Thai woman gives birth mid-air, flight makes emergency landing in Kolkata

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, Jan 9: The U.S. and Iran stepped back from the brink of possible war Wednesday as President Donald Trump signaled he would not retaliate militarily for Iran's missile strikes on Iraqi bases housing U.S. troops. No one was harmed in the strikes, but U.S. forces in the region remained on high alert.

Speaking from the White House, Trump seemed intent on deescalating the crisis, which spiralled after he authorized the assassination of Iran's top general, Qassem Soleimani. Iran responded overnight by firing more than a dozen missiles at two installations in Iraq, its most direct assault on America since the 1979 seizure of the U.S. Embassy in Tehran.

Trump's takeaway was that “Iran appears to be standing down, which is a good thing for all parties concerned and a very good thing for the world.”

The region remained on edge, however, and American troops including a quick-reaction force dispatched over the weekend were on high alert. Hours after Trump spoke, an ‘incoming’ siren went off in Baghdad's Green Zone after what seemed to be small rockets “impacted” the diplomatic area, a Western official said. There were no reports of casualties.

Iran's Supreme Leader Ayatollah Ali Khamenei said the overnight strike was not necessarily the totality of Iran's response. “Last night they received a slap,” Khamenei said. “These military actions are not sufficient (for revenge). What is important is that the corrupt presence of America in this region comes to an end.”

The strikes had pushed Tehran and Washington perilously close to all-out conflict and left the world waiting to see whether the American president would respond with more military force. Trump, in his nine-minute, televised address, spoke of a robust U.S. military with missiles that are “big, powerful, accurate, lethal and fast.'' But then he added: “We do not want to use it."

Iran for days had been promising to respond forcefully to Soleimani's killing, but its limited strike on two bases--one in the northern Iraqi city of Irbil and the other at Ain al-Asad in western Iraq--appeared to signal that it too was uninterested in a wider clash with the U.S. Foreign minister Mohammad Javad Zarif tweeted that the country had “concluded proportionate measures in self-defence.”

Trump said the U.S. was “ready to embrace peace with all who seek it.” That marked a sharp change in tone from his warning a day earlier that “if Iran does anything that they shouldn't be doing, they're going to be suffering the consequences, and very strongly.”

Trump opened his remarks at the White House by reiterating his promise that “Iran will never be allowed to have a nuclear weapon.” Iran had announced in the wake of Soleimani's killing that it would no longer comply with any of the limits on uranium enrichment in the 2015 nuclear deal crafted to keep it from building a nuclear device.

The president, who had earlier pulled the U.S. out of the deal, seized on the moment of calm to call for negotiations toward a new agreement that would do more to limit Iran's ballistic missile programmes and constrain regional proxy campaigns like those led by Soleimani.

Trump spoke of new sanctions on Iran, but it was not immediately clear what those would be.