The present invention provides a spin-valve magnetoresistance sensor in which are formed, on top of the substrate, free layers, and pinned layers, enclosing a nonmagnetic spacer layer, and an antiferromagnetic layer adjacent to the pinned layers. An output signal based on the trigger signal is generated as a short electrical pulse at an output or at one output or at both outputs of the logic gate. Owing that this invention employs special electrode paste composition and special manufacturing technique, the chargingdischarging performance of the cell is enhanced, and the cell is more suitable for power supply. The fixation assembly further includes at least one fixation member supported by the housing and movable from a retracted position to an extended position, whereby in the extended position the fixation member extends out from the housing and into one of the vertebral bodies. The system also includes a controller programmed to control operation of the system. The tandem mass spectrometer can also be instructed to perform an analysis of the sample before instructing the tandem mass spectrometer to perform the at least two scans of the sample.