Skeletal muscle contractions can be broadly separated into twitch, summation, and tetanic contractions. In a twitch contraction, a single action potential, whether from a motor neuron or from within the muscle, causes the muscle fiber to produce a single contraction and relaxation cycle called a twitch.uscle contractions can be described based on two variables: length and tension. A muscle contraction is described as isometric if the muscle tension changes but the muscle length remains the same. In contrast, a muscle contraction is isotonic if muscle length changes but the muscle tension remains the same.
Â© A Dictionary of Earth Sciences 1999, originally published by Oxford University Press 1999. Gutenberg discontinuity The seismic-velocity discontinuity between the Earth's mantle and core. The boundary is at a depth of about 2600 km and is thought to have surface irregularities of a few kilometres. Cite this article. Pick a style below, and copy the text for your bibliography.
Surface contain. irregularities include uneven weld bead ripples, excessive weld reinforcement, excessively. concave or fillet weldconvexs, unevenleg fillet weld- s, undercut, overlap, herringbone, pockmarks, mouse footmarks, and underfill. Weld discontinuities can be defined as an. interruption of the typical structure of a weld, such as a lack of homogeneity in the mechanical, metallurgical or physical characteristics of weld.. Weld discontinuities include porosity, the. slag inclusions, incomplete fusion, incomplete joint penetration, excessive melt-through, cold. cracks, and hot cracks. However, a surface irregularity or weld discontinuity is not a rejectable.