Obama leaves for India

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.

Hong Kong, Jun 10: The Hong Kong police on Wednesday said they had arrested 53 people during demonstrations on Tuesday evening which were called to mark the one-year anniversary of the protest against a bill proposing extraditions to mainland China. That protest grew into a pro-democracy movement and sparked seven months of protests against Beijing's rule.

Hundreds of activists took to the streets in Hong Kong yesterday, at times blocking roads in the heart of the city, before police fired pepper spray to disperse crowds, Al Jazeera reported.

The police informed that 36 males and 17 females were arrested for offenses including unlawful assembly and disorderly conduct.

Protesters had defied a ban on gatherings of more than eight people introduced by the Hong Kong government to prevent the spread of the coronavirus.

"Lawful protests are always respected, but unlawful acts are to be rejected. Please stop breaking the law," police said in a tweet.

More protests are being planned in the coming days, with pro-democracy supporters fearing the proposed national security legislation will stifle freedoms in the city.

While details of the security law or how it will operate have yet to be revealed, authorities in Beijing and Hong Kong have said there is no cause for concern and the legislation will target a minority of "troublemakers".

But critics say the law would destroy the civil liberties Hong Kong residents enjoy under the "one country, two systems" agreement put in place when the United Kingdom handed the territory back to China in 1997. The agreement is set to end in 2047.

Japan had already issued a statement independently expressing serious concern about Beijing's move on May 28, the day China approved the decision and called in the Chinese ambassador to convey its view.

The United States, Britain, Australia, and Canada also condemned the move, with Washington saying it would revoke Hong Kong's special trading status granted under a 1992 law on the condition that the city retains key freedoms and autonomy.

China blames the protests in part on foreign intervention and is rushing to enact the national security law aimed at curbing secessionist and subversive activities in Hong Kong.

Paris, Jun 28: More than 10 million cases of the new coronavirus have been officially declared around the world, half of them in Europe and the United States, according to an AFP tally on Sunday based on official sources.

At least 10,003,942 infections, including 498,779 deaths, have been registered globally.

Europe remains the hardest hit continent with 2,637,546 cases including 195,975 fatalities, while the United States has 2,510,323 infections including 125,539 deaths.

The rate of infections worldwide continues to rise, with one million new cases recorded in just six days.

The tallies, using data collected by AFP from national authorities and information from the World Health Organization (WHO), probably reflect only a fraction of the actual number of infections.

Many countries are testing only symptomatic or the most serious cases and some do not have the capacity to carry out widescale testing.