Researchers glimpse the inside of a photonic crystal

first_img More information: T. Denis, B. Reijnders, J. H. H. Lee, P. J. M. van der Slot, W. L. Vos and K.-J. Boller. “Mapping individual electromagnetic field components inside a photonic crystal.” Optics Express, Vol. 20, Issue 20, pp. 22902-22913 (2012) DOI: 10.1364/OE.20.022902Also at arXiv:1207.2004 [physics.optics] (—While today’s smart phones, tablets, and other small electronic devices rely on electrical data connections, in the future they may use optical connections in order to become even faster and smaller. Photonic crystals are ideal tools for this purpose, since they can guide and bend light on the nanometer scale. So far, researchers have not been able to look inside photonic crystals to measure how the light intensity is distributed. Now in a new study, a team of researchers from the MESA+ Institute at the University of Twente, The Netherlands, has developed a method that can measure the intensity distribution of light inside photonic crystals. © 2012 Citation: Researchers glimpse the inside of a photonic crystal (2012, October 2) retrieved 18 August 2019 from Scientists shed light on glowing materials How to measure the light intensity inside a photonic crystal: (Top) The photonic crystal, indicated by the ordered yellow circles, is placed between two mirrors. Only one color, blue, resonates. (Middle) When a bead is inserted at a specific location in the cavity and the light intensity is low, a slight color change to green occurs. (Bottom) When the light intensity is strong at the bead location, the color changes even further and becomes red. The right panel indicates how using the bead to change the resonating color can allow the light intensity to be mapped throughout the photonic crystal. Image courtesy of T. Denis To map the strength of the electromagnetic field at different locations inside photonic crystals, the researchers set up an experiment in which they placed a photonic crystal between two aluminum mirrors. Inside the cavity, light bounces back and forth between the mirrors. Since light is a wave, only waves whose wavelengths fit the length of the cavity can build up. In other words, only a specific color can exist inside the cavity. After measuring the crystal’s resonating color, or frequency, the researchers then investigated how the frequency would be altered when they lowered a 2-mm bead hanging from a nylon string inside the crystal. The bead scatters nearby electromagnetic waves, changing the crystal’s frequency in a way that is proportional to the light intensity at that location. By measuring the frequency shift when moving the bead to various locations, the researchers could map the electromagnetic field strength throughout the inside of the photonic crystal. “For example, in the figure above, the cavity limits the build-up of light to blue light,” Denis said. “When placing the bead inside the photonic crystal, this leads to scattering, which changes the light color that resonates in the cavity. The waves have to make a small detour around the scattering object. Therefore, the color where the light resonates is changed, which can be measured. In the figure it varies from green to red depending on the position of the bead. By moving the bead throughout the cavity, this allows us to map the light intensity at all locations by measuring the resulting color shift.”The researchers also explained that the electric field inside the photonic crystal has six components, and each of these components can be measured separately by choosing a bead with a suitable material, shape, and orientation so that only one component contributes to the frequency shift. In the future, the researchers also want to perform modified experiments, such as placing the bead on a carbon nanotube acting as the string. An atomic force microscope could control the nanotube’s position and provide high spatial resolution of the field inside the crystal. Ultimately, the ability to map the inside of a photonic crystal provides a valuable tool for using these devices in future applications. Explore further Journal information: Optics Express The study, which is published in a recent issue of Optics Express, may lead to new insights into photonic crystals that could assist in the development of new applications.As the researchers explain, photonic crystals are materials with an intricate three-dimensional structure that manipulates light in ways similar to how semiconductors control electrons. Photonic crystals have a periodic structure with a length scale on the order of the wavelength of light. An example of a photonic crystal found in nature is the gem opal, which consists of a regular array of tiny silicate spheres that are ordered like atoms in a crystal lattice, but on a length scale a thousand times larger than the atoms in a photonic crystal.A major goal in this area of research is to make photonic crystals interact with light strongly enough to achieve a “photonic band gap,” which is a range of light colors that are prevented from propagating in any direction. Band gaps can result from disorder in a crystal, since disorder leads to localized states that effectively trap light in a cage. This type of control can allow researchers to harness light beams and steer them around tiny optical chips.In order to control light in this way, it’s helpful to know the electromagnetic field distribution inside the photonic crystals. So far, the only optical method to map local fields is near-field scanning optical microscopy, which scans the surface of the crystal. However, this technique has several drawbacks because it cannot probe the fields inside the crystal, whereas the new method presented here can.”We have demonstrated for the first time how to look into the inside of photonic crystals,” lead author Thomas Denis of the University of Twente told “With an astonishingly simple method we were able to map the absolute strength of an individual field component inside a photonic crystal. Such a method should be of high importance for the design of novel photonic crystal devices, such as fast optical interconnects on computer chips.” This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Overcoming multiple herbicide resistance

