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Créer du plasma à partir de raisins : le mystère est enfin résolu

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Depuis plusieurs années, une question hantait plusieurs millions d’internautes, du moins si l’on en croit YouTube. Pourquoi des raisins entrent-ils en combustion spontanée lorsqu’on les place dans un four à micro-ondes? Des chercheurs canadiens ont récemment fait appel à la science pour y répondre.

Cette question trouve son origine dans plusieurs vidéos virales montrant un phénomène assez étrange, où des flammes jaillissent entre deux moitiés de raisins tout à fait ordinaires après quelques secondes de cuisson au four à micro-ondes.

L’expérience a été reproduite des centaines de fois par les internautes et, même si plusieurs explications avançaient le terme plasma, aucune n’était adéquate pour rendre compte du phénomène.

Après avoir sacrifié de nombreux fruits ainsi qu’une dizaine de fours à micro-ondes, les chercheurs ont trouvé une explication (Nouvelle fenêtre) qui implique certaines propriétés qui ne sont pas uniques aux raisins.

Un « piège à radiations »

Le plasma est le quatrième état de la matière, après le solide, le liquide et le gazeux. C’est un état où des atomes sont chauffés à un point tel que les électrons qui les entourent leur sont arrachés et commencent à se déplacer librement, formant une « soupe » d’ions et d’électrons.

Cet étrange état rend la matière très sensible aux champs magnétiques ou aux courants électriques. Le plasma peut se trouver dans des endroits très variés, allant des étoiles à la foudre et jusqu’aux tubes au néon qui nous servent d’éclairage.

Alors, comment un simple fruit serait-il en mesure de produire du plasma? D’abord, il lui faut une source d’énergie que seul un four à micro-ondes peut offrir. Ces fours cuisent notre nourriture en émettant des radiations électromagnétiques de type micro-ondes, dont la longueur d’onde réagit avec la matière en faisant vibrer les molécules d’eau qu’elle contient, augmentant ainsi sa chaleur.

Pour la vaste majorité des aliments qu’on place dans ces fours, il en résulte une cuisson. Il en va de même pour un raisin, mais lorsqu’une micro-onde pénètre à l’intérieur de ce fruit, la forte teneur en eau de celui-ci va raccourcir la longueur des ondes émises par le four, au point où elles auront à un moment donné la même taille que le raisin.

Ce phénomène piège les radiations à l’intérieur du fruit, avec un maximum de chaleur en son centre. Or, en observant les fruits à l’aide de différentes caméras, thermiques ou ultrarapides, les chercheurs ont remarqué que, lorsqu’on place deux raisins côte à côte dans un four, les ondes piégées commencent à interagir les unes avec les autres.

Les micro-ondes seront amplifiées dans le minuscule espace entre les deux fruits, créant un champ électromagnétique de plus en plus puissant jusqu’à ce que la chaleur y arrache les électrons des atomes présents, avec pour conséquence l’apparition de plasma, d’abord sous la forme de flammèches, puis dans un jet qui prendra rapidement de l’expansion.

De science virale à science fondamentale

Selon des explications qui accompagnaient les vidéos YouTube avant la publication de cet article, pour réussir cette expérience, il fallait couper un raisin en deux en faisant bien attention de laisser un mince morceau de pelure reliant les deux moitiés. Cette mince pellicule servirait alors de fil conducteur qui transférerait l’énergie entre les deux moitiés.

Or, les chercheurs ont montré que cette connexion n’était pas nécessaire pour engendrer le phénomène. En fait, cette expérience ne nécessite même pas de raisin; n’importe quel objet de taille et de composition en eau similaires est suffisant pour créer du plasma maison, tant qu’on est prêt à courir le risque de détruire un électroménager.

Les chercheurs ont recréé le plasma avec d’autres baies et même avec des billes d’hydrogel, un matériau transparent composé à 99,9 % d’eau.

Cette étude montre que deux sphères peuvent concentrer des ondes électromagnétiques en un point fixe entre les deux. En variant les tailles des sphères et les longueurs d’onde, les chercheurs croient que ce principe pourrait être appliqué pour concentrer les radiations électromagnétiques jusqu’à des échelles nanométriques.

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A big test of reusable packaging for groceries comes to Canada

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An online store has launched in Ontario selling groceries and household items from Loblaws in containers it will take back and refill — a test of whether Canadian consumers are ready to change their habits. Industry-watchers say it is breaking ground for reusable packaging.

The store, called Loop, launched in Canada on Feb. 1, in partnership with supermarket giant Loblaws, and offers items like milk, oats, ice cream and toothpaste for delivery in most of Ontario. Loop is already operating in the continental U.S., the U.K and France. 

Included so far are some products from well-known brands such as PC sauces and oils, Häagen-Dazs ice cream, Heinz ketchup, Chipits chocolate chips and Ocean Spray cranberries. 

“The goal is really validating that this is something the Canadian public is interested in,” said Tom Szaky, founder and CEO of Loop and its parent company TerraCycle.

Unlike existing small no-waste retailers, they want to offer “your favourite product at your favourite retailer in a reusable and convenient manner.”

The involvement of a huge retailer makes the launch notable in terms of scale and who it will reach, said Tima Bansal, Canada Research Chair in business sustainability at Western University in London, Ont. 

