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.
Backgouging: The removal of weld metal and base metal from the weld root side of a welded joint to facilitate complete fusion and complete joint penetration upon subsequent welding from that side. Backhand Welding: A welding technique in which the welding torch or gun is directed opposite to the progress of welding. Backing Gas: Backing in the form of a shielding gas employed primarily to provide a protective atmosphere.