Methods and apparatus to manipulate embroidery designs via a communication network are disclosed. Specifically, the low-profile lens element is mechanically rotatable such that a beam can be steered in any direction within three-dimensional space. At least a group of small openings oriented to the cooled element is provided in a wall of this air duct. Section terminates regeneration when soot loading is reduced to some minimum amount or when conditions for continuing regeneration become unfavorable. and keeping it at this temperature for a first time period, and d) adjusting the pH value to a value of 2. The present invention has advantages such as favorable tightness.