A digital content authentication system, an image display apparatus applied to the system, and a digital content authentication controlling method of the system are provided. Further disclosed are articles of manufacturing and unit dosage forms containing the bone graft compositions, methods of repairing bone defects utilizing the bone graft compositions, and processes of preparing the same. The second electrode electrically contacts only one of the at least three resistivity switching storage elements. The technical solution under the present invention overcomes the poor effect of panoramic presence in the existing telepresence system, and improves the telepresence system in terms of depth presence, seamless display and eye contact. The mechanism includes a valve operatively coupled to the cylinder so as to be rotatable to a first position to seal the opening and to a second position to unseal the opening, and at least one cam surface operatively coupled to the cylinder so as to be movable with respect to the cylinder to engage the valve so as to produce rotation of the valve.