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We have calculated the light intensity distribution behind ruled halftone screens of the type used in the graphic arts industry. The resulting formulas, which are derived from the theory of partial coherence, include diffraction effects at both the lens aperture and the screen. Their form is that of rapidly converging summations rather than expressions requiring numerical integrations for their evaluation. The method of solution is general in that it treats arbitrarily shaped lens apertures and both straightline and crossline screens with either conventional absorbing or transparent phase rulings. Theoretical predictions for the phase screen and a variety of circular apertures, wavelengths, and screen spacings agree very well with the experimentally measured intensity patterns.

The photographic characteristics of photoactive pigment electrographic imaging systems are investigated by analysis of two model configurations. The results establish which physical parameters control the photographic characteristics. An analysis of electrophoretic display devices is also presented. The models give estimates for the ultimate performance of these systems and make it possible to correlate photographic measurements with related physical phenomena.

We used a mixture of low molecular weight polymers of polyethylene glycol (PEG) to study intestinal permeability in children with chronic diarrhea. After an oral load, urinary recovery of the longer chain, higher molecular weight polymers was significantly decreased compared with that in healthy adults and infants without disease of the gastrointestinal mucosa. A correlation was observed between clinical severity of disease, histopathologic condition of the small bowel mucosa, and PEG scores. These results indicate that intestinal permeability in children can be studied by noninvasive means and that an assessment of mucosal integrity can be obtained.

The differential passive permeation of polymers of different lengths across the intestinal mucosa has been proposed as a probe to test mucosal integrity under a variety of physiologic and pathologic conditions. Polyethylene glycol (PEG) 400 contains a series of polymers whose pattern of urinary recovery after oral administration has been used to characterize intestinal mucosal function. To extend this method to the low levels of PEG polymers found in the urine of children with diarrhea, we have introduced three methodologic innovations. These alterations involve (1) formulation of a balanced PEG polymer mixture, (2) improved isolation, derivatization, and gas chromatography techniques, and (3) a new quantification of the pattern of PEG urinary recoveries. Urinary recovery of orally administered PEG was assessed in four normal adults, six hospitalized infants without gastrointestinal complains, two infants with prolonged diarrhea and carbohydrate malabsorption, and two children with cystic fibrosis. A parameter characterizing the urinary recovery of PEG, N1/2, which is the theoretical number of subunits in the polymer whose recovery is reduced to 50% of the value of the polymer whose recovery is maximal, gave stable, reproducible, and consistent results in normal adults and infants.

The optical properties of an electrophotographic film comprised of closely packed submicron selenium spheres embedded in a polymer matrix were investigated. In one case the spheres were arranged in a monolayer; in a second the particles were dispersed throughout the polymer matrix. The optical transmission of these structures was measured as a function of wavelength and particle size and compared with physical models based on Mie theory.