implanted. The first follow-up examination was scheduled for postoperative week 6. In the lightweight mesh group, the mean group, operating time per patient was 61 min, corresponding to a calculated time per hernia of 41 min. Two intraoperative major complications occurred: an injury to the cecum and an injury to the bladder. In 12 cases (2%), bleeding from epigastric, testicular, or pubic bone vessels was observed. No injuries to pelvic vessels were seen. One patient was underwent an endoscopic revision to deal with an anticoagulation-related bleed. The mortality rate was 0%. In 12 patients, postoperative hematomas developed. One preperitoneal lipoma had to be extirpated. No infections of the mesh occurred. The median follow-up period for 371 patients (92.3%) was 7.2 weeks (range, 4-14 weeks). These 343 patients (with 504 hernias) had been provided with a lightweight titanium-coated polypropylene mesh (16 g PP/m2) (follow-up rate, 93.2%). Of these patients, 3.5% reported persistent ingunial pain, 1.7% described a sensation of rigidity in the region of the groin, and 3.2% reported dysesthesia. The early recurrence rate was 0.2%. The TEP procedure can be performed safely and effectively with the appreciably material-reduced and titanium

  12. Oral, intestinal, and skin bacteria in ventral hernia mesh implants

    PubMed Central

    Langbach, Odd; Kristoffersen, Anne Karin; Abesha-Belay, Emnet; Enersen, Morten; Røkke, Ola; Olsen, Ingar

    2016-01-01

    Background In ventral hernia surgery, mesh implants are used to reduce recurrence. Infection after mesh implantation can be a problem and rates around 6–10% have been reported. Bacterial colonization of mesh implants in patients without clinical signs of infection has not been thoroughly investigated. Molecular techniques have proven effective in demonstrating bacterial diversity in various environments and are able to identify bacteria on a gene-specific level. Objective The purpose of this study was to detect bacterial biofilm in mesh implants, analyze its bacterial diversity, and look for possible resemblance with bacterial biofilm from the periodontal pocket. Methods Thirty patients referred to our hospital for recurrence after former ventral hernia mesh repair, were examined for periodontitis in advance of new surgical hernia repair. Oral examination included periapical radiographs, periodontal probing, and subgingival plaque collection. A piece of mesh (1×1 cm) from the abdominal wall was harvested during the new surgical hernia repair and analyzed for bacteria by PCR and 16S rRNA gene sequencing. From patients with positive PCR mesh samples, subgingival plaque samples were analyzed with the same techniques. Results A great variety of taxa were detected in 20 (66.7%) mesh samples, including typical oral commensals and periodontopathogens, enterics, and skin bacteria. Mesh and periodontal bacteria were further analyzed for similarity in 16S rRNA gene sequences. In 17 sequences, the level of resemblance between mesh and subgingival bacterial colonization was 98–100% suggesting, but not proving, a transfer of oral bacteria to the mesh. Conclusion The results show great bacterial diversity on mesh implants from the anterior abdominal wall including oral commensals and periodontopathogens. Mesh can be reached by bacteria in several ways including hematogenous spread from an oral site. However, other sites such as gut and skin may also serve as sources for the

  13. Foreign Body Reaction Associated with PET and PET/Chitosan Electrospun Nanofibrous Abdominal Meshes

    PubMed Central

    Veleirinho, Beatriz; Coelho, Daniela S.; Dias, Paulo F.; Maraschin, Marcelo; Pinto, Rúbia; Cargnin-Ferreira, Eduardo; Peixoto, Ana; Souza, José A.; Ribeiro-do-Valle, Rosa M.; Lopes-da-Silva, José A.

    2014-01-01

    Electrospun materials have been widely explored for biomedical applications because of their advantageous characteristics, i.e., tridimensional nanofibrous structure with high surface-to-volume ratio, high porosity, and pore interconnectivity. Furthermore, considering the similarities between the nanofiber networks and the extracellular matrix (ECM), as well as the accepted role of changes in ECM for hernia repair, electrospun polymer fiber assemblies have emerged as potential materials for incisional hernia repair. In this work, we describe the application of electrospun non-absorbable mats based on poly(ethylene terephthalate) (PET) in the repair of abdominal defects, comparing the performance of these meshes with that of a commercial polypropylene mesh and a multifilament PET mesh. PET and PET/chitosan electrospun meshes revealed good performance during incisional hernia surgery, post-operative period, and no evidence of intestinal adhesion was found. The electrospun meshes were flexible with high suture retention, showing tensile strengths of 3 MPa and breaking strains of 8–33%. Nevertheless, a significant foreign body reaction (FBR) was observed in animals treated with the nanofibrous materials. Animals implanted with PET and PET/chitosan electrospun meshes (fiber diameter of 0.71±0.28 µm and 3.01±0.72 µm, respectively) showed, respectively, foreign body granuloma formation, averaging 4.2-fold and 7.4-fold greater than the control commercial mesh group (Marlex). Many foreign body giant cells (FBGC) involving nanofiber pieces were also found in the PET and PET/chitosan groups (11.9 and 19.3 times more FBGC than control, respectively). In contrast, no important FBR was observed for PET microfibers (fiber diameter = 18.9±0.21 µm). Therefore, we suggest that the reduced dimension and the high surface-to-volume ratio of the electrospun fibers caused the FBR reaction, pointing out the need for further studies to elucidate the mechanisms underlying

  14. Performance of Stainless Steel Mesh Cathode and PVDF-graphite Cathode in Microbial Fuel Cells

    NASA Astrophysics Data System (ADS)

    Huang, Liping; Tian, Ying; Li, Mingliang; He, Gaohong; Li, Zhikao

    2010-11-01

    Inexpensive and conductive materials termed as stainless steel mesh and polyvinylidene fluoride (PVDF)-graphite were currently used as the air cathode electrodes in MFCs for the investigation of power production. By loading PTFE (poly(tetrafluoroethylene)) on the surface of stainless steel mesh, electricity production reached 3 times as high as that of the naked stainless steel. A much high catalytic activity for oxygen reduction was exhibited by Pt based and PTFE loading stainless steel mesh cathode, with an electricity generation of 1144±44 mW/m2 (31±1 W/m3) and a Coulombic efficiency (CE) of 77±2%. When Pt was replaced by an inexpensive transition metal based catalyst (cobalt tetramethylphenylporphyrin, CoTMPP), power production and CE were 845±21 mW/m2 (23±1 W/m3) and 68±1%, respectively. Accordingly, power production from PVDF-graphite (hydrophobic) MFC and PVDF-graphite (hydrophile) MFC were 286±20 mW/m2(8±1 W/m3) and 158±13 mW/m2(4±0.4 W/m3), respectively using CoTMPP as catalyst. These results give us new insight into materials like stainless steel mesh and PVDF-graphite as low cost cathode for reducing the costs of MFCs for wastewater treatment applications.

  15. Integration of Mesh Optimization with 3D All-Hex Mesh Generation, LDRD Subcase 3504340000, Final Report

    SciTech Connect

    KNUPP,PATRICK; MITCHELL,SCOTT A.

    1999-11-01

    In an attempt to automatically produce high-quality all-hex meshes, we investigated a mesh improvement strategy: given an initial poor-quality all-hex mesh, we iteratively changed the element connectivity, adding and deleting elements and nodes, and optimized the node positions. We found a set of hex reconnection primitives. We improved the optimization algorithms so they can untangle a negative-Jacobian mesh, even considering Jacobians on the boundary, and subsequently optimize the condition number of elements in an untangled mesh. However, even after applying both the primitives and optimization we were unable to produce high-quality meshes in certain regions. Our experiences suggest that many boundary configurations of quadrilaterals admit no hexahedral mesh with positive Jacobians, although we have no proof of this.

