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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, Jan 15: The Delhi government Wednesday told the high court that execution of the death row convicts in the Nirbhaya gangrape and murder case will not take place on January 22 as a mercy plea has been filed by one of them.

The four convicts -- Vinay Sharma (26), Mukesh Kumar (32), Akshay Kumar Singh (31) and Pawan Gupta (25) -- are to be hanged on January 22 at 7 am in Tihar jail. A Delhi court had issued their death warrants on January 7.

Justices Manmohan and Sangita Dhingra Sehgal were told by the Delhi government and the Centre that the petition filed by convict Mukesh, challenging his death warrant, was premature.

The Delhi government and the prison authorities informed the court that under the rules, it will have to wait for the mercy plea to be decided before executing the death warrant.

They also said that none of the four convicts can be executed on January 22 unless the present mercy plea is decided.

The Supreme Court had on Tuesday dismissed the curative pleas of Mukesh and Vinay.

The mercy plea hearing began Wednesday morning and will continue in the afternoon.

New Delhi, May 29: With the highest spike of 7,466 more COVID-19 cases and 175 deaths reported in the past 24 hours, India's COVID-19 tally reached 1,65,799 on Friday, according to the Union Ministry of Health and Family Welfare.

The number of active coronavirus cases stands at 89,987 while 71,105 people have been cured or recovered and one patient has migrated, it said. The death toll due to the infection has reached 4,706 in the country.

Maharashtra is the worst affected state with 59,546 cases. Tamil Nadu has recorded as many as 19,372 cases while Gujarat and Delhi have recorded 15,562 and 16,281 coronavirus cases respectively.