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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 D.C: One of the greatest spectacles of modern art is still thriving in the Australian outback as confirmed by satellite imagery of NASA. The Marree Man is a massive geoglyph depicting an aboriginal hunter, that spans over 2.6 miles in the Southern Australian region.

Discovered by a pilot in 1998, its origin still remains a mystery even to this date.

The Marree Man was given a new lease of life in 2016 when a group of people from the neighboring town of Marree plowed its lines to avert its fading due to erosion.

After NASA shared the image of the art-work that was taken in June, the efforts of the good samaritans turned out to be a total success, reported CNN Travel.

The restoration team believes that the refurbished Marree Man would last longer than its original version.

According to NASA, "They [the team] created wind grooves, designed to trap water and encourage the growth of vegetation. They hope that eventually, the man will turn green."

In a previous article, CNN reported that an entrepreneur by the name of Dick Smith took upon himself to unravel the geoglyph's mystery in 2016. His team combed through all the available evidence but couldn't find anything conclusive.

In 2018 he even offered a 5,000 Australian dollar reward for anyone who knows the identity of its creator.

Nobody turned up with an answer but it was speculated that unknown artist lives in Alice Springs or even might be an American.

Google has indexed invite links to private WhatsApp group chats, meaning anyone can join various private chat groups (including several porn-sharing groups) with a simple search.

According to a report in Motherboard, invitations to WhatsApp group chats were being indexed by Google.

The team found private groups using specific Google searches and even joined a group intended for NGOs accredited by the UN and had access to all the participants and their phone numbers.

Journalist Jordan Wildon said on Twitter that he discovered that WhatsApp's "Invite to Group Link" feature lets Google index groups, making them available across the internet since the links are being shared outside of WhatsApp's secure private messaging service.

"Your WhatsApp groups may not be as secure as you think they are," Wildon tweeted on Friday, adding that using particular Google searches, people can discover links to the chats.

According to app reverse-engineer Jane Wong, Google has around 470,000 results for a simple search of "chat.whatsapp.com", part of the URL that makes up invites to WhatsApp groups.

WhatsApp spokesperson Alison Bonny said: "Like all content that is shared in searchable public channels, invite links that are posted publicly on the internet can be found by other WhatsApp users."

"The links that users wish to share privately with people they know and trust should not be posted on a publicly accessible website," Bonny told The Verge.

Danny Sullivan, Google's public search liaison, tweeted: "Search engines like Google & others list pages from the open web. That's what's happening here. It's no different than any case where a site allows URLs to be publicly listed. We do offer tools allowing sites to block content being listed in our results."