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London, May 20: The current physical distancing guidelines of 6 feet may be insufficient to prevent COVID-19 transmission, according to a study which says a mild cough in low wind speeds can propel saliva droplets by as much as 18 feet.

Researchers, including those from the University of Nicosia in Cyprus, said a good baseline for studying the airborne transmission of viruses, like the one behind the COVID-19 pandemic, is a deeper understanding of how particles travel through the air when people cough.

In the study, published in the journal Physics of Fluids, they said even with a slight breeze of about four kilometres per hour (kph), saliva travels 18 feet in 5 seconds.

"The droplet cloud will affect both adults and children of different heights," said study co-author Dimitris Drikakis from the University of Nicosia.

According to the scientists, shorter adults and children could be at higher risk if they are located within the trajectory of the saliva droplets.

They said saliva is a complex fluid, which travels suspended in a bulk of surrounding air released by a cough, adding that many factors affect how saliva droplets travel in the air.

These factors, the study noted, include the size and number of droplets, how they interact with one another and the surrounding air as they disperse and evaporate, how heat and mass are transferred, and the humidity and temperature of the surrounding air.

In the study, the scientists created a computer simulation to examine the state of every saliva droplet moving through the air in front of a coughing person.

The model considered the effects of humidity, dispersion force, interactions of molecules of saliva and air, and how the droplets change from liquid to vapour and evaporate, along with a grid representing the space in front of a coughing person.

Each grid, the scientists said, holds information about variables like pressure, fluid velocity, temperature, droplet mass, and droplet position.

The study analysed the fates of nearly 1,008 simulated saliva droplets, and solved as many as 3.7 million equations.

"The purpose of the mathematical modelling and simulation is to take into account all the real coupling or interaction mechanisms that may take place between the main bulk fluid flow and the saliva droplets, and between the saliva droplets themselves," explained Talib Dbouk, another co-author of the study.

However, the researchers added that further studies are needed to determine the effect of ground surface temperature on the behaviour of saliva in air.

They also believe that indoor environments, especially ones with air conditioning, may significantly affect the particle movement through air.

This work is important since it concerns safety distance guidelines, and advances the understanding of the transmission of airborne diseases, Drikakis said.

New Delhi, Mar 16: Reliance Group Chairman Anil Ambani has been summoned by the ED in connection with its money laundering probe against Yes Bank promoter Rana Kapoor and others, officials said on Monday.

They said Ambani was asked to depose at the Enforcement Directorate office in Mumbai on Monday as his group companies are among the big entities whose loans went bad after borrowing from the crisis-hit bank.

The officials said Ambani, 60, has sought exemption from appearance on some personal grounds and he may be issued a new date.

Ambani's group companies are stated to have taken loans of about Rs 12,800 crore from the bank that turned NPAs.

Finance Minister Nirmala Sitharaman had said in a March 6 press conference that the Anil Ambani Group, Essel, ILFS, DHFL and Vodafone were among the stressed corporates Yes Bank had exposure to.

Officials said promoters of all the big companies who had taken large loans from the beleaguered bank which later turned bad are being summoned for questioning in the case to take investigation forward.

Ambani's statement will be recorded under the Prevention of Money Laundering Act (PMLA) upon deposition, they said.

Kapoor, 62, is at present in ED custody after he was arrested by the central probe agency early this month.

The ED has accused Kapoor, his family members and others of laundering "proceeds of crime" worth Rs 4,300 crore by receiving alleged kickbacks in lieu of extending big loans through their bank that later turned NPA.