Trump fires chief US lawyer who defied him on migrant ban

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.

Aboard Air Force One, Jan 6: US President Donald Trump threatened sanctions against Baghdad on Sunday after Iraq's parliament called on US troops to leave the country, and the president said if troops did leave, Baghdad would have to pay Washington for the cost of the air base there.

"We have a very extraordinarily expensive air base that's there. It cost billions of dollars to build, long before my time. We're not leaving unless they pay us back for it," Trump told reporters on Air Force One.

Trump said that if Iraq asked US forces to leave and it was not done on a friendly basis, "we will charge them sanctions like they've never seen before ever. It'll make Iranian sanctions look somewhat tame."

Geneva, Jul 2: The World Health Organization (WHO) has estimated the overall number of coronavirus cases globally at 10,357,662, with 508,055 people having died from the disease.

The UN health agency said in the situation report published on late Wednesday that 163,939 new cases had been recorded in the past day, while further 4,188 patients had died.

Americas continue to lead the count with over 5.2 million cases, followed by Europe with more than 2.7 million.

The WHO declared the COVID-19 outbreak a pandemic on March 11.