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Elements for that clustering regarding inertial allergens from the inertial range of isotropic disturbance.
In the present paper, the three-dimensional structure and macroscopic mechanical response of electrospun poly(L-lactide) membranes is predicted based only on the geometry and elasto-plastic mechanical properties of single fibres supplemented by measurements of membrane weight and volume, and the resulting computational models are used to study the non-affine micro-kinematics of electrospun networks. To this end, statistical parameters describing the in-plane fibre morphology are extracted from scanning electron micrographs of the membranes, and computational network models are generated by matching the porosity of the real mats. Selleckchem Alectinib The virtual networks are compared against computed tomography scans in terms of structure, and against uniaxial tension tests with respect to their macroscopic mechanical response. The obtained virtual network structure agrees well with the fibre disposition in real networks, and the rigorous prediction of the mechanical response of two membranes with mean diameters of 1.10μm and 0.70μm captures the experimental behaviour qualitatively. Favourable quantitative agreement, however, is obtained only after lowering the Young's moduli, yield stresses and hardening slopes determined in single fibre tests, and after reducing the density of inter-fibre bonds in the model of the membrane with thinner fibres. The simulations thus demonstrate the validity and merits of the approach to study the multi-scale mechanics of electrospun networks, but also point to potential discrepancies between the properties of electrospun fibres within a network and those produced for single fibre characterisation, and highlight the existing uncertainty on the density and quality of bonds between fibres in electrospun networks. Compromised osteoblast attachment on hydroxyapatite could be involved in the development of bone healing failure. We developed a bone-compatible scaffold that mimics bone structure with sub-micron hydroxyapatite (HA) surfaces, so that we could evaluate the effects of nitrogen-containing bisphosphonate (N-BP) on osteoblast behavior and bone healing. Human osteoblasts were seeded onto the bone-compatible scaffold with or without N-BP, and cell attachment and spreading behavior were evaluated 4 and 24 h after seeding. Then, mineralization was evaluated at 7 and 14 days. The osteoconductive activity of the scaffold was evaluated by implantation for 3 and 6 weeks into a rat cranial bone defect. The numbers of osteoblasts and their diameters were significantly less in N-BP-binding scaffolds than in untreated scaffolds at 4 and 24 h. Mineralization were also significantly less in the N-BP-binding scaffolds than in controls at 7 and 14 days. In vivo study revealed bone formation in N-BP-binding scaffolds was significantly less than in untreated scaffolds at 3 and 6 weeks. These results suggest that N-BP-binding to HA inhibited osteoblast attachment and spreading, thereby compromising bone healing process in the injured bone defect site. The effect of melt electrospun writing fiber arrangement on cellular behavior has not yet been thoroughly investigated. Cellular orientation is particularly important in the context of ligament tissue engineering for orthopedic applications whereby a high degree of cell alignment is present in the native tissue. The aim of this study was to investigate the response of human mesenchymal stem cells (hMSC) to three different patterned porous polycaprolactone scaffolds (aligned, crimped and random) fabricated by melt electrospinning writing, resulting in 20 μm diameter electrospun fibers. Cell orientation was investigated over 4 weeks in vitro and it was demonstrated that the aligned pattern was capable of orientating the hMSCs towards the main direction of the fibers and this feature was maintained over the entire culture period whereas the orientation was rapidly lost in the crimped pattern. In order to fabricate a functional scaffold for ligament tissue engineering, the scaffolds were rolled in three bundles, subsequently braided and combined with a bone compartment (consisting of a melt electrospun scaffold seeded with osteogenically induced hMSCs) for the development of a Bone-Ligament-Bone (BLB) construct. The mechanical properties of non-cellularized and cellularized BLB constructs were assessed under both quasi-static and cyclic conditions. This revealed that the in vitro maturation significantly softened the BLB constructs and that the mechanical properties were several fold lower than those of native tissue. The cyclic testing demonstrated that the presence of cell sheets resulted in increased resilience and elasticity, even though the global mechanical properties were decreased for the in vitro matured constructs (regardless of the pattern). In conclusion, we demonstrated that melt electrospinning writing fiber organization can induce spontaneous cell alignment and that large cellularized BLB constructs with complex geometry can achieve mechanical resilience under cyclic stretching. This study investigates the effect of needle tip geometry on the needle deflection and tissue sampling length in biopsy. Advances in medical imaging have allowed the identification of suspicious cancerous lesions which then require needle biopsy for tissue sampling and subsequent confirmatory pathological analysis. Precise needle insertion and adequate tissue sampling are essential for accurate cancer diagnosis and individualized treatment decisions. However, the single-bevel needles in current hand-held biopsy devices often deflect significantly during needle insertion, causing variance in the targeted and actual locations of the sampled tissue. This variance can lead to inaccurate sampling and false-negative results. There is also a limited understanding of factors affecting the tissue sampling length which is a critical component of accurate cancer diagnosis. This study compares the needle deflection and tissue sampling length between the existing single-bevel and exploratory multi-bevel needle tip geometrd adequate tissue sampling for the needle biopsy procedures. In order to produce anatomical models that feel realistic to the touch, artificial materials need to be found that mimic tactile properties of biological tissues. The aim of this study was to provide a guideline for identifying materials that feel similar to biological tissues, based on a quantifiable and reproducible measure. For this, a testing procedure was developed to identify mechanical properties that contribute to tactility. Bovine and porcine liver tissues were compared to different silicone elastomers and a soft 3D printed polymer. Macroindentation was chosen to simulate the palpation of material cubes with loading occurring during actual finger and material interaction. Elastic behaviour was considered by conducting quasistatic loading and unloading for extracting contact stiffness S and equivalent spring stiffness k. Viscoelasticity was quantified by means of force relaxation for calculating loss tangent tanδ based on a Prony series approach. Furthermore, Shore 00 hardness H was measured with a hand-held durometer.
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