In vitro assessment of ultraviolet protection of coloured cotton knitted fabrics with different structures under stretched and wet conditions.

Clothing provides intrinsic ultraviolet (UV) protection that can be improved by colouration. However, the daily wearing condition can undermine the UV protection of coloured clothing wherein garments are stretched by body movement and/or wetted by perspiration of wearers. Knitwear is an indispensable clothing in summer, but its UV protection against wearing conditions lacks extensive study especially in a fabric structural approach. This article aimed at narrowing the research gap by focusing on the UV protection against stretch and wetness provided by various knitted fabric constructions incorporating the knit, tuck and miss stitches. The results show that the black knitted fabrics exhibit a significant reduction in the UV protection factor by 53% on average at a 10% stretch level. Knitted fabrics with miss stitches retained good UV protection even when the fabrics were stretched by 20% of its original dimensions.

The environmental scanning electron microscope and its applications.

An environmental scanning electron microscope can be made by incorporating a pressure limiting aperture at some distance below the objective aperture of an SEM, and by providing independent pumping between these two apertures. Tilting of the pressure limiting aperture with respect to the axis of the electron optics column redirects the gas jet which develops above the pressure limiting aperture and which otherwise would inject excessive gas through the objective aperture into the column. The detection of backscattered and multiple-backscattered electrons is achieved below the pressure limiting aperture in the region confined by the sample, the detector and the aperture grid. Wet specimens can be examined in the environmental scanning electron microscope at 7kV and TV rates by placing them at a sufficiently close distance to the pressure limiting aperture. Live seedlings and ants have been observed in this way. Wet (fresh) rat tissues, wool fibers subjected to various treatments, crystallization and rewetting of salts, and some radiation effects have been observed and recorded under the environmental scanning electron microscope. Examination of specimens in the full pressure range, 0-1013 mbar, is possible. A detector-aperture system which will allow the signal originating from the sample to be detected simultaneously both below and above the aperture is under construction. Further development of environmental scanning electron microscopy now depends upon close co-ordination between microscope manufacturers and research groups involved in such fields as biology, fiber technology, radiation and physical chemistry.