  16. Lichtenstein Mesh Repair (LMR) v/s Modified Bassini’s Repair (MBR) + Lichtenstein Mesh Repair of Direct Inguinal Hernias in Rural Population – A Comparative Study

    PubMed Central

    Patil, Santosh M; Kumar, Ashok; Kumar, Kuthadi Sravan; Mithun, Gorre

    2016-01-01

    Introduction Lichtenstein’s tension free mesh hernioplasty is the commonly done open technique for inguinal hernias. As our hospital is in rural area, majority of patients are labourers, open hernias are commonly done. The present study was done by comparing Lichtenstein Mesh Repair (LMR) v/s Modified Bassini’s repair (MBR) + Lichtenstein mesh repair (LMR) of direct Inguinal Hernias to compare the technique of both surgeries and its outcome like postoperative complications and recurrence rate. Materials and Methods A comparative randomized study was conducted on patients reporting to MNR hospital, sangareddy with direct inguinal hernias. A total of fifty consecutive patients were included in this study of which, 25 patients were operated by LMR and 25 patients were operated by MBR+LMR and followed up for a period of two years. The outcomes of the both techniques were compared. Results Study involved 25 each of Lichtenstein’s mesh repair (LMR) and modified bassini’s repair (MBR) + LMR, over a period of 2 years. The duration of surgery for lichtenstein mesh repair is around 34.56 min compared to LMR+MBR, which is 47.56 min which was statistically significant (p-value is <0.0001). In this study the most common complication for both the groups was seroma. The pain was relatively higher in LMR+MBR group in POD 1, but not statistically significant (p-value is 0.0949) and from POD 7 the pain was almost similar in both groups. The recurrence rate is 2% for LMR and 0% for MBR+LMR. Conclusion LMR+MBR was comparatively better than only LMR in all direct inguinal hernias because of low recurrence rate (0%) and low postoperative complications, which showed in our present study. PMID:27042517

  17. Selection of finite-element mesh parameters in modeling the growth of hydraulic fracturing cracks

    NASA Astrophysics Data System (ADS)

    Kurguzov, V. D.

    2016-12-01

    The effect of the mesh geometry on the accuracy of solutions obtained by the finite-element method for problems of linear fracture mechanics is investigated. The guidelines have been formulated for constructing an optimum mesh for several routine problems involving elements with linear and quadratic approximation of displacements. The accuracy of finite-element solutions is estimated based on the degree of the difference between the calculated stress-intensity factor (SIF) and its value obtained analytically. In problems of hydrofracturing of oil-bearing formation, the pump-in pressure of injected water produces a distributed load on crack flanks as opposed to standard fracture mechanics problems that have analytical solutions, where a load is applied to the external boundaries of the computational region and the cracks themselves are kept free from stresses. Some model pressure profiles, as well as pressure profiles taken from real hydrodynamic computations, have been considered. Computer models of cracks with allowance for the pre-stressed state, fracture toughness, and elastic properties of materials are developed in the MSC.Marc 2012 finite-element analysis software. The Irwin force criterion is used as a criterion of brittle fracture and the SIFs are computed using the Cherepanov-Rice invariant J-integral. The process of crack propagation in a linearly elastic isotropic body is described in terms of the elastic energy release rate G and modeled using the VCCT (Virtual Crack Closure Technique) approach. It has been found that the solution accuracy is sensitive to the mesh configuration. Several parameters that are decisive in constructing effective finite-element meshes, namely, the minimum element size, the distance between mesh nodes in the vicinity of a crack tip, and the ratio of the height of an element to its length, have been established. It has been shown that a mesh that consists of only small elements does not improve the accuracy of the solution.

  18. Evaluation of tension-free mesh inguinal hernia repair in Nigeria: a preliminary report.

    PubMed

    Arowolo, O A; Agbakwuru, E A; Adisa, A O; Lawal, O O; Ibrahim, M H; Afolabi, A I

    2011-01-01

    Tension-free mesh inguinal hernia repair is becoming increasingly popular worldwide. However, reports are sparse in Nigeria. To evaluate the impact, outcome and cost implication of tension free inguinal hernia repair in a Nigerian setting. A prospective study of all consecutive adults patients with uncomplicated inguinal hernia who had mesh repair over a period of 12 months was undertaken. A large sheet of 900cm2 polyproylene mesh material was used for all the patients in the study. All wounds were opened on the third postoperative day while sutures were removed on the eight day. Patients were followed up for one year. A total number of 30 patients had tension-free mesh ingunal hernia repair. Their ages ranged from 21 to 78 years (mean 47.2±15.5) years with a female to male ratio of 1:15. Complete inguinoscrotal hernia was the commonest type of groin hernia accounting for 40% of the cases. The repair of posterior wall which entailed placement of mesh was completed at a median time of 15 minutes. While two (6.7%) and one (3.3%) had wound oedema and groin pain respectively at one month, none of the patients had these complications or recurrence at a median of five months follow-up period. Tension-free mesh inguinal hernia repair was well tolerated and affordable to our patients. Pain and infections, reported to be the common complications of this procedure were infrequent in this study. A larger study is recommended to help confirm these findings.

  19. Lightweight partially absorbable monofilament mesh (polypropylene/poliglecaprone 25) for TAPP inguinal hernia repair: initial experience.

    PubMed

    Agresta, Ferdinando; Baldazzi, Gian Andrea; Ciardo, Luigi Francesco; Trentin, Giuseppe; Giuseppe, Sansonetti; Ferrante, Furio; Bedin, Natalino

    2007-04-01

    An ideal mesh should produce slight foreign-body reactions and be compatible with the human organisms. Studies focusing on these aspects indicate that the use of mesh with less nonabsorbable material may reduce postoperative complications, insofar the web structure and its rigidity play an important role in compatibility. We evaluated retrospectively the patients of the past 1 year, who underwent laparoscopic transabdominal preperitoneal (TAPP) hernioplasty (without the use any trocar and/or instrument of 10 mm in diameter) focusing attention on the feasibility of the technique and on the incidence of complications, especially those possibly related to the new type of mesh implanted. Between June 2004 and September 2005, 76 patients have been operated on by using TAPP hernioplasty (bilateral or unilateral) without any 10 mm instrument/optic/trocar, and by applying a lightweight composite mesh fixed by "glues" (fibrin sealant and N-butyl 2-cyanoacrylate). The mean overall operative time was 55.57 (+/-15.2) minutes. All the procedures have been performed on a day surgery basis. We have registered any kind of major or minor morbidity (early or late), relapse, prosthesis rejection, and/or infection. We have registered no severe pain at 10 days; whereas a mild pain is still reported in 10.5% of our cases at a 3-month follow-up. The mean follow-up is 12.4 (+/-5.1; range 4 to 19) months. On the basis of this our initial experience, TAPP hernioplasty with a lightweight composite mesh is feasible, effective, and easy to perform by experienced hands, with good results. The well-known characteristics of a mini-invasive and gentle approach, together with the type of mesh implanted and its fixation of related glues, might explain the encouraging results of our experience.

  20. Combining spray nozzle simulators with meshes: characterization of rainfall intensity and drop properties

    NASA Astrophysics Data System (ADS)

    Carvalho, Sílvia C. P.; de Lima, João L. M. P.; de Lima, M. Isabel P.

    2013-04-01

    Rainfall simulators can be a powerful tool to increase our understanding of hydrological and geomorphological processes. Nevertheless, rainfall simulators' design and operation might be rather demanding, for achieving specific rainfall intensity distributions and drop characteristics. The pressurized simulators have some advantages over the non-pressurized simulators: drops do not rely on gravity to reach terminal velocity, but are sprayed out under pressure; pressurized simulators also yield a broad range of drop sizes in comparison with drop-formers simulators. The main purpose of this study was to explore in the laboratory the potential of combining spray nozzle simulators with meshes in order to change rainfall characteristics (rainfall intensity and diameters and fall speed of drops). Different types of spray nozzles were tested, such as single full-cone and multiple full-cone nozzles. The impact of the meshes on the simulated rain was studied by testing different materials (i.e. plastic and steel meshes), square apertures and wire thicknesses, and different vertical distances between the nozzle and the meshes underneath. The diameter and fall speed of the rain drops were measured using a Laser Precipitation Monitor (Thies Clima). The rainfall intensity range and coefficients of uniformity of the sprays and the drop size distribution, fall speed and kinetic energy were analysed. Results show that when meshes intercept drop trajectories the spatial distribution of rainfall intensity and the drop size distribution are affected. As the spray nozzles generate typically small drop sizes and narrow drop size distributions, meshes can be used to promote the formation of bigger drops and random their landing positions.

