UN calls for safe release of Indian engineers

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.

Tehran, Jan 12: Iranian police dispersed students chanting “radical” slogans during a Saturday gathering in Tehran to honour the 176 people killed when an Ukrainian airliner was mistakenly shot down, Fars news agency reported.

News agency correspondents said hundreds of students gathered early in the evening at Amir Kabir University, in downtown Tehran, to pay respects to those killed in the air disaster. The tribute later turned into an angry demonstration.

The students chanted slogans denouncing "liars" and demanded the resignation and prosecution of those responsible for downing the plane and allegedly covering up the accidental action.

Iran said Saturday that the Ukraine International Airlines Boeing 737 was “unintentionally” shot down on Wednesday shortly after taking off from Tehran's main airport. All 176 people on board died, mostly Iranians and Canadians, many of whom were students.

Fars, which is close to conservatives, said the protesting students chanted “destructive” and “radical” slogans. The news agency said some of the students tore down posters of Qasem Soleimani, the Iranian general killed on January 3 in a US drone strike on Baghdad.

Fars published pictures of demonstrators gathered around a ring of candles during the tribute and a picture of a torn poster bearing the image of a smiling Soleimani. It said that police "dispersed" them as they left the university and blocked streets, causing a traffic jam.

In an extremely unusual move, state television mentioned the protest, reporting that the students shouted "anti-regime" slogans.

A video purportedly of the protest circulated online showing police firing tear gas at protesters and a man getting up after apparently being hit in the leg by a projectile. It was not possible to verify the location of the video, or when it was filmed.

Iran's acknowledgement on Saturday that the plane had been shot down in error came after officials had for days categorically denied Western claims that it had been struck by a missile. The aerospace commander of Iran's Revolutionary Guards accepted full responsibility.

But Brigadier General Amirali Hajizadeh said the missile operator acted independently, shooting down the Boeing 737 after mistaking it for a "cruise missile".