KT Irfan first Indian athlete to qualify for Tokyo 2020

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.

Melbourne, Jan 23: Sania Mirza's return to her first Grand Slam after a two-year break was cut short on Thursday when the former world number one was forced to retire midway through her first round match in women's doubles at the Australian Open due to a calf injury.

India's Mirza, who won six Grand Slam doubles titles, took a break from the game after the China Open in October 2017 and gave birth to her son a year later.

The 33-year-old made a winning return to the WTA Tour at this month's Hobart International with Ukrainian Nadiia Kichenok, picking up her 42nd WTA doubles title and the first since winning the women's doubles in Brisbane in 2017.

Mirza said she strained her calf muscle in her right leg during the Hobart final.

"It just got worse in the match. It was bit of a bad strain, but I had a few days off," she told reporters. "So I obviously had to try to do whatever I could to try to get on the court.

"It felt okay when I went on the court, but it was tough to move right. I just felt like I'm gonna tear it or something pretty bad."

Mirza won her first Grand Slam in mixed doubles at the Australian Open in 2009 and also bagged the women's doubles in 2016.

Mirza always believed there was tennis left in her which inspired her comeback, she told Reuters on Sunday.

She had already pulled out of the Australian Open mixed doubles, where she was to partner compatriot Rohan Bopanna.

Mirza and Kichenok were trailing the Chinese pair of Xinyun Han and Lin Zhu 6-2 1-0 on Thursday when the Indian had to call it quits due to the injury.

"As a tennis player you want to compete, it is the Grand Slam. If it's any other tournament, you would probably take a call and be like 'I don't want to risk it'," she said.

Mirza, who is married to former Pakistan cricket captain Shoaib Malik, said she would take two weeks to recover and was hoping to play at next month's Dubai championships.

"When you play a professional sport, injuries are really part of it. And it's something that you have to accept," she said. "Sometimes the timing is really not ideal, it's tough that it happened in a Grand Slam, or just before a Grand Slam."