  1. Parallel deterministic transport sweeps of structured and unstructured meshes with overloaded mesh decompositions

    DOE PAGES

    Pautz, Shawn D.; Bailey, Teresa S.

    2016-11-29

    Here, the efficiency of discrete ordinates transport sweeps depends on the scheduling algorithm, the domain decomposition, the problem to be solved, and the computational platform. Sweep scheduling algorithms may be categorized by their approach to several issues. In this paper we examine the strategy of domain overloading for mesh partitioning as one of the components of such algorithms. In particular, we extend the domain overloading strategy, previously defined and analyzed for structured meshes, to the general case of unstructured meshes. We also present computational results for both the structured and unstructured domain overloading cases. We find that an appropriate amountmore » of domain overloading can greatly improve the efficiency of parallel sweeps for both structured and unstructured partitionings of the test problems examined on up to 105 processor cores.« less

  2. Parallel deterministic transport sweeps of structured and unstructured meshes with overloaded mesh decompositions

    SciTech Connect

    Pautz, Shawn D.; Bailey, Teresa S.

    2016-11-29

    Here, the efficiency of discrete ordinates transport sweeps depends on the scheduling algorithm, the domain decomposition, the problem to be solved, and the computational platform. Sweep scheduling algorithms may be categorized by their approach to several issues. In this paper we examine the strategy of domain overloading for mesh partitioning as one of the components of such algorithms. In particular, we extend the domain overloading strategy, previously defined and analyzed for structured meshes, to the general case of unstructured meshes. We also present computational results for both the structured and unstructured domain overloading cases. We find that an appropriate amount of domain overloading can greatly improve the efficiency of parallel sweeps for both structured and unstructured partitionings of the test problems examined on up to 105 processor cores.

  3. Improved mesh based photon sampling techniques for neutron activation analysis

    SciTech Connect

    Relson, E.; Wilson, P. P. H.; Biondo, E. D.

    2013-07-01

    The design of fusion power systems requires analysis of neutron activation of large, complex volumes, and the resulting particles emitted from these volumes. Structured mesh-based discretization of these problems allows for improved modeling in these activation analysis problems. Finer discretization of these problems results in large computational costs, which drives the investigation of more efficient methods. Within an ad hoc subroutine of the Monte Carlo transport code MCNP, we implement sampling of voxels and photon energies for volumetric sources using the alias method. The alias method enables efficient sampling of a discrete probability distribution, and operates in 0(1) time, whereas the simpler direct discrete method requires 0(log(n)) time. By using the alias method, voxel sampling becomes a viable alternative to sampling space with the 0(1) approach of uniformly sampling the problem volume. Additionally, with voxel sampling it is straightforward to introduce biasing of volumetric sources, and we implement this biasing of voxels as an additional variance reduction technique that can be applied. We verify our implementation and compare the alias method, with and without biasing, to direct discrete sampling of voxels, and to uniform sampling. We study the behavior of source biasing in a second set of tests and find trends between improvements and source shape, material, and material density. Overall, however, the magnitude of improvements from source biasing appears to be limited. Future work will benefit from the implementation of efficient voxel sampling - particularly with conformal unstructured meshes where the uniform sampling approach cannot be applied. (authors)

  4. Preclinical Bioassay of a Polypropylene Mesh for Hernia Repair Pretreated with Antibacterial Solutions of Chlorhexidine and Allicin: An In Vivo Study

    PubMed Central

    Pérez-Köhler, Bárbara; García-Moreno, Francisca; Brune, Thierry; Pascual, Gemma; Bellón, Juan Manuel

    2015-01-01

    Introduction Prosthetic mesh infection constitutes one of the major complications following hernia repair. Antimicrobial, non-antibiotic biomaterials have the potential to reduce bacterial adhesion to the mesh surface and adjacent tissues while avoiding the development of novel antibiotic resistance. This study assesses the efficacy of presoaking reticular polypropylene meshes in chlorhexidine or a chlorhexidine and allicin combination (a natural antibacterial agent) for preventing bacterial infection in a short-time hernia-repair rabbit model. Methods Partial hernia defects (5 x 2 cm) were created on the lateral right side of the abdominal wall of New Zealand White rabbits (n = 21). The defects were inoculated with 0.5 mL of a 106 CFU/mL Staphylococcus aureus ATCC25923 strain and repaired with a DualMesh Plus antimicrobial mesh or a Surgipro mesh presoaked in either chlorhexidine (0.05%) or allicin-chlorhexidine (900 μg/mL-0.05%). Fourteen days post-implant, mesh contraction was measured and tissue specimens were harvested to evaluate bacterial adhesion to the implant surface (via sonication, S. aureus immunolabeling), host-tissue incorporation (via staining, scanning electron microscopy) and macrophage response (via RAM-11 immunolabeling). Results The polypropylene mesh showed improved tissue integration relative to the DualMesh Plus. Both the DualMesh Plus and the chlorhexidine-soaked polypropylene meshes exhibited high bacterial clearance, with the latter material showing lower bacterial yields. The implants from the allicin-chlorhexidine group displayed a neoformed tissue containing differently sized abscesses and living bacteria, as well as a diminished macrophage response. The allicin-chlorhexidine coated implants exhibited the highest contraction. Conclusions The presoaking of reticular polypropylene materials with a low concentration of chlorhexidine provides the mesh with antibacterial activity without disrupting tissue integration. Due to the

  5. Assessment of Gel-Coated Delayed Self-Gripping Mesh

    PubMed Central

    Gutman, Mordechai; Lebedyev, Alexander

    2014-01-01

    Background: Mesh hernia repair is one of the most frequently performed procedures in general surgery. Recently, use of the self-gripping mesh demonstrated a beneficial effect on postoperative pain in inguinal hernia repairs. However, in intra-abdominal placement, the use of this novel mesh requires greater laparoscopic skill and dexterity because of the mesh's tendency to fold and adhere to itself and to any surrounding tissues. We hypothesized that gel-like coverage of a self-gripping mesh with a water-soluble film would allow delaying the immediate surface adhesion of the mesh to the tissue, which may allow greater freedom and ease in mesh placement for laparoscopic surgeons. Methods: In this ex vivo animal study, gel-coated self-gripping mesh (ProGrip) was compared with a control uncoated mesh in bovine and porcine tissue specimens and assessed for dislodgement shear forces before and after dissolving of the gel. Results: Gel coating of the mesh reduced preperitoneal dislodgement forces in a porcine abdominal wall specimen by 81% (8.05 ± 0.66 vs 1.53 ± 0.82 N, P < .01). Dissolving the gel markedly increased the anchoring forces (10.62 ± 3.70 vs 1.53 ± 0.82 N, P < .0001), and after dissolving the gel, the mesh shear dislodgement forces were similar and noninferior to the control mesh (8.05 ± 0.66 vs 10.62 ± 3.70 N, P = NS). Conclusions: We believe that water-soluble gel coating does not impair the adhesive features of the self-gripping mesh and may simplify its use in open and laparoscopic procedures by allowing controlled activation of the self-gripping mechanism. PMID:25516704

  6. Comparison of three different methods for effective introduction of platelet-rich plasma on PLGA woven mesh.

    PubMed

    Lee, Ji-Hye; Nam, Jinwoo; Kim, Hee Joong; Yoo, Jeong Joon

    2015-03-11

    For successful tissue regeneration, effective cell delivery to defect site is very important. Various types of polymer biomaterials have been developed and applied for effective cell delivery. PLGA (poly lactic-co-glycolic acid), a synthetic polymer, is a commercially available and FDA approved material. Platelet-rich plasma (PRP) is an autologous growth factor cocktail containing various growth factors including PDGF, TGFβ-1 and BMPs, and has shown positive effects on cell behaviors. We hypothesized that PRP pretreatment on PLGA mesh using different methods would cause different patterns of platelet adhesion and stages which would modulate cell adhesion and proliferation on the PLGA mesh. In this study, we pretreated PRP on PLGA using three different methods including simple dripping (SD), dynamic oscillation (DO) and centrifugation (CE), then observed the amount of adhered platelets and their activation stage distribution. The highest amount of platelets was observed on CE mesh and calcium treated CE mesh. Moreover, calcium addition after PRP coating triggered dramatic activation of platelets which showed large and flat morphologies of platelets with rich fibrin networks. Human chondrocytes (hCs) and human bone marrow stromal cells (hBMSCs) were next cultured on PRP-pretreated PLGA meshes using different preparation methods. CE mesh showed a significant increase in the initial cell adhesion of hCs and proliferation of hBMSCs compared with SD and DO meshes. The results demonstrated that the centrifugation method can be considered as a promising coating method to introduce PRP on PLGA polymeric material which could improve cell-material interaction using a simple method.

