Subdivision Of Cells Research Articles

Accurate numerical evaluation of domain integrals in 3D boundary element method for transient heat conduction problem

This paper presents an improved approach for the numerical evaluation of domain integrals that appear in the solution of transient heat conduction problems when using a time-dependent boundary integral equation method. An implementation of this method requires the accurate evaluation of the domain integrals. As the time step value is very small, the integrand in the domain integral is close to singular, thus rendering accurate evaluation of the integral difficult. First a closest point is introduced when the source point is close to, but not on the cell in the present method. Then a coordinate transformation coupled with a cell subdivision technique is proposed considering the position of the source point or the closest point and the relations between the size of the cell and the time step value. With the new method, accurate evaluation of domain integrals can be obtained. Numerical examples have demonstrated the accuracy and efficiency of the proposed method.

Method of isolation and characterization of Girardia tigrina stem cells.

Tissue regeneration is widely studied due to its importance for understanding the biology of stem cells, aiming at their application in medicine for therapeutic and various other purposes. The establishment of experimental models is necessary, as certain invertebrates and vertebrates have different regeneration abilities depending on their taxon position on the evolutionary scale. Planarians are an efficacious in vivo model for stem cell biology, but the correlation between planarian cellular and molecular neoblast pluripotency mechanisms and those of mammalian stem cells is unknown. The present study had the following objectives: i) Establish Girardia tigrina cell culture, ii) determine the time required for complete cell disintegration and iii) obtain neoblasts by cell subdivision. Twenty-four specimens were deprived of food for seven days. After this time, disintegration was performed by incubation protected at three temperatures for 48 h in an antibiotic, antimycotic and trypsin solution, after which the suspension was homogenized and centrifuged. Histopaque® 1077 was used for cell separation and interphases were collected and monitored by optical and fluorescence microscopy. Optical microscopy analysis informed the nucleus-to-cytoplasm ratio, cell morphology and cell size. Under fluorescence microscopy, interphase 1 (I1) was subdivided into two groups and neoblasts were marked for characterization; one group was stained with 4',6-diamidino-2-phenylindole and the other was immunolabeled with octamer-binding transcription factor 4 (OCT4) and isolated and observed after 10 days of cultivation. Neoblasts predominated in I1 with a small amount of other cell types. In conclusion, sample disintegration with a trypsin and antibiotic solution was effective at 18˚C and Iscove's modified Dulbecco's medium supplemented with fetal bovine serum was adequate for the establishment of primary cell cultures after 48-h incubation and centrifugation. Antibody anti-OCT4 was used for the characterization of stem cells and was successfully labeled with concentrated neoblasts on interphase 1.

Bézier projection: A unified approach for local projection and quadrature-free refinement and coarsening of NURBS and T-splines with particular application to isogeometric design and analysis

We introduce Bézier projection as an element-based local projection methodology for B-splines, NURBS, and T-splines. This new approach relies on the concept of Bézier extraction and an associated operation introduced here, spline reconstruction, enabling the use of Bézier projection in standard finite element codes. Bézier projection exhibits provably optimal convergence and yields projections that are virtually indistinguishable from global L2 projection. Bézier projection is used to develop a unified framework for spline operations including cell subdivision and merging, degree elevation and reduction, basis roughening and smoothing, and spline reparameterization. In fact, Bézier projection provides a quadrature-free approach to refinement and coarsening of splines. In this sense, Bézier projection provides the fundamental building block for hpkr-adaptivity in isogeometric analysis.

A grid generation algorithm for reservoir domains with discrete fracture networks

In this paper, development of an algorithm for generation of unstructured grids applicable to combined discrete fracture networks (DFNs) and continuum reservoir media is described. Automatic grid refinement, grid size control, grid distribution, and grid quality enhancement are among the algorithm’s capabilities. Grid refinement is based on a combination of point insertion and cell subdivision methods. Edge/face-based and cell-based connectivity matrices along with grid size control, grid distribution, and grid quality enhancement measures were automatically employed to refine unstructured grids. Computational unstructured grids are generated in two and three-dimensional fractured reservoir models to demonstrate the algorithm applications.