first_img Journal information: Proceedings of the National Academy of Sciences A new way to use herbicides: To sterilize, not kill weeds Explore further Black-grass and rye-grass are considered by farmers, to be weeds. They are not only invasive—causing reduced yields in fields where they mix with crops—but can also harbor ergot, a type of fungus that can spread to crops, killing them. For these reasons, farmers have used herbicides to keep the grasses at bay. Unfortunately, the grasses have begun to develop immunity to the toxins traditionally used to kill them. In this new effort, the research group has found what appears to be the source of the plants’ new-found strength, and perhaps, a way towards creating a new way to kill them.Specifically, the team found that a gene called AmGSTF1, appears to be responsible for causing overproduction of an enzyme called glutathione transferase. In plants, the result is the production of more than normal amounts of antioxidants, which help ward off the toxins meant to kill them. The team made this discovery by adding the AmGSTF1 gene to thale cress, which does not have MHR. Doing so, they found, caused the thale cress to become just as resistant to herbicides as black or rye grass. Interestingly, the same enzyme has been found to be at least partly responsible for doing something similar with tumors that grow inside of humans. Because the enzyme has been known to help tumors in humans fight off toxic drugs, researchers have developed another drug called 4-chloro-7-nitro-benzoxadiazole—it blocks the production of glutathione transferase and as a result makes tumors easier to kill. Because of that, the researchers studying the invasive grasses tried spraying it on the thale cress that had been made resistant to herbicides and found that doing so caused it to lose its new-found abilities and to be once again susceptible to the chemicals meant to kill them. Unfortunately for farmers, the same drug cannot be used on invasive weeds because it’s toxic to people as well. But, the researchers suggest another similar drug might be developed that could do the job without harming those that eat the crops the farmers are trying to protect. Citation: Overcoming multiple herbicide resistance (2013, March 26) retrieved 18 August 2019 from More information: Key role for a glutathione transferase in multiple-herbicide resistance in grass weeds, PNAS, Published online before print March 25, 2013, doi: 10.1073/pnas.1221179110AbstractMultiple-herbicide resistance (MHR) in black-grass (Alopecurus myosuroides) and annual rye-grass (Lolium rigidum) is a global problem leading to a loss of chemical weed control in cereal crops. Although poorly understood, in common with multiple-drug resistance (MDR) in tumors, MHR is associated with an enhanced ability to detoxify xenobiotics. In humans, MDR is linked to the overexpression of a pi class glutathione transferase (GSTP1), which has both detoxification and signaling functions in promoting drug resistance. In both annual rye-grass and black-grass, MHR was also associated with the increased expression of an evolutionarily distinct plant phi (F) GSTF1 that had a restricted ability to detoxify herbicides. When the black-grass A. myosuroides (Am) AmGSTF1 was expressed in Arabidopsis thaliana, the transgenic plants acquired resistance to multiple herbicides and showed similar changes in their secondary, xenobiotic, and antioxidant metabolism to those determined in MHR weeds. Transcriptome array experiments showed that these changes in biochemistry were not due to changes in gene expression. Rather, AmGSTF1 exerted a direct regulatory control on metabolism that led to an accumulation of protective flavonoids. Further evidence for a key role for this protein in MHR was obtained by showing that the GSTP1- and MDR-inhibiting pharmacophore 4-chloro-7-nitro-benzoxadiazole was also active toward AmGSTF1 and helped restore herbicide control in MHR black-grass. These studies demonstrate a central role for specific GSTFs in MHR in weeds that has parallels with similar roles for unrelated GSTs in MDR in humans and shows their potential as targets for chemical intervention in resistant weed management. ( —British scientists from several research facilities across the country have found that an enzyme called glutathione transferase which is known to neutralize toxins meant to stem the growth of tumors in humans, also appears to be responsible for helping two kinds of invasive grasses develop multiple herbicide resistance (MHR). The team has published the results of their study in the Proceedings of the National Academy of Sciences. © 2013 This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Chaos could improve performance of wireless communication systems

