Former student Nikolas Cruz shoots 17 people to death in Florida school

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.

May 12: Gunmen stormed a hospital on Tuesday in an ongoing attack in the Afghan capital Kabul, as a suicide blast killed 15 people at a funeral in the country's restive east.

Special forces rescued 80 people including mothers and babies from the Kabul hospital after three gunmen launched a morning assault, killing at least four people, the interior ministry said in a statement.

Heavily armed forces were seen carrying babies wrapped in blankets away from the scene, as the clearance operation continued.

The facility, which has a large maternity ward, is located in the west of the city, home to the capital's minority Shiite Hazara community -- a frequent target of Sunni militants from the Islamic State group.

The flare-up in violence comes as Afghanistan grapples with myriad crises including a rise in militant operations across the country and a surge in coronavirus infections.

A paediatrician who fled the hospital told AFP he heard a loud explosion at the entrance of the building.

"The hospital was full of patients and doctors, there was total panic inside," he said, asking not to be named.

The maternity services at the hospital are supported by humanitarian organisation Doctors Without Borders (MSF).

"Hospitals and health workers must not be attacked. We call on all sides to stop attacking hospitals and health workers," said deputy health minister in the city, Waheed Majroh.

Around an hour later, a suicide bomber killed at least 15 people at the funeral of a local police commander in the country's eastern Nangarhar province, according to provincial spokesman Ataullah Khogyani.

The attacker detonated his explosives in the middle of the ceremony.

Zaher Adel, spokesman for the government hospital in Jalalabad, earlier said 12 bodies had arrived from the blast site and more than 50 people were being treated for injuries.

Amir Mohammad, who was wounded in the blast, said thousands of people had gathered for the funeral, an event which often draws huge crowds in Afghanistan.

The violence comes just a day after four roadside bombs exploded in a northern district of Kabul, wounding four civilians including a child.

The bombings were later claimed by the Islamic State group, according to the SITE intelligence group.

They were just the latest in a string of IS attacks on the capital.

In March, at least 25 people were killed by a gunman at a Sikh temple in Kabul, which was later claimed by the group.

IS is also responsible for an infamous attack in March 2017 on one of the country's largest hospitals, when gunmen disguised as doctors stormed the Kabul building and killed dozens.

In recent months, the jihadist group has suffered mounting setbacks after being hunted by US and Afghan forces as well as Taliban offensives targeting their fighters, but it still retains the ability to launch major assaults on urban centres.

The Taliban have largely refrained from launching large attacks on Afghan cities since February when they signed a landmark withdrawal deal with the US meant to pave the way for peace talks with the Kabul government.

Under the agreement, the Taliban promised not to target forces from the US-led coalition, but made no such pledge toward Afghan troops and have stepped up attacks in the provinces.

The Taliban have denied involvement in both of Tuesday's attacks.

Washington, Jun 2: US President Donald Trump said that peaceful protests following the death of African-American man George Floyd in police custody were derailed by acts of domestic terrorism.

"These are not acts of peaceful protests, these are acts of domestic terror - the destruction of innocent life, and the spilling of innocent blood is an offence to humanity and a crime against God," Trump said during a press briefing on Monday.

Trump also added that the chaos is the work of professional agitators and provocateurs - anarchists and the far-left movement Antifa, among others - and put them on notice, vowing to enforce law and order.

He further said, "Those who threaten innocent life and property will be arrested, detained and prosecuted to the fullest extent of the law. I want the organizers of this terror to be on notice that you will face severe criminal penalties and lengthy sentences in jail. This includes Antifa and others who are leading instigators."

The US president also that he is invoking an 1807 law to mobilize the military around the country to "quickly solve the problem."

"I am also taking swift and decisive action to protect our capital Washington DC. As we speak, I am dispatching thousands and thousands of heavily armed soldier, military personnel and enforcement officers to stop the rioting," Trump said during a press briefing.

"I am mobilizing all available federal resources, civilian and military, to stop the rioting and looting, to end the destruction and arson. And to protect the rights of law-abiding Americans, including your Second Amendment rights," he added.

Trump said mayors and governors must establish an "overwhelming law enforcement presence until the violence has been quelled." If the city or state refuses to take the actions, Trump said he would deploy the US military.

Trump on Monday also said that all Americans are rightly 'sickened by the brutal death' of George Floyd and his administration is fully committed to providing justice to George and his family.

"All Americans were rightly sickened and revolted by the brutal death of George Floyd. My administration is fully committed, the justice will be fully served for George and his family and He will not have died in vain," Trump said.

"My first and highest duty as president is to defend and protect the great country and the American people. I have sworn an oath to uphold the laws of our nation and that is exactly what I will do," he added.

After the media address, Trump made a surprise visit to the damaged St Johns church near White House, walking through park violently cleared of protesters. He walked to the church across the street from the White House after tear gas was fired at protesters in the area.