The Experts below are selected from a list of 87855 Experts worldwide ranked by ideXlab platform
Reza Hedayati - One of the best experts on this subject based on the ideXlab platform.
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hybrid anisotropic pentamode mechanical metamaterial produced by additive Manufacturing Technique
Applied Physics Letters, 2020Co-Authors: Kaivan Mohammadi, M R Movahhedy, Igor Shishkovsky, Reza HedayatiAbstract:Pentamode metamaterials are a type of extremal designer metamaterials, which are able to demonstrate extremely high rigidity in one direction and extremely high compliance in other directions. Pentamodes can, therefore, be considered as building blocks of exotic materials with any arbitrarily selected thermodynamically admissible elasticity tensor. The pentamode lattices can then be envisioned to be combined to construct intermediate extremal materials, such as quadramodes, trimodes, and bimodes. In this study, we constructed several primary types of anisotropic pentamode lattices (with midpoint positioning of 10%, 15%, 20%, 25%, 30%, 35%, and 42% of the main unit cell diagonal) and then combined them mutually to explore the dependence of elastic properties of hybrid pentamodes on those of individual constructing lattices. Several anisotropic individual and hybrid pentamode lattice structures were produced using the MultiJet Additive Manufacturing Technique and then mechanically tested under compression. Finite element models were also created using the COMSOL Multiphysics package. Two-component hybrid pentamode lattices composed of individual lattices with extensively different (as large as two orders of magnitudes) B / G ratios were constructed and analyzed. It was demonstrated that it is possible to design and construct composite intermediate extremal materials with arbitrary eigenvalues in the elastic tensor. It is concluded that the elastic E, shear G, and bulk moduli B of the hybrid structure are the superpositions of the corresponding moduli of the individual lattice structures. Poisson's ratio ν of the hybrid pentamode structure equals that of individual structure with higher Poisson's ratio. The yield stress σ y of the hybrid pentamode lattice structure depends on the elastic moduli of the constructing lattice structures, as well as the yield stress of the weaker lattice structure.
Claudia Dellavia - One of the best experts on this subject based on the ideXlab platform.
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In vivo osseointegration of a randomized trabecular titanium structure obtained by an additive Manufacturing Technique
Journal of Materials Science: Materials in Medicine, 2020Co-Authors: Vincenza Ragone, Massimo Arosio, Matteo Olimpo, Lisa Adele Piras, Mitzy Mauthe Von Degerfeld, Davide Augusti, Riccardo D’ambrosi, Elena Canciani, Claudia DellaviaAbstract:The additive Manufacturing Techniques (AM) are able to realize three-dimensional trabecular structures that mimic the trabecular structure of the bone. An in vivo study in sheep was carried out with the aim of assessing the bone response and the trend of osteointegration of a randomized trabecular titanium structure produced by the AM Technique. In 6 sheep were implanted 84 specimens with a trabecular titanium structure (4 implants in the femur distal epiphysis; 4 implants in the tibial plate; 6 implants in the tibial shaft). Sheep were sacrificed at 3 postoperative time-points: 6 weeks, 10 weeks, 14 weeks. Histomorphometric analysis was performed for the evaluation of Bone Implant Contact, and Bone Ingrowth. A standard push-out test was used to analyze the mechanical characteristics of the bone-implant interface. The histomorphometric data and biomechanical tests showed a fast osseointegration of the specimens both in the cancellous and in the cortical bone. The quantitative analysis of osseointegration data in cancellous bone showed the percentage of the surface of the implant in direct contact with the regenerated bone matrix significantly improved from 28% at 6 weeks to 54% at 14 weeks. An early osseointegration occurred in cortical bone showing that 75% of surface of implant was in direct contact with regenerated bone after 6 weeks; this value increased to 85% after 14 weeks. Mechanical tests revealed an early improvement of mean peak load of implants at 10 weeks (4486 N ± 528 N) compared to values at 6 weeks (2516 N ± 910 N) confirming the high rate of progression of osseointegration in the cortical bone. The non-mineralized matrix followed an increasing process of mineralization almost completely after 14 weeks. The results of this study have showed a rapid osseointegration and excellent biocompatibility for a randomized trabecular titanium structure that should be confirmed by clinical investigations.