  7. Preparation of Superhydrophilic and Underwater Superoleophobic Nanofiber-Based Meshes from Waste Glass for Multifunctional Oil/Water Separation.

    PubMed

    Ma, Qinglang; Cheng, Hongfei; Yu, Yifu; Huang, Ying; Lu, Qipeng; Han, Shikui; Chen, Junze; Wang, Rong; Fane, Anthony G; Zhang, Hua

    2017-03-17

    The deterioration of water resources due to oil pollution, arising from oil spills, industrial oily wastewater discharge, etc., urgently requires the development of novel functional materials for highly efficient water remediation. Recently, superhydrophilic and underwater superoleophobic materials have drawn significant attention due to their low oil adhesion and selective oil/water separation. However, it is still a challenge to prepare low-cost, environmentally friendly, and multifunctional materials with superhydrophilicity and underwater superoleophobicity, which can be stably used for oil/water separation under harsh working conditions. Here, the preparation of nanofiber-based meshes derived from waste glass through a green and sustainable route is demonstrated. The resulting meshes exhibit excellent performance in the selective separation of a wide range of oil/water mixtures. Importantly, these meshes can also maintain the superwetting property and high oil/water separation efficiency under various harsh conditions. Furthermore, the as-prepared mesh can remove water-soluble contaminants simultaneously during the oil/water separation process, leading to multifunctional water purification. The low-cost and environmentally friendly fabrication, harsh-environment resistance, and multifunctional characteristics make these nanofiber-based meshes promising toward oil/water separation under practical conditions.

  8. Polypropelene-mesh properties and type of anchoring do not influence strength of parietal ingrowth.

    PubMed

    Harsløf, S; Zinther, N; Harsløf, T; Danielsen, C; Wara, P; Friis-Andersen, H

    2017-07-21

    In laparoscopic ventral hernia repair, parietal ingrowth of the mesh is of crucial importance. Until significant ingrowth occurs integrity of the repair depends solely on mesh overlap and anchoring device. Relatively few studies have addressed the effect of mesh properties and anchoring device on long-term parietal ingrowth. In 20 sheep, using laparoscopy, we inserted two different polypropylene-based meshes, Physiomesh™ and Ventralight™ ST, anchored with Protack™, SecureStrap™, or Glubran™. After 6 and 12 months, 10 sheep at each time point were euthanized, and we harvested the meshes with corresponding fascia. Mesh with fascia was attached on an Alwetron™ materials testing machine and pulled apart obtaining the peel-off energy (kilojoule (kJ)). The strength of parietal ingrowth at 6 months was 5.99 ± 0.54 kJ (mean ± SEM), 4.94 ± 0.54 kJ and 7.35 ± 0.55 kJ when anchored with Protack™, Glubran™, or SecureStrap™, respectively. At 6 months, the strength of parietal ingrowth of SecureStrap™ was significantly higher than Glubran™ (p = 0.04). No significant difference was seen between any other combinations. Parietal ingrowth at 12 months was 7.05 ± 0.56 kJ, 7.55 ± 0.54 kJ, and 5.73 ± 0.54 kJ when anchored with Protack™, Glubran™, and SecureStrap™, respectively. No significant difference in strength of parietal ingrowth was seen between the three types of anchoring, (p = 1.00, p = 1.00, and p = 0.29). At 12 months, the strength of parietal ingrowth was the same for all comparisons. The two polypropylene meshes showed equal strength of parietal ingrowth independent of mesh properties and anchoring devices used.

  9. Generation of multi-million element meshes for solid model-based geometries: The Dicer algorithm

    SciTech Connect

    Melander, D.J.; Benzley, S.E.; Tautges, T.J.

    1997-06-01

    The Dicer algorithm generates a fine mesh by refining each element in a coarse all-hexahedral mesh generated by any existing all-hexahedral mesh generation algorithm. The fine mesh is geometry-conforming. Using existing all-hexahedral meshing algorithms to define the initial coarse mesh simplifies the overall meshing process and allows dicing to take advantage of improvements in other meshing algorithms immediately. The Dicer algorithm will be used to generate large meshes in support of the ASCI program. The authors also plan to use dicing as the basis for parallel mesh generation. Dicing strikes a careful balance between the interactive mesh generation and multi-million element mesh generation processes for complex 3D geometries, providing an efficient means for producing meshes of varying refinement once the coarse mesh is obtained.

  10. Perspective on the Lagrange-Jacobi mesh

    NASA Astrophysics Data System (ADS)

    Rampho, Gaotsiwe J.

    2016-07-01

    This paper presents a unified treatment of the kinetic energy matrix elements related to a number of Lagrange functions associated with the Lagrange-Jacobi mesh. The matrix elements can be readily modified for application to problems requiring eigenfunction expansion with Lagrange-Legendre, Lagrange-Chebyshev, Lagrange-Gegenbauer, as well as the Lagrange-Jacobi functions. The applicability of and the accuracy attainable with the matrix elements is demonstrated with the solution to the Schrödinger equation for confining trigonometric Pöschl-Teller potentials. The results obtained are within machine accuracy when appropriate choices of the basis functions are used.

  11. On Convergence Acceleration Techniques for Unstructured Meshes

    NASA Technical Reports Server (NTRS)

    Mavriplis, Dimitri J.

    1998-01-01

    A discussion of convergence acceleration techniques as they relate to computational fluid dynamics problems on unstructured meshes is given. Rather than providing a detailed description of particular methods, the various different building blocks of current solution techniques are discussed and examples of solution strategies using one or several of these ideas are given. Issues relating to unstructured grid CFD problems are given additional consideration, including suitability of algorithms to current hardware trends, memory and cpu tradeoffs, treatment of non-linearities, and the development of efficient strategies for handling anisotropy-induced stiffness. The outlook for future potential improvements is also discussed.

  12. Tolerance and Long-Term MRI Imaging of Gadolinium-Modified Meshes Used in Soft Organ Repair

    PubMed Central

    Letouzey, Vincent; Huberlant, Stéphanie; Cornille, Arnaud; Blanquer, Sébastien; Guillaume, Olivier; Lemaire, Laurent; Garric, Xavier; de Tayrac, Renaud

    2015-01-01

    Background Synthetic meshes are frequently used to reinforce soft tissues. The aim of this translational study is to evaluate tolerance and long-term MRI visibility of two recently developed Gadolinium-modified meshes in a rat animal model. Materials and Methods Gadolinium-poly-ε-caprolactone (Gd-PCL) and Gadolinium-polymethylacrylate (Gd-PMA) modified meshes were implanted in Wistar rats and their tolerance was assessed daily. Inflammation and biocompatibility of the implants were assessed by histology and immunohistochemistry after 30 days post implantation. Implants were visualised by 7T and 3T MRI at day 30 and at day 90. Diffusion of Gadolinium in the tissues of the implanted animals was assessed by Inductively Coupled Plasma Mass Spectrometry. Results Overall Gd-PMA coated implants were better tolerated as compared to those coated with Gd-PCL. In fact, Gd-PMA implants were characterised by a high ratio collagen I/III and good vascularisation of the integration tissues. High resolution images of the coated mesh were obtained in vivo with experimental 7T as well as 3T clinical MRI. Mass spectrometry analyses showed that levels of Gadolinium in animals implanted with coated mesh were similar to those of the control group. Conclusions Meshes coated with Gd-PMA are better tolerated as compared to those coated with Gd-PCL as no signs of erosion or significant inflammation were detected at 30 days post implantation. Also, Gd-PMA coated meshes were clearly visualised with both 7T and 3T MRI devices. This new technique of mesh optimisation may represent a valuable tool in soft tissue repair and management. PMID:25811855

  13. A Proximal Straining Mesh Location Is Associated With De Novo Stress Urinary Incontinence After Transobturator Mesh Procedures.

