in this investigation the thickness of enamel in the gingival, middle, and incisal thirds of the labial surface of the anterior teeth were measured regarding preparation of the teeth for porcelain laminate veneers.part one, 20 extracted intact human maxillary central and lateral incisors ten of each were selected. the teeth were imbedded in autopolimerize acrylic resin. cross section was prefor...

A general rule of thumb is to tackle the hardest part of a search problem first. Many heuristics therefore try to branch on the most constrained variable. To test their effectiveness at this, we measure the constrainedness of a problem during search. We run experiments in several different domains, using both random and non-random problems. In each case, we observe a constrainedness "knlfe-edge...

The regular production of a satisfactory edge on a microtome knife for the cutting of sections as thin as 2 u, which are free from scores and other blemishes, is a serious technical problem in histological laboratories. Eyen when a good edge is produced on a knife, its life is generally limited because contact with any hard material in the specimen may damage the delicate edge, causing it to sc...

The knife-edge technique for measurements of micrometer-sized beams is extended to two-dimensional imaging by tomographic reconstruction of multiangular knife-edge data. Two-dimensional intensity distributions at optical (633-nm) and soft-x-ray (13.5-nm) wavelengths at the focal region of a Schwarzschild objective are presented. The resolution is limited by the 200-nm step size used in the data...

The operation of the knife-edge viscometer requires knowledge of the interfacial velocity profile in order to determine the viscous traction between the surface film and the knife edge and hence measure the surface shear viscosity of the film. The interfacial velocity profile can be obtained analytically in two limiting regimes. One is the limit of the surface shear viscosity going to infinity,...

We report a method for characterizing the focussing laser beam exiting the objective in a laser scanning microscope. This method provides the size of the optical focus, the divergence of the beam, the ellipticity and the astigmatism. We use a microscopic-scale knife edge in the form of a simple transmission electron microscopy grid attached to a glass microscope slide, and a light-collecting op...