1. The theory which Crowther has advanced to account for the variation of the lethal dose of roentgen rays among the individuals of a group of Colpidium colpoda is reviewed. 2. It is shown that the use of his small-body theory to explain the small value of lambda(e) leads to certain further assumptions about the nature of the destructive effect. 3. An alternative hypothesis is discussed.

BACKGROUND The ultraviolet properties of textiles dyed with synthetic dyes have been widely reported in literature. However, no study has investigated the ultraviolet properties of natural fabrics dyed with natural colorants. This study reports the Ultraviolet Protection Factor (UPF) of cotton fabrics dyed with colorants of plant and insect origins. METHODS Three cotton fabrics were dyed with...

Basal cell carcinoma is the most common skin cancer mainly caused by prolonged exposure to ultraviolet rays. It is also known as rodent ulcer or basal cell epithelioma. The main mechanism suggested is prolonged exposure to high intensity ultraviolet rays, which causes DNA damage. Pigmented basal cell carcinoma is a rare variety of basal cell carcinoma. Usually, it presents as pigmented nodular ...

on photosynthetic competence or light-interception. It is concluded that O 3 depletion and the concurrent rise This critical review of recent literature questions earlin UV-B irradiance is not a direct threat to photosynier predictions that photosynthetic productivity of thetic productivity of crops and natural vegetation. higher plants is vulnerable to increased ultraviolet-B (UV-B) radiation ...

Our knowledge of the effects of increased levels of ultraviolet-B radiation (UV-B) on plant fitness is limited mainly to yield studies in a few crop species. Previous greenhouse and garden studies of Brassica have found greater detrimental effects of UV-B on fitness in gardens than in the greenhouse, suggesting the possibility that additional stresses in the field decrease the ability of Brassi...

1. Through use of the pollen tube technique it has been possible to study the sensitivity of prophase stages to x-rays and ultraviolet, and to correlate the varying sensitivity with changes in the generative nucleus of Tradescantia. 2. Sensitivity to ultraviolet decreases from the 2 hour stage until at 11 hours after germination there is no further production of breaks. The 0 and 1 hour stages ...