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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.

Islamabad, May 24: Pakistan recorded 32 coronavirus-related deaths during the last 24 hours, taking the total number of fatalities in the country to 1,133, the health ministry said on Sunday.

The total number of COVID-19 patients in Pakistan also jumped to 54,601, it said.

Read: Coronavirus India update: State-wise total number of confirmed cases, deaths

Sindh reported the maximum number of 21,645 coronavirus cases, followed by Punjab at 19,557, Khyber-Pakhtukhwa at 7,685, Balochistan at 3,306, Islamabad at 1,592, Gilgit-Baltistan at 619 and Pakistan-occupied Kashmir (PoK) at 197.

According to the health ministry, 17,198 coronavirus patients have recovered and 473,607 tests, including 12,915 in the last 24 hours, have been conducted so far.

The government also issued strict instructions to observe social distancing while offering Eid prayer and asked people to avoid visiting relatives and hosting parties.

Eid congregations were held at open places, mosques and Eidgahs in all major cities and towns while following strict standard operating procedures (SOPs) of social distancing and other precautionary measures.

Pakistan Prime Minister's Special Assistant on Health Zafar Mirza on Friday said the deadly infection would continue to multiply if precautions are not taken.

Earlier this month, the government had announced the lifting of the countrywide lockdown imposed to curb the spread of the virus in phases, even as infections continued to rise in the country.

Prime Minister Imran Khan had cited the economic havoc the virus restrictions had wreaked on citizens as the reason behind the decision.

The prime minister on Saturday urged Pakistanis to forgo traditional Eid festivity in view of the hundreds of fatalities caused by the coronavirus and the lives lost in Friday's plane crash in Karachi.

Ninety-seven people, including nine children, were killed and two passengers miraculously survived a fiery crash when a Pakistan International Airlines plane with 99 travellers on board plunged into a densely populated residential area near the Jinnah International Airport in Karachi. Most of the victims were travelling home to celebrate Eid.

Jun 25: Tencent Holdings Ltd.'s $40 billion surge this week and the recent ascent of Pinduoduo Inc. have reshuffled the ranking of China's richest people.

The country's largest game developer has surpassed Alibaba Group Holding Ltd. as Asia's most-valuable company, with its shares rising above HK$500 in intraday trading Wednesday for the first time. Pinduoduo, a Groupon-like shopping app also known as PDD, has more than doubled this year.

The rallies have propelled the wealth of their founders, with an added twist: Tencent's Pony Ma, worth $50 billion, has surpassed Jack Ma's $48 billion fortune, becoming China's richest person. And Colin Huang of PDD, whose net worth stands at $43 billion, has squeezed real estate mogul Hui Ka Yan of China Evergrande Group out of the top three earlier this year, according to the Bloomberg Billionaires Index.

The coronavirus pandemic has accelerated the digitization of the workplace and changed consumers' habits, boosting shares of many internet companies. Now tech tycoons are dominating the ranks of China's richest people. They occupy four of the top five spots: Ding Lei of Tencent peer NetEase Inc. follows China Evergrande's Hui.

‘Perform Strongly'

Tencent has come a long way since hitting a low in 2018, when China froze the approval process for new games. Since then, the stock has almost doubled, and last month the tech giant reported a 26 per cent jump in first-quarter revenue.

“Tencent's online games segment will probably perform strongly through the Covid-19 pandemic, and most of its other businesses are relatively unscathed,” said Vey-Sern Ling, a Bloomberg Intelligence analyst.

That has been a boon for Pony Ma, 48, who owns a 7 per cent stake in the company and pocketed about $757 million from selling some 14.6 million of his Tencent shares this year, data complied by Bloomberg show.

The native of China's southern Guangdong province studied computer science at Shenzhen University and was a software developer at a supplier of telecom services and products before co-founding Tencent with four others in the late 1990s. At the time, the company focused on instant-messaging services.

It has been a long comeback for Pony Ma. He overtook real estate tycoon Wang Jianlin as China's second-richest person in 2013 and topped Baidu Inc.'s Robin Li as the wealthiest in early 2014. Later that year, Alibaba went public in the U.S., catapulting Jack Ma's fortune.

Bloomberg Intelligence's Ling notes, however, that Tencent's jump this year has lagged behind some internet peers, especially those in e-commerce, games and online entertainment. Just consider: Tencent shares have climbed 31 per cent in 2020, while PDD's American depositary receipts have more than doubled. Alibaba, meanwhile, has advanced just 6.9 per cent.