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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.

London, Jun 25: British Prime Minister Boris Johnson has called on India and China to engage in dialogue to sort out their border issues as he described the escalation in eastern Ladakh as "a very serious and worrying situation" which the UK is closely monitoring.

The first official statement of Mr Johnson came during his weekly Prime Minister's Questions (PMQs) in the House of Commons on Wednesday.

Responding to Conservative Party MP Flick Drummond on the implications for British interests of a dispute between a "Commonwealth member and the world's largest democracy on the one side, and a state that challenges our notion of democracy on the other," he described the escalation in eastern Ladakh as "a very serious and worrying situation", which the UK is "monitoring closely".

"Perhaps the best thing I can say... is that we are encouraging both parties to engage in dialogue on the issues on the border and sort it out between them," the Prime Minister said.

In a statement in New Delhi on Wednesday, the Ministry of External Affairs (MEA) said India and China have agreed that expeditious implementation of the previously agreed understanding on disengagement of troops from standoff points in eastern Ladakh would help ensure peace and tranquillity in the border areas.

During the diplomatic talks between India and China, the situation in the region was discussed in detail and the Indian side conveyed its concerns over the violent face-off in Galwan Valley on June 15. Twenty Indian Army personnel were killed in the clash. There were reports of several casualties for the Chinese army too, but China hasn't declared any official number yet.

The talks were held in the midst of escalating tension between the two countries following the violent clashes in Galwan Valley on June 15.

The Indian and Chinese armies are engaged in the standoff in Pangong Tso, Galwan Valley, Demchok and Daulat Beg Oldie in eastern Ladakh. A sizable number of Chinese Army personnel even transgressed into the Indian side of the Line of Actual Control in several areas including Pangong Tso.

Sydney, Jan 6: Reserve troops fanned out across fire-ravaged regions in three Australian states on Monday after a horror weekend, as the government pledged $1.4 billion over two years to help recover from the devastating months-long crisis.

Catastrophic bushfires have turned swathes of land into smouldering, blackened hellscapes and destroyed an area about the size of the island of Ireland, according to official figures, with authorities warning the disaster still has weeks or months to run.

Prime Minister Scott Morrison, whose government has been criticised for its slow response to the emergency, pledged Australian $2 billion ($1.4 billion) of taxpayer money for a national recovery fund.

"It's a long road ahead and we will be with these communities every step of the way as they rebuild," Morrison said.

Firefighters joined by fresh teams from the US and Canada were taking advantage of rainy and cooler conditions to tackle out-of-control blazes ahead of rising temperatures forecast later this week.

In the biggest-ever call up of reserves, military teams were deployed across eastern Australia to help emergency services assess the damage, restore power and deliver supplies of food, water and fuel to cut-off communities.

For the first time in Australian history the government also deployed its medical assistance team, normally sent to other nations to lend support in the aftermath of their disasters to help evacuees.

"There is no room for complacency, especially as we have over 130 fires burning across (New South Wales) state still," Premier of New South Wales state Gladys Berejiklian said on Monday.

New normal

Almost five million hectares (50,000 square kilometres) have been razed across New South Wales and more than 1.2 million hectares in Victoria since late September, officials said.

That took the total amount of land burnt close to eight million hectares, around the size of the island of Ireland or South Carolina.

Twenty-four people have lost their lives so far, with over 1,800 homes damaged.

Two people are missing in New South Wales, the nation's most populous state.

In Victoria, Premier Daniel Andrews established a bushfire recovery agency to help devastated towns. It will be a permanent body, he said, as intense fires will become commonplace.

"We should just be honest about the fact that we're going to see more and more fires, more and more damage as each fire season comes... this is the new normal," Andrews told reporters.

The chair of the newly established Victoria state's bushfire appeal fund, Pat McNamara, added that this year's summer bushfire season was a "creeping disaster".

"We're still not even into what we would regard as the peak of the fire season," McNamara told national broadcaster ABC.

In the usually picturesque southeastern town of Eden, Holly Spence said she spent more than 12 hours defending her family's farm on Saturday, less than a week after saving it on New Year's Eve.

"We don't want to go through this for a third time," the 28-year-old told AFP.

Fiona Kennelly, 50, who evacuated with 24 members of her extended family to a motel outside Eden, said she was relieved the easing conditions allowed them to get some respite from the crisis.

"It's good to see daylight at the right time again," she told AFP, adding that the skies had been turning pitch-black in the afternoons.

Public anger

The impact of the bushfires has spread beyond affected communities, with heavy smoke engulfing the country's second-largest city Melbourne and the national capital Canberra.

Some government departments were shut in Canberra as the city's air quality was once-again ranked the world's poorest, according to independent online air-quality index monitor Air Visual.

The disaster has sparked growing public anger with Morrison. Rallies are planned on Friday to call on his government to step up efforts to tackle climate change, which experts say have helped fuel the fires.

In Los Angeles, Hollywood superstar Russell Crowe said he was back home fighting the fires and that the disaster was "climate change-based".

"We need to act on science, move our global workforce to renewable energy and respect our planet for the unique and amazing place it is. That way, we all have a future," he said in a message read out by Jennifer Aniston.

Australian actress Cate Blanchett praised the volunteer firefighters battling the blazes, adding: "When one country faces a climate disaster, we all face a climate disaster. We're in it together."