The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform

Michael J Doughty - One of the best experts on this subject based on the ideXlab platform.

  • prevalence of non Hexagonal Cells in the corneal endothelium of young caucasian adults and their inter relationships
    Ophthalmic and Physiological Optics, 1998
    Co-Authors: Michael J Doughty
    Abstract:

    Abstract The corneal endothelium is often described as a mosaic of Hexagonal Cells, despite numerous reports that the relative number of ‘Hexagonal’ Cells is often only around 65%. Such estimates also cannot define the relative area contribution to the cell mosaic of either these Cells, or those that are not 6-sided. Specular micrographs were therefore taken of 20 healthy young Caucasian adults aged 21 to 34 years and the apical surface areas of at least 105 contiguous Cells from each central corneal endothelium measured by planimetry. The numbers of each cell type and their surface areas were assessed so that the summated area occupied by each cell type could be calculated. The results reveal that endothelia that show only modest variance in cell areas are usually composed of 4-, 5-, 6-, 7- and 8-sided Cells. Assessments of relative contribution of each cell type to the mosaic indicates that the 6-sided Cells can be expected to constitute just over 60% of the total cell area. Increases in the variance in the areas across all the Cells can be strongly correlated with a reduction in the 6-sided Cells and increases in the 5- and 7-sided Cells. Each cell type (4-, 5-, 6-sided etc) has a preferred area that is proportional to other Cells. The results firmly indicate that the mosaic is not random and follows a specific order that is presumably dictated by the physics of cell packing. These methods of comparing endothelia should allow distinctions to be made between endothelia that are different, versus being abnormal (i.e. with disease).

  • concerning the symmetry of the Hexagonal Cells of the corneal endothelium
    Experimental Eye Research, 1992
    Co-Authors: Michael J Doughty
    Abstract:

    Abstract Modeling studies are presented to show how the figure coeffcient and hexagon deviation index values decrease as a six-sided endothelial cell is systematically distorted from a completely symmetrical geometric shape (a regular hexagon). By use of scanning electron micrographs of rabbit corneal endothelium and an analysis of published specular micrographs of rabbit corneal endothelium, it is shown that the six-sided Cells are not necessarily very symmetrical. Such Cells should thus be reported as six-sided Cells rather than as ‘hexagons’ which carries the inherent risk of implying regularity (and thus supposed stability in a tesselated mosaic) of such Cells.

Daiheng Chen - One of the best experts on this subject based on the ideXlab platform.

  • flexural rigidity of honeycomb consisting of Hexagonal Cells
    Acta Mechanica Sinica, 2011
    Co-Authors: Daiheng Chen
    Abstract:

    In this study, the flexural rigidity of a honeycomb consisting of regular Hexagonal Cells is investigated. It is found that the honeycomb bending can not be evaluated by using the equivalent elastic moduli obtained from the in-plane deformation because the moments acting on the inclined cell wall are different for in-plane deformation and bending deformation. Based on the fact that the inclined wall is twisted under the condition of the rotation angle in both connection edges being zero, a theoretical technique for calculating the flexural rigidity of honeycombs is proposed, and the validity of the present analysis is demonstrated by numerical results obtained by BFM.

  • bending deformation of honeycomb consisting of regular Hexagonal Cells
    Composite Structures, 2011
    Co-Authors: Daiheng Chen
    Abstract:

    In this study, the flexural rigidity of a honeycomb consisting of regular Hexagonal Cells is investigated. It is found that the bending deformation of the honeycomb cannot be evaluated by using the equivalent elastic moduli obtained from the in-plane deformation since the moments acting on inclined walls of honeycomb cell are different for the in-plane deformation and bending deformation. Based on the fact that the inclined wall of the honeycomb is twisted under the condition that the rotation angle in both connection edges is zero in bending deformation, a theoretical technique for calculating the honeycomb flexural rigidity is proposed. In the theoretical analysis, a torsion problem of a thin plate was solved by using the generalized variational principle. The validity of the present analysis is demonstrated by numerical results obtained by the finite element method.

  • Analysis of equivalent elastic modulus of asymmetrical honeycomb
    Composite Structures, 2010
    Co-Authors: Daiheng Chen, L. Yang
    Abstract:

    Abstract In this report, elastic moduli of honeycomb consisting of asymmetrical Hexagonal Cells are studied by using a theoretical approach and the finite element method (FEM). Based on the change in the shape of the Hexagonal cell, explicit equations describing the equivalent elastic moduli of honeycomb with cell wall parallel to the y-axis are proposed. In the analysis of honeycomb deformation, the shear deformation was considered in addition to bending deformation and tensile deformation. As a result, the equivalent elastic moduli could be calculated with extremely high precision.