    PubMed

    Huang, Wen-Chen; Yang, Jenn-Ming

    2017-03-01

    The purpose of this study was to explore the association between mesh location and de novo stress urinary incontinence (SUI) after transvaginal mesh procedures. We retrospectively analyzed a database of women who had received transvaginal mesh procedures for stage III or greater cystocele according to the Pelvic Organ Prolapse Quantification system. Only data for women who neither reported SUI preoperatively nor had received concomitant anti-incontinence surgery were included for analyses. The mesh location was investigated by sonography via the percentage of the urethra covered by mesh, defined as the number calculated by dividing the portion of the urethral length covered by mesh (the distance from the bladder neck to the point of the urethra, which was indicated by an imaginary line at the level of the lower [caudal] mesh end and perpendicular to the urethra) by the total urethral length (the distance from the bladder neck to the external urethral meatus) in the sagittal plane. The resting, straining, coughing, and squeezing mesh locations of women who did (n = 29) and did not (n = 54) report SUI at the 12-month follow-up were compared. At the 12-month follow-up, women who reported SUI had a significantly smaller straining percentage of the urethra covered by mesh (mean ± SD, 28.5% ± 9.6%) compared with continent women (35.2% ± 15.8%), indicating a more proximal straining mesh location. Sonography is useful in investigating the location of the transvaginal mesh. De novo SUI after transvaginal mesh procedures is associated with a more proximal straining mesh location. © 2017 by the American Institute of Ultrasound in Medicine.

  14. Materials

    NASA Technical Reports Server (NTRS)

    Glaessgen, Edward H.; Schoeppner, Gregory A.

    2006-01-01

    NASA Langley Research Center has successfully developed an electron beam freeform fabrication (EBF3) process, a rapid metal deposition process that works efficiently with a variety of weldable alloys. The EBF3 process can be used to build a complex, unitized part in a layer-additive fashion, although the more immediate payoff is for use as a manufacturing process for adding details to components fabricated from simplified castings and forgings or plate products. The EBF3 process produces structural metallic parts with strengths comparable to that of wrought product forms and has been demonstrated on aluminum, titanium, and nickel-based alloys to date. The EBF3 process introduces metal wire feedstock into a molten pool that is created and sustained using a focused electron beam in a vacuum environment. Operation in a vacuum ensures a clean process environment and eliminates the need for a consumable shield gas. Advanced metal manufacturing methods such as EBF3 are being explored for fabrication and repair of aerospace structures, offering potential for improvements in cost, weight, and performance to enhance mission success for aircraft, launch vehicles, and spacecraft. Near-term applications of the EBF3 process are most likely to be implemented for cost reduction and lead time reduction through addition of details onto simplified preforms (casting or forging). This is particularly attractive for components with protruding details that would require a significantly large volume of material to be machined away from an oversized forging, offering significant reductions to the buy-to-fly ratio. Future far-term applications promise improved structural efficiency through reduced weight and improved performance by exploiting the layer-additive nature of the EBF3 process to fabricate tailored unitized structures with functionally graded microstructures and compositions.

  15. Significant improvement of biocompatibility of polypropylene mesh for incisional hernia repair by using poly-ε-caprolactone nanofibers functionalized with thrombocyte-rich solution

    PubMed Central

    Plencner, Martin; Prosecká, Eva; Rampichová, Michala; East, Barbora; Buzgo, Matej; Vysloužilová, Lucie; Hoch, Jiří; Amler, Evžen

    2015-01-01

    Incisional hernia is the most common postoperative complication, affecting up to 20% of patients after abdominal surgery. Insertion of a synthetic surgical mesh has become the standard of care in ventral hernia repair. However, the implementation of a mesh does not reduce the risk of recurrence and the onset of hernia recurrence is only delayed by 2–3 years. Nowadays, more than 100 surgical meshes are available on the market, with polypropylene the most widely used for ventral hernia repair. Nonetheless, the ideal mesh does not exist yet; it still needs to be developed. Polycaprolactone nanofibers appear to be a suitable material for different kinds of cells, including fibroblasts, chondrocytes, and mesenchymal stem cells. The aim of the study reported here was to develop a functionalized scaffold for ventral hernia regeneration. We prepared a novel composite scaffold based on a polypropylene surgical mesh functionalized with poly-ε-caprolactone (PCL) nanofibers and adhered thrombocytes as a natural source of growth factors. In extensive in vitro tests, we proved the biocompatibility of PCL nanofibers with adhered thrombocytes deposited on a polypropylene mesh. Compared with polypropylene mesh alone, this composite scaffold provided better adhesion, growth, metabolic activity, proliferation, and viability of mouse fibroblasts in all tests and was even better than a polypropylene mesh functionalized with PCL nanofibers. The gradual release of growth factors from biocompatible nanofiber-modified scaffolds seems to be a promising approach in tissue engineering and regenerative medicine. PMID:25878497

  16. Significant improvement of biocompatibility of polypropylene mesh for incisional hernia repair by using poly-ε-caprolactone nanofibers functionalized with thrombocyte-rich solution.

    PubMed

    Plencner, Martin; Prosecká, Eva; Rampichová, Michala; East, Barbora; Buzgo, Matej; Vysloužilová, Lucie; Hoch, Jiří; Amler, Evžen

    2015-01-01

    Incisional hernia is the most common postoperative complication, affecting up to 20% of patients after abdominal surgery. Insertion of a synthetic surgical mesh has become the standard of care in ventral hernia repair. However, the implementation of a mesh does not reduce the risk of recurrence and the onset of hernia recurrence is only delayed by 2-3 years. Nowadays, more than 100 surgical meshes are available on the market, with polypropylene the most widely used for ventral hernia repair. Nonetheless, the ideal mesh does not exist yet; it still needs to be developed. Polycaprolactone nanofibers appear to be a suitable material for different kinds of cells, including fibroblasts, chondrocytes, and mesenchymal stem cells. The aim of the study reported here was to develop a functionalized scaffold for ventral hernia regeneration. We prepared a novel composite scaffold based on a polypropylene surgical mesh functionalized with poly-ε-caprolactone (PCL) nanofibers and adhered thrombocytes as a natural source of growth factors. In extensive in vitro tests, we proved the biocompatibility of PCL nanofibers with adhered thrombocytes deposited on a polypropylene mesh. Compared with polypropylene mesh alone, this composite scaffold provided better adhesion, growth, metabolic activity, proliferation, and viability of mouse fibroblasts in all tests and was even better than a polypropylene mesh functionalized with PCL nanofibers. The gradual release of growth factors from biocompatible nanofiber-modified scaffolds seems to be a promising approach in tissue engineering and regenerative medicine.

  17. Split Bregman's algorithm for three-dimensional mesh segmentation

    NASA Astrophysics Data System (ADS)

    Habiba, Nabi; Ali, Douik

    2016-05-01

    Variational methods have attracted a lot of attention in the literature, especially for image and mesh segmentation. The methods aim at minimizing the energy to optimize both edge and region detections. We propose a spectral mesh decomposition algorithm to obtain disjoint but meaningful regions of an input mesh. The related optimization problem is nonconvex, and it is very difficult to find a good approximation or global optimum, which represents a challenge in computer vision. We propose an alternating split Bregman algorithm for mesh segmentation, where we extended the image-dedicated model to a three-dimensional (3-D) mesh one. By applying our scheme to 3-D mesh segmentation, we obtain fast solvers that can outperform various conventional ones, such as graph-cut and primal dual methods. A consistent evaluation of the proposed method on various public domain 3-D databases for different metrics is elaborated, and a comparison with the state-of-the-art is performed.

  18. Anisotropic mesh adaptivity for multi-scale ocean modelling.

    PubMed

    Piggott, M D; Farrell, P E; Wilson, C R; Gorman, G J; Pain, C C

    2009-11-28

    Research into the use of unstructured mesh methods in oceanography has been growing steadily over the past decade. The advantages of this approach for domain representation and non-uniform resolution are clear. However, a number of issues remain, in particular those related to the computational cost of models produced using unstructured mesh methods compared with their structured mesh counterparts. Mesh adaptivity represents an important means to improve the competitiveness of unstructured mesh models, where high resolution is only used when and where necessary. In this paper, an optimization-based approach to mesh adaptivity is described where emphasis is placed on capturing anisotropic solution characteristics. Comparisons are made between the results obtained with uniform isotropic resolution, isotropic adaptive resolution and fully anisotropic adaptive resolution.

