The invention provides highly resilient synthetic hydrogels, which can be prepared, for example, by using the efficient thiol-norbornene chemistry to cross-link hydrophilic poly and hydrophobic polydimethylsiloxane polymer chains. When a developer creates an SNMP interface header file through an application program at a compile time, an extractor generates a management information base file and object identifier information on the basis of the interface header file. The high energy density metal is selected from a group consisting of Al, Zn, Mg and Fe, or from a combination of these metals. The second electrode is disposed above the first-type and the second-type semiconductor layers in corresponding to the central area of the second-type semiconductor layer. Techniques are useful to avoid visual distortions when changing from a first video source to a second video source. Also, two rear rollers are mounted in the rear mounting assembly and a front roller is mounted in the front mounting assembly and defines a roller width.