Time series analysis of jaw muscle contraction and tissue deformation during mastication in miniature pigs

Masticatory muscle contraction causes both jaw movement and tissue deformation during function. Natural chewing data from 25 adult miniature pigs were studied by means of time series analysis. The data set included simultaneous recordings of electromyography (EMG) from bilateral masseter (MA), zygomaticomandibularis (ZM) and lateral pterygoid muscles, bone surface strains from the left squamosal bone (SQ), condylar neck (CD) and mandibular corpus (MD), and linear deformation of the capsule of the jaw joint measured bilaterally using differential variable reluctance transducers. Pairwise comparisons were examined by calculating the cross-correlation functions. Jaw-adductor muscle activity of MA and ZM was found to be highly cross-correlated with CD and SQ strains and weakly with MD strain. No muscle’s activity was strongly linked to capsular deformation of the jaw joint, nor were bone strains and capsular deformation tightly linked. Homologous muscle pairs showed the greatest synchronization of signals, but the signals themselves were not significantly more correlated than those of non-homologous muscle pairs. These results suggested that bone strains and capsular deformation are driven by different mechanical regimes. Muscle contraction and ensuing reaction forces are probably responsible for bone strains, whereas capsular deformation is more likely a product of movement.

Perturbative analysis of the triply differential cross section and circular dichroism in photo-double-ionization of He

We extend application of our lowest-order perturbative approach (in electron-electron correlation) for analysis of photo-double-ionization (PDI) of He [A.Y. Istomin et al., J. Phys. B 35, L543 (2002)] to excess energies up to 450 eV and to analysis of circular dichroism. We find that account of electron correlation in the final state to first order provides predictions for the triply differential cross section and circular dichroism that are in reasonable agreement with absolute data for excess energies up to 80 eV. For an excess energy of 450 eV, account of electron correlation in both initial and final states is necessary and the predicted triply differential cross sections are in agreement with absolute data only for large mutual ejection angles. We find that at excess energies of a few tens of eV, the PDI is dominated by the "virtual" knock-out mechanism, while the "direct" (on-shell) knock-out process gives only small contributions for large mutual ejection angles. As a result, we conclude that the circular dichroism effect at these energies originates from the nonzero electron Coulomb phase shifts.