Investigating the effects of external pressure on coronary arteries with plaques and its role in coronary artery disease.

The risk of an acute coronary event stems from the amount and type of plaque present, as well as the fluid and structural dynamics in the coronary artery. If the plaque's structural stress exceeds the mechanical strength, the fibrous cap may rupture and lead to thrombosis. The patient is then likely to face a sudden myocardial infarction. An association between Coronary Heart Disease (CHD) and Sudden Cardiac Death (SCD) has been long recognised. For the first time, we are reporting a correlation between applied external pressure, such as Cardiopulmonary Resuscitation (CPR), coughing, sneezing, blowing one's nose, etc., and diseased coronary artery plaque via 3 D coronary artery models and two-way Fluid-Solid Interaction (FSI) models. Shear and von Mises stresses inside arteries and plaques have been shown to play a major role in plaque development, progression of disease, and the likelihood of plaque rupture. Our results show a drastic change in maximum shear (300%) and von Mises stresses (500%) with increasing external pressure. This change may indicate an onset of imminent plaque rupture. Furthermore, FSI modelling indicates a strong correlation between plaque thickness, location, and external pressure. With further clinical and simulation studies, this information could be helpful in understanding potential limit pressure in the CPR process for patients with CHD.

Quantum Magnetic Properties in Perovskite with Anderson Localized Artificial Spin-1/2.

Quantum magnetic properties in a geometrically frustrated lattice of spin-1/2 magnet, such as quantum spin liquid or solid and the associated spin fractionalization, are considered key in developing a new phase of matter. The feasibility of observing the quantum magnetic properties, usually found in geometrically frustrated lattice of spin-1/2 magnet, in a perovskite material with controlled disorder is demonstrated. It is found that the controlled chemical disorder, due to the chemical substitution of Ru ions by Co-ions, in a simple perovskite CaRuO3 creates a random prototype configuration of artificial spin-1/2 that forms dimer pairs between the nearest and further away ions. The localization of the Co impurity in the Ru matrix is analyzed using the Anderson localization formulation. The dimers of artificial spin-1/2, due to the localization of Co impurities, exhibit singlet-to-triplet excitation at low temperature without any ordered spin correlation. The localized gapped excitation evolves into a gapless quasi-continuum as dimer pairs break and create freely fluctuating fractionalized spins at high temperature. Together, these properties hint at a new quantum magnetic state with strong resemblance to the resonance valence bond system.