Additive manufacturing has attracted keen interest in the medical field in recent decades, especially for bone regeneration. Many additive manufacturing processes have been used to print medical ...devices such as implants, prostheses, and surgical guides, and for surgical planning in different medical fields, especially orthopedic, maxillofacial and dental surgery. Many materials can be manufactured by 3D printing with metal, ceramic, polymer or composite materials. Composite materials with organic and mineral components have been investigated to mimic bone functional and structural characteristics. In addition to the chemical composition, the modeling and optimization of the design can be optimized to enhance the biological and mechanical performance of the printed scaffolds. This review presents a comparative evaluation of different material/additive manufacturing processes, and describes the best compromises for targeted clinical applications. The advantages and drawbacks of each additive manufacturing process are described in light of the biological results and essential properties expected by patients and clinicians. Statement of significance: 3D (bio)printing appears to be an outstanding manufacturing route to revolutionize patient care with personalized medicine. Moreover, there are growing trends in the use of 3D printing in the medical education field and for surgical planning to alleviate surgeon practice and optimize esthetic results. Many reviews have described the growth of the different additive manufacturing techniques developed over time, their advantages and drawbacks and the work required to develop an accurate printable biomaterial fitting the 3D additive manufacturing process and the expectations of the final users and beneficiaries. In this review, an emphasis is placed on the expectations of patients and clinicians regarding specific final clinical applications in craniomaxillofacial, orthopedic or dental fields for a specific biomaterial/additive material
•Extension of the ZIBC framework for an improved simulation of complex geometries.•Wall model based on the Spalart-Allmaras model and coupled with a compact IB method.•Novel and efficient strategy ...for the resolution of ODE based wall-models.•Accurate prediction of unsteady loads including viscous components on IB using ZDES.•The contribution of this approach is significant for unsteady simulations.
One of the main limitations in computational aerodynamics lies in the ability of CFD solvers to handle complex geometries while maintaining their accuracy. Among the currently available strategies, the Zonal Immersed Boundary Conditions (ZIBC) has shown its capability to introduce complex geometrical details for the simulations of high Reynolds turbulent flows. In this context, this work aims to extend the ZIBC framework, initially adapted to reproduce blockage effects, to take into account configurations where the influence of spatially developing boundary layers has to be accurately predicted. For this purpose, a compact sharp interface immersed boundary method has been developed for curvilinear grids. Moreover, a Thin Boundary Layer Equations (TBLE) wall model based on one-dimensional RANS Spalart-Allmaras equations is coupled with the IBC to model the inner part of compressible turbulent boundary layers. The coupling with the Zonal Detached Eddy Simulation (ZDES) approach is improved and permits to simulate turbulent flows capturing accurately the wall-normal gradients with a limited grid resolution. This strategy is applied to the simulation of a generic missile configuration (FG5) with an angle of attack of 10∘ using RANS and ZDES approaches. For the first time, wall quantities such as unsteady loads, including the viscous contribution, are accuratly reproduced on surfaces modelled with IBC using hybrid RANS/LES (ZDES) computations and for a realistic configuration at high Reynolds number. Such a reconstruction of physical quantities at the wall is achieved thanks to a precise reconstruction procedure using a TBLE wall model.
•Generalization of the 2014 version of the ZIBC combining RANS/LES and the IB method.•Extended presentation of the Zonal Immersed Boundary Conditions approach.•First RANS/LES and IBC application to a ...full space launcher at high Reynolds number.•ZDES/IBC is highly validated for both the statistical field and the spectral content.
One of the next foreseen challenges in CFD consists in the capability to simulate quantitatively the spectral content of the turbulent flow around realistic geometries. In this context, the present work focuses on a new methodology named ZIBC standing for Zonal Immersed Boundary Conditions enabling to account for complex configurations at high Reynolds numbers. The numerical strategy allowing the coupling between a turbulence modeling method (e.g. RANS, URANS, ZDES, LES or DNS) and IBC (Immersed Boundary Conditions) is detailed. In this paper, the modeling method retained is the Zonal Detached Eddy Simulation (ZDES) which has reached a high level of maturity on turbulent separated flow simulations. This methodology is applied to a full space launcher configuration to assess its capability to return the interactions between the technological details, modeled with IBC, and the simplified afterbody, modeled with a body-fitted (BF) approach consisting in classical no-slip boundary conditions, in the turbulent flow field surrounding the main stage of the space launcher afterbody. The proposed method is thoroughly assessed on a realistic geometry of the European Ariane 5 launcher and the ZIBC simulation is successfully compared with the available experiments.
