Abstract: A multimode optical fiber waveguide with graded refractive index for lessening modal dispersion with the gradient produced at least in part by radially decreasing boron oxide content outwardly from the core center within a high silica glass core minimizes modal dispersion by use of a non-parabolic grading function. The optimum gradient for a simple binary borosilicate system for a wavelength of from approximately 0.5 to 1.1 micrometers corresponds with .alpha. = 1.77 .+-. 10 percent in the equation n = n.sub.1 [1-2.DELTA.(r/a).sup..alpha.].sup.1/2, in which n.sub.1 is the axial core index r is the distance from the fiber axis, a is the core radius, .DELTA. is the relative index difference between core center and cladding and .alpha. is a power law exponent which characterizes the profile.

Abstract: Vaccines affording protection against the diseases resulting from infection of cats with feline leukemia virus are produced from cells infected with that virus or from the virus alone.

Abstract: High silica content optical glasses, containing more volatile oxides such as GeO.sub.2 and B.sub.2 O.sub.3, are produced by plasma fusion of powders without inordinately high loss of the more volatile constituents. The powders are produced by a process including the heat treatment of intimately mixed materials, which include the glass forming constituents. Small quantities of GeO.sub.2 are included in borosilicate glass to suppress bubble formation. Pairs of glass compositions have been found, with sufficient index of refraction difference to produce guidance in optical transmission lines, while possessing sufficient thermal expansion match to reduce stresses in the line.