An automatic unstructured grid generation method for viscous flow simulations

High aspect-ratio grids are required for accurate solution of boundary layer and wake flow. An approach for the efficient generation of isotropic and stretched viscous unstructured grids is introduced in this paper. The proposed grid generation algorithm starts with a very coarse initial grid. In far field regions, isotropic cells of excellent quality are produced using a combination of point insertion and cell subdivision techniques. Simultaneously, a directional grid refinement strategy is used to construct highly stretched triangular cells in viscous dominated regions. First, anisotropic unstructured grids are produced in the stream-wise direction. Then, cells close to the solid surface are refined to highly stretched layer of triangles suitable for boundary layer region. The accuracy of the current grid generation approach is assessed by laminar and turbulent compressible flow solutions around NACA0012, RAE2822, and NHLP multi-element airfoils. Numerical flow simulation results are compared with published data. Comparisons point to accuracy of the proposed unstructured viscous grid generation procedure.

Finite Element Method Used in the Calculation of Earth-Rock Dam Seepage Reflections

This paper analyzes the problems which exist in finite element calculations of the earth dam seepage which is free surface solution, cell subdivision improper, the transformation of the free surface boundary conditions and the permeability coefficient values at the interface of different materials, boundary conditions and other issues. Put forward the corresponding solution. Applies common general finite element software to calculate the seepage. Works in conjunction with a stable levee seepage analysis and get better results.

Preclinical and Clinical Studies on Application of Human Myoblasts in Regeneration of the Postinfarction Heart

Principal definitions of stem cell subdivisions as well as of the physiology of the renewal of their descendants have been elucidated in recent years. Regeneration mechanisms have been outlined using as an example the intestinal villus niche. Sources of stem cells for preclinical studies and the main conclusions from clinical trials have been developed in the vast majority in the 21st century. Meta-analyses and summaries have been focused so far on bone marrow stem cells and muscle-derived stem cells, which have been most often tried to date. Polish clinical trials on postinfarcted hearts have been consistent with the world literature regarding the major conclusions for myocardial regeneration. The controversies include possible side effects of stem cell applications. The necessity for genetic modification of the stem cells, which are mainly myoblasts, has been justified by the results of recently performed trials, initial examples including transfections of proangiogenic factors into human primary myoblast suspensions.

General 3D offsetting of a triangular net using an implicit function and the distance fields

A novel approach which uses the distance fields based on cell subdivision and an implicit surface interpolation based on the radial basis function is proposed in order to get an accurate and error-free offset model of arbitrary shapes composed of a large number of triangle meshes. In the method, the space bounding the original model is divided into smaller cells. For the efficient calculation of distance fields, valid cells which will generate a portion of offset model are selected previously by the proposed detection algorithm. These valid cells are divided again into much smaller voxels which assure required accuracy. At each voxel, the distance fields are created by calculating the minimum distances between the corner points of voxels and the triangle meshes. For the more efficient calculation of distance fields, valid vertices among the triangle meshes which will generate minimum distances with current cell are selected by checking the intersection between current cell and a cone prism generated at each vertex of triangle meshes. In addition, a new approach based on an implicit surface interpolation scheme is proposed to perform two types of offsetting operations including uniform and non-uniform offsetting in the same framework. In the method, a smooth implicit surface is generated from the discrete offset distance values given by the user. After generating the whole distance fields, the offset surface was constructed by using the conventional marching cube algorithm together with mesh smoothing scheme. The effectiveness and validity of this new offset method was demonstrated by performing numerical experiments for the various types of triangle meshes.

