US pastor burns Quran again

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.

China on Tuesday justified the killing of an army officer and two soldiers of India and accused Indian troops of crossing a disputed border between the two countries.

Foreign ministry spokesman Zhao Lijian said Indian troops crossed the border line twice on Monday, "provoking and attacking Chinese personnel, resulting in a serious physical confrontation between border forces on the two sides".

An Indian Army officer and two soldiers have been killed in a "violent face-off" with Chinese troops along the Line of Actual Control (LAC), disrupting the fragile peace talks.

"During the de-escalation process underway in the Galwan Valley, a violent face-off took place last night with casualties on both sides," the Indian Army said in a statement.
 

Beijing, Jun 4: Around 40 students and staff members of a primary school in China were stabbed by a security guard, official media reported today.

The incident happened at a school in China's Guangxi province, state-run China Daily said in a brief report.

Further details about the attack are awaited.

Knife attacks by disgruntled people have been taking place in different parts of China in the past few years, reported news agency Press Trust of India.

The attackers targeted mainly kindergarten and primary schools besides public transport, the news agency reported.