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Melbourne, Jul 24: Home-made cloth face masks may need a minimum of two layers, and preferably three, to prevent the dispersal of viral droplets associated with Covid-19, according to a study.

Researchers, including those from the University of New South Wales in Australia, noted that viral droplets are generated by those infected with the novel coronavirus when they cough, sneeze, or speak.

As face masks have been proven to protect healthy people from inhaling infectious droplets as well as reducing the spread from those who are already infected, several types of material have been suggested for these, but based on little or no evidence of how well they work, the scientists said.

In the current study, published in the journal Thorax, the researchers compared the effectiveness of single and double-layer cloth face coverings with a surgical face mask (Bao Thach) at reducing droplet spread.

They said the single layer covering was made from a folded piece of cotton T shirt and hair ties, and the double layer covering was made using the sew method described by the US Centers for Disease Control and Prevention (CDC).

The scientists used a tailored LED lighting system and a high-speed camera to film the dispersal of airborne droplets produced by a healthy person with no respiratory infection, during speaking, coughing, and sneezing while wearing each type of mask.

Their analysis showed that the surgical face mask was the most effective at reducing airborne droplet dispersal, although even a single layer cloth face covering reduced the droplet spread from speaking.

But the study noted that a double layer covering was better than a single layer in reducing the droplet spread from coughing and sneezing.

According to the researchers, the effectiveness of cloth face masks is dependent on the number of layers of the covering, the type of material used, design, fit as well as the frequency of washing.

Based on their observations, they said a home made cloth mask with at least two layers is preferable to a single layer mask.

"Guidelines on home-made cloth masks should stipulate multiple layers," the scientists said, adding that there is a need for more research to inform safer cloth mask design.

Washington, Jan 7: Facebook will ban deepfake videos ahead of the US elections but the new policy will still allow heavily edited clips so long as they are parody or satire, the social media giant said Tuesday.

Deepfake videos are hyper-realistic doctored clips made using artificial intelligence or programs that have been designed to accurately fake real human movements.

In a blog published following a Washington Post report, Facebook said it would begin removing clips that were edited--beyond for clarity and quality--in ways that "aren't apparent to an average person" and could mislead people.

Clips would be removed if they were "the product of artificial intelligence or machine learning that merges, replaces or superimposes content onto a video, making it appear to be authentic," the statement from Facebook vice-president Monika Bickert said.

However, the statement added: "This policy does not extend to content that is parody or satire, or video that has been edited solely to omit or change the order of words."

US media noted the new guidelines would not cover videos such as the 2019 viral clip -- which was not a deepfake -- of House Speaker Nancy Pelosi that appeared to show her slurring her words.

Facebook also gave no indication on the number of people assigned to identify and take down the offending videos, but said videos failing to meet its usual guidelines would be removed, and those flagged clips would be reviewed by teams of third-party fact-checkers -- among them AFP.

The news agency has been paid by the social media giant to fact-check posts across 30 countries and 10 languages as part of a program starting in December 2016, and including more than 60 organisations.

Content labeled "false" is not always removed from newsfeeds but is downgraded so fewer people see it -- alongside a warning explaining why the post is misleading.

In an unprecedented crisis despite Prime Minister Narendra Modi assuring the continuation of essential services like food and groceries, online marketplaces like Flipkart and Amazon along with delivery platforms like Bigbasket, Grofers and FreshToHomes hit a major blockade on Wednesday as local authorities shut warehouses and sent delivery boys back, even harassed them.

Millions of people across cities were left helpless at homes as essential items like fruits and vegetables, dairy and milk, meat and fish etc did not reach their doors despite placing orders well in advance. Later, the orders went dry.

While Grofers' warehouse in Faridabad was closed by the local law enforcement agencies, Bigbasket complained that the police stopped its delivery partners and "some of them were even beaten up by for no fault of theirs".

"We are not operational due to restrictions imposed by local authorities on movement of goods in spite of clear guidelines provided by central authorities to enable essential services. We are working with the authorities to be back soon,' Bigbasket tweeted.

In a statement to IANS, Bigbasket said that it will help to have better coordination between the Centre and state, and between the state and local police to "ensure that our delivery vans and bikes don't get stopped by the police. Bigbasket and bb daily are not taking new orders".

Furious people stormed the social media platforms, writing their plight to NITI Aayog CEO Amitabh Kant on Twitter.

"Sir, all e-commerce are down. Believe me I tried everything (Grofers, Bigbasket, Flipkart, Amazon, Big Bazaar), no delivery till 31st March or Server Down or No Service. Need to think how we can enable them through digital India," tweeted one user.

Kant tweeted back to Bigbasket: "They should give me specifics - State & location. I will act on it by getting in touch with concerned authorities & sorting it out. Govt guidelines exempt them. We will ensure that citizens are not impacted".

Kant also responded to Grofers: "Cold storages & Warehouses as well as delivery of all essentials goods including food, pharma thru E-Commerce are exempted under MHA order. I have spoken to CS & DGP, Haryana . They have taken immediate action to ensure that supply chains efficiently function for the citizens".

The subscription-based hyperlocal delivery startup FreshToHome sent messages to its customers, saying that despite the government declaring food delivery as essential, "we are facing hardships in continuing our operations".

"Please bear with us as we are working hard to unblock local authority hurdles," said the FreshToHome team.

Reports later surfaced that the Department for Promotion of Industry and Internal Trade (DPIIT) has initiated talks with the state Chief Secretaries asking them not to restrict movement of people engaged in home delivery of essential items, mentioned in the list of exempted items circulated by the Home Ministry.

Meanwhile, Flipkart said it has temporarily suspended its operations and services - including grocery items. The marketplace has decided to halt all orders from March 25 for all three supply chains -- groceries, non-large goods and large items.

"Flipkart has temporarily suspended orders as we assess the possibilities of operating in the lockdown. We are prioritising the safety of our delivery executives and seeking the support of the local governments and police authorities to meet the needs of our customers as they stay home during this lockdown," Rajneesh Kumar, Chief Corporate Affairs Officer, Flipkart, said in a statement.

E-commerce giant Amazon said the company has to "temporarily stop taking orders and disable shipments for lower-priority products.

"For all pending customer orders on lower-priority products, we are reaching out to customers and giving them a choice to cancel their orders, and receive a refund for prepaid items," said the company.

Witnessing a surge in demand, supermarket chain Biz Bazaar entered the fray, with launching doorstep delivery services in major cities like Delhi, Mumbai, Bengaluru and Gurugram.

However, within no time, Big Bazaar was flooded with calls, forcing the company to issue a statement, saying that "In light of the recent announcement, we are receiving an unprecedented number of requests for doorstep delivery. There could be a delay due to the restrictions on movements".

Already battling massive surge in demand, the online delivery platforms faced other issues too, including zero access to several high-rises across the country which have gone under complete lockdown with all entry and exit gates locked.