Deadly attack on Karachi airport, 23 dead

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, Jun 1: Police fired tear gas outside the White House late Sunday as major US cities were put under curfew to suppress rioting as anti-racism protestors again took to the streets to voice fury at police brutality.

With the Trump administration branding instigators of six nights of rioting as domestic terrorists, there were more confrontations between protestors and police and fresh outbreaks of looting.

Violent clashes erupted repeatedly in a small park next to the White House, with authorities using tear gas, pepper spray and flash bang grenades to disperse crowds who lit several large fires and damaged property.

Local US leaders appealed to citizens to give constructive outlet to their rage over the death of an unarmed black man in Minneapolis, while night-time curfews were imposed in cities including Washington, Los Angeles and Houston.

One closely watched protest was outside the state capitol in Minneapolis' twin city of St. Paul, where several thousand people gathered before marching down a highway.

"We have black sons, black brothers, black friends, we don't want them to die. We are tired of this happening, this generation is not having it, we are tired of oppression," said Muna Abdi, a 31-year-old black woman who joined the protest.

"I want to make sure he stays alive," she added in reference to her son, aged three.

Hundreds of police and National Guard troops were deployed ahead of the protest.

At one point, some of the protestors who had reached a bridge were forced to scramble for cover when a truck drove at speed after having apparently breached a barricade.

The driver was later taken to hospital after the protestors hauled him from the vehicle, although there were no immediate reports of other casualties.

There were other large-scale protests in cities including New York and Miami.

Washington's mayor ordered a curfew from 11:00 pm until 6:00 am, as a report in the New York Times said that President Donald Trump had been rushed by Secret Service agents into an underground bunker at the White House on Friday night during an earlier protest.

Stores ransacked

Large-scale violence has rocked many US cities in recent days, and looters ransacked stores in a neighborhood of Philadelphia on Sunday.

In the Los Angeles suburb of Santa Monica, looting was reported at stores in a popular beachside shopping center.

Officials in LA -- a city scarred by the 1992 riots over the police beating of Rodney King, an African-American man -- imposed a curfew from 4:00 pm Sunday until dawn.

"Please, use your discretion and go early, go home, stay home and help us make sure that those who want to change this conversation from being about racial justice to be about burning things and looting things, don't win the day," the city's mayor Eric Garcetti said on CNN.

The shocking videotaped death last Monday of an unarmed black man, George Floyd, at the hands of police in Minneapolis ignited the nationwide wave of outrage over law enforcement's repeated use of lethal force against unarmed African Americans.

Floyd stopped breathing after Minneapolis police officer Derek Chauvin knelt on his neck for nearly nine minutes.

Chauvin has been charged with third-degree murder and is due to make his first appearance in court on Monday. Three other officers with him have been fired but for now face no charges.

Governor Tim Walz has mobilized all of Minnesota's National Guard troops  -- the state guard's biggest mobilization ever -- to help restore order.

Police fired tear gas and stun grenades to clear streets of curfew violators Saturday night in Minneapolis.

Walz extended a curfew for a third night Sunday and praised police and guardsmen for holding down violence. "They did so in a professional manner. They did so without a single loss of life and minimal property damage," he said.

"Congratulations to our National Guard for the great job they did immediately upon arriving in Minneapolis, Minnesota, last night," President Donald Trump tweeted, adding that they "should be used in other States before it is too late!"

The Department of Defense said that around 5,000 National Guard troops had been mobilized in 15 states as well as the capital Washington, with another 2,000 on standby.

The widespread resort to uniformed National Guards units is rare, and it evoked disturbing memories of the rioting in US cities in 1967 and 1968 in a turbulent time of protest over racial and economic disparities.

Trump blamed the extreme left for the violence, saying he planned to designate a group known as Antifa as a terrorist organization.

"The violence instigated and carried out by Antifa and other similar groups in connection with the rioting is domestic terrorism and will be treated accordingly," added Attorney General Bill Barr.

'A nation in pain'

Atlanta Mayor Keisha Lance Bottoms said Trump, who has often urged police to use tough tactics, was not helping matters.

"We are beyond a tipping point in this country, and his rhetoric only enflames that," she said on CBS.

Joe Biden, Trump's likely Democratic opponent in November's presidential election, visited the scene of one anti-racism protest.

"We are a nation in pain right now, but we must not allow this pain to destroy us," Biden tweeted, posting a picture of him speaking with an African-American family at the site where protesters had gathered in Delaware late Saturday.

