Abstract: A lighting device for foreign object debris (FOD) detection is included. The lighting device includes a light source configured to emit light onto a surface, and a diffuser coupled to the light source and configured to cause the emitted light to impinge the surface in at least a partially planar pattern, so as to create a darkfield lighting effect with respect to the surface. The lighting device further includes a cylindrical rod including a first end portion and a second end portion, in which the first end portion is configured to couple to the light source and the diffuser and the second end portion is configured to be manually held by a user of the portable lighting device.

Abstract: Heat transfer fluids consisting essentially of about, by weight:A. 20 to about 40 percent diphenyl ether;B. 40 to about 60 percent of a 2-biphenylylphenyl ether (2-bippe) and 4-biphenylylphenyl ether (4-bippe) mixture at a 2-bippe:4-bippe weight ratio of at least about 2:1; andC. 12 to about 25 percent of a polyphenylphenol mixtureExhibit freeze points of -18.degree. C or less. These heat transfer fluids have excellent fluidity over a broad temperature range and display unexpectedly good thermal stability.