Usha Sinha | Searcharxiv

arXiv2024

Klippings Ten Commandments

This is a short historical note about the visit of Prof. G. Klipping of Fritz Haber Institute, Germany, to the low temperature physics laboratory of Indian Institute of Technology, Madras. During his visit in 1979, Klipping delivered a series of lectures on cryogenic practices and low temperature physics in the physics department. The authors, both Masters degree students at that time, with a specialization in cryogenics, attended these lectures arranged by Prof. R. Srinivasan then head of the Low Temperature laboratory. In this non technical note, the authors attempt to portray the research philosophy and attitudes of Klipping as captured through many wise remarks and snippets which formed an integral part of his lectures. In the 1970-80s Klipping made invaluable contributions to the development of cryogenics research in India.

physics.hist-ph↗

arXiv2023

Investigating the Correlation between Force Output, Strains, and Pressure for Active Skeletal Muscle Contractions

Measuring the forces of individual muscles in a muscle group around a joint is non-trivial, and researchers have suggested using surrogates for individual muscle forces instead. Traditionally, experimentalists have shown that the force output of the skeletal muscle tissue can be correlated to the intra-muscular pressure (IMP) generated by the muscle belly. However, IMP proves difficult to measure in vivo, due to variations from sensor placement and invasiveness of the procedure. Numerical biomechanical simulations offer a tool to analyze muscle contractions, enabling new insights into the correlations among non-invasive experimentally measurable quantities such as strains, and the force output. In this work, we investigate the correlations between the muscle force output, the principal, shear and volumetric strains experienced by the muscle, as well as the pressure developed within the muscle belly as the tissue undergoes isometric contractions with varying activation profiles and magnitudes. It is observed that pressure does not correlate well with force output under higher sub-maximal and maximal activation levels, especially at locations away from the center of the muscle belly due to pressure relaxation effects. This study reveals strong correlations between force output and the strains at all locations of the belly, irrespective of the type of activation considered. This observation offers evidence for further in vivo studies using experimentally measurable principal and volumetric strains in the muscle belly as proxies for the force generation by the individual muscle and consequently enables the estimation on the contribution of various muscle groups to the total force.

q-bio.TO↗