We present Svetlana (SuperVised sEgmenTation cLAssifier for NapAri), an open-source Napari plugin dedicated to the manual or automatic classification of segmentation results. A few recent software ...tools have made it possible to automatically segment complex 2D and 3D objects such as cells in biology with unrivaled performance. However, the subsequent analysis of the results is oftentimes inaccessible to non-specialists. The Svetlana plugin aims at going one step further, by allowing end-users to label the segmented objects and to pick, train and run arbitrary neural network classifiers. The resulting network can then be used for the quantitative analysis of biophysical phenoma. We showcase its performance through challenging problems in 2D and 3D and provide a comprehensive discussion on its strengths and limits.
A turbulent inflow for a rapid and low noise switch from RANS to Wall-Modelled LES on curvilinear grids with compressible flow solvers is presented. It can be embedded within the computational domain ...in practical applications with WMLES grids around three-dimensional geometries in a flexible zonal hybrid RANS/LES modelling context. It relies on a physics-motivated combination of Zonal Detached Eddy Simulation (ZDES) as the WMLES technique together with a Dynamic Forcing method processing the fluctuations caused by a Zonal Immersed Boundary Condition describing roughness elements. The performance in generating a physically-sound turbulent flow field with the proper mean skin friction and turbulent profiles after a short relaxation length is equivalent to more common inflow methods thanks to the generation of large-scale streamwise vorticity by the roughness elements. Comparisons in a low Mach-number zero-pressure-gradient flat-plate turbulent boundary layer up to Reθ=6100 reveal that the pressure field is dominated by the spurious noise caused by the synthetic turbulence methods (Synthetic Eddy Method and White Noise injection), contrary to the new low-noise approach which may be used to obtain the low-frequency component of wall pressure and reproduce its intermittent nature. The robustness of the method is tested in the flow around a three-element airfoil with WMLES in the upper boundary layer near the trailing edge of the main element. In spite of the very short relaxation distance allowed, self-sustainable resolved turbulence is generated in the outer layer with significantly less spurious noise than with the approach involving White Noise. The ZDES grid count for this latter test case is more than two orders of magnitude lower than the Wall-Resolved LES requirement and a unique mesh is involved, which is much simpler than some multiple-mesh strategies devised for WMLES or turbulent inflow.
•Low-noise switch from RANS to WMLES on curvilinear grids.•Physics-motivated combination of hybrid methods with Dynamic Forcing and Zonal IBC.•1st RANS/LES compressible flat-plate TBL with no inflow corruption of wall pressure.•Application of the new source-term based methodology on a high Re 3-element airfoil.
Space launchers experience high fluctuating pressure levels during the ascent (for both expendable and reusable launch vehicles) and return phases (for reusable launch vehicles only). To simulate the ...fluctuating pressure field occurring on such configurations accurately, a numerical workflow combining ZDES Mode 2 (2020) and a hybrid scheme ensuring robustness in shock wave regions and low dissipation levels in vortical regions is used in the framework of bi-species inert flows. The assessment of the performance of this numerical strategy is based on the simulation of a four-nozzle launcher model previously studied experimentally by Musial and Ward (Base flow characteristics for several four-clustered rocket configurations at Mach numbers from 2.0 to 3.5. (Technical Report, NASA, 1961)). A comparison of pressure coefficients shows that ZDES gives an improvement in the capability of predicting the base pressure over standard RANS models. Spectral analysis of the fluctuating pressure at the wall shows that the flow is dominated by the antisymmetric mode
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Different techniques have been developed to overcome the recalcitrant nature of lignocellulosic biomass and extract lignin biopolymer. Lignin has gained considerable interest owing to its attractive ...properties. These properties may be more beneficial when including lignin in the preparation of highly desired value-added products, including hydrogels. Lignin biopolymer, as one of the three major components of lignocellulosic biomaterials, has attracted significant interest in the biomedical field due to its biocompatibility, biodegradability, and antioxidant and antimicrobial activities. Its valorization by developing new hydrogels has increased in recent years. Furthermore, lignin-based hydrogels have shown great potential for various biomedical applications, and their copolymerization with other polymers and biopolymers further expands their possibilities. In this regard, lignin-based hydrogels can be synthesized by a variety of methods, including but not limited to interpenetrating polymer networks and polymerization, crosslinking copolymerization, crosslinking grafted lignin and monomers, atom transfer radical polymerization, and reversible addition–fragmentation transfer polymerization. As an example, the crosslinking mechanism of lignin–chitosan–poly(vinyl alcohol) (PVA) hydrogel involves active groups of lignin such as hydroxyl, carboxyl, and sulfonic groups that can form hydrogen bonds (with groups in the chemical structures of chitosan and/or PVA) and ionic bonds (with groups in the chemical structures of chitosan and/or PVA). The aim of this review paper is to provide a comprehensive overview of lignin-based hydrogels and their applications, focusing on the preparation and properties of lignin-based hydrogels and the biomedical applications of these hydrogels. In addition, we explore their potential in wound healing, drug delivery systems, and 3D bioprinting, showcasing the unique properties of lignin-based hydrogels that enable their successful utilization in these areas. Finally, we discuss future trends in the field and draw conclusions based on the findings presented.
