'New light-absorbent material to cool buildings, cars'

February 5, 2017

Los Angeles, Feb 5: Scientists have developed a thin, flexible, lightweight material that can block thermal detection and absorb light from every angle to keep buildings and cars cool on hot summer days.

absorbentThe material, developed by engineers at the University of California San Diego in the US, is called a near-perfect broadband absorber.

It absorbs more than 87 per cent of near-infrared light (1,200 to 2,200 nanometre wavelengths), with 98 per cent absorption at 1,550 nanometres, the wavelength for fiber optic communication.

The material is capable of absorbing light from every angle. It also can theoretically be customised to absorb certain wavelengths of light while letting others pass through.

Materials that "perfectly" absorb light already exist, but they are bulky and can break when bent. They also cannot be controlled to absorb only a selected range of wavelengths, which is a disadvantage for certain applications.

Imagine if a window coating used for cooling not only blocked infrared radiation, but also normal light and radio waves that transmit television and radio programmes.

By developing a novel nanoparticle-based design, a team led by professors Zhaowei Liu and Donald Sirbuly at the UC San Diego has created a broadband absorber that is thin, flexible and tunable.

"This material offers broadband, yet selective absorption that could be tuned to distinct parts of the electromagnetic spectrum," said Liu.

The absorber relies on optical phenomena known as surface plasmon resonances, which are collective movements of free electrons that occur on the surface of metal nanoparticles upon interaction with certain wavelengths of light.

Metal nanoparticles can carry a lot of free electrons, so they exhibit strong surface plasmon resonance - but mainly in visible light, not in the infrared.

The researchers reasoned that if they could change the number of free electron carriers, they could tune the material's surface plasmon resonance to different wavelengths of light.

"Make this number lower, and we can push the plasmon resonance to the infrared. Make the number higher, with more electrons, and we can push the plasmon resonance to the ultraviolet region," said Sirbuly.

The problem with this approach is that it is difficult to do in metals. To address this challenge, engineers designed and built an absorber from materials that could be modified, or doped, to carry a different amount of free electrons: semiconductors.

Researchers used a semiconductor called zinc oxide, which has a moderate number of free electrons, and combined it with its metallic version, aluminium-doped zinc oxide, which houses a high number of free electrons — not as much as an actual metal, but enough to give it plasmonic properties in the infrared.

The study was published in the journal Proceedings of the National Academy of Sciences.

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Agencies
June 9,2020

Soon, you may be able to withdraw cash from an ATM without touching any part of the machine. AGS Transact Technologies, a provider of cash and digital payment solutions and automation technology, on Monday said it has successfully developed and tested a touchless ATM solution in light of the COVID-19 pandemic.

The ‘contactless' solution, currently under demo at interested banks, enables a customer to perform all the steps required to withdraw cash from an ATM using the mobile app itself. 

The customer simply has to scan the QR code displayed on the ATM screen and follow the directions on their respective bank's mobile application. 

This includes entering the amount and mPIN required to dispense the cash from the ATM machine. 

According to the company, the QR code feature makes cash withdrawals quicker and more secure, and negates the chances of compromising the ATM Pin or card skimming.

"The new Touchless ATM solution is an extension of the flagship QR Cash solution which ensures safety of the users and will provide a seamless cash withdrawal experience with enhanced security," said Ravi B. Goyal, Chairman and MD, AGS Transact Technologies Ltd.

With minimum investment, the banks can enable this solution for their ATM networks by upgrading the existing software.

AGSTTL has so far installed, maintained and managed a network of over 72,000 ATMs across the country and also provides customised solutions to leading banks. 

The company earlier introduced UPI-QR based Cash withdrawal solution in partnership with Bank of India. 

This is how the solution works.

Open the Bank mobile application on your smartphone and select QR Cash Withdrawal. Enter the amount you wish to withdraw on the mobile app and scan the QR code on the ATM screen.

Next, confirm the amount by clicking on ‘proceed' in the app and enter the mPin to authenticate the transaction. Now collect the cash and receipt and you are done.

"The seamless, cardless and touchless withdrawal method is designed to provide easy transaction flow, without the need to touch the ATM screen or enter the pin," said Mahesh Patel, President and Group Chief Technology Officer, AGS Transact Technologies.

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News Network
March 18,2020

San Francisco, Mar 18: Facebook said a bug in its anti-spam system temporarily blocked the publication of links to news stories about the coronavirus. Guy Rosen, Facebook's vice president of integrity, said on Twitter Tuesday that the company was working on a fix for the problem.

Users complained that links to news stories about school closings and other information related to the virus outbreak were blocked by the company's automated system.

Later on Tuesday, Rosen tweeted that Facebook had restored all the incorrectly deleted posts, which also covered topics beyond the coronavirus.

