922 research outputs found
Elastin is responsible for the rigidity of the ligament under shear and rotational stress : a mathematical simulation study
Background
An accurate understanding of the mechanical response of ligaments is important for preventing their damage and rupture. To date, ligament mechanical responses are being primarily evaluated using simulations. However, many mathematical simulations construct models of uniform fibre bundles or sheets using merely collagen fibres and ignore the mechanical properties of other components such as elastin and crosslinkers. Here, we evaluated the effect of elastin-specific mechanical properties and content on the mechanical response of ligaments to stress using a simple mathematical model.
Methods
Based on multiphoton microscopic images of porcine knee collateral ligaments, we constructed a simple mathematical simulation model that individually includes the mechanical properties of collagen fibres and elastin (fibre model) and compared with another model that considers the ligament as a single sheet (sheet model). We also evaluated the mechanical response of the fibre model as a function of the elastin content, from 0 to 33.5%. Both ends of the ligament were fixed to a bone, and tensile, shear, and rotational stresses were applied to one of the bones to evaluate the magnitude and distribution of the stress applied to the collagen and elastin at each load.
Results
Uniform stress was applied to the entire ligament in the sheet model, whereas in the fibre model, strong stress was applied at the junction between collagen fibres and elastin. Even in the same fibre model, as the elastin content increased from 0 to 14.4%, the maximum stress and displacement applied to the collagen fibres during shear stress decreased by 65% and 89%, respectively. The slope of the stress–strain relationship at 14.4% elastin was 6.5 times greater under shear stress than that of the model with 0% elastin. A positive correlation was found between the stress required to rotate the bones at both ends of the ligament at the same angle and elastin content.
Conclusions
The fibre model, which includes the mechanical properties of elastin, can provide a more precise evaluation of the stress distribution and mechanical response. Elastin is responsible for ligament rigidity during shear and rotational stress
Synthetic Manipulation of PIP2 Levels and PIP2-Associated Chemotactic Signaling Dissection in Dictyostelium
Local SiC photoluminescence evidence of non-mutualistic hot spot formation and sub-THz coherent emission from a rectangular BiSrCaCuO mesa
From the photoluminescence of SiC microcrystals uniformly covering a
rectangular mesa of the high transition temperature superconductor
BiSrCaCuO, the local surface temperature
was directly measured during simultaneous sub-THz emission from the
intrinsic Josephson junctions (IJJs) in the mesa. At high bias currents and
low bath temperatures K, the center of a large
elliptical hot spot with jumps dramatically with little
current-voltage characteristic changes. The hot spot doesn't alter the
ubiquitous primary and secondary emission conditions: the ac Josephson relation
and the electromagnetic cavity resonance excitation, respectively. Since the
intense sub-THz emission was observed for high K in
the low bias regime where hot spots are absent, hot spots can not provide
the primary mechanisms for increasing the output power, the tunability, or for
promoting the synchronization of the IJJs for the sub-THz emission, but can
at best coexist non-mutualistically with the emission. No standing
waves were observed
Calcium-Antimony Alloys as Electrodes for Liquid Metal Batteries
The performance of a calcium-antimony (Ca-Sb) alloy serving as the positive electrode in a Ca∥Sb liquid metal battery was investigated in an electrochemical cell, Ca(in Bi) | LiCl-NaCl-CaCl[subscript 2] | Ca(in Sb). The equilibrium potential of the Ca-Sb electrode was found to lie on the interval, 1.2–0.95 V versus Ca, in good agreement with electromotive force (emf) measurements in the literature. During both alloying and dealloying of Ca at the Sb electrode, the charge transfer and mass transport at the interface are facile enough that the electrode potential varies linearly from 0.95 to 0.75 V vs Ca(s) as current density varies from 50 to 500 mA cm[superscript −2]. The discharge capacity of the Ca∥Sb cells increases as the operating temperature increases due to the higher solubility and diffusivity of Ca in Sb. The cell was successfully cycled with high coulombic efficiency (∼100%) and small fade rate (<0.01% cycle[superscript −1]). These data combined with the favorable costs of these metals and salts make the Ca∥Sb liquid metal battery attractive for grid-scale energy storage.United States. Advanced Research Projects Agency-Energy (Award DE-AR0000047)TOTAL (Firm)Marubun Research Promotion FoundationMurata Overseas Scholarship Foundatio
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