Primary motions

Fig. 17. Composite structural motions of subunits can be described with translation, libration, and screw-axis (TLS) analysis of the NCP. Analysis of the histone subunits are shown here, (a) Composite motion of histones H2A (blue) and H2B (blue) considered as individual elements and combined as H2A H2B dimer (red). Note for the individual histones that the axis of motion is parallel with the medial a-helix of the histone. The origin of the TLS axes are within the structural positions of the histone. The composite motion for the H2A H2B dimer is dominated by the motion of H2A, as is seen in the similarity of orientation and position of the two axes, (b) The orientation and motion of the two H2A H2B dimers appear symmetric across the dyad axis of the NCP. (c) H3 H4 composite motions when considered as dimers (blue) and as the tetramer (red). Interpretation is more complex because of the asymmetric magnitude of motion for the two dimers, and the different position in the axis of primary motion for the tetramer. These motions are most likely the consequence of packing interactions, described in greater detail in the text.

Their detailed analysis shows that the phenylene group in this polymer undergoes two types of motion simultaneously, both about the C1-C4, axis. The primary motion consists of large-angle jumps between two sites whereas the secondary motion involves restricted rotational diffusion over limited angular amplitude. These motions have been described by an inhomogeneous distribution of correlation times [43]. 

The primary motion of the knee joint is flexion-extension rotation around an axis passing through the medial and lateral femoral condyles. The three-dimensional motions of the knee other than flexion-extension rotation are constrained by ligaments, menisci, and articular surface configuration. The biomechanical functions of the ACL are mainly to resist anterior tibial translation, and secondly to resist internal and valgus tibial rotation, or combined motions. 

The shedding mechanism is one of the primary motions of a loom. A Jacquard shedding mechanism is used for weaving 3D preforms because the individual warp fibers are controlled independently by Jacquard harness cords. A 3D fabric and preforms can be woven on a 2D conventional rapier loom, but there is a fabric thickness limitation when using any conventional 2D loom. 

The occipitoatlantal articulation consists of the superior articular facets of the atlas and the two occipital condyles. The superior facets of the atlas face backward, upward, and medially, and are concave in both anteroposterior and transverse diameters. The surfaces of the occipital condyles match the facets of the atlas, and the joint is best thought of as a sphere (the occiput) gliding on the articular surfaces of the atlas (Fig. 24-1). The freely movable occiput is limited by its muscular and ligamentous attachments, which make flexion-extension the primary motion, producing a smaii-amplitude nodding of the head. Flexion of the occiput on the atlas is accompanied by a posterior translatory slide of the occiput extension is accompanied by an anterior translatory slide. 

The primary motion of the acromioclavicular joint is axial rotation. 

As with many of the arthritic conditions, the primary dysfunction of the wrist and hand occur with the secondary motions more than the primary motions. Some dysfunctions of the carpal joints occur involving multiple joints. One of the most typical of the carpal dysfunctions involves restriction of glide of the lunate bone. It tends to have a preferential glide into the ventral direction and can contribute to the narrowing of the space of the carpal tunnel. The dysfunctions of... 

The primary motion of the occiput on the atlas is flexion-extension, with the occipital condyles convex and the superior articular facets of the atlas concave. 

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