A conserved Six–Eya cassette acts downstream of Wnt signaling to direct non-myogenic versus myogenic fates in the C. elegans postembryonic mesoderm

The subdivision of mesodermal cells into muscle and non-muscle cells is crucial to animal development. In the C. elegans postembryonic mesoderm, this subdivision is a result of an asymmetric cell division that leads to the formation of striated body wall muscles and non-muscle coelomocytes. Here we report that the Six homeodomain protein CEH-34 and its cofactor Eyes Absent, EYA-1, function synergistically to promote the non-muscle fate in cells also competent to form muscles. We further show that the asymmetric expression of ceh-34 and eya-1 is regulated by a combination of 1) mesodermal intrinsic factors MAB-5, HLH-1 and FOZI-1, 2) differential POP-1 (TCF/LEF) transcriptional activity along the anterior–posterior axis, and 3) coelomocyte competence factor(s). These factors are conserved in both vertebrates and invertebrates, suggesting a conserved paradigm for mesoderm development in metazoans.

高精度気液二相流数値解析における非構造解適合格子法の開発 : 第1報,2次元非構造解適合格子法の開発と検証(流体工学,流体機械)

A high-precision simulation method for gas-liquid two-phase flows on unstructured meshes has been developed as a part of numerical studies on a gas entrainment phenomenon in the sodium-cooled fast reactor (JSFR). In this study, a two-dimensional unstructured adaptive mesh algorithm is developed because an adaptive mesh technique is necessary to simulate the local gas entrainment phenomenon accurately in large size JSFR. In a proposed two-dimensional adaptive mesh algorithm, each cell is isotropically subdivided to reduce distortions of the mesh. In addition, a connection cell is formed to eliminate the edge incompatibility between a refined and a non-refined cells. When forming connection cells, patterns of each connection cell is determined by subdivision condisions of neighboring cells. After checking the developed two-dimensional unstructured adaptive mesh manipulations (subdivision and merging of cells and construction of connection cells), the present adaptive mesh algorithm is verified by solving well-kwon driven cavity problem. As the result, the present unstructured adaptive mesh algorithm succeeds in reproducing vortical flow field in the cavity using relatively small cell number.

Surface markers for the murine oval cell response†

The biology of progenitor activation in the liver is of considerable medical and scientific interest. The powerful genetic tools available for the mouse make it an ideal model system to study this complex process involving many different cell types. However, reagents for the isolation and study of distinct hepatic subpopulations have been quite limited compared to those available for hematopoietic cells. To produce cell surface reactive reagents more specific for the oval cell response, we generated a new collection of monoclonal antibodies by immunization of Fischer rats with enzymatically dispersed nonparenchymal cells from the livers of adult mice treated with 3,5-diethoxycarbonyl-1,4-dihydrocollidine. Each of the resulting antibodies recognized a surface antigen present on a liver cell subset and permitted the viable isolation of the associated subpopulation by fluorescence-activated cell sorting. Differential activity was observed on normal liver cells and at different stages of oval cell activation, indicating potential utility for progenitor cell identification. The subdivision of liver cells using these tools should facilitate the study of the biology of ductal and periductal hepatic cell types, including progenitors. A new panel of surface reactive monoclonal antibodies to support investigation of the murine oval cell response has been developed.

A Generic Scheme for Progressive Point Cloud Coding

In this paper, we propose a generic point cloud encoder that provides a unified framework for compressing different attributes of point samples corresponding to 3D objects with arbitrary topology. In the proposed scheme, the coding process is led by an iterative octree cell subdivision of the object space. At each level of subdivision, positions of point samples are approximated by the geometry centers of all tree-front cells while normals and colors are approximated by their statistical average within each of tree-front cells. With this framework, we employ attribute-dependent encoding techniques to exploit different characteristics of various attributes. All of these have led to significant improvement in the rate-distortion (R-D) performance and a computational advantage over the state of the art. Furthermore, given sufficient levels of octree expansion, normal space partitioning and resolution of color quantization, the proposed point cloud encoder can be potentially used for lossless coding of 3D point clouds.

