Marijuana and vision--after ten years' use in Costa Rica

Several tests of visual function were applied to an abstaining user (10 years or more) group and a nonuser group carefully preselected to be free of clinical signs of eye disease. The groups were matched on several criteria. The results show that all findings from both groups are within established limits of normalcy. Small differences and trends were found between the groups. These would have been undetected without large samples. Relative to the nonuser group, tests showed these user trends: increased basal lacrimation, increased intraocular pressure, increased photosensitivity, decreased dark adaptation, decreased color-match limits, and decreased Snellen acuity. These differences were associated with statistical probabilities, p=0.07 to p=0.001. There were no significant differences or clear trends between the user and nonuser groups in incidence of pathological fundus signs, conjunctival hyperemia, pterygia, or color-match midpoints.     

Heat transfer during fluidized-bed coating

A fully implicit numerical method for linear parabolic free boundary problems with coupled and integral boundary conditions is described. The partial differential equation and the boundary conditions are time discretized with the method of lines. An auxiliary function is introduced to remove the coupled and integral boundary conditions from the resulting free boundary problem for ordinary differential equations. Once separated boundary conditions are obtained, invariant imbedding is used to solve the free boundary problem numerically. The method is illustrated by solving the heat transfer equations for the fluidized-bed coating of a thin-walled cylinder.     

Back-scattering energy loss parameter measurements in thin metal films

The back-scattering energy loss parameter [S] has been determined directly from evaporated metal layers of Ti, V, Ni, Mo and Ta for 2.0 MeV He⁺ ions and a back-scattering angle θ = 168°. Reasonable agreement has been found with [S] values calculated from experimental dE/dx results tabulated by Ziegler and Chu. Discrepancies in [S] values occurred for thin Mo and Ta layers (< 500 Å) and for Ti and V layers evaporated in a poor vacuum. Variations are thought to be due to film growth effects and impurity incorporation during deposition. A correlation of [S] values with layer superconducting properties has been observed.