  19. Femoro-distal bypass with varicose veins covered by prosthetic mesh.

    PubMed

    Carella, Giuseppe S; Stilo, Francesco; Benedetto, Filippo; David, Antonio; Risitano, Domenica C; Buemi, Michele; Spinelli, Francesco

    2011-06-15

    The great saphenous vein (GSV) is the material of choice in distal bypass for critical limb ischemia (CLI). Varicosities have been reported as the cause of inadequacy of vein in up to 20% of patients. The hypothesis of this study is to consider the external mesh as a technique to use like conduit, in patients with varicose veins and in young patients with ecstatic veins, with results that at least overlap the traditional technique. We report our experience with bypass surgery using autologous varicose vein covered with prosthetic mesh. From May 2005 to July 2008, 249 infrapopliteal bypasses were performed to treat CLI. Twenty-one patients were selected from this group to receive bypass covered by polyester external mesh (ProVena; BBraun, Aesculap, Tuttlingen, Germany). Seventeen patients had varicose veins, four young patients had venous ectasia or previous bypass failure for dilatation. Graft patency was evaluated at 1, 3, 6, and 12 mo, and every 6 mo thereafter. All patients underwent epidural anesthesia with ropivacain 0.75%. The mean follow-up time was 32 mo. No dilatation or infection was found in this period. Two early bypass thromboses were recorded and treated immediately. Two lesions were treated at 3 and 8 mo with surgical substitution of the distal portion and PTA of focal intermediate stenosis, respectively. Primary patency at 24 mo was 57.1% (SE ± 3.9), assisted 81% (SE ± 3.2), and had an amputation-free survival rate of 85.7% (SE ± 2.8). In other bypass without mesh, primary patency was 63.8%, secondary 80.5%, and amputation-free survival rate 89.3% at 24 mo. Polyester external mesh is a valid method to perform bypass with autologous material, as ecstatic or varicose veins. Moreover, in young patients with long-term bypass patency expectancy, it prevents vein dilatation during arterialization process. Copyright © 2011 Elsevier Inc. All rights reserved.

  20. Mesh Generation and Microstructure Extraction based on 3D Porous Medium Images

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Xing, H.; Guan, Z.

    2009-12-01

    With the development of SEM and/or MRI based techniques, it is increasingly easy to get the high quality 3D images of porous medium with the microscopic structure information. Once the pixel information for a block of porous medium is obtained, a point array description for this porous medium is defined, and both coordination and material property information are included. To analyze such related data and apply them into the further numerical modeling, a mesh generator is developed. It has following steps: (1) Reading data from a 3D image with material property/microstructure information and extracting points with the specified material property; (2) Performing a well-known Delaunay triangulation on the related points and constraining the boundary of different materials; (3) Extracting boundary which describes the microscopic structure of porous medium; (4) Smoothing boundary based on Curvature and shape of the porous medium including mesh coarsening/refining. (5) Using the smoothed boundary as an input closed triangular surface and taking a constrained Delaunay triangulation based on this surface; (6) Adaptively refining the generated tetrahedron and transporting the property of porous medium to the related tetrahedrons; (7) Output the mesh for the further numerical (e.g. FEM, FDM, FVM) analysis.

  1. Dynamic Mesh Adaptation for Front Evolution Using Discontinuous Galerkin Based Weighted Condition Number Mesh Relaxation

    SciTech Connect

    Greene, Patrick T.; Schofield, Samuel P.; Nourgaliev, Robert

    2016-06-21

    A new mesh smoothing method designed to cluster mesh cells near a dynamically evolving interface is presented. The method is based on weighted condition number mesh relaxation with the weight function being computed from a level set representation of the interface. The weight function is expressed as a Taylor series based discontinuous Galerkin projection, which makes the computation of the derivatives of the weight function needed during the condition number optimization process a trivial matter. For cases when a level set is not available, a fast method for generating a low-order level set from discrete cell-centered elds, such as a volume fraction or index function, is provided. Results show that the low-order level set works equally well for the weight function as the actual level set. Meshes generated for a number of interface geometries are presented, including cases with multiple level sets. Dynamic cases for moving interfaces are presented to demonstrate the method's potential usefulness to arbitrary Lagrangian Eulerian (ALE) methods.

  2. 3D Compressible Melt Transport with Adaptive Mesh Refinement

    NASA Astrophysics Data System (ADS)

    Dannberg, Juliane; Heister, Timo

    2015-04-01

    Melt generation and migration have been the subject of numerous investigations, but their typical time and length-scales are vastly different from mantle convection, which makes it difficult to study these processes in a unified framework. The equations that describe coupled Stokes-Darcy flow have been derived a long time ago and they have been successfully implemented and applied in numerical models (Keller et al., 2013). However, modelling magma dynamics poses the challenge of highly non-linear and spatially variable material properties, in particular the viscosity. Applying adaptive mesh refinement to this type of problems is particularly advantageous, as the resolution can be increased in mesh cells where melt is present and viscosity gradients are high, whereas a lower resolution is sufficient in regions without melt. In addition, previous models neglect the compressibility of both the solid and the fluid phase. However, experiments have shown that the melt density change from the depth of melt generation to the surface leads to a volume increase of up to 20%. Considering these volume changes in both phases also ensures self-consistency of models that strive to link melt generation to processes in the deeper mantle, where the compressibility of the solid phase becomes more important. We describe our extension of the finite-element mantle convection code ASPECT (Kronbichler et al., 2012) that allows for solving additional equations describing the behaviour of silicate melt percolating through and interacting with a viscously deforming host rock. We use the original compressible formulation of the McKenzie equations, augmented by an equation for the conservation of energy. This approach includes both melt migration and melt generation with the accompanying latent heat effects. We evaluate the functionality and potential of this method using a series of simple model setups and benchmarks, comparing results of the compressible and incompressible formulation and

  3. A mechanism of mesh-related post-herniorrhaphy neuralgia.

    PubMed

    Bendavid, R; Lou, W; Grischkan, D; Koch, A; Petersen, K; Morrison, J; Iakovlev, V

    2016-06-01

    The objective is to compare nerve densities in explanted polypropylene meshes in patients with or without chronic pain. Pain has supplanted recurrences as a complication of hernia surgery. The increased incidence of pain mirrors a parallel increase in the use of polypropylene meshes. Neither triple neurectomy nor careful nerve preservation has brought relief. Perhaps because we have forgotten that nerves, in response to some evolutionary mechanism, tend to regenerate, undergo changes imposed by prosthetic elements and architecture, mimicking entrapment and compartment syndromes. A total of 33 hernia meshes have been analyzed: 17 excised due to severe pain, two for combined pain and recurrence, 14 sampled during revision for recurrence without pain. Each mesh had standardized sampling for histology and the nerves were highlighted by S100 stain. Nerve densities were assessed within the mesh spaces and in tissue outside the mesh. The density of nerves present in the standardized mesh samples of patients complaining of pain was much more elevated than in the mesh of those patients who had a recurrence but no pain. The difference was statistically significant (p < 0.001). Excluding two patients who had both pain and recurrence, the difference was even more marked (p < 0.0001). Re-innervation and neo-innervation are known to take place following hernia repairs in indigenous tissue as well as through polypropylene meshes. However, when pain is an overriding issue dictating mesh explant, the degree of mesh innervation is significantly higher when compared to mesh excised for recurrence. That increase has been confirmed statistically.

  4. Hexahedral mesh generation via the dual arrangement of surfaces

    SciTech Connect

    Mitchell, S.A.; Tautges, T.J.