Nenad Trinajstic - One of the best experts on this subject based on the ideXlab platform.

  • the area generating function for simple 2 column polyominoes with Hexagonal Cells
    International Journal of Chemical Modeling, 2010
    Co-Authors: Svjetlan Feretic, Nenad Trinajstic
    Abstract:

    Column-convex polygons were first counted by area several decades ago, and the result was found to be a simple, rational, generating function. In this chapter we generalize that result. Let a p-column polyomino be a polyomino whose columns can have 1, 2, . . . , p connected components. Then column-convex polygons are equivalent to 1-convex polyominoes. The area generating function of even the simplest generalization, namely to 2-column polyominoes, is unlikely to be solvable. We therefore define a class of polyominoes which interpolates between column-convex polygons and 2-column polyominoes. We derive the area generating function of that class, using an extension of an existing algorithm. The growth constant of the new class is greater than the growth constant of column-convex polyominoes. A rather tight lower bound on the growth constant complements a compelling numerical analysis.

  • the area generating function for simple 2 column polyominoes with Hexagonal Cells
    arXiv: Combinatorics, 2009
    Co-Authors: Svjetlan Feretic, Nenad Trinajstic
    Abstract:

    Column-convex polygons were first counted by area several decades ago, and the result was found to be a simple, rational, generating function. In this chapter we generalize that result. Let a p-column polyomino be a polyomino whose columns can have 1, 2,..., p connected components. Then column-convex polygons are equivalent to 1-convex polyominoes. The area generating function of even the simplest generalization, namely to 2-column polyominoes, is unlikely to be solvable. We therefore define a class of polyominoes which interpolates between column-convex polygons and 2-column polyominoes. We derive the area generating function of that class, using an extension of an existing algorithm. The growth constant of the new class is greater than the growth constant of column-convex polygons. A rather tight lower bound on the growth constant complements a compelling numerical analysis.

Svjetlan Feretic - One of the best experts on this subject based on the ideXlab platform.

  • the area generating function for simple 2 column polyominoes with Hexagonal Cells
    International Journal of Chemical Modeling, 2010
    Co-Authors: Svjetlan Feretic, Nenad Trinajstic
    Abstract:

    Column-convex polygons were first counted by area several decades ago, and the result was found to be a simple, rational, generating function. In this chapter we generalize that result. Let a p-column polyomino be a polyomino whose columns can have 1, 2, . . . , p connected components. Then column-convex polygons are equivalent to 1-convex polyominoes. The area generating function of even the simplest generalization, namely to 2-column polyominoes, is unlikely to be solvable. We therefore define a class of polyominoes which interpolates between column-convex polygons and 2-column polyominoes. We derive the area generating function of that class, using an extension of an existing algorithm. The growth constant of the new class is greater than the growth constant of column-convex polyominoes. A rather tight lower bound on the growth constant complements a compelling numerical analysis.

  • the area generating function for simple 2 column polyominoes with Hexagonal Cells
    arXiv: Combinatorics, 2009
    Co-Authors: Svjetlan Feretic, Nenad Trinajstic
    Abstract:

    Column-convex polygons were first counted by area several decades ago, and the result was found to be a simple, rational, generating function. In this chapter we generalize that result. Let a p-column polyomino be a polyomino whose columns can have 1, 2,..., p connected components. Then column-convex polygons are equivalent to 1-convex polyominoes. The area generating function of even the simplest generalization, namely to 2-column polyominoes, is unlikely to be solvable. We therefore define a class of polyominoes which interpolates between column-convex polygons and 2-column polyominoes. We derive the area generating function of that class, using an extension of an existing algorithm. The growth constant of the new class is greater than the growth constant of column-convex polygons. A rather tight lower bound on the growth constant complements a compelling numerical analysis.

Shmuel Levinger - One of the best experts on this subject based on the ideXlab platform.

  • anterior chamber gas bubbles after corneal flap creation with a femtosecond laser
    Journal of Cataract and Refractive Surgery, 2005
    Co-Authors: Tova Lifshitz, Jaime Levy, Itamar Klemperer, Shmuel Levinger
    Abstract:

    A 48-year-old woman had bilateral wavefront-guided laser in situ keratomileusis for myopia with IntraLase corneal flap creation. In the right eye the cavitation bubbles were observed not only in the interface between the flap and the corneal bed but also in the anterior chamber disappearing after 30 minutes. After the procedure, uncorrected visual acuity is 20/25 in both eyes; and specular microscopy shows normal Hexagonal Cells and density. Although no postoperative complications were observed in our case, further follow-up is needed to examine the long-term effect of this phenomenon of IntraLase.