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U of T's Sajeev John receives Gerhard Herzberg Canada Gold Medal for work on harnessing flow of photons – News@UofT

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Theoretical physicist Sajeev John has received Canada’s highest science and engineering honour, the prestigious Gerhard Herzberg Canada Gold Medal.

John is receiving the award for his groundbreaking research and fundamental advancements in confining and harnessing the flow of photons of light in a manner analogous to harnessing the flow of electrons.

The medal also recognizes John for his leadership in efforts to transform this research into groundbreaking applications in optical micro-chips, optical communications and information processing, laser technologies, solar-energy harvesting and clinical medicine – including life-saving surgical tools and techniques.

“I am profoundly honoured and feel singularly energized to bring to broader fruition the work I began on light-trapping crystals,” says John, a University Professor in the Faculty of Arts & Science’s department of physics.

“The Herzberg Gold Medal offers a unique opportunity for creativity and unfettered pursuit of essential applications such as the world’s most efficient, lightweight silicon solar cells; light-trapping to enhance artificial photosynthesis for solar fuel production; development of the most compact lab-in-a-photonic-crystal sensors for early-stage disease detection and diagnosis; and much more.”

Named after the Canadian physicist and Nobel laureate in chemistry, the Gerhard Herzberg Canada Gold Medal recognizes the excellence and impact of a recipient’s research. It is awarded annually by the Natural Sciences and Engineering Research Council of Canada (NSERC).

“Professor John is truly deserving of the country’s highest scientific honour,” says Melanie Woodin, dean of the Faculty of Arts & Science. “Not only has his work been foundational, it has also had an impact in physics, chemistry, engineering and medicine, and is leading to advancements that are benefiting people’s lives.”

John’s research provides a solution to the problem that photons do not tend to flow along confined pathways like electrons but instead disperse or are absorbed.

According to Kim Strong, chair of the department of physics, “Professor John’s research laid out the theoretical foundation for special materials – called Photonic Band Gap (PBG) materials – that allow confinement, or localization, of photons to a microscopic region with the size of the wavelength of light.”

“Once you know how to confine photons to a single location,” she says, “you can confine their motion along prescribed microscopic circuit paths, analogous to the way the motion of electrons is controlled on the nanometer scale in semiconductors.”

Following up on his theoretical work, John and his collaborators built the first large-scale silicon PBG material out of a synthetic opal and have created PBG materials that are even easier and cheaper to manufacture.

The groundbreaking work has sparked the development of novel micro-structured materials known as photonic crystals, now referred to as “semiconductors of light.” Ultimately, the breakthrough will enable computer chips to operate with photons instead of electrons.

Among many impacts beyond the lab, research into PBG materials has already produced life-saving advancements in clinical medicine. In 2004, laser surgery was performed on a patient to remove a previously treated tumour that was recurring and remained life-threatening. A final, successful surgery was carried out using a hollow-core photonic band gap fibre. Thousands of similar procedures have been performed using PBG fibres and several major medical centres are now testing PBG-fibre-based laser surgery tools.

“The University of Toronto congratulates Sajeev John on this important recognition,” says Professor Leah Cowen, U of T’s associate vice-president of research. “From his groundbreaking work on confining and harnessing the flow of photons to his leadership in exploring applications for his research in optical micro-chips, optical communications and information processing, laser technologies, solar energy-harvesting and clinical medicine – his impact has been remarkable.” 

In 1984, John received his PhD in physics from Harvard University, where he published the original paper on light localization. He was an assistant professor at Princeton University, where he pioneered the concept of photonic band gap materials. He joined U of T in 1989.

John’s research and scientific leadership earned him the 2001 King Faisal International Prize in Science (with Nobel laureate C.N. Yang). In 2007, the Institute of Electrical and Electronics Engineers (IEEE) awarded him with the International Quantum Electronics Award for “the invention of and development of light-trapping crystals and the elucidation of their properties and applications.”

He is holder of a Canada Research Chair in optical sciences and was named an Officer of the Order of Canada in 2017.

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NASA aims to replace ISS with a commercial space station by 2030 – The Tribune

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Washington, Dec 1

The US space agency is planning to replace the International Space Station (ISS) with one or more commercial space stations by 2030.

NASA’s auditing body, the Office of Audits, has produced a report detailing the agency’s commitment to replace the orbiting lab with commercial space stations.

Astronauts have lived and worked onboard the ISS orbiting roughly 250 miles above the Earth’s surface for more than 20 years.

“The ISS costs about $3 billion a year, roughly a third of NASA’s annual human space flight budget, and while current plans call for the Station’s retirement in 2024, an extension to 2030 is likely,” the US space agency said in the audit report.

Anticipating its retirement, NASA has committed to replacing the ISS with one or more commercially owned and operated space destinations.

“In the fiscal year (FY) that ended September 30, 2021, Congress authorised $17 million to that end — a fraction of the $150 million the Agency said it needed. NASA’s plans for long-term, deep space human exploration missions depend on continuous access to a research laboratory in low-Earth orbit,” it added.

The Artemis mission, aimed at returning humans to the Moon and ultimately landing astronauts on Mars, is not feasible without continued human health research and technology demonstrations being conducted on the ISS and its eventual replacement.

“As long as humans intend to travel in space, NASA expects research and testing will be needed in the microgravity environment of low-Earth orbit,” the audio report mentioned.

While overall ISS operations and maintenance costs remained steady at about $1.1 billion a year from FY2016 through FY2020, systems maintenance and upgrade costs trended upward 35 per cent in the same 5-year period, rising to approximately $169 million in FY2020 due primarily to upgrades.

