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Cell Adhesion in Animal Cell Culture: Physiological and Fluid-Mechanical Implications
Published in Martin A. Hjortso, Joseph W. Roos, Cell Adhesion, 2018
Manfred R. Koller, Eleftherios T. Papoutsakis
Although endothelial cells play a critical role in vivo by controlling the egress of mature blood cells into the circulation from the marrow cavities through transient migration pores, they are not believed to be a crucial component for establishing in vitro hematopoiesis (149). Adventitial reticular cells are fibroblasts that extend fine cytoplasmic processes forming an extensive network within which the hematopoietic cells proliferate and differentiate. These cells are preferentially associated with developing granulocytic cells. Hemonectin, a protein of the marrow ECM that specifically binds granulocytic precursors, has been implicated in the localization of granulopoiesis that occurs in localized compartments both within the bone marrow and in LTBM cultures (150). Mature granulocytes were found to adhere less strongly to hemonectin, and this loss of attachment may be the signal that allows mature granulocytes to enter the circulation. A similar mechanism has already been documented for the release of mature erythrocytes into the circulation (151). As these cells mature, expression of the fibronectin receptor is lost such that the maturing erythrocytes become nonadherent and are able to leave the marrow. In addition to its role as an anchorage protein, fibronectin also increases the sensitivity of immature erythrocytes to erythropoietin, a major erythroid growth factor (152). Erythropoiesis proceeds in isolated islets surrounding an associated macrophage nurse cell, which produces the necessary erythropoietin for the development of erythrocytes (153). The role of adipocytes that form in these cultures is unclear. In vivo, the large presence of fat cells in marrow (yellow marrow) corresponds to low hematopoietic activity as compared with marrow containing fewer fat cells (red marrow) (154). In contrast, most investigators report that the formation of adipocytes in vitro is required for a stroma that will support hematopoiesis (140,145,155–157), while only a few report that adipocytes are not important for LTBM culture (158,159).
A novel objective wrinkle evaluation method for printed fabrics based on multi-view stereo algorithm
Published in The Journal of The Textile Institute, 2022
Na Deng, Yiliang Wang, Binjie Xin, Wenzhen Wang
With the development of artificial intelligence technology, digital image processing method with the advantages of non-contact, fast processing speed and repeatable measurement has been widely investigated and applied in the textile field. For example, Chen et al. (1999) provided a new way based on the fractal dimensions of gray level surface by reticular cell counting method to evaluate the fabric wrinkling appearance. Hesarian (2010) was reported to study the wrinkle property of fabrics by using the projected profile light line technique. Sun et al. (2011) presented a wrinkle evaluation method that used modified wavelet coefficients and optimized support vector machine classifications to characterize and classify the wrinkling appearance of fabric. Their experiment result indicated that the recognition accuracy was approximately 75%.
A New Dual-Mode Wear Model of Abrasion–Fatigue for Plane (100Cr6)-Cylinder (C45E4) Steel Pairs With Fractal Surfaces
Published in Tribology Transactions, 2021
Wenbo Zhang, Wenjun Gong, Yunxia Chen, Mengwei Li
From the generalized model of Eq. [17], fractal parameters G and D reflecting the morphological characteristics of the worn surfaces have significant effects on the wear behaviors, and their values depend on the distribution of the contour heights on the rough surface. In the actual wear process, the real wear loss can change the height of the surface contour over time, causing the fractal parameters to exhibit time-dependent attributes as follows: where is the surface profile location vector and is the distribution of the profile height on the rough surface at time t. It is noted that D and G values at different wear time points are obtained by discretely recording the corresponding contour curves on the specimen surface. In terms of fitting the functional relationships and between the fractal parameters (D and G) and profile curve the structural function method (SFM) can be applied with a low error rate compared with other methods, such as the power spectrum method (PSM) and reticular cell counting method (RCCM) (30).
Numerical and experimental assessment of the mechanical properties of 3D printed 18-Ni300 steel trabecular structures produced by Selective Laser Melting – a lean design approach
Published in Virtual and Physical Prototyping, 2019
Consequently, it is evident that a critical aspect in the numerical modelling of the mechanical behaviour of reticular structures is a proper and reliable material model including plasticity and damage. Therefore, in the first part of the present research, the parameters of the ductile damage model were calibrated for the 18-Ni300 steel, performing experimental tests on samples having different geometries and thus different level of triaxiality. In the second part of the research, trabecular structures were tested (compression) while, at the same time, a full 3D FE model of the phenomenon is set up. Eventually, the comparison between measurements and computations show good accordance demonstrating the robustness of the applied material calibration procedure adopted. Although the accuracy of the full 3D model, the computational effort required limits its extensive employment for the design of real full-scale components (calculation time of days on high performances workstation to simulate just few cells). It is hence suggested by the authors as an alternative approach able to guarantee a similar accuracy, but, at the same time, granting a practical feasible duration of the analysis. It consists of the numerical simulation of the behaviour of a single reticular cell under base load cases (shear, traction, torsion and combinations of them) obtaining the stiffness of the cell along different directions. The results in terms of force–displacement/torque–rotation are used as inputs for a lean lumped parameter model that represents an effective compromise between accuracy and computation costs, but, most of all, it is suitable for industrial applications.