'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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January 22,2020

New Delhi, Jan 22: "Don't get into a trap. Your security is in your hands," the Border Security Force (BSF) has said issuing its social media rules for its officers and men. It has directed them not to use 42 mobile applications and show caution while using Facebook, Twitter and WhatsApp.

"Be cautious while using social media," said the BSF in a circular issued recently.

"Before using WhatsApp, Facebook, Twitter and other social media platforms, one needs to keep in mind that you are border guarding force and Central Civil Services (Conduct) Rules rule duly are applicable," it said.

It further pointed out that by commenting/writing about or forwarding unverified reports and rumours one violates laws of land.

"Several times unverified reports would be presented in way that they are absolutely true and start believing it. Seeing such post always use your commonsense and never get into the trap (sic.)," it state adding that the anti-national elements uses social media to propagate their agenda to cause unrest in India.

A picture clicked by Border Security Force personnel and posted on a social media platform remains there for always. Therefore, one should use officially approved pictures about any incident or untoward incidents related to Border Security Force, stated the circular. It pointed that unauthorised persons should not engage into taking pictures of the incidents.

It also highlighted how through social media, a few BSF personnel have fallen into trap of espionage racket carried out by enemy countries.

"Our security and respect is in our hands. Always think twice whether you are doing correct by accepting friendship requests from unknown persons, especially women and girls," it cautioned the troopers and officers.

It also highlighted that while going on leave and joining back the force, always follow the rules and regulations laid out for safety and security. "This is for your own safety," it stressed in the end.

The BSF has also issued a list of 42 mobile applications that needs to be completely avoided by serving BSF officers and jawans.

They are MI store, Weibo, Wechat, Shareit, Truecaller, UC News, UC Browser, Beautyplus, NewsDog, Viva Video - QU video Inc, Parallel Space, Apus Browser, Perfect Corp, Virus Cleaner - HI Security Lab, CM browser, MI Community, DU recorder, Vault Hide - No mobile Security, Youcam Makeup, Cachecleaner DU Apps Studio, DU battery saver, DU privacy, 360 security, DU Browser,Clean master - Cheeta Mobile, Baidu Translate, Wonder Camera - Bindu Inc, ES Ifle Explorer, Photo Wonder, QQ international , QQ music, QQ Mail, AA player, QQ News Feed, Wesync, QQ security Center, Selfie City, Mail Master, Mi Video Call -Xaomi and QQ launcher.

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July 2,2020

Leiden, Jul 2: Astronomers have discovered a luminous galaxy caught in the act of reionizing its surrounding gas only 800 million years after the Big Bang.

The research, led by Romain Meyer, PhD student at UCL in London, UK, has been presented at the virtual annual meeting of the European Astronomical Society (EAS).

Studying the first galaxies that formed 13 billion years ago is essential to understanding our cosmic origins. One of the current hot topics in extragalactic astronomy is 'cosmic reionization,' the process in which the intergalactic gas was ionized (atoms stripped of their electrons).

Cosmic reionization is similar to an unsolved murder: We have clear evidence for it, but who did it, how and when? We now have strong evidence that hydrogen reionization was completed about 13 billion years ago, in the first billion years of the universe, with bubbles of ionized gas slowly growing and overlapping.

The objects capable of creating such ionized hydrogen bubbles have however remained mysterious until now: the discovery of a luminous galaxy in which 60-100 percent of ionizing photons escape, is likely responsible for ionizing its local bubble. This suggests the case is closer to being solved.

The two main suspects for cosmic reionization are usually 1) a population of numerous faint galaxies leaking ~10 percent of their energetic photons, and 2) an 'oligarchy' of luminous galaxies with a much larger percentage (>50 percent) of photons escaping each galaxy.

In either case, these first galaxies were very different from those today: galaxies in the local universe are very inefficient leakers, with only <2-3 percent of ionizing photons escaping their host. To understand which galaxies governed cosmic reionization, astronomers must measure the so-called escape fractions of galaxies in the reionization era.

The detection of light from excited hydrogen atoms (the so-called Lyman-alpha line) can be used to infer the fraction of escaping photons. On the one hand, such detections are rare because reionization-era galaxies are surrounded by neutral gas which absorbs that signature hydrogen emission.

On the other hand, if this hydrogen signal is detected it represents a 'smoking gun' for a large ionized bubble, meaning we have caught a galaxy reionizing its surroundings. The size of the bubble and the galaxy's luminosity determines whether it is solely responsible for creating this ionized bubble or if unseen accomplices are necessary.

The discovery of a luminous galaxy 800 million years after the Big Bang supports the scenario where an 'oligarchy' of bright leakers emits most of the ionizing photons.

"It is the first time we can point to an object responsible for creating an ionized bubble, without the need for a contribution from unseen galaxies.

Additional observations with the upcoming James Webb Space Telescope will enable us to study further what is likely one of the best suspects for the unsolved case of cosmic reionization," said Meyer.

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January 20,2020

Washington D.C., Jan 20: An American bride asked for money from her invitees so that they can be on the 'exclusive guest list'.

Weddings can be surely expensive. But is it feasible for one to charge the guests to make up for the expenses?

According to Fox News, that is exactly what happened in a recent American wedding. A 19-year-old shared on Reddit that her cousin was getting married on Sunday and announced that she would charge 50 dollars to those who wanted to attend her wedding.

"She said that they can Venmo her money so there won't be no [sic] problems and everyone who paid will be added onto the 'exclusive guest list' which basically means you won't have to wait in line while other guests pay," wrote the user named DaintySheep.

While she refused to pay for entry into her cousin's wedding the bride-to-be contacted the elders in the family which ended up in an embarrassing situation.

"She wanted to get the money she spent on her special day back. I told her I wouldn't be able to come because this was outrageous and that I wish her well on her special day. She contacted my aunt and my aunt called me cheap and rude. My parents offered to pay for my entry, but I refused," continued the disheartened girl.

While in almost every nook and cranny of the world gifting the bride-groom with money is a tradition, asking for money from friends and family to replenish the money spent on a wedding is can be said to be a rare scenario.

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