Slow force response and auto-regulation of contractility in heterogeneous myocardium

Classically, the slow force response (SFR) of myocardium refers to slowly developing changes in cardiac muscle contractility induced by external mechanical stimuli, e.g. sustained stretch. We present evidence for an intra-myocardial SFR (SFRIM), caused by the internal mechanical interactions of muscle segments in heterogeneous myocardium. Here we study isometric contractions of a pair of end-to-end connected functionally heterogeneous cardiac muscles (an in-series muscle duplex). Duplex elements can be either biological muscles (BM), virtual muscles (VM), or a hybrid combination of BM and VM. The VM implements an Ekaterinburg-Oxford mathematical model accounting for the ionic and myofilament mechanisms of excitation-contraction coupling in cardiomyocytes. SFRIM is expressed in gradual changes in the overall duplex force and in the individual contractility of each muscle, induced by cyclic auxotonic deformations of coupled muscles. The muscle that undergoes predominant cyclic shortening shows force enhancement upon return to its isometric state in isolation, whereas average cyclic lengthening may decrease the individual muscle contractility. The mechanical responses are accompanied with slow and opposite changes in the shape and duration of both the action potential and Ca2+ transient in the cardiomyocytes of interacting muscles. Using the mathematical model we found that the contractility changes in interacting muscles follow the alterations in the sarcoplasmic reticulum loading in cardiomyocytes which result from the length-dependent Ca2+ activation of myofilaments and intracellular mechano-electrical feedback. The SFRIM phenomena unravel an important mechanism of cardiac functional auto-regulation applicable to the heart in norm and pathology, especially to hearts with severe electrical and/or mechanical dyssynchrony. © 2012 Elsevier Ltd

Comparing Five and Lower-Dimensional Grain Boundary Character and Energy Distributions in Copper : Experiment and Molecular Statics Simulation

The misorientation of 515 grain boundaries has been determined using electron backscatter diffraction data from an 18 μm thick copper foil with columnar grain structure and a preferential {110} surface orientation. The energy of the grain boundaries was determined from the dihedral angles in the vicinity of grain boundary thermal grooves. The experimental grain boundary energy vs. misorientation angle shows deep minima for the low-angle grain boundaries and small minima corresponding to the Σ3 and Σ9 grain boundaries. Only a small fraction of the coincidence site lattice grain boundaries demonstrate an increased occurrence frequency (compared to a random orientation distribution) and low energy. In parallel, the grain boundary energy for a subset of 400 symmetrical tilt grain boundaries was calculated using molecular statics simulations. There is a good agreement between the experiment and molecular statics modeling

Aroma Molecules as Dynamic Volatile Surfactants: Functionality Beyond the Scent

Understanding of non-equilibrium processes at dynamic interfaces is indispensable for advancing design and fabrication of solid state and soft materials.The research presented here unveils specific interfacial behavior of aroma molecules and justifies their usage as multifunctional volatile surfactants. As non-conventional volatile amphiphiles we study commercially available poorly water-soluble compounds from the classes of synthetic and essential flavor oils. Their distinctive feature is high dynamic interfacial activity, so that they decrease the surface tension of aqueous solutions on a time scale of milliseconds. Another potentially useful property of such amphiphiles is their volatility, so that they notably evaporate from interfaces on a time scale of seconds. This behavior allows for control of wetting and spreading processes. A revealed synergetic interfacial behavior of mixtures of conventional and volatile surfactants is attributed to a decrease of the adsorption barrier as a result of high statistical availability of new sites at the surface upon evaporation of the volatile component. Our results offer promising advantages in manufacturing technologies which involve newly creating interfaces, such as spraying, coating technologies, ink-jet printing, microfluidics, laundry, stabilization of emulsions in cosmetic and food industry, as well as in geosciences for controlling aerosols formation

The Influence of Co Additive on the Sintering, Mechanical Properties, Cytocompatibility, and Digital Light Processing Based Stereolithography of 3Y-TZP-5Al2O3 Ceramics

Nanocrystalline 3 mol% yttria-tetragonal zirconia polycrystal (3Y-TZP) ceramic powder containing 5 wt.% Al2O3 with 64 m2/g specific area was synthesized through precipitation method. Different amounts of Co (0–3 mol%) were introduced into synthesized powders, and ceramic materials were obtained by heat treatment in the air for 2 h at 1350–1550 °C. The influence of Co addition on the sintering temperature, phase composition, microstructure, mechanical and biomedical properties of the obtained composite materials, and on the resolution of the digital light processing (DLP) printed and sintered ceramic samples was investigated. The addition of a low amount of Co (0.33 mol%) allows us to decrease the sintering temperature, to improve the mechanical properties of ceramics, to preserve the nanoscale size of grains at 1350–1400 °C. The further increase of Co concentration resulted in the formation of both substitutional and interstitial sites in solid solution and appearance of CoAl2O4 confirmed by UV-visible spectroscopy, which stimulates grain growth. Due to the prevention of enlarging grains and to the formation of the dense microstructure in ceramic based on the tetragonal ZrO2 and Al2O3 with 0.33 mol% Co the bending strength of 720 ± 33 MPa was obtained after sintering at 1400 °C. The obtained materials demonstrated the absence of cytotoxicity and good cytocompatibility. The formation of blue CoAl2O4 allows us to improve the resolution of DLP based stereolithographic printed green bodies and sintered samples of the ceramics based on ZrO2-Al2O3. The developed materials and technology could be the basis for 3D manufacturing of bioceramic implants for medicine