first_imgResearchers have found that the information transmitted by a chaotic signal in a wireless communication system is not modified by the wireless channel as it is for non-chaotic signals. These figures show reconstructions of wireless signals traveling in different wireless channels. Credit: Hai-Peng Ren, et al. ©2013 American Physical Society Explore further The researchers, Hai-Peng Ren at Xi’an University of Technology in Xi’an, China, and the University of Aberdeen in Aberdeen, UK; Murilo S. Baptista at the University of Aberdeen; and Celso Grebogi at Freiburg University in Freiburg, Germany, have published their paper on wireless communication with chaos in a recent issue of Physical Review Letters.Although this is the first time that researchers have investigated how chaotic signals can be used in a wireless communication system, there has been a large amount of research on using chaotic signals in wired communication systems. The use of chaos in communication systems is appealing due to several intrinsic properties of chaos and the fact that chaotic signals can be generated by low-power, low-cost, small-area electronic circuits. “A chaotic signal is generated by a non-linear system that has sensitivity dependence on initial conditions,” Baptista, on behalf of his coauthors, told “Small perturbations in the system at a given time produce large changes at a later time—a property that is measured by the Lyapunov exponent. A chaotic signal has at least one positive Lyapunov exponent (two nearby initial conditions diverge exponentially fast from each other), but also negative ones. A chaotic signal is also aperiodic and broadband (it processes infinitely many frequencies). This last property is the consequence of the fact that a chaotic trajectory stays very close to an infinite set of periodic signals of infinitely many periods. “A non-chaotic signal, such as a periodic one, is characterized by having a well-defined period (it always returns after completing one period; it is not aperiodic), it is generated by a system that does not have sensitivity to initial conditions, and it has only one well-defined frequency (not broadband).”Scientists have previously shown that chaotic signals in wired communication systems can achieve higher bit rates (resulting in faster information transmission) in a commercial wired fiber-optic channel compared with non-chaotic signals. In the new paper, the scientists’ main result is that, although a chaotic signal itself is strongly modified by the wireless physical media through which it propagates, the information transmitted by the signal is not modified. That is, the information remains exactly the same when it is picked up at the receiver as it was when it was sent by the transmitter, despite having traveled through open space.The researchers attribute this finding to the fact that chaotic signals preserve their spectra of positive Lyapunov exponents after being transmitted through wireless channels. The researchers also calculated that the amount of information in a transmitted chaotic signal is equal to its positive Lyapunov exponent, allowing them to determine a chaotic signal’s information capacity.”The fact that the positive Lyapunov exponent(s) of any chaotic signal is (are) preserved in the wireless channel means that the information transmitted arrives to the receiver and is available to be ‘collected’ (decoded),” Baptista said. “Decoding is possible because the negative Lyapunov exponents are also preserved, and allow us to use chaotic signals that, despite being modified, preserve their topological form (dimension).”This capability of chaotic signals to propagate through open space while preserving their information is very different from the behavior of non-chaotic signals, where both the signal and the information it carries are modified by the physical media. One of the biggest causes of modification is multipath propagation, which occurs when a signal is disrupted so that it travels along many different paths and arrives many times at the receiving location. Interference and noise occur as a result, preventing information from being transmitted at a high bit rate. Multipath propagation is caused by reflection and refraction from the atmosphere, water, and terrestrial objects.As the researchers explain, wireless chaotic signals are not affected by multipath effects. This is because a chaotic signal that is used to communicate wirelessly has an information capacity (the amount of information per unit of time) that depends on the Lyapunov exponents of the signal—which is a property of the chaotic signal itself—but does not depend on the properties of the physical wireless channel, i.e., the multipath. It is as if multipath does not exist in the wireless channel. On the other hand, the amount of information per unit of time that can be transmitted wirelessly using non-chaotic signals depends on the properties of the multipath. As a result, chaos provides a natural way to create high-capacity communication systems.The researchers are currently developing a prototype chaos-based wireless communication system based on the ability of wireless chaotic signals to preserve their Lyapunov exponents after transmission. They predict that it will possible to develop a large-scale chaos-based wireless communication system that would have excellent performance by overcoming the interference and noise that negatively affect today’s non-chaotic wireless signals. © 2013 All rights reserved. Chaos proves superior to order More information: Hai-Peng Ren, et al. “Wireless Communication with Chaos.” PRL 110, 184101 (2013). DOI: 10.1103/PhysRevLett.110.184101 This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Journal information: Physical Review Letters Citation: Chaos could improve performance of wireless communication systems (2013, May 13) retrieved 18 August 2019 from ( —In today’s wireless communication systems, the wireless signals are non-chaotic, meaning they have a well-defined period and frequency. Non-chaotic wireless signals are used in many applications, such as satellite communications, GPS navigation, cell phones, and Wi-Fi devices. However, as many people know first-hand, wireless systems usually have inferior performance compared to wired systems. The problem is due to physical impediments that the wireless signal faces in open space caused by the atmosphere, water, mountains, buildings, and other different media. Now in a new study, researchers have investigated how wireless communication could be implemented with chaotic signals, and found that chaotic signals could overcome some of these physical constraints and lead to superior performance.last_img read more