“I think it’s at the scale that’s needed to create the change in the community in Canada more generally,” she said.

How it works for customers

Szaky likens Loop to the reusable bottle system for beer in Canada “but expanding it to any product that wants to play in the [North American] ecosystem.”

The ultimate goal, he said, is to give people a greener way to consume that limits the amount of mining and farming needed to produce packaging.

“This allows us to greatly reduce the need to extract new materials, which is the biggest drain on our environment.

Loopstore.ca currently lists just 98 products, although many are sold out or “coming soon.” 

As with other online grocery stores, customers fill their virtual shopping cart, but in addition to the cost of the item itself, they pay a deposit for its container. That can range from 50 cents for glass President’s Choice salsa jars like the ones that are normally at the supermarket to $5 for a stainless steel Häagen-Dazs ice cream tub. 

The items are delivered to a customer’s home by courier FedEx for a $25 fee, although the fee is waived for orders over $50.

Once you’ve spooned out all the salsa or ice cream or squeezed out all the toothpaste, the container doesn’t go in the recycling bin. Instead, you toss them into the tote bag they came in — even if they’re dented or damaged — and they get picked up.

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This wearable device beeps when workers get too close to each other

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It’s a device that emits a high-pitched beep, buzzes and lights up if your coworker steps too close.

While some introverts would have bought this device before the pandemic to stave off chatty colleagues near the coffee machine, ZeroKey designed the product with a more important purpose — helping employees physically distance to reduce the risk of spreading coronavirus. 

The Calgary tech company’s “Safe Space” device looks like a small plastic badge that can be worn on a wrist or clipped to a shirt pocket or belt. 

“Our products, in a nutshell, localize or figure out where things are in 3D space and our big claim to fame is we do it very precisely, more precisely than anyone else in the world,” said Matt Lowe, co-founder and CEO of ZeroKey.

The company says its location-tracking technology passively monitors the distance between each device and is accurate down to 1.5 millimetres. The distance on devices can be set — so if, say, science determines three metres apart is actually safer that two, that can be tweaked. 

Lowe says the company came from humble beginnings — he and a co-founder, working out of a room in his house. The company has grown from two to 30 employees and has more openings it’s looking to fill.

Inspired by sci-fi

Their inspiration comes, as so many technological innovations have, from sci-fi. 

Lowe recalls watching Minority Report, and being transfixed with the gesture-based user interface Tom Cruise’s character operates. 

“Wouldn’t it be awesome if we had an interface that was more in tune with how humans operate naturally with their hands. So if you could just walk up to a new piece of technology … and just immediately be proficient,” he said. 

But applying that tech to the COVID-19 era wasn’t something the company had anticipated.

Lowe said some of the company’s clients in the manufacturing industry approached ZeroKey with a request.

“They came to us and said, ‘hey … we have the data where people are, can you build some sort of system so that we can do contact tracing and we can let people know if they’re closer than two metres?’ And we said, ‘absolutely … that’s easier than what we normally do,'” he said.

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Blistering rallies spur Canadian tech world to repeat equity sales

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Canadian technology companies have been making multiple trips to the equity market over the past year, capitalizing on a rally in tech shares that’s helping them raise cash at ever higher valuations.

Dye & Durham Ltd., which makes software used by law firms, took advantage of a more than sixfold rally in its shares since its July IPO to raise $500 million (US$394 million) in a bought deal of stock and convertible debentures, the company said Tuesday. Dye & Durham, which went public at $7.50 a share, received $50.50 per share in the private placement. Peers including Lightspeed POS Inc. and Docebo Inc. have made similar moves.

Shares of technology companies have gained since the onset of the pandemic as their corporate customers increasingly turned to cloud-based applications to support their remote workforces, said Anurag Rana, an analyst at Bloomberg Intelligence. The technology sector was one of the few places investors could look for growth during the crisis, with huge swaths of the economy including retailers, restaurants, airlines, hotels and casinos hammered by lockdowns, he said.

“Issuers and private-equity investors are not stupid, and they know somewhere down the road that valuations may come back,” Rana said. “So this is the time when they sell.”

Canada’s S&P/TSX Information Technology Index has risen 82 per cent in the past year, fuelled by rallies in Lightspeed and Shopify Inc. That compares with a 36 per cent advance for the U.S. S&P 500 Information Technology Index.

Those gains are giving early investors in tech companies an opportunity to take some profits. In conjunction with Dye & Durham’s private deal announced Tuesday, some investors agreed with the underwriters to sell 1.98 million shares at the $50.50 price as well.

Lightspeed, which provides cloud-based point-of-sale systems for retailers and restaurants, has also seized the moment. The company went public in Canada in February 2019 and last year followed that up with a U.S. IPO, selling shares for US$30.50 apiece. The deal raised US$332.3 million for the company and US$65.4 million for some shareholders.

After Lightspeed’s share price more than doubled, it went back to the market again last week with a public offering of shares for US$70 each, raising US$620.2 million for the company and US$56 million for other shareholders.

Docebo, which sells cloud-based learning software, has tapped the market multiple times over the past year. The firm, which went public in Canada in October 2019, completed a bought deal of shares atC$50 apiece in August. The move raised $25 million for the company and $50 million for investors including founder and Chief Executive Officer Claudio Erba, Chief Revenue Officer Alessio Artuffo and top outside investor Intercap Equity Inc.

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