In this paper, we study alternating direction methods for solving constrained total-variation image restoration and reconstruction problems. Alternating direction methods can be implementable ...variants of the classical augmented Lagrangian method for optimization problems with separable structures and linear constraints. The proposed framework allows us to solve problems of image restoration, impulse noise removal, inpainting, and image cartoon+texture decomposition. As the constrained model is employed, we need only to input the noise level, and the estimation of the regularization parameter is not required in these imaging problems. Experimental results for such imaging problems are presented to illustrate the effectiveness of the proposed method. We show that the alternating direction method is very efficient for solving image restoration and reconstruction problems. PUBLICATION ABSTRACT
Celotno besedilo
Dostopno za:
CEKLJ, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The osteochondral (OC) unit plays a pivotal role in joint lubrication and in the transmission of constraints to bones during movement. The OC unit does not spontaneously heal; therefore, OC defects ...are considered to be one of the major risk factors for developing long‐term degenerative joint diseases such as osteoarthritis. Yet, there is currently no curative treatment for OC defects, and OC regeneration remains an unmet medical challenge. In this context, a plethora of tissue engineering strategies have been envisioned over the last two decades, such as combining cells, biological molecules, and/or biomaterials, yet with little evidence of successful clinical transfer to date. This striking observation must be put into perspective with the difficulty in comparing studies to identify overall key elements for success. This systematic review aims to provide a deeper insight into the field of material‐assisted strategies for OC regeneration, with particular considerations for the therapeutic potential of the different approaches (with or without cells or biological molecules), and current OC regeneration evaluation methods. After a brief description of the biological complexity of the OC unit, the recent literature is thoroughly analyzed, and the major pitfalls, emerging key elements, and new paths to success are identified and discussed.
Bioengineering osteochondral tissues for osteochondral defect repair is a major biomedical challenge. While a broad variety of tissue engineering approaches have been proposed, little progress has been made. By scrutinizing the methodologies and outcomes of more than five years of research worldwide, a complete overview of the field is drawn, allowing to identify limitations and potential key elements for success.
Repairing or replacing damaged human tissues has been the ambitious goal of regenerative medicine for over 25years. One promising approach is the use of hydrated three-dimensional scaffolds, known as ...hydrogels, which have had good results repairing tissues in pre-clinical trials. Benefiting from breakthrough advances in the field of biology, and more particularly regarding cell/matrix interactions, these hydrogels are now designed to recapitulate some of the fundamental cues of native environments to drive the local tissue regeneration. We highlight the key parameters that are required for the development of smart and biomimetic hydrogels. We also review the wide variety of polymers, crosslinking methods, and manufacturing processes that have been developed over the years. Of particular interest is the emergence of supramolecular chemistries, allowing for the development of highly functional and reversible biohydrogels. Moreover, advances in computer assisted design and three-dimensional printing have revolutionized the production of macroporous hydrogels and allowed for more complex designs than ever before with the opportunity to develop fully reconstituted organs. Today, the field of biohydrogels for regenerative medicine is a prolific area of research with applications for most bodily tissues. On top of these applications, injectable hydrogels and macroporous hydrogels (foams) were found to be the most successful. While commonly associated with cells or biologics as drug delivery systems to increase therapeutic outcomes, they are steadily being used in the emerging fields of organs-on-chip and hydrogel-assisted cell therapy. To highlight these advances, we review some of the recent developments that have been achieved for the regeneration of tissues, focusing on the articular cartilage, bone, cardiac, and neural tissues. These biohydrogels are associated with improved cartilage and bone defects regeneration, reduced left ventricular dilation upon myocardial infarction and display promising results repairing neural lesions. Combining the benefits from each of these areas reviewed above, we envision that an injectable biohydrogel foam loaded with either stem cells or their secretome is the most promising hydrogel solution to trigger tissue regeneration. A paradigm shift is occurring where the combined efforts of fundamental and applied sciences head toward the development of hydrogels restoring tissue functions, serving as drug screening platforms or recreating complex organs.
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•Biohydrogels are 3D scaffolds designed for the field of regenerative medicine.•Hydrogels are increasingly used to study cell/matrix interactions.•Hydrogels can incorporate cells and/or biologics to improve therapeutic outcomes.•Injectable hydrogels and foams are increasingly used for clinical applications.•Injectable biohydrogel foams offer unequalled handling and biological properties.
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