Scientists say Russian meteor shockwave went twice around globe

first_imgMeteor trail over eastern Russia is seen in this image from the Russian Emergency Ministry. Credit: Russian Emergency Ministry More information: Geophysical Research Letters DOI: 10.1002/grl.50619Planetary and Space Science DOI: 10.1016/j.pss.2013.05.003 The 10,000-ton space rock burned up above Chelyabinsk. The BBC said Alexis Le Pichon, Atomic Energy Commission in France, and his research colleagues reported that the explosive energy of the impact was equivalent to 460 kilotons of TNT. Writing in the Geophysical Research Letters journal, their article is titled “Russian Fireball Largest Ever Detected by CTBTO infrasound sensors.” Authors are Alexis Le Pichon, Lars Ceranna, Christoph Pilger, Pierrick Mialle, David Brown, Pascal Herry, and Nicolas Brachet.”On 15 February 2013,” they wrote, “a large Earth-impacting fireball disintegrated over the Ural Mountains. This extraordinary event is, together with the 1908 Tunguska fireball, among the most energetic events ever instrumentally recorded.” The 1908 reference is to the event that occurred that year in Siberia.As for the February event, the authors noted that, after circling the globe, it generated infrasound returns at distances up to ~85,000?km, and was detected at 20 infrasonic stations of the global International Monitoring System. Multiple arrivals involving waves that traveled twice round the globe were identified. “A preliminary estimate of the explosive energy using empirical period-yield scaling relations gives a value of 460 kilotons of TNT equivalent. In the context of the future verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), this event provides a prominent milestone for studying in detail infrasound propagation around the globe for almost three days as well as for calibrating the performance of the IMS network.”Their numbers suggest the February asteroid event is the most energetic event reported since the 1908 Tunguska meteor in Siberia. Turning to Tunguska, another team of scientists published a study offering their evidence of the meteoritic origin of the Tunguska cosmic body. Their discussion of the 1908 fireball is in the journal Planetary and Space Science. Diamond–lonsdaleite–graphite micro-samples collected from peat after the 1908 catastrophic blast in the Tunguska area were studied with scanning (SEM) and transmission electron (TEM) microscopy, NanoSecondary Ion Mass Spectrometry (NanoSIMS) and an X-ray synchrotron technique. © 2013 Citation: Scientists say Russian meteor shockwave went twice around globe (2013, June 29) retrieved 18 August 2019 from ( —Scientists have determined that an asteroid that burned up over Russia in February resulted in a shock wave so powerful that it traveled twice around the globe. They made that determination by means of a system of sensors used to detect evidence of nuclear tests. Researchers studied data from the International Monitoring System network operated by the Comprehensive Nuclear-Test-Ban Treaty Organization. Its stations monitor ultra-low frequency acoustic waves, or infrasound, from nuclear test explosions. The system can also detect blasts from other sources. According to BBC News, it was the most powerful event ever recorded by the network. Russian fireball largest ever detected by CTBTO’s infrasound sensors Explore further , Planetary and Space Science Journal information: Geophysical Research Letters This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Japanese firm proposes LUNA RING to send solar energy from moon to