Non-linear boundary element analysis of floor slabs reinforced with rectangular beams

In this work, a numerical model to perform non-linear analysis of building floor structures is proposed. The presented model is derived from the Kirchhoff's plate bending formulation of the boundary element method (BEM) for zoned domains, in which the plate stiffness is modified by the presence of membrane effects. In this model, no approximation of the generalized forces along the interface is required and the compatibility and equilibrium conditions along interfaces are imposed at the integral equation level. In order to reduce the number of degrees of freedom, the Navier–Bernoulli hypothesis is assumed to simplify the strain field for the thin sub-regions (rectangular beams). The non-linear formulation is obtained from the linear formulation by incorporating initial internal force fields, which are approximated by using the well-known cell sub-division. Then, the non-linear solution of algebraic equations is obtained by using the concept of the consistent tangent operator. The Von Mises criterion is adopted to govern the elasto-plastic material behaviour checked at points along the plate thickness and along the rectangular beam element axes. The numerical representations are accurately obtained by either computing analytically the element integrals or performing the numerical integration accurately using an appropriate sub-elementation scheme.

A cell subdivision strategy for r‐nearest neighbors computation

Due to the popularity of optical digitizing devices which can digitize an object easily and densely, the processing of a huge amount of data points has become important. Searching is one of the fundamental computational tasks in data analysis algorithms as it often dominates the computational efficiency significantly. The purpose of this study is to provide algorithms based on cell subdivision to search for the nearest neighbors adjacent to a given entity, where the given entity can be a point, a line segment or a triangle. The nearest‐points search is used to find a set of points closest to a given point; the nearest‐edges search is to find the edges that intersect the given edge; the nearest‐triangles search is to find the mapping triangles of a given point or a given triangle. A detailed discussion for each of the above algorithms is described. Several examples are provided also to demonstrate the feasibility of the proposed algorithms.

Atypical Squamous Cells Cannot Rule Out High-grade Squamous Intraepithelial Lesions: Is the Subdivision of Atypical Squamous Cells Clinically Relevant?

Atypical Squamous Cells Cannot Rule Out High-grade Squamous Intraepithelial Lesions: Is the Subdivision of Atypical Squamous Cells Clinically Relevant?

Assessment of model uncertainty for soil moisture through ensemble verification

The Community Land Model (CLM2.0) has been used to simulate land surface processes in a small corn field. The subdivision of grid cells into patches in the CLM2.0 was explored for the generation of Monte Carlo simulations for use in calibration and ensemble generation. A distributed multiobjective calibration was developed for the optimal estimation of parameters and initial state variables for 36 soil moisture profiles. Since the resulting parameter and initial state values did not lead to perfect simulations for soil moisture, and in order to better understand the forecast uncertainty, ensemble runs were generated. The ensembles generated by CLM2.0 have been verified by several methods that are commonly used in meteorology. It was shown that the perfect model approach cannot be applied for bounded hydrological applications and that perturbation of parameters is a necessity to obtain a realistic assessment of the forecast error. Perturbation of forcings only captures more of the model uncertainty than perturbation of initial conditions only, but also causes a too limited spread in the ensembles. The generation of ensemble members through perturbation of the parameter set, found through calibration, does not necessarily result in ensembles that surround the calibrated deterministic control run for soil moisture. This is partially due the nonlinearity of the model in the parameters. It may also indicate that some parameter sets are not robust and not appropriate to perturb for ensemble generation. Consequently, the resulting ensemble mean may not represent the best forecast or a priori state estimation. During periods of extreme drought or precipitation, the ensemble probability density function (pdf) deviates far from normality and the model behaves very nonlinearly. For state estimation, methods like the ensemble Kalman filter are best suited for the propagation of the first moments to account for the nonlinear dynamics during crucial events for hydrological simulations. However, the a posteriori estimate for this technique will only be optimal in the limited class of linear filters, since the underlying pdfs cannot be assumed to be Gaussian.

A Parallel Adaptation Package For Three-Dimensional Mixed-Element Unstructured Meshes

Parallel mesh adaptation methods are developed to treat decomposed, mixed-element unstructured meshes comprised of any combination of basic element types. Emphasis is placed on developing conforming mesh modification methods that are solver-independent. Specificdevelopmentsincludetheimplementationofatreatmentforviscous,highaspectratio near wall tetrahedra, and cell subdivision methods for pyramids, prisms, and hexahedra. Rebalancingoftheadaptedgrid,andparticularlyissuesassociatedwithprocessorassignment of parent/child cell sets, is addressed. The new methods are demonstrated on decomposed, mixed-element meshes employing up to 64 processors. The resulting parallel adaptation package is a powerful, versatile tool for obtaining grid-converged, steady state results, and may readily be applied to other unstructured flow solvers.

