New solar cell may be most efficient in the world

July 13, 2017

Washington, Jul 13: Scientists have designed a new solar cell that converts direct sunlight to electricity with 44.5 per cent efficiency, and may potentially be the most efficient solar cell in the world.solar

The prototype integrates multiple cells stacked into a single device capable of capturing nearly all of the energy in the solar spectrum, researchers said.

The approach developed by researchers at George Washington University (GWU) in the US is different from the solar panels one might commonly see on rooftops or in fields.

The new device uses concentrator photovoltaic (CPV) panels that employ lenses to concentrate sunlight onto tiny, micro-scale solar cells.

Due to their small size - less than one millimetre square - solar cells utilising more sophisticated materials can be developed cost effectively, researchers said.

The stacked cell acts almost like a sieve for sunlight, with the specialised materials in each layer absorbing the energy of a specific set of wavelengths.

By the time the light is funnelled through the stack, just under half of the available energy has been converted into electricity. By comparison, the most common solar cell today converts only a quarter of the available energy into electricity.

"Around 99 per cent of the power contained in direct sunlight reaching the surface of Earth falls between wavelengths of 250 nanometres (nm) and 2,500 nm, but conventional materials for high-efficiency multi-junction solar cells cannot capture this entire spectral range," said Matthew Lumb, lead author of the study published in the journal Advanced Energy Materials.

"Our new device is able to unlock the energy stored in the long-wavelength photons, which are lost in conventional solar cells, and therefore provides a pathway to realising the ultimate multi-junction solar cell," said Lumb.

While scientists have worked towards more efficient solar cells for years, this approach has two novel aspects.

First, it uses a family of materials based on gallium antimonide (GaSb) substrates, which are usually found in applications for infra-red lasers and photodetectors. The novel GaSb-based solar cells are assembled into a stacked structure along with high efficiency solar cells grown on conventional substrates that capture shorter wavelength solar photons.

In addition, the stacking procedure uses a technique known as transfer-printing, which enables three dimensional assembly of these tiny devices with a high degree of precision.

This particular solar cell is very expensive, however researchers believe it was important to show the upper limit of what is possible in terms of efficiency.

Despite the current costs of the materials involved, the technique used to create the cells shows much promise, researchers said.

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Agencies
January 7,2020

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.

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Agencies
June 8,2020

Washington DC, Jun 8: Astronomers acting on a hunch have likely resolved a mystery about young, still-forming stars and regions rich in organic molecules closely surrounding some of them.

They used the National Science Foundation's Karl G Jansky Very Large Array (VLA) to reveal one such region that previously had eluded detection and that revelation answered a longstanding question.

The regions around the young protostars contain complex organic molecules which can further combine into prebiotic molecules that are the first steps on the road to life.

The regions, dubbed "hot corinos" by astronomers, are typically about the size of our solar system and are much warmer than their surroundings, though still quite cold by terrestrial standards.

The first hot corino was discovered in 2003 and only about a dozen have been found so far. Most of these are in binary systems, with two protostars forming simultaneously.

Astronomers have been puzzled by the fact that, in some of these binary systems, they found evidence for a hot corino around one of the protostars but not the other.

"Since the two stars are forming from the same molecular cloud and at the same time, it seemed strange that one would be surrounded by a dense region of complex organic molecules and the other wouldn't," said Cecilia Ceccarelli, of the Institute for Planetary Sciences and Astrophysics at the University of Grenoble (IPAG) in France.

The complex organic molecules were found by detecting specific radio frequencies, called spectral lines, emitted by the molecules. Those characteristic radio frequencies serve as "fingerprints" to identify the chemicals.

The astronomers noted that all the chemicals found in hot corinos had been found by detecting these "fingerprints" at radio frequencies corresponding to wavelengths of only a few millimetres.

"We know that dust blocks those wavelengths, so we decided to look for evidence of these chemicals at longer wavelengths that can easily pass through dust," said Claire Chandler of the National Radio Astronomy Observatory, and principal investigator on the project.

