Importance of the field: Effective vascularization of thick three-dimensional engineered tissue constructs is a problem in tissue engineering. As in native organs, a tissue-engineered intra-organ vascular tree must be comprised of a network of hierarchically branched vascular segments. Despite this requirement, current tissue-engineering efforts are still focused predominantly on engineering either large-diameter macrovessels or microvascular networks.Areas covered in this review: We present the emerging concept of organ printing or robotic additive biofabrication of an intra-organ branched vascular tree, based on the ability of vascular tissue spheroids to undergo self-assembly.What the reader will gain: The feasibility and challenges of this robotic biofabrication approach to intra-organ vascularization for tissue engineering based on organ-printing technology using self-assembling vascular tissue spheroids including clinically relevantly vascular cell sources are analyzed.Take home message: It is not p...

Towards organ printing: engineering an intra-organ branched vascular tree

https://hal-upec-upem.archives-ouvertes.fr/hal-01140963/document

A phase field method to simulate crack nucleation and propagation in strongly heterogeneous materials from direct imaging of their microstructure

The paper aims at providing a comprehensive and up-to-date review on the latest achievements made in the context of particle methods, in particular the projection-based ones, with applications in ocean engineering. The latest achievements corresponding to stability, accuracy, energy conservation and boundary condition enhancements as well as advancements related to improved simulations of multiphase flows, surface tension and fluid–structure interactions are reviewed. The future perspectives for enhancement of applicability and reliability of these methods for ocean engineering applications are also highlighted.

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Current achievements and future perspectives for projection-based particle methods with applications in ocean engineering

A review on 3D-FE adaptive remeshing techniques for crack growth modelling

Abstract A multilevel finite element mesh superposition technique aimed at hierarchically improving the quality of numerical solutions and mathematical models for a certain class of problems is developed. A posteriori error estimates, adaptive mesh overlay schemes, iterative solution procedures, data structures, and numerical experiments are described in the context of linear elastostatics.

On the adaptive multilevel superposition of finite element meshes for linear elastostatics

Bone is a complex system with functions including those of adaptation and repair. To understand how bone cells can create a structure adapted to the mechanical environment, we propose a simple bone remodeling model based on a reaction-diffusion system influenced by mechanical stress. Two-dimensional bone models were created and subjected to mechanical loads. The conventional finite element method (FEM) was used to calculate stress distribution. A stress-reactive reaction-diffusion model was constructed and used to simulate bone remodeling under mechanical loads. When an external mechanical stress was applied, stimulated bone formation and subsequent activation of bone resorption produced an efficient adaptation of the internal shape of the model bone to a given stress, and demonstrated major structures of trabecular bone seen in the human femoral neck. The degree of adaptation could be controlled by modulating the diffusion constants of hypothetical local factors. We also tried to demonstrate the deformation of bone structure during osteoporosis by the modulation of a parameter affecting the balance between formation and resorption. This simple model gives us an insight into how bone cells can create an architecture adapted to environmental stress, and will serve as a useful tool to understand both physiological and pathological states of bone based on structural information.

Computer-simulated bone architecture in a simple bone-remodeling model based on a reaction-diffusion system

Fatigue crack growth simulation in heterogeneous material using s-version FEM

Background: In the craniofacial skeleton, osseous fixation techniques for stabilization include stainless steel wire, miniplates or bioresorbable plates; in some cases, stainless steel wires are still indicated. Most recently, several case reports have demonstrated that microplates or stainless steel wires migrate intracranially when used in the craniofacial skeleton in neonates. Patient: We present the case of a 7-year-old male who underwent treatment of brachycephaly at the age of 5 months. In this patient, internal migration of wires was observed. Conclusion: In our opinion, there is a difference between migration of wires and of plates in the growing cranium. Factors affecting the incidence of material migration in cranioplasty are believed to include (1) age, (2) site and (3) the material itself.

Yoshitaka Wada

Papers

Computer-simulated bone architecture in a simple bone-remodeling model based on a reaction-diffusion system

Fatigue crack growth simulation in heterogeneous material using s-version FEM

Intracranial migration of fixation wires following correction of craniosynostosis in an infant.

Crack growth analysis in a weld-heat-affected zone using S-version FEM

Surface crack growth simulation under mixed mode cyclic loading condition