first_img Japanese firm wants to transform the Moon into a giant solar power plant Explore further It’s quite possible that Shimizu has no intention of actually attempting to carry out its proposed project, but is instead using it as showcase to demonstrate the great lengths it and the country are willing to go to restore the electrical infrastructure of their country. It’s also possible that other, less difficult projects or new technologies could make the construction of LUNA RING moot by the time the company is ready to start building it. Since the earthquake and tsunami that struck Japan back in March 2011 (which led to closing the country’s nuclear power plants) scientists there (and elsewhere) have been scrambling to find ways to create electricity for the country in other ways. In this latest proposal, a private company is reaching, quite literally, for the sky.The idea, company reps say, is to lay down a band of concrete (which can be made from moon soil) 250 miles wide all the way around the moon’s equator (a distance of approximately 6,800 miles), using robots directed by humans back here on Earth. Next, the concrete would be covered with solar panels, which would be connected via cables to microwave and laser transmission stations. The energy beams sent from the moon would be directed at receiving stations on Earth, allowing for a round-the-clock source of energy as there are no clouds or other bad weather on the moon. Shimizu claims that such a system would be capable of sending 13,000 terawatts of power back to Earth and that construction could begin on the project as early as 2035.Not addressed are the costs and considerable hurdles such a project would have to overcome—foremost among them would be building such a massive structure from such a great distance—nothing like it has ever been attempted. There are also issues of getting the international community to go along with the project and overcoming seemingly simple problems, such as lunar soil disrupting the robots and their construction efforts—not to mention dusting the solar cells once in place. Citation: Japanese firm proposes LUNA RING to send solar energy from moon to Earth (2013, November 29) retrieved 18 August 2019 from read more

