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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.

Beijing:  Around 5,000 people have signed up for the phase I clinical trial of recombinant novel coronavirus vaccine in Chinese city Wuhan where the virus first emerged late last year.

The recruitment for participants ended this week with nearly 5,000 volunteers signing up for the trial, state-run Beijing News reported on Wednesday.

A single-centre, open and dose-escalation phase I clinical trial for recombinant novel coronavirus vaccine (adenoviral vector) will be tested in healthy adults aged between 18 and 60 years, according to the ChiCTR (China Clinical Trial Register).

The trial, led by experts from the Academy of Military Medical Sciences, gained its approval on March 16 and the research is expected to last half a year.

Requiring at least 108 participants, the trial will be conducted in Wuhan, capital of Hubei province, the region worst-affected by the virus in the country, state-run China Daily reported.

Participants will experience 14-day quarantine restrictions after being vaccinated and their health condition will be recorded every day.

Chinese scientists are hastening the development of COVID-19 vaccines through five approaches --- inactivated vaccines, genetic engineering subunit vaccines, adenovirus vector vaccines, nucleic acid vaccines and vaccines using attenuated influenza virus as vectors.

So far, most teams are expected to complete preclinical research in April and some are moving forward faster, Wang Junzhi, an academician with the Chinese Academy of Engineering said.

Wang noted that research and development of COVID-19 vaccines in China is not slower than foreign counterparts and has been carried out in a scientific, standardised and orderly way.

China has stepped up the process to finalise vaccines to counter COVID-19 after Kaiser Permanente research facility in Seattle and Washington stole the march and began human trials.

China lifted tough restrictions on the Hubei province on Wednesday after a months-long lockdown as the country reported no new domestic cases.

But there were another 47 imported infections from overseas, the National Health Commission said. In total, 474 imported infections have been diagnosed in China -- mostly Chinese nationals returning home.

Washington, Jan 12: The US State Department has described the recent visit of envoys of 15 countries to Jammu and Kashmir as an "important step" but expressed concern over the continued detention of political leaders and restrictions on internet in the region.

Alice Wells, the Acting Assistant Secretary of State for South Asia, tweeted on Saturday that she was "closely following" the visit of the envoys to Kashmir, describing it an "important step".

Wells, who will be visiting India this week, added: "We remain concerned by detention of political leaders and residents and Internet restrictions. We look forward to a return to normalcy."

The group of diplomats made a two-day visit to the Union Territory on Thursday and Friday to see the conditions thereafter Jammu and Kashmir's special constitutional status was removed last August.

While some US politicians and media have criticised the action by Prime Minister Narendra Modi's government, the US has officially appeared to support the abrogation of the Constitution's Article 370 on the special status.

Last October, Wells told the House of Representatives Subcommittee on Asia and the Pacific that the State Department supported the objectives behind it, while not directly mentioning the abrogation.

"The Indian government has argued that its decision on Article 370 was driven by a desire to increase economic development, reduce corruption, and uniformly apply all national laws in Jammu and Kashmir, particularly in regard to women and minorities.

"While we support these objectives, the Department remains concerned about the situation in the Kashmir Valley, where daily life for the nearly eight million residents has been severely impacted since August 5," she had said.

Washington has banked on India's democratic institutions - the judiciary and public debates - being able to steer the country.

Bearing this out, the Supreme Court last week ordered the government to review its decision to shut down the internet in Kashmir, which it declared was a fundamental right, thus taking a step to address Wells's concern.