Floyd's death has triggered protests beyond the United States, with hundreds rallying outside the US embassy in London in solidarity.

"I'm here because I'm tired, I'm fed up with it. When does this stop?" Doreen Pierre told AFP at the protest.

In Germany, England football international Jadon Sancho marked one of his three goals for Borussia Dortmund against Paderborn by lifting his jersey to reveal a T-shirt bearing the words "Justice for George Floyd".

New Delhi, May 28: Twitter CEO Jack Dorsey today reinforced his stance on pointing out "incorrect or disputed information about elections globally", a day after US President Donald Trump threatened to shutter social media over Twitter's actions on his posts.

Mr Dorsey appealed to "leave our employees out of this" as the face-off with Mr Trump is likely to escalate.

"Fact check: there is someone ultimately accountable for our actions as a company, and that's me. Please leave our employees out of this. We'll continue to point out incorrect or disputed information about elections globally. And we will admit to and own any mistakes we make," Mr Dorsey tweeted.

"This does not make us an 'arbiter of truth.' Our intention is to connect the dots of conflicting statements and show the information in dispute so people can judge for themselves. More transparency from us is critical so folks can clearly see the why behind our actions," said the Twitter CEO.

Fact check: there is someone ultimately accountable for our actions as a company, and that's me. Please leave our employees out of this. We'll continue to point out incorrect or disputed information about elections globally. And we will admit to and own any mistakes we make.

— jack (@jack) May 28, 2020

"Per our Civic Integrity policy (https://help.twitter.com/en/rules-and-policies/election-integrity-policy), the tweets yesterday may mislead people into thinking they don't need to register to get a ballot (only registered voters receive ballots). We're updating the link on

@realDonaldTrump tweet to make this more clear," Mr Dorsey tweeted.

Twitter had tagged two of Mr Trump's tweets in which he claimed that more mail-in voting would lead to what he called a "rigged election" this November. There is no evidence that attempts are being made to rig the election, and under the tweets Twitter posted a link which read: "Get the facts about mail-in ballots."

Five states in the US already conduct elections primarily by mail-in vote: Utah, Colorado, Hawaii, Washington and Oregon.

For years, Twitter has been accused of ignoring the US President's violation of platform rules with his daily, often hourly barrages of personal insults and inaccurate information sent to more than 80 million followers, news agency AFP reported.

But Twitter's slap on the wrist was enough to drive Mr Trump into a tirade - on Twitter - in which "Republicans feel that Social Media Platforms totally silence conservatives voices. We will strongly regulate, or close them down, before we can ever allow this to happen," Mr Trump said.

He said that an increase in mail-in ballots - seen in some states as vital for allowing people to avoid crowds during the COVID-19 pandemic - will undermine the election.

"It would be a free for all on cheating, forgery and the theft of Ballots," wrote Mr Trump, whose re-election campaign has been knocked off track by the coronavirus crisis. His torrent of angry tweets earned a top-10 trending hashtag: #TrumpMeltdown.

Facebook chief Mark Zuckerberg also waded in to the row, telling Fox News that his social network - still the biggest in the world - has a different policy. "I just believe strongly that Facebook should not be the arbiter of truth of everything that people say online," Mr Zuckerberg said in a snippet of the interview posted online Wednesday by Fox.

"I think, in general, private companies, especially these platform companies, shouldn't be in the position of doing that," he said.

 he claimed that the political right in the US is being censored.

"Republicans feel that Social Media Platforms totally silence conservatives voices. We will strongly regulate, or close them down, before we can ever allow this to happen," Mr Trump said.

He said that an increase in mail-in ballots - seen in some states as vital for allowing people to avoid crowds during the COVID-19 pandemic - will undermine the election.

"It would be a free for all on cheating, forgery and the theft of Ballots," wrote Mr Trump, whose re-election campaign has been knocked off track by the coronavirus crisis. His torrent of angry tweets earned a top-10 trending hashtag: #TrumpMeltdown.

Facebook chief Mark Zuckerberg also waded in to the row, telling Fox News that his social network - still the biggest in the world - has a different policy. "I just believe strongly that Facebook should not be the arbiter of truth of everything that people say online," Mr Zuckerberg said in a snippet of the interview posted online Wednesday by Fox.

"I think, in general, private companies, especially these platform companies, shouldn't be in the position of doing that," he said.