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The US space agency has thrown open a challenge to win over Rs 26 lakh, calling the global community to send novel design concepts for compact toilets that can operate in both microgravity and lunar gravity.

NASA is preparing for return to the Moon and innumerable activities to equip, shelter, and otherwise support future astronauts are underway.

The astronauts will be eating and drinking, and subsequently urinating and defecating in microgravity and lunar gravity.

NASA said that while astronauts are in the cabin and out of their spacesuits, they will need a toilet that has all the same capabilities as ones here on Earth.

The public designs for space toilet may be adapted for use in the Artemis lunar landers that take humans back to the Moon.

"Although space toilets already exist and are in use (at the International Space Station, for example), they are designed for microgravity only," the US space agency said in a statement.

NASA's Human Landing System Programme is looking for a next-generation device that is smaller, more efficient, and capable of working in both microgravity and lunar gravity.

The new NASA challenge includes a Technical category and Junior category and the last date to send designs is August 17.

NASA's Artemis Moon mission will land the first woman and next man on the lunar surface by 2024.

The Artemis programme is part of America's broader Moon to Mars exploration approach, in which astronauts will explore the Moon and experience gained there to enable humanity's next giant leap, sending humans to Mars.

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.

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."