Airflows generated by an impacting drop.

A drop impacting a solid surface with sufficient velocity will splash and emit many small droplets. However, lowering the ambient air pressure suppresses splashing completely. This effect, robustly found for different liquid and substrate properties, raises the fundamental question of how air affects a spreading drop. In a combined experimental and numerical study we characterize the flow of air induced by the drop after it hits the substrate, using a modified Schlieren optics technique combined with high-speed video imaging and Lattice-Boltzmann simulations. Our experiments reveal the emergence of air structures on different length scales. On large scales, the airflow induced in the drop's wake leads to vortex structures due to interaction with the substrate. On smaller scales, we visualize a ring structure above the outer edge of the spreading liquid generated by the spreading of the drop. Our simulations reveal the interaction between the wake vorticity and the flows originating from the rapidly escaping air from below the impacting drop. We show that the vorticity is governed by a balance between inertial and viscous forces in the air, and is unrelated to the splashing threshold.

Computational investigation of the role of ventricular remodelling in HFpEF: The key to phenotype dissection.

Recent clinical studies have reported that heart failure with preserved ejection fraction (HFpEF) can be divided into two phenotypes based on the range of ejection fraction (EF), namely HFpEF with higher EF and HFpEF with lower EF. These phenotypes exhibit distinct left ventricle (LV) remodelling patterns and dynamics. However, the influence of LV remodelling on various LV functional indices and the underlying mechanics for these two phenotypes are not well understood. To address these issues, this study employs a coupled finite element analysis (FEA) framework to analyse the impact of various ventricular remodelling patterns, specifically concentric remodelling (CR), concentric hypertrophy (CH), and eccentric hypertrophy (EH), with and without LV wall thickening on LV functional indices. Further, the geometries with a moderate level of remodelling from each pattern are subjected to fibre stiffening and contractile impairment to examine their effect in replicating the different features of HFpEF. The results show that with severe CR, LV could exhibit the characteristics of HFpEF with higher EF, as observed in recent clinical studies. Controlled fibre stiffening can simultaneously increase the end-diastolic pressure (EDP) and reduce the peak longitudinal strain (ell) without significant reduction in EF, facilitating the moderate CR geometries to fit into this phenotype. Similarly, fibre stiffening can assist the CH and 'EH with wall thickening' cases to replicate HFpEF with lower EF. These findings suggest that potential treatment for these two phenotypes should target the bio-origins of their distinct ventricular remodelling patterns and the extent of myocardial stiffening.

Whole-body exposure to filtered fraction of diesel exhaust induced localized testicular damage through attenuated functional response of glutathione-s-transferase in adult male Wistar rats.

The possible vulnerability of the male reproductive system to environmental pollutants such as air pollution necessitates a thorough investigation of the underlying mechanisms involved in the dysregulation of male reproductive function. The present study was designed to investigate the influence of the filtered fraction of diesel exhaust (predominantly comprising gases) on male reproductive function in Wistar rat model. Adult male rats were randomly assigned into three groups (n=8/group): Control (unexposed) group (CG-A), the Clean air group in WBE chamber (CAG-A), and Filtered diesel exhaust group in WBE chamber (FDG-A). The exposure protocol for CAG-A and FDG-A was 6 h/day x 5d/week x 6 weeks,evaluation of sperm parameters, testicular histopathology, quantification of hormones (testosterone, LH, FSH, 17ß-Estradiol, and prolactin), and GST levels were performed. Results showed that WBE to FDE leads to a significant decline in sperm concentration (p=0.008, CG-A vs FDG-A; p=0.014, CAG-A vs FDG-A), motility (p=0.008, CG-A vs FDG-A; p=0.029, CAG-A vs FDG-A), serum testosterone (p=0.024, CG-A vs FDG-A; p=0.007, CAG-A vs FDG-A), testicular testosterone (p=0.008, CG-A vs FDG-A; p=0.028, CAG-A vs FDG-A), 17ß-Estradiol (p=0.007, CG-A vs FDG-A), and GST levels (p=0.0002, CG-A vs FDG-A; p=0.0019, CAG-A vs FDG-A). These findings demonstrate the disruption of testosterone-estradiol balance in the intratesticular milieu without significant alterations in other principal pituitary hormones in adult rats exposed to FDE. The predominant presence of gaseous components in FDE can cause testicular damage due to oxidative imbalance. This underscores the causality of FDE exposure and impaired male reproductive outcomes.

Surface instability of a thin electrolyte film undergoing coupled electroosmotic and electrophoretic flows in a microfluidic channel.

We consider the stability of a thin liquid film with a free charged surface resting on a solid charged substrate by performing a general Orr-Sommerfeld (O-S) analysis complemented by a long-wave (LW) analysis. An externally applied field generates an electroosmotic flow (EOF) near the solid substrate and an electrophoretic flow (EPF) at the free surface. The EPF retards the EOF when both the surfaces have the same sign of the potential and can even lead to the flow reversal in a part of the film. In conjunction with the hydrodynamic stress, the Maxwell stress is also considered in the problem formulation. The electrokinetic potential at the liquid-air and solid-liquid interfaces is modelled by the Poisson-Boltzmann equation with the Debye-Hückel approximation. The O-S analysis shows a finite-wavenumber shear mode of instability when the inertial forces are strong and an LW interfacial mode of instability in the regime where the viscous force dominates. Interestingly, both the modes are found to form beyond a critical flow rate. The shear (interfacial) mode is found to be dominant when the film is thick (thin), the electric field applied is strong (weak), and the zeta-potentials on the liquid-air and solid-liquid interfaces are high (small). The LW analysis predicts the presence of the interfacial mode, but fails to capture the shear mode. The change in the propagation direction of the interfacial mode with the zeta-potential is predicted by both O-S and LW analyses. The parametric range in which the LW analysis is valid is thus demonstrated.