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In Vivo Osseointegration Of A Randomized Trabecular Titanium Structure Obtained By Additive Manufacturing Technique
2019Co-Authors: Anna V. Ragone, Massimo Arosio, Elena Canciani, Claudia Dellavia, E.r. GallieraAbstract:Background Osteoarthritis of the hip is a very common disease in the population over the age of 50, with a prevalence of women. The replacement of the joint with surgical therapy makes use of prosthetic implants in titanium alloy, which allow a direct anchorage to the bone and a walking gait immediately after the intervention. Osseointegration, that is the direct contact between bone and prosthesis without interposition of connective tissue, is the key to the long-term success of these devices. Thanks to additive Manufacturing Techniques, it is able to realize three-dimensional titanium trabecular structures that mimic the trabecular structure of the bone. In order to test the bone response of the prosthetic devices with a randomized trabecular titanium structure produced by selective laser melting Technique (SLM) an in vivo animal study was performed. Objectives An in vivo study in sheep was carried out with the aim of assessing the bone response and the speed of osteointegration of the trabecular structure by means of histological, histomorphometric analysis and biomechanical push-out test for the implant removal (Authorization of the Ministry of Health No. 496 / 2017- PR. 16/07/2017). Study Design & Methods In 6 sheep were implanted 48 specimens with a trabecular titanium structure according to the following scheme: - N 2 implants for right and left site at the distal epiphysis of the femur; - N 2 for right and left site at the level of the tibial plate; - N 3 implants for right and left site at the level of the tibial shaft. Three sheep were sacrificed after 6 weeks and 3 after 14 weeks. On the biopsy samples, 3 histological sections were obtained per site by means of a processing Technique for hard tissues which involves inclusion in the resin and subsequent abrasion. Histomorphometric analysis was performed for the evaluation of Bone Implant Contact (BIC), e il Bone Ingrowth (BIN). Results In all the sections, no inflammatory infiltrate was found and the observed tissues were characterized by the presence of numerous blood vessels, a sign of good tissue trophism. The histomorphometric data obtained from BIC and BIN were used to calculate the mean and standard deviation of each group and showed a different regenerative behavior between compact bone, faster in the process, than the cancellous bone (BIC: 85% and 53,5%; BIN: 84% and 43,5% at last follow-up time). Osseointegration is already present at the first follow-up time, and is also correlated with a good value of BIN, which shows how the mineralized matrix at different stages of calcification, is present among the sample trabeculae in all the samples. The biomechanical push-out tests showed a rapid osseointegration of the specimens with trabecular structure, both in the spongiosa and in the cortical one (4,7kN and 1,5kN in compact and cancellous bone respectively at last follow-up time). Conclusions The three-dimensional metallic structure used for the realization of an acetabular cup for total hip arthroplasty is able to increase the bone response. All specimens were well fastly osseointegrated. The regenerated bone between the titanium trabeculae and in the peripheral area of the scaffold presents the peculiar characteristics of the new bone at various levels of mineralization
Kaivan Mohammadi - One of the best experts on this subject based on the ideXlab platform.
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hybrid anisotropic pentamode mechanical metamaterial produced by additive Manufacturing Technique
Applied Physics Letters, 2020Co-Authors: Kaivan Mohammadi, M R Movahhedy, Igor Shishkovsky, Reza HedayatiAbstract:Pentamode metamaterials are a type of extremal designer metamaterials, which are able to demonstrate extremely high rigidity in one direction and extremely high compliance in other directions. Pentamodes can, therefore, be considered as building blocks of exotic materials with any arbitrarily selected thermodynamically admissible elasticity tensor. The pentamode lattices can then be envisioned to be combined to construct intermediate extremal materials, such as quadramodes, trimodes, and bimodes. In this study, we constructed several primary types of anisotropic pentamode lattices (with midpoint positioning of 10%, 15%, 20%, 25%, 30%, 35%, and 42% of the main unit cell diagonal) and then combined them mutually to explore the dependence of elastic properties of hybrid pentamodes on those of individual constructing lattices. Several anisotropic individual and hybrid pentamode lattice structures were produced using the MultiJet Additive Manufacturing Technique and then mechanically tested under compression. Finite element models were also created using the COMSOL Multiphysics package. Two-component hybrid pentamode lattices composed of individual lattices with extensively different (as large as two orders of magnitudes) B / G ratios were constructed and analyzed. It was demonstrated that it is possible to design and construct composite intermediate extremal materials with arbitrary eigenvalues in the elastic tensor. It is concluded that the elastic E, shear G, and bulk moduli B of the hybrid structure are the superpositions of the corresponding moduli of the individual lattice structures. Poisson's ratio ν of the hybrid pentamode structure equals that of individual structure with higher Poisson's ratio. The yield stress σ y of the hybrid pentamode lattice structure depends on the elastic moduli of the constructing lattice structures, as well as the yield stress of the weaker lattice structure.
Chris Vervaet - One of the best experts on this subject based on the ideXlab platform.
