By its very nature, vitamin A causes drying of the skin and exfoliation. A bevy of prescription and OTC vitamin A topical preparations make use of this side effect to treat a variety of skin concerns. The term Retinoid refers to any Vitamin A based molecule. It's a category, similar to saying antibiotic. They may be related, but some are stronger and more effective than others.
Pototype sheets for Weld Quality Workmanship Standard. Undercut. Definition: A groove cut at the toe of the weld by the welding arc and left. unfilled. Depth of undercut shall not exceed 1/32.
This method may be used to inspect plate edges prior to welding, in process inspection of each weld pass or layer, postweld evaluation and to inspect repairs - Fig. 3. It is a good method for detecting surface cracks of all sizes in both the weld and adjacent base metal, subsurface cracks, incomplete fusion, undercut and inadequate penetration in the weld, as well as defects on the repaired edges of the base metal.