Meanwhile, NASA and Roscosmos are investigating the cause and long-term impacts of cracks and leaks that were recently discovered in the Station’s Service Module Transfer Tunnel, which connects the Service Module to one of eight docking ports on the Station.

“Causes being explored include structural fatigue, internal damage, external damage, and material defects. Notably, based on the models NASA used to assess the structure, the cracks should not have occurred, suggesting the possibility of an earlier-than-projected obsolescence for at least one element of the Station,” the US space agency noted. IANS

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Arctic rainfall could dominate snowfall earlier than expected: study – Global Times

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A view of Arctic Photo: VCG

Rainfall could start replacing snowfall in the Arctic decades sooner than previously thought, a study found Tuesday, warning the change caused by global warming could have effects beyond the region.

The Arctic is warming much faster than the rest of the planet, melting sea ice and adding moisture to the air that is likely to increase precipitation.

Comparing the latest projections to previous climate models, the study published in the scientific journal Nature Communications estimates the switch from snowfall-dominated annual precipitation to one dominated by rain will come about “one or two decades earlier.”

“Changes are going to be more severe and occur much earlier than projected and so will have huge implications for life in and beyond the Arctic,” the study’s main author Michelle McCrystall told AFP.

“In autumn, for example, when the greatest changes occur, the central Arctic may transition around 2070 in the latest set of models compared to 2090 in the previous set,” added McCrystall, a researcher at Canada’s University of Manitoba.

But everything depends on the degree of global warming.

At the current rate of warming rain could dominate snow in the Arctic before the end of the century, the study says. But it says limiting warming to 1.5 C could mean the Arctic stays dominated by snow.

Gavin Schmidt, director of the NASA Goddard Institute for Space Studies, said the results “imply that the worst impacts can be avoided if countries match their stated intentions to cut emissions in line with the Paris agreement.”

But Schmidt added that he felt the study did not prove the change would come sooner than expected.

Whenever it comes, the switch from snow to rain is likely to have major effects on the Arctic ecosystem. 

More rainfall on top of current snow cover could lead to increased surface ice that would make it impossible for caribou and reindeer to forage for food.

Less snow cover also means the Arctic will lose some of its capacity to deflect solar heat and light away from the Earth’s surface and thus contribute to warming.

AFP

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NASA resets spacewalk after ruling out immediate threat from orbital debris – Financial Post

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A spacewalk planned for Tuesday to replace a faulty antenna on the International Space Station has been postponed for 48 hours, after mission control concluded that the position of orbital debris cited for the delay posed no risk to the repair operation, NASA said.

Two U.S. astronauts were originally due to venture outside the space station on Tuesday morning to begin their work, despite what NASA officials acknowledged was a slightly elevated risk level from debris scattered in low-Earth orbit by a Russian anti-satellite missile test this month.

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But about five hours before the outing was to have begun, the National Aeronautics and Space Administration announced the spacewalk had been temporarily called off after mission control was alerted that the U.S. military’s Space Surveillance Network had detected debris that could collide with the space station. The origin of the debris was not made clear in the NASA announcement.

On Tuesday afternoon, NASA said its evaluation of the situation “determined the orbit of the debris does not pose a risk to a scheduled spacewalk” or space station operations.

The antenna repair was rescheduled for Thursday, with astronauts Tom Marshburn, 61, and Kayla Barron, 34, set to begin their planned 6-1/2-hour spacewalk starting at 7:10 a.m. EST (1210 GMT).

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A NASA spokesman, Gary Jordan, said there was no information available about the size of the debris, its proximity to the space station, which is orbiting about 250 miles (402 km) above the Earth, or whether one or more objects were involved.

“We have no indications that this is related” to the Russian missile test weeks earlier, Jordan added in an email to Reuters.

The planned “extravehicular activity,” or EVA, will mark the fifth spacewalk for Marshburn, a medical doctor and former flight surgeon with two previous trips to orbit, and a first for Barron, a U.S. Navy submarine officer and nuclear engineer on her debut spaceflight for NASA.

Their objective is to remove a faulty S-band radio communications antenna assembly, now more than 20 years old, and replace it with a new spare stowed outside the space station.

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According to plans, Marshburn will work with Barron while positioned at the end of a robotic arm operated from inside the station by German astronaut Matthias Maurer of the European Space Agency, with help from NASA crewmate Raja Chari.

The four arrived at the station on Nov. 11 in a SpaceX Crew Dragon capsule launched from the Kennedy Space Center in Florida, joining two Russian cosmonauts and a NASA astronaut already aboard the space laboratory.

Four days later, Russia fired a missile into one of its own defunct satellites in an unannounced space weapons test, generating a large orbital debris field that prompted an emergency aboard the space station. All seven crew members scrambled to take shelter in their docked spaceships to allow for a quick getaway until the immediate danger passed, according to NASA.

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The residual debris cloud from the blasted satellite has since dispersed, according to Dana Weigel, NASA deputy manager of the space station program.

But NASA calculates that remaining fragments continue to pose a “slightly elevated” background risk to the orbiting platform as a whole, and a 7% higher risk of spacewalkers’ suits being punctured, as compared to before Russia’s missile test, Weigel told reporters on Monday.

Although NASA has yet to fully quantify hazards posed by more than 1,700 larger fragments it is tracking around the station’s orbit, the 7% higher risk to spacewalkers falls “well within” fluctuations previously seen in “the natural environment,” Weigel said. (Reporting by Steve Gorman; Editing by Gerry Doyle and Peter Cooney)

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