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prilling as Manufacturing Technique for multiparticulate lipid peg fixed dose combinations
European Journal of Pharmaceutics and Biopharmaceutics, 2014Co-Authors: Anouk Vervaeck, Lien Saerens, T De Beer, Tinne Monteyne, J P Remon, Chris VervaetAbstract:This study focused on the evaluation of prilling as a Technique for the Manufacturing of multiparticulate dosage forms. Prills, providing controlled and immediate drug release, were processed and finally combined in capsules yielding a fixed-dose combination. Metoprolol tartrate (MPT) and hydrochlorothiazide (HCT) were used as controlled and immediate release model drugs, respectively. These drugs were embedded in matrices composed of fatty acids and polyethylene glycol (PEG). In order to tailor drug release from the prills, the type of fatty acid, the PEG molecular weight and the fatty acid/PEG ratio were varied. To provide controlled drug release, MPT was embedded in matrices containing PEG and behenic acid. Using different PEG molecular weights (PEG 4000, 6000 and 10,000), MPT release could be tailored over a wide range. To obtain immediate release, HCT was incorporated in matrices composed of PEG and stearic acid. Since high amounts (at least 60%) of PEG were needed for acceptable immediate release, HCT release was independent on PEG molecular weight. Solid state characterization revealed that MPT crystallinity was decreased, while HCT was molecularly dispersed throughout the matrix. Drug release of both MPT and HCT prills was stable during storage. Compared to a fixed-dose reference, oral co-administration of the MPT and HCT prills to dogs yielded a similar bioavailability for the HCT prills, while the MPT prills resulted in a significant higher bioavailability.
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co extrusion as Manufacturing Technique for fixed dose combination mini matrices
European Journal of Pharmaceutics and Biopharmaceutics, 2012Co-Authors: Lien Dierickx, Lien Saerens, Jean Paul Remon, T De Beer, A. Almeida, Chris VervaetAbstract:Abstract The aim of this study was to develop a multilayer (core/coat) dosage form via co-extrusion, the core providing sustained drug release and the coat immediate drug release. In this study polymers were selected which can be combined in a co-extruded dosage form. Several thermoplastic polymers were hot-melt extruded and evaluated for processability and macroscopic properties (surface smoothness, die swell). Metoprolol tartrate (MPT) and hydrochlorothiazide (HCT) were incorporated as sustained and immediate release model drugs, respectively. Based on the polymer screening experiments a combination of polycaprolactone (core) and polyethylene oxide (coat) was selected for co-extrusion trials, taking into account their drug release profiles and extrusion temperature (70 °C). This combination (containing 10% HCT in the coat and 45% MPT in the core) was successfully co-extruded (diameter core: 3 mm/thickness coat: 0.5 mm). Adhesion between the two polymer layers was good. HCT release from the coat was complete within 30 min, while MPT release was sustained over 24 h (55%, 70%, 85% and 100% after 4, 8, 12 and 24 h, respectively). DSC, XRD and Raman spectroscopy revealed that MPT remained crystalline during extrusion, whereas HCT was dissolved in the polyethylene oxide matrix. The in vivo study revealed no significant differences between the experimental formulation and the reference formulation (Zok-Zid® tablet). Fixed-dose combination mini-tablets with good in vitro and in vivo performance were successfully developed by means of co-extrusion, using a combination of polycaprolactone and polyethylene oxide.
Vincenza Ragone - One of the best experts on this subject based on the ideXlab platform.
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In vivo osseointegration of a randomized trabecular titanium structure obtained by an additive Manufacturing Technique
Journal of Materials Science: Materials in Medicine, 2020Co-Authors: Vincenza Ragone, Massimo Arosio, Matteo Olimpo, Lisa Adele Piras, Mitzy Mauthe Von Degerfeld, Davide Augusti, Riccardo D’ambrosi, Elena Canciani, Claudia DellaviaAbstract:The additive Manufacturing Techniques (AM) are able to realize three-dimensional trabecular structures that mimic the trabecular structure of the bone. An in vivo study in sheep was carried out with the aim of assessing the bone response and the trend of osteointegration of a randomized trabecular titanium structure produced by the AM Technique. In 6 sheep were implanted 84 specimens with a trabecular titanium structure (4 implants in the femur distal epiphysis; 4 implants in the tibial plate; 6 implants in the tibial shaft). Sheep were sacrificed at 3 postoperative time-points: 6 weeks, 10 weeks, 14 weeks. Histomorphometric analysis was performed for the evaluation of Bone Implant Contact, and Bone Ingrowth. A standard push-out test was used to analyze the mechanical characteristics of the bone-implant interface. The histomorphometric data and biomechanical tests showed a fast osseointegration of the specimens both in the cancellous and in the cortical bone. The quantitative analysis of osseointegration data in cancellous bone showed the percentage of the surface of the implant in direct contact with the regenerated bone matrix significantly improved from 28% at 6 weeks to 54% at 14 weeks. An early osseointegration occurred in cortical bone showing that 75% of surface of implant was in direct contact with regenerated bone after 6 weeks; this value increased to 85% after 14 weeks. Mechanical tests revealed an early improvement of mean peak load of implants at 10 weeks (4486 N ± 528 N) compared to values at 6 weeks (2516 N ± 910 N) confirming the high rate of progression of osseointegration in the cortical bone. The non-mineralized matrix followed an increasing process of mineralization almost completely after 14 weeks. The results of this study have showed a rapid osseointegration and excellent biocompatibility for a randomized trabecular titanium structure that should be confirmed by clinical investigations.
