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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.

Washington, Feb 1: The Indian economy experienced some abrupt slowdown in 2019 due to turbulence in non-banking financial institutions and major reform measures such as GST and demonetisation, but it is not in a recession, IMF Managing Director Kristalina Georgieva has said.

"The Indian economy indeed has experienced an abrupt slowdown in 2019. We had to revise our growth projections, downwards to four percent for last year. We are expecting 5.8 per cent (growth rate) in 2020 and then an upward trajectory to 6.5 percent in 2021," Georgieva told a group of foreign journalists here on Friday.

"It appears that the main reason for this slowdown was the non-banking financial institutions experiencing a turbulence," she said on the eve of Union Finance Minister Nirmala Sitharaman presenting the annual budget in Parliament on Saturday.

She said India had undertaken some important reforms that over the longer term would be beneficial for the country, but they do have some short-term impact.

"For example, coming with the unified tax system, and the demonetisation that took place. These are steps that over time are beneficial, but of course they might, might be somewhat disruptive over short term," Georgieva said in response to a question.

The International Monetary Fund (IMF) Managing Director said that there is not a lot of fiscal space in India. “But we also recognise that the policies of the government on that side, on the fiscal side have been prudent. We will see how the reading of the budget, the submission of the budget goes, tomorrow,” she said.

In the medium-term, she said, the IMF remains optimistic about India. “This is why we see that upswing potential for the growth in the country,” she said.

Georgieva said that the current economic slowdown cannot be described as a recession. "No.... You're far from that. But it is a significant slowdown, not the recession," she said.

The IMF managing Director noted that the consumption in India also slowed down and that contributed to the overall slowdown in the economy. The IMF would be keen to see what India does to get relatively sound macroeconomic fundamentals to pay off in terms of better growth trajectory, she said ahead of the budget.

One thing that is important for India is that budgetary revenue have been below target. "The country knows that. The finance minister knows it. They need to increase budgetary revenue collection so they can improve their fiscal position. I said it's tight on the spending side, but I also want to stress that there is room to improve collection on the revenue side," she said.