Clinton 'absolutely ready' to be commander-in-chief: Michelle

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.

Washington D.C, Jul 8:  US Secretary of State, Mike Pompeo on Tuesday (local time) announced visa restrictions on some Chinese officials under the Reciprocal Access to Tibet Act, 2018.

"Today I am announcing visa restrictions on PRC government and Chinese Communist Party officials determined to be "substantially involved in the formulation or execution of policies related to access for foreigners to Tibetan areas," pursuant to the Reciprocal Access to Tibet Act of 2018," Pompeo said.

"Access to Tibetan areas is increasingly vital to regional stability, given the PRC's human rights abuses there, as well as Beijing's failure to prevent environmental degradation near the headwaters of Asia's major rivers," he said.

The US Secretary of State pointed out that Beijing has continued "systematically to obstruct travel to the Tibetan Autonomous Region (TAR) and other Tibetan areas" by U.S. diplomats and other officials, journalists, and tourists, while PRC officials and other citizens enjoy far greater access to the United States.

"The United States will continue to work to advance the sustainable economic development, environmental conservation, and humanitarian conditions of Tibetan communities within the People's Republic of China and abroad," he said.

Pompeo said US also remains "committed to supporting meaningful autonomy for Tibetans, respect for their fundamental and unalienable human rights, and the preservation of their unique religious, cultural, and linguistic identity".

"In the spirit of true reciprocity, we will work closely with the U.S. Congress to ensure U.S. citizens have full access to all areas of the People's Republic of China, including the TAR and other Tibetan areas," he said.

Paris, Jun 13: The coronavirus pandemic has killed 425,000 people since it emerged in China late last year, according to an AFP tally of official sources at 0130 GMT on Saturday.

A total of 425,282 deaths have now been recorded from 7,632,517 cases.

Europe has registered 186,843 deaths from 2,363,538 cases, but the epidemic is progressing most rapidly in Latin America, where there have been a total of 76,343 deaths recorded from 1,569,938 cases.

The United States remains the country with the most recorded deaths at 114,643, ahead of Brazil which on Friday became the second worst-hit nation with 41,828 deaths. Britain is next with 41,481 deaths, followed by Italy (34,223) and France (29,374).