Rosen said the problems were unrelated to any changes in Facebook's content-moderator workforce. The company reportedly sent its human moderators home this week because of the coronavirus outbreak.

A representative for Facebook did not immediately respond to questions on the status of Facebook's content moderators, many of whom do not work directly for the company and are not always able to work from home.

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News Network
April 17,2020

Paris, Apr 17: Even as virologists zero in on the virus that causes COVID-19, a very basic question remains unanswered: do those who recover from the disease have immunity?

There is no clear answer to this question, experts say, even if many have assumed that contracting the potentially deadly disease confers immunity, at least for a while.

"Being immunised means that you have developed an immune response against a virus such that you can repulse it," explained Eric Vivier, a professor of immunology in the public hospital system in Marseilles.

"Our immune systems remember, which normally prevents you from being infected by the same virus later on."

For some viral diseases such a measles, overcoming the sickness confers immunity for life.

But for RNA-based viruses such as Sars-Cov-2 -- the scientific name for the bug that causes the COVID-19 disease -- it takes about three weeks to build up a sufficient quantity of antibodies, and even then they may provide protection for only a few months, Vivier told AFP.

At least that is the theory. In reality, the new coronavirus has thrown up one surprise after another, to the point where virologists and epidemiologists are sure of very little.

"We do not have the answers to that -- it's an unknown," Michael Ryan, executive director of the World Health Organization's Emergencies Programme said in a press conference this week when asked how long a recovered COVID-19 patient would have immunity.

"We would expect that to be a reasonable period of protection, but it is very difficult to say with a new virus -- we can only extrapolate from other coronaviruses, and even that data is quite limited."

For SARS, which killed about 800 people across the world in 2002 and 2003, recovered patients remained protected "for about three years, on average," Francois Balloux director of the Genetics Institute at University College London, said.

"One can certainly get reinfected, but after how much time? We'll only know retroactively."

A recent study from China that has not gone through peer review reported on rhesus monkeys that recovered from Sars-Cov-2 and did not get reinfected when exposed once again to the virus.

"But that doesn't really reveal anything," said Pasteur Institute researcher Frederic Tangy, noting that the experiment unfolded over only a month.

Indeed,several cases from South Korea -- one of the first countries hit by the new coronavirus -- found that patients who recovered from COVID-19 later tested positive for the virus.

But there are several ways to explain that outcome, scientists cautioned.

While it is not impossible that these individuals became infected a second time, there is little evidence this is what happened.

More likely, said Balloux, is that the virus never completely disappeared in the first place and remains -- dormant and asymptomatic -- as a "chronic infection", like herpes.

As tests for live virus and antibodies have not yet been perfected, it is also possible that these patients at some point tested "false negative" when in fact they had not rid themselves of the pathogen.

"That suggests that people remain infected for a long time -- several weeks," Balloux added. "That is not ideal."

Another pre-publication study that looked at 175 recovered patients in Shanghai showed different concentrations of protective antibodies 10 to 15 days after the onset of symptoms.

"But whether that antibody response actually means immunity is a separate question," commented Maria Van Kerhove, Technical Lead of the WHO Emergencies Programme.

"That's something we really need to better understand -- what does that antibody response look like in terms of immunity."

Indeed, a host of questions remain.

"We are at the stage of asking whether someone who has overcome COVID-19 is really that protected," said Jean-Francois Delfraissy, president of France's official science advisory board.

For Tangy, an even grimmer reality cannot be excluded.

"It is possible that the antibodies that someone develops against the virus could actually increase the risk of the disease becoming worse," he said, noting that the most serious symptoms come later, after the patient had formed antibodies.

For the moment, it is also unclear whose antibodies are more potent in beating back the disease: someone who nearly died, or someone with only light symptoms or even no symptoms at all. And does age make a difference?

Faced with all these uncertainties, some experts have doubts about the wisdom of persuing a "herd immunity" strategy such that the virus -- unable to find new victims -- peters out by itself when a majority of the population is immune.

"The only real solution for now is a vaccine," Archie Clements, a professor at Curtin University in Perth Australia, told AFP.

At the same time, laboratories are developing a slew of antibody tests to see what proportion of the population in different countries and regions have been contaminated.

Such an approach has been favoured in Britain and Finland, while in Germany some experts have floated the idea of an "immunity passport" that would allow people to go back to work.

"It's too premature at this point," said Saad Omer, a professor of infectious diseases at the Yale School of Medicine.

"We should be able to get clearer data very quickly -- in a couple of months -- when there will be reliable antibody tests with sensitivity and specificity."

One concern is "false positives" caused by the tests detecting antibodies unrelated to COVID-19.

The idea of immunity passports or certificates also raises ethical questions, researchers say.

"People who absolutely need to work -- to feed their families, for example -- could try to get infected," Balloux.

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