Just being jazzy

first_imgGroups of old and young women and men swinging and tapping as they stand in front of the kiosks with headphones listening to Jazz were spotted at the Art Gallery of the Kamladevi Block at the India International Center (IIC). A few people were also seen jotting down notes from the panels that trace the history of jazz in India from early 1900 to the present days. Some of them looked in wonder at the cartoon-sketches by Mario de Miranda from the Jazz Yatra of 1980 and ‘90s. Besides lot of jazz performances happening around, perhaps, this was the first time the city witnessed an exhibition based on Archival collections, curated by Naresh Fernandes, which showcased the history of Jazz in India that started on 26 November. Also Read – ‘Playing Jojo was emotionally exhausting’The five-day exhibition was based on two collections – Niranjan Jhaveri Jazz Collection and Naresh Fernandes Collection which are extremely rich in archival content. Niranjan Jhaveri who was the spirit behind the biennial jazz festival – JazzYatra – from 1978 to 2003 was successful in bringing international artistes like Sonny Rollins, Stan Getz and jazz bands from different parts of the globe to promote Jazz in India. The exhibition had a huge section on these Yatra years which has established Jazz, further, as an Indo-Afro-Euro-American music performed by Indian artistes like Pandit Ravi Shankar, Trilok Gurtu, Asha Puthli and others. Also Read – Leslie doing new comedy special with NetflixSoli Sorabji an ardent lover and enthusiast of jazz inaugurated the exhibition. He also attended the concert on the third day, Jazz in the Swing Era by Rohit Gupta Trio which saw a good strength of audience – all cheering and enjoying with all the exhibited material around them.For Arjun Sengupta, listening to the concert inside the exhibition hall was a surreal feeling. On the second day, Naresh Fernandes, the author of the book Taj Mahal Foxtrot, gave a lecture ‘A Short History of how Jazz became an Indian Music’ to a house full of jazz lovers, academicians, students, and enthusiasts. Fernandes traced the origin of Jazz from the music of plantation workers which found its place in New Orleans to how it travelled to India. The first all Negro American band performing in 1935 at the Taj Mahal hotel in Mumbai started the beginning of Jazz-era in India which now hosts the third generation of jazz performers. The African-American pioneers like Leon Abbey and Herb Flemming influenced many Indian jazz performers like Chic Chocolate who was regarded as the Louis Armstrong of India. The audio tracks and photographs of Indian pioneers like Chic Chocolate, Frank Fernand and Micky Correa in the exhibition brought back the golden era of Indian Jazz to the city. Jazz has also influenced the Hindi Cinema in Mumbai, as Fernandes pointed out at popular tracks like Ina-mina-dika and Sunday ke Sunday. Many of us sing these without even knowing what genre they fit into.Shubha Chaudhuri, Associate Director General of the Archives and Research Centre for Ethnomusicology (ARCE), American Institute of Indian Studies said that she has been working with her team for more than a year on these two jazz collections to digitise and conserve some of the rare photographs, reels and documents. The recently concluded jazz exhibition of ARCE, ‘Jazz in India’ was curated by Naresh Fernandes and supported by the Ministry of Culture, Government of India and IIC. Both the collections on Jazz are accessible and available for academic and research purpose at the ARCE, AIIS.last_img read more

KMC cleans up Esplanade in less than an hour

first_imgKolkata: The Kolkata Municipal Corporation (KMC) on Saturday did a commendable job to clean up the road in and around Esplanade where lakhs of Trinamool Congress supporters from all parts of the state had assembled for the Martyrs’ Day programme. The elaborate arrangements by the civic body’s Solid Waste Management (SWM) department ensured that the road was restored to its normal condition in terms of cleanliness in less than an hour after the rally ended. Also Read – Rain batters Kolkata, cripples normal life”We had pressed 4 mechanical sweepers and as many as 7 mobile compactor machines. The usual normal garbage carrying handcarts and some battery-operated cleaning vehicles were also deployed for the purpose along with a number of sweepers for physical cleaning,” Debabrata Majumder, Member Mayor-in-Council (SWM) said. It was noticed that immediately after the programme ended at around 2.20 pm, the civic body started cleaning up the stretch. Senior TMC leaders including Firhad Hakim and Subrata Bakshi appealed to the party supporters over the microphone to vacate the place quickly to ensure that the cleaning operations could begin immediately.last_img read more

Get hitched to cut down on alcohol

first_imgBeing in a relationship could be wonderful in more ways than one. A new study indicates that people who are married, or cohabiting, generally tend to drink less – that’s fewer drinks, and less frequently. Singles are more inclined to drink more often, and in larger quantities, the findings showed.“It seems that intimate relationships may provide a real benefit in terms of drinking behaviour, maybe through mechanisms such as a monitoring effect that partners have on each other,” said lead study author Diana Dinescu from the University of Virginia. Also Read – Add new books to your shelfFor the study, the researchers compared the reported drinking patterns of twins in and out of relationships. “By using twins, our study allows us to eliminate entire classes of alternative explanations, such as genetic predispositions and upbringing influences, and brings us a step closer to understanding the true impact of relationships on drinking behaviour,” Dinescu said.The researchers culled their data from the Washington State Twin Registry, a database of twins who participate in health and behaviour research. Their sample included 1,618 female pairs and 807 male pairs. Registry participants stated on forms whether they were married, divorced, widowed, separated, never married or living with a partner. They also included information about their level of alcohol consumption.last_img read more