According to the present invention, methods and apparatus are provided to allow efficient switching of frames for transmission between a Layer 2 Virtual Local Area Network such as a Metro Ethernet Network and an external network. The invention further provides an image-based measurement system or method in which active images of a subject of measurement can be used to derive a reference image, for example a CAD design image. The collet and backcap may be utilized in a welding torch. Here we describe genetic delivery of a pro-drug converting system in order to enable targeted cellular ablation in zebrafish.