    1997-12-31

    Given a general three-dimensional geometry with a prescribed quadrilateral surface mesh, the authors consider the problem of constructing a hexahedral mesh of the geometry whose boundary is exactly the prescribed surface mesh. Due to the specialized topology of hexahedra, this problem is more difficult than the analogous one for tetrahedra. Folklore has maintained that a surface mesh must have a constrained structure in order for there to exist a compatible hexahedral mesh. However, they have proof that a surface mesh need only satisfy mild parity conditions, depending on the topology of the three-dimensional geometry, for there to exist a compatible hexahedral mesh. The proof is based on the realization that a hexahedral mesh is dual to an arrangement of surfaces, and the quadrilateral surface mesh is dual to the arrangement of curves bounding these surfaces. The proof is constructive and they are currently developing an algorithm called Whisker Weaving (WW) that mirrors the proof steps. Given the bounding curves, WW builds the topological structure of an arrangement of surfaces having those curves as its boundary. WW progresses in an advancing front manner. Certain local rules are applied to avoid structures that lead to poor mesh quality. Also, after the arrangement is constructed, additional surfaces are inserted to separate features, so e.g., no two hexahedra share more than one quadrilateral face. The algorithm has generated meshes for certain non-trivial problems, but is currently unreliable. The authors are exploring strategies for consistently selecting which portion of the surface arrangement to advance based on the existence proof. This should lead us to a robust algorithm for arbitrary geometries and surface meshes.

  5. Collagen/Polypropylene composite mesh biocompatibility in abdominal wall reconstruction.

    PubMed

    Lukasiewicz, Aleksander; Skopinska-Wisniewska, Joanna; Marszalek, Andrzej; Molski, Stanislaw; Drewa, Tomasz

    2013-05-01

    Intraperitoneal placement of polypropylene mesh leads to extensive visceral adhesions and is contraindicated. Different coatings are used to improve polypropylene mesh properties. Collagen is a protein with unique biocompatibility and cell ingrowth enhancement potential. A novel acetic acid extracted collagen coating was developed to allow placement of polypropylene mesh in direct contact with viscera. The authors' aim was to evaluate the long-term influence of acetic acid extracted collagen coating on surgical aspects and biomechanical properties of polypropylene mesh implanted in direct contact with viscera, including complications, adhesions with viscera, strength of incorporation, and microscopic inflammatory reaction. Forty adult Wistar rats were divided into two groups: experimental (polypropylene mesh/acetic acid extracted collagen coating) and control (polypropylene mesh only). Astandardized procedure of mesh implantation was performed. Animals were killed 3 months after surgery and analyzed for complications, mesh area covered by adhesions, type of adhesions, strength of incorporation, and intensity of inflammatory response. The mean adhesion area was lower for polypropylene mesh/acetic acid extracted collagen coating (14.5 percent versus 69.9 percent, p < 0.001). Adhesion severity was decreased in the experimental group: grades 0 and 1 were more frequent (p < 0.04 and p < 0.002, respectively) and grade 3 was less frequent (p < 0.0001). An association between adhesion area and severity was found (p < 0.0001). Complications, strength of incorporation, and intensity of inflammatory response to the mesh were similar. Visceral adhesions to polypropylene mesh are significantly reduced because of acetic acid extracted collagen coating. The collagen coating does not increase complications or induce alterations of polypropylene mesh incorporation.

  6. Gear mesh stiffness and load sharing in planetary gearing

    NASA Technical Reports Server (NTRS)

    Kasuba, R.; August, R.

    1984-01-01

    An interactive computerized analysis was developed for determining load sharing among planetary gears. The load sharing is established as a function of transmitted torque, degree of sun gear fixity, component flexibility, gear tooth quality, and phasing of individual planet gears. A nonlinear variable gear tooth mesh stiffness model was used to simulate the sun/plant and planet/ring gear meshes. The determined load sharing and gear mesh stiffness parameters then can be used for the subsequent assessment of dynamic load factors.

  7. A comparison of mesh morphing methods for shape optimization.

    SciTech Connect

    Staten, Matthew L.; Owen, Steven James

    2010-08-01

    The ability to automatically morph an existing mesh to conform to geometry modifications is a necessary capability to enable rapid prototyping of design variations. This paper compares six methods for morphing hexahedral and tetrahedral meshes, including the previously published FEMWARP and LBWARP methods as well as four new methods. Element quality and performance results show that different methods are superior on different models. We recommend that designers of applications that use mesh morphing consider both the FEMWARP and a linear simplex based method.

  8. Optical characterisation of metallic meshes for space antennas transformable reflectors

    NASA Astrophysics Data System (ADS)

    Mironov, RA; Reznik, SV; Rukavishnikov, RV; Shishulina, VA; Zavaruev, VA

    2016-10-01

    The paper deals with metallic meshes for space antenna transformable reflectors. Optical characteristics of four metallic meshes (15 micron tungsten, 15 micron gold-plated tungsten, 20 micron molybdenum, and 50 micron Ni-coated steel) were investigated with the Nikolet IS50 spectrophotometer. The spectral optical characteristics of these metallic meshes in the range from 0.4 to 2.5 microns are required for thermal design of space antenna reflectors.

  9. Finding Regions of Interest on Toroidal Meshes

    SciTech Connect

    Wu, Kesheng; Sinha, Rishi R; Jones, Chad; Ethier, Stephane; Klasky, Scott; Ma, Kwan-Liu; Shoshani, Arie; Winslett, Marianne

    2011-02-09

    Fusion promises to provide clean and safe energy, and a considerable amount of research effort is underway to turn this aspiration intoreality. This work focuses on a building block for analyzing data produced from the simulation of microturbulence in magnetic confinementfusion devices: the task of efficiently extracting regions of interest. Like many other simulations where a large amount of data are produced,the careful study of ``interesting'' parts of the data is critical to gain understanding. In this paper, we present an efficient approach forfinding these regions of interest. Our approach takes full advantage of the underlying mesh structure in magnetic coordinates to produce acompact representation of the mesh points inside the regions and an efficient connected component labeling algorithm for constructingregions from points. This approach scales linearly with the surface area of the regions of interest instead of the volume as shown with bothcomputational complexity analysis and experimental measurements. Furthermore, this new approach is 100s of times faster than a recentlypublished method based on Cartesian coordinates.

  10. Adaptive Mesh Refinement for ICF Calculations

    NASA Astrophysics Data System (ADS)

    Fyfe, David

    2005-10-01

    This paper describes our use of the package PARAMESH to create an Adaptive Mesh Refinement (AMR) version of NRL's FASTRAD3D code. PARAMESH was designed to create an MPI-based AMR code from a block structured serial code such as FASTRAD3D. FASTRAD3D is a compressible hydrodynamics code containing the physical effects relevant for the simulation of high-temperature plasmas including inertial confinement fusion (ICF) Rayleigh-Taylor unstable direct drive laser targets. These effects include inverse bremmstrahlung laser energy absorption, classical flux-limited Spitzer thermal conduction, real (table look-up) equation-of-state with either separate or identical electron and ion temperatures, multi-group variable Eddington radiation transport, and multi-group alpha particle transport and thermonuclear burn. Numerically, this physics requires an elliptic solver and a ray tracing approach on the AMR grid, which is the main subject of this paper. A sample ICF calculation will be presented. MacNeice et al., ``PARAMESH: A parallel adaptive mesh refinement community tool,'' Computer Physics Communications, 126 (2000), pp. 330-354.

  11. Finding regions of interest on toroidal meshes

    NASA Astrophysics Data System (ADS)

    Wu, Kesheng; Sinha, Rishi R.; Jones, Chad; Ethier, Stephane; Klasky, Scott; Ma, Kwan-Liu; Shoshani, Arie; Winslett, Marianne

    2011-01-01

    Fusion promises to provide clean and safe energy, and a considerable amount of research effort is under way to turn this aspiration into a reality. This work focuses on a building block for analyzing data produced from the simulation of microturbulence in magnetic confinement fusion devices: the task of efficiently extracting regions of interest. Like many other simulations where a large number of data are produced, the careful study of 'interesting' parts of the data is critical to gain understanding. In this paper, we present an efficient approach for finding these regions of interest. Our approach takes full advantage of the underlying mesh structure in magnetic coordinates to produce a compact representation of the mesh points inside the regions and an efficient connected component labeling algorithm for constructing regions from points. This approach scales linearly with the surface area of the regions of interest instead of the volume as shown with both computational complexity analysis and experimental measurements. Furthermore, this new approach is hundreds of times faster than a recently published method based on Cartesian coordinates.

