A method for trimming an effective refractive index of optical waveguiding structures made for example in a high refractive index contrast material system. The screw shaft support includes first and second spacer bearings disposed on the first and second screw shafts, and a first cross member including first and second loops slidably coupled to the first and second spacer bearings. Therefore, compared to a p-channel TFT whose sourcedrain regions contain an n-type impurity and a higher concentration of p-type impurity, the gettering efficiency is inferior in a channel region of the n-channel transistor. For example, this may involve reading the past or historical message data from messages logs or having a system point to the message data in existing data storage.