New laser technology can make objects invisible

Agencies
September 14, 2017

London, Sept 14: Scientists have developed a cloaking technology that can make opaque materials invisible by using light waves from lasers, paving the way for novel ways of camouflaging objects.

A completely opaque material is irradiated from above with a specific wave pattern - with the effect that light waves from the left can pass through the material without any obstruction.

The technique can be applied to different kinds of waves, and should work with sound waves just as well as with light waves, researchers said.

"Complex materials such as a sugar cube are opaque, because light waves inside them are scattered multiple times," said Stefan Rotter, from Technische Universitat Wien (TU Wien) in Austria.

"A light wave can enter and exit the object, but will never pass through the medium on a straight line. Instead, it is scattered into all possible directions," said Rotter.

For years many different attempts have been made to outwit this kind of scattering, creating a "cloak of invisibility."

Special materials have been worked out, for example, which are able to guide light waves around an object. Alternatively, also experiments have been performed with objects that can emit light by themselves.

When an electronic display sends out exactly the same light as it absorbs in the back, it can appear invisible, at least when looked at in the right angle.

"We did not want to reroute the light waves, nor did we want to restore them with additional displays. Our goal was to guide the original light wave through the object, as if the object was not there at all," said Andre Brandstotter, one of the authors of the study.

"This sounds strange, but with certain materials and using our special wave technology, it is indeed possible," said Brandstotter.

To make the laser shine, energy has to be supplied by means of a pump beam. Otherwise, the laser material behaves just like any other material - it absorbs part of the incident light.

"The crucial point is to pump energy into the material in a spatially tailored way such that light is amplified in exactly the right places, while allowing for absorption at other parts of the material," said Konstantinos Makris from the University of Crete in Greece.

"To achieve this, a beam with exactly the right pattern has to be projected onto the material from above - like from a standard video projector, except with much higher resolution," said Makris.

If this pattern perfectly corresponds to the inner irregularities of the material which usually scatter the light, then the projection from above can effectively switch off the scattering, and another beam of light travelling through the material from one side can pass without any obstruction, scattering or loss.

"Mathematically, it is not immediately obvious that it is at all possible to find such a pattern," said Rotter.

"Every object we want to make transparent has to be irradiated with its own specific pattern - depending on the microscopic details of the scattering process inside," he said.

"The method we developed now allows us to calculate the right pattern for any arbitrary scattering medium," he added.

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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
January 16,2020

Claiming that e-commerce giants like Amazon import as much as 80 per cent of the items sold on their platforms, small manufacturers' body has said that their business models do not benefit local industry and are creating jobs of delivery boys only.

"Neither manufacturers nor traders are getting any benefit from the business models of Amazon and Flipkart because they largely import their products from China and Korea and sell here. Nearly 80 per cent of their products are imported," said Anil Bhardwaj, Secretary General, Federation of Indian Micro and Small & Medium Enterprises (FISME).

Bhardwaj said that the global e-commerce players generally source and sell products through their own preferred suppliers and as a result a large number of local manufacturers and traders get crowded out.

He listed out deep discounting and buying products from preferred companies as unfair practices.

"Even if they buy products from local suppliers the commission charged is very high," Bhardwaj said adding that the issues related to unfair practices have been raised with Commerce Ministry on multiple occasions.

FISME maintains that the technology-driven retail is way forward and one cannot be oblivious of the benefits it brings to consumers but at the same time the local industry can also not be ignored given its role in job creation.

"If both traders and local manufacturers are crowded out then how would the local industry survive and employment be generated?" asked Bhardwaj.

As Amazon Founder and CEO Jeff Bezos is currently on his three-day visit to India, the local traders are up in arms against the "unfair" trade practices of the tech giant. Delhi-based Confederation of All India Traders (CAIT) has launched a countrywide protest against the company and has organised protests across 300 cities.

In a setback to Amazon and Walmart-backed Flipkart, the fair market watchdog Competition Commission of India (CCI) has ordered probe into the business operations of both the companies on multiple counts including deep-discounts and exclusive tie-up with preferred sellers.

"For the first time some concrete step has been taken against Amazon and Flipkart who are continuously violating the FDI policy in indulging in a vicious racket of controlling and monopolising not only the e-commerce but even the retail trade as well," CAIT National Secretary General Praveen Khandelwal said after the CCI order.

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Agencies
June 12,2020

Mumbai, Jun 12: Following an overwhelming response for the mega rights issue of Mukesh Ambani-owned Reliance Industries, the partly paid-up rights shares are set to debut on stock exchanges on June 15.

The biggest ever Rs 53,124 crore rights issue was subscribed 1.59 times and received bids worth Rs 84,000 crore on June 3.

Reliance said the rights issue saw a huge investor interest, including from lakhs of small investors and thousands of institutional investors, both Indian and foreign.

In 2019, Ambani said in the Reliance's annual general meeting that the company will be net zero debt by March 2021. The company is on course to achieve its target ahead of the deadline.

"In spite of the COVID-19 crisis and the lockdowns, the due-diligence by Saudi Aramco for the planned investment in the O2C business is on track as both the parties are committed and actively engaged," he said recently.

"With a strong visibility to these equity infusions, Reliance is set to achieve net zero debt status ahead of its own aggressive timeline. We believe rights issue was a part of the company's strategy of deleveraging its balance sheet," said Ambani. 

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