  12. Almost isometric mesh parameterization through abstract domains.

    PubMed

    Pietroni, Nico; Tarini, Marco; Cignoni, Paolo

    2010-01-01

    In this paper, we propose a robust, automatic technique to build a global hi-quality parameterization of a two-manifold triangular mesh. An adaptively chosen 2D domain of the parameterization is built as part of the process. The produced parameterization exhibits very low isometric distortion, because it is globally optimized to preserve both areas and angles. The domain is a collection of equilateral triangular 2D regions enriched with explicit adjacency relationships (it is abstract in the sense that no 3D embedding is necessary). It is tailored to minimize isometric distortion, resulting in excellent parameterization qualities, even when meshes with complex shape and topology are mapped into domains composed of a small number of large continuous regions. Moreover, this domain is, in turn, remapped into a collection of 2D square regions, unlocking many advantages found in quad-based domains (e.g., ease of packing). The technique is tested on a variety of cases, including challenging ones, and compares very favorably with known approaches. An open-source implementation is made available.

  13. Current sheets, reconnection and adaptive mesh refinement

    NASA Astrophysics Data System (ADS)

    Marliani, Christiane

    1998-11-01

    Adaptive structured mesh refinement methods have proved to be an appropriate tool for the numerical study of a variety of problems where largely separated length scales are involved, e.g. [R. Grauer, C. Marliani, K. Germaschewski, PRL, 80, 4177, (1998)]. A typical example in plasma physics are the current sheets in magnetohydrodynamic flows. Their dynamics is investigated in the framework of incompressible MHD. We present simulations of the ideal and inviscid dynamics in two and three dimensions. In addition, we show numerical simulations for the resistive case in two dimensions. Specifically, we show simulations for the case of the doubly periodic coalescence instability. At the onset of the reconnection process the kinetic energy rises and drops rapidly and afterwards settles into an oscillatory phase. The timescale of the magnetic reconnection process is not affected by these fast events but consistent with the Sweet-Parker model of stationary reconnection. Taking into account the electron inertia terms in the generalized Ohm's law the electron skin depth is introduced as an additional parameter. The modified equations allow for magnetic reconnection in the collisionless regime. Current density and vorticity concentrate in extremely long and thin sheets. Their dynamics becomes numerically accessible by means of adaptive mesh refinement.

  14. The Tera Multithreaded Architecture and Unstructured Meshes

    NASA Technical Reports Server (NTRS)

    Bokhari, Shahid H.; Mavriplis, Dimitri J.

    1998-01-01

    The Tera Multithreaded Architecture (MTA) is a new parallel supercomputer currently being installed at San Diego Supercomputing Center (SDSC). This machine has an architecture quite different from contemporary parallel machines. The computational processor is a custom design and the machine uses hardware to support very fine grained multithreading. The main memory is shared, hardware randomized and flat. These features make the machine highly suited to the execution of unstructured mesh problems, which are difficult to parallelize on other architectures. We report the results of a study carried out during July-August 1998 to evaluate the execution of EUL3D, a code that solves the Euler equations on an unstructured mesh, on the 2 processor Tera MTA at SDSC. Our investigation shows that parallelization of an unstructured code is extremely easy on the Tera. We were able to get an existing parallel code (designed for a shared memory machine), running on the Tera by changing only the compiler directives. Furthermore, a serial version of this code was compiled to run in parallel on the Tera by judicious use of directives to invoke the "full/empty" tag bits of the machine to obtain synchronization. This version achieves 212 and 406 Mflop/s on one and two processors respectively, and requires no attention to partitioning or placement of data issues that would be of paramount importance in other parallel architectures.

  15. A two-dimensional adaptive mesh generation method

    NASA Astrophysics Data System (ADS)

    Altas, Irfan; Stephenson, John W.

    1991-05-01

    The present, two-dimensional adaptive mesh-generation method allows selective modification of a small portion of the mesh without affecting large areas of adjacent mesh-points, and is applicable with or without boundary-fitted coordinate-generation procedures. The cases of differential equation discretization by, on the one hand, classical difference formulas designed for uniform meshes, and on the other the present difference formulas, are illustrated through the application of the method to the Hiemenz flow for which the Navier-Stokes equation's exact solution is known, as well as to a two-dimensional viscous internal flow problem.

  16. Triangulated manifold meshing method preserving molecular surface topology.

    PubMed

    Chen, Minxin; Tu, Bin; Lu, Benzhuo

    2012-09-01

    Generation of manifold mesh is an urgent issue in mathematical simulations of biomolecule using boundary element methods (BEM) or finite element method (FEM). Defects, such as not closed mesh, intersection of elements and missing of small structures, exist in surface meshes generated by most of the current meshing method. Usually the molecular surface meshes produced by existing methods need to be revised carefully by third party software to ensure the surface represents a continuous manifold before being used in a BEM and FEM calculations. Based on the trace technique proposed in our previous work, in this paper, we present an improved meshing method to avoid intersections and preserve the topology of the molecular Gaussian surface. The new method divides the whole Gaussian surface into single valued pieces along each of x, y, z directions by tracing the extreme points along the fold curves on the surface. Numerical test results show that the surface meshes produced by the new method are manifolds and preserve surface topologies. The result surface mesh can also be directly used in surface conforming volume mesh generation for FEM type simulation. Copyright © 2012 Elsevier Inc. All rights reserved.

  17. Hexahedral finite element mesh coarsening using pillowing technique

    DOEpatents

    Staten, Matthew L [Pittsburgh, PA; Woodbury, Adam C [Provo, UT; Benzley, Steven E [Provo, UT; Shepherd, Jason F [Edgewood, NM

    2012-06-05

    A techniques for coarsening a hexahedral mesh is described. The technique includes identifying a coarsening region within a hexahedral mesh to be coarsened. A boundary sheet of hexahedral elements is inserted into the hexahedral mesh around the coarsening region. A column of hexahedral elements is identified within the boundary sheet. The column of hexahedral elements is collapsed to create an extraction sheet of hexahedral elements contained within the coarsening region. Then, the extraction sheet of hexahedral elements is extracted to coarsen the hexahedral mesh.

  18. Ethyl alcohol boiling heat transfer on multilayer meshed surfaces

    NASA Astrophysics Data System (ADS)

    Dåbek, Lidia; Kapjor, Andrej; Orman, Łukasz J.

    2016-06-01

    The paper presents the problem of heat transfer enhancement with the application of multilayer metal mesh structures during boiling of ethyl alcohol at ambient pressure. The preparation of samples involved sintering fine copper meshes with the copper base in the reduction atmosphere in order to prevent oxidation of the samples. The experiments included testing up to 4 layers of copper meshes. Significant augmentation of boiling heat transfer is possible, however, considerable number of meshes actually hinders heat transfer conditions and leads to the reduction in the heat flux transferred from the heater surface.

  19. Mesh-matrix analysis method for electromagnetic launchers

    NASA Technical Reports Server (NTRS)

    Elliott, David G.

    1989-01-01

    The mesh-matrix method is a procedure for calculating the current distribution in the conductors of electromagnetic launchers with coil or flat-plate geometry. Once the current distribution is known the launcher performance can be calculated. The method divides the conductors into parallel current paths, or meshes, and finds the current in each mesh by matrix inversion. The author presents procedures for writing equations for the current and voltage relations for a few meshes to serve as a pattern for writing the computer code. An available subroutine package provides routines for field and flux coefficients and equation solution.

  20. Numerical Differentiation for Adaptively Refined Finite Element Meshes

    NASA Technical Reports Server (NTRS)

    Borgioli, Andrea; Cwik, Tom

    1998-01-01

    Postprocessing of point-wise data is a fundamental process in many fields of research. Numerical differentiation is a key operation in computational electromagnetics. In the case of data obtained from a finite element method with automatic mesh refinement much work needs still to be done. This paper addresses some issues in differentiating data obtained from a finite element electromagnetic code with adaptive mesh refinement, and it proposes a methodology for deriving the electric field given the magnetic field on a mesh of linear triangular elements. The procedure itself is nevertheless more general and might be extended for numerically differentiating any point-wise solution based on triangular meshes.