A Multisegment Dynamic Model of Ski Jumping

This paper presents a planar, four-segment, dynamic model for the flight mechanics of a ski jumper. The model consists of skis, legs, torso and head, and anns. Inputs include net joint torques that are used to vary the relative body configurations of the jumper during fiight. The model also relies on aerodynamic data from previous wind tunnel tests that incorporate the effects of varying body configuration and orientation on lift, drag, and pitching moment. A symbolic manipulation program, "Macsyma," is used to derive the equations of motion automatically. Experimental body segment orientation data during the fiight phase arc presented for three ski jumpers which show how jumpers of varying ability differ in flight and demonstrate tlie need for a more complex analytical model than that previously presented in the literature. Simulations are presented that qualitatively match the measured trajectory for a good jumper. The model can be used as a basis for the study of optimal jumper behavior in fiight which maximizes jump distance

Simultaneous patch-clamp and photometric fluorescence ratio measurements of optical probes for ions using a computer-based data acquisition system, PhoCal

This demonstration will present a new computer program and analytical system - PhoCal - which permits the simultaneous measurement of (a) low light levels of fluorescence from optical probes for ions and (b) up to two channels of physiological data which can include patch-clamp current and voltage, or voltage from other probes such as extracellular pH electrodes or other transducers and (c) an event marker channel. The system is PC-based and uses high speed analogto-digital circuitry operating in parallel with a two-channel photon counter which collects data from one or two photomultiplier tubes. All data is logged directly to hard disk and the system can operate at speeds in excess of an aggregate of 1000 samples per second