Electroporation safety factor of 300 nanosecond and 10 millisecond defibrillation in Langendorff-perfused rabbit hearts

Aims Recently, a new defibrillation modality using nanosecond pulses was shown to be effective at much lower energies than conventional 10 millisecond monophasic shocks in ex vivo experiments. Here we compare the safety factors of 300 nanosecond and 10 millisecond shocks to assess the safety of nanosecond defibrillation. Methods and results The safety factor, i.e. the ratio of median effective doses (ED50) for electroporative damage and defibrillation, was assessed for nanosecond and conventional (millisecond) defibrillation shocks in Langendorff-perfused New Zealand white rabbit hearts. In order to allow for multiple shock applications in a single heart, a pair of needle electrodes was used to apply shocks of varying voltage. Propidium iodide (PI) staining at the surface of the heart showed that nanosecond shocks had a slightly lower safety factor (6.50) than millisecond shocks (8.69), p = 0.02; while PI staining cross-sections in the electrode plane showed no significant difference (5.38 for 300 ns shocks and 6.29 for 10 ms shocks, p = 0.22). Conclusions In Langendorff-perfused rabbit hearts, nanosecond defibrillation has a similar safety factor as millisecond defibrillation, between 5 and 9, suggesting that nanosecond defibrillation can be performed safely.

Parametric study of multiple shock-wave/turbulent-boundary-layer interactions with a Reynolds stress model

The flow of high-speed air in ducts may result in the occurrence of multiple shock-wave/boundary-layer interactions. Understanding the consequences of such interactions, which may include distortion of the velocity field, enhanced turbulence production, and flow separation, is of great importance in understanding the operating limits and performance of a number of systems, for example, the high-speed intake of an air-breathing missile. In this paper, the results of a computational study of multiple shock-wave/boundary-layer interactions occurring within a high-speed intake are presented. All of the results were obtained using the in-house computational fluid dynamics solver of Glasgow University, HMB3. First simulations of a Mach $$M=1.61$$ M = 1.61 multiple shock-wave/boundary-layer interaction in a rectangular duct were performed. The $$M=1.61$$ M = 1.61 case, for which experimental data is available, was used to establish a robust numerical approach, particularly with respect to initial and boundary conditions. A number of turbulence modelling strategies were also investigated. The results suggest that Reynolds-stress-based turbulence models are better suited than linear eddy-viscosity models. This is attributed to better handling of complex strain, in particular modelling of the corner separation. The corner separations affect the separation at the centre of the domain which in turn alters the structure of the initial shock and the subsequent interaction. Having established a robust numerical approach, the results of a parametric study investigating the effect of Mach number, Reynolds number, and confinement on the baseline solution are then presented. Performance metrics are defined to help characterize the effect of the interactions. The results suggest that reduced flow confinement is beneficial for higher-pressure recovery.

COVID-19

This paper analyzes the economic impact of the COVID-19 pandemic on a small tourism dependent open economy. The lockdown affected both the demand side and the supply side of the economy, as production of goods and services dramatically dropped due to firms’ shutdowns, broken supply chains, or bankruptcies, and aggregate demand diminished due to lower consumer confidence and investment cutbacks, accompanied by a dramatic fall in international tourism demand, in particular due to travel restrictions. We look on these supply and demand changes through the lens of a macroeconomic model of a small open economy, comprising an industrial and a tourism sector. For this purpose, we modify Schubert’s (2013) model by introducing a multiple shock which reflects (i) reduced sectoral productivities due to, e.g., broken supply chains, (ii) a drop in employment due to firms’ lockdowns, and (iii) a sharp decline in international tourism demand. We find that the multiple shock leads to an immediate drop in GDP and a boost of the short-run unemployment rate, followed by a gradual transition back to steady state. The adverse effects on the tourism sector are the more severe the slower international tourism demand reverts to pre-crisis levels, but they do not strongly spill over to the industrial sector. Furthermore, even if international tourism demand recovers quickly, the effects on the industrial sector barely change. The length of the industrial sector’s recovery basically depends on the speed of restoring its sectoral productivity rather than on international tourism demand. The reason for this result can be found in the absorbing effect of the relative price of tourism services in terms of the industrial good.

Multiwavelength investigation of extended green object G19.88-0.53: revealing a protocluster

ABSTRACT A multiwavelength analysis of star formation associated with the extended green object, G19.88-0.53 is presented in this paper. With multiple detected radio and millimetre components, G19.88-0.53 unveils as harbouring a protocluster rather than a single massive young stellar object. We detect an ionized thermal jet using the upgraded Giant Meterwave Radio Telescope, India, which is found to be associated with a massive, dense and hot ALMA 2.7 mm core driving a bipolar CO outflow. Near-infrared spectroscopy with UKIRT–UIST shows the presence of multiple shock-excited H2 lines concurrent with the nature of this region. Detailed investigation of the gas kinematics using ALMA data reveals G19.88-0.53 as an active protocluster with high-mass star-forming components spanning a wide evolutionary spectrum from hot cores in accretion phase to cores driving multiple outflows to possible UCH ii regions.