Ectodermal dysplasia is a rare disease which affects at least two ectodermal-derived structures such as hair, nails, skin, sweat glands and teeth. Approximately 200 different conditions have been classified as an ectodermal dysplasia and X-linked hypohidrotic ectodermal dysplasia (XHED) represents the commonest form. Clinically, XHED is characterized by hypotrichosis, hypohidrosis and hypodontia. A variety of ocular manifestations have been reported in XHED, the most common being dryness of eyes due to tear deficiency and instability of the film secondary to the absence of meibomian gland function. Here we report a child with the distinctive clinical features of XHED confirmed with molecular diagnosis who presented with infantile bilateral glaucoma, in addition to the classical ocular involvement in XHED.
The workspace of a general 4R manipulator is analyzed by examining its cross-section evaluation to investigate its main characteristics and how they are affected by link parameters. An algebraic formulation is deduced for a workspace boundary of a general 4R manipulator from the geometry of an envelope generation. This algebraic formulation is also useful for direct computation of the workspace volume and for detection of holes and voids. In addition, both analysis and synthesis criteria are deduced from this algebraic formulation, taking into account the geometric nature of the 4R manipulator workspace as a volume of revolution. Several numerical examples show general geometries of 4R manipulator workspaces.
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