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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, May 21: Prime Minister Narendra Modi on Thursday paid tributes to Rajiv Gandhi on his death anniversary.

Former prime minister Gandhi was assassinated on this day in 1991 in Tamil Nadu's Sriperumbudur by a suicide bomber during an election campaign.
 
"On his death anniversary, tributes to former PM Shri Rajiv Gandhi," Modi tweeted.

New Delhi, Mar 4: A court in Delhi on Wednesday convicted expelled BJP MLA Kuldeep Singh Sengar of culpable homicide not amounting to murder in the death of the Unnao rape victim's father.

District judge Dharmesh Sharma said Sengar had no intention of killing the victim's father. “He was beaten in a brutal manner that led to his death,” the judge said.

The court had sent Sengar to jail on December 20 for the “remainder of his natural biological life” for raping the woman in 2017, when she was a minor.

The Central Bureau of Investigation (CBI) had examined 55 witnesses in support of the case and the defence examined nine witnesses.

The court had recorded the statements of the rape survivor's uncle, mother, sister and one of her father's colleague who claimed to be an eyewitness to the incident.

Charges were framed against Sengar, his brother Atul, Bhadauria, sub-inspector Kamta Prasad, constable Amir Khan and six others in the case.

The case was transferred to Delhi from a trial court in Uttar Pradesh on the directions of the Supreme Court on August 1 last year.

In July, 2019 a truck rammed into the car the rape victim was travelling in with some family members and her lawyer.

Two of her aunts died in the incident. She was airlifted from a hospital in Lucknow and to AIIMS in Delhi.

The victim has been provided accommodation in Delhi and is under CRPF protection.