Geometry-guided progressive lossless 3D mesh coding with octree (OT) decomposition

A new progressive lossless 3D triangular mesh encoder is proposed in this work, which can encode any 3D triangular mesh with an arbitrary topological structure. Given a mesh, the quantized 3D vertices are first partitioned into an octree (OT) structure, which is then traversed from the root and gradually to the leaves. During the traversal, each 3D cell in the tree front is subdivided into eight childcells. For each cell subdivision, both local geometry and connectivity changes are encoded, where the connectivity coding is guided by the geometry coding. Furthermore, prioritized cell subdivision is performed in the tree front to provide better rate-distortion (RD) performance. Experiments show that the proposed mesh coder outperforms the kd-tree algorithm in both geometry and connectivity coding efficiency. For the geometry coding part, the range of improvement is typically around 10%~20%, but may go up to 50%~60% for meshes with highly regular geometry data and/or tight clustering of vertices.

Pleomorphic conidiogenesis among strains of Knufia cryptophialidica

Pleomorphic conidiogenesis was examined in four strains of Knufia cryptophialidica Hutchison & Untereiner in culture. The ex-type strain (DAOM 216555) was the most plastic, exhibiting various patterns of conidiogenesis, and was the only strain that produced phialides, that is, the most important diagnostic structure of the genus, although many of these phialides were aberrant and produced abnormally swollen conidia that appeared to lack cytoplasm. Subsequently, hyphae emerged from the aberrant phialides and some of these hyphae later disarticulated to form thallic-arthric conidia. The ex-type strain ceased to produce normal phialides after several serial transfers onto malt extract agar. Endoconidiogenesis in K. cryptophialidica, reported here for the first time, involved subdivision of conidiogenous cells by septation and schizolysis through the septa, and their release was by rupture and subsequent degeneration of the conidiogenous cell wall. Both thallic-arthric and endogenous conidia occurred in all strains and may serve as more reliable diagnostic characters of K. cryptophialidica than phialidic conidia.Key words: black meristematic fungus, endoconidia, phialides.

Identification and characterization of a second CD4-like gene in teleost fish

In fish, T cell subdivision is not well studied, although CD8 and CD4 homologues have been reported. This study describes a second teleost CD4-like gene, CD4-like 2 ( CD4L-2). Two rainbow trout copies of this gene were found, -2a and -2b, encoding molecules sharing 81% aa identity. The 2a/ 2b duplication may be related to tetraploid ancestry of salmonid fishes. In the Fugu genome CD4L-2 lies head to tail with an earlier reported, very different CD4-like gene [Suetake, H., Araki, K., Suzuki, Y., 2004. Cloning, expression, and characterization of fugu CD4, the first ectothermic animal CD4. Immunogenetics 56, 368–374], which was designated CD4L-1 in the present article. The flanking genes of the Fugu CD4L-1 and CD4L-2 are reminiscent of the genes surrounding CD4 and LAG-3 in mammals. However, neither synteny nor phylogenetic analysis could decide between CD4 and LAG-3 identity for the fish CD4L genes. CD4L-1 and CD4L-2 share a tyrosine protein kinase p56 lck binding motif in the cytoplasmic tail with CD4 but not with LAG-3. Trout CD4L-2 expression is highest in the thymus, similar to mammalian and chicken CD4, whereas Fugu CD4L-1 expression was highest in the spleen. However, CD4L-2 encodes only two IG-like domains, whereas CD4L-1, CD4 and LAG-3 encode four. The CD4- like genes 1 and 2 in fish apparently went through an evolution different from that of LAG-3 and CD4 in higher vertebrates.