"It struck us that dust might be what was preventing us from detecting the molecules in one of the twin protostars," added Chandler.

The astronomers used the VLA to observe a pair of protostars called IRAS 4A, in a star-forming region about 1,000 light-years from Earth. They observed the pair at wavelengths of centimetres.

At those wavelengths, they sought radio emissions from methanol, CH3OH (wood alcohol, not for drinking). This was a pair in which one protostar clearly had a hot corino and the other did not, as seen using the much shorter wavelengths.

The result confirmed their hunch. "With the VLA, both protostars showed strong evidence of methanol surrounding them. This means that both protostars have hot corinos. The reason we did not see the one at shorter wavelengths was because of dust," said Marta de Simone, a graduate student at IPAG who led the data analysis for this object.

The astronomers cautioned that while both hot corinos now are known to contain methanol, there still may be some chemical differences between them. That, they said, can be settled by looking for other molecules at wavelengths not obscured by dust.

"This result tells us that using centimetre radio wavelengths is necessary to properly study hot corinos," Claudio Codella of Arcetri Astrophysical Observatory in Florence, Italy, said.

"In the future, planned new telescopes such as the next-generation VLA and SKA, will be very important to understanding these objects," added Codella.

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Agencies
February 5,2020

San Francisco, Feb 5: After a German artist, Simon Weckert, demonstrated how he "hacked" Google Maps with 99 smartphones and a wagon to create "virtual traffic jams" on the streets of Berlin, Google responded to the incident saying it "appreciates" creative use of maps.

Admitting that it has not quite cracked travelling by wagon, the tech giant also hinted that it might use cases like this to improve how its maps work.

"We appreciate seeing creative uses of Google Maps like this as it helps us make maps work better over time," 9to5Google quoted a Google spokesperson as saying.

In a YouTube video, Weckert showed that he put 99 smartphones with Google Maps onto a small wagon cart and then wheeled that cart around various streets in Berlin, including outside the Google office, Android Authority reported on Monday.

The smartphones "apparently fooled Google Maps" into thinking that there was a high concentration of users on those streets.

Because the second-hand phones were in a cart, Maps was further tricked into believing that the traffic was slow-moving.

As a result, the navigation app started showing virtual traffic jams by turning green streets to red in the online navigational tool, showcasing how digital technology can have a real impact on the real world.

"Traffic data in Google Maps is refreshed continuously thanks to information from a variety of sources, including aggregated anonymised data from people who have location services turned on and contributions from the Google Maps community," the Google spokesperson said.

"We've launched the ability to distinguish between cars and motorcycles in several countries including India, Indonesia and Egypt, though we haven't quite cracked travelling by wagon," the statement added. After a German artist, Simon Weckert, demonstrated how he "hacked" Google Maps with 99 smartphones and a wagon to create "virtual traffic jams" on the streets of Berlin, Google responded to the incident saying it "appreciates" creative use of maps.

Admitting that it has not quite cracked travelling by wagon, the tech giant also hinted that it might use cases like this to improve how its maps work.

"We appreciate seeing creative uses of Google Maps like this as it helps us make maps work better over time," 9to5Google quoted a Google spokesperson as saying.

In a YouTube video, Weckert showed that he put 99 smartphones with Google Maps onto a small wagon cart and then wheeled that cart around various streets in Berlin, including outside the Google office, Android Authority reported on Monday.

The smartphones "apparently fooled Google Maps" into thinking that there was a high concentration of users on those streets.

Because the second-hand phones were in a cart, Maps was further tricked into believing that the traffic was slow-moving.

As a result, the navigation app started showing virtual traffic jams by turning green streets to red in the online navigational tool, showcasing how digital technology can have a real impact on the real world.

"Traffic data in Google Maps is refreshed continuously thanks to information from a variety of sources, including aggregated anonymised data from people who have location services turned on and contributions from the Google Maps community," the Google spokesperson said.

"We've launched the ability to distinguish between cars and motorcycles in several countries including India, Indonesia and Egypt, though we haven't quite cracked travelling by wagon," the statement added.

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