Researchers analyze performance of first updatable holographic 3D display

first_imgThese digital camera images show holograms created with the photorefractive polymer in an updatable holographic 3D display. Image credit: Christenson, et al. ©2010 IEEE. As the researchers explain, there is a big jump between developing static holograms, such as those that appear on credit cards and drivers’ licenses, and updatable holograms. A variety of materials can be used to make full-color, large-size static holograms, but none of these materials are updatable. As the researchers’ previous study showed, photorefractive polymers have the potential to offer colorful images and large sizes in an updatable display. The display they demonstrated was, at 4 in. x 4 in., the largest yet created. It could display new images every 3 minutes, and images could be viewed for several hours without the need for refreshing. With these features, the display could serve as the basis for future displays that could offer a variety of glasses-free 3D applications in medical, industrial, military, and entertainment imaging. “Photorefractive polymers are primarily beneficial because the method for achieving an index of refraction change is reversible and can be very fast, which is necessary for a real-world display,” coauthor Cory Christenson from the University of Arizona told PhysOrg.com. “Some materials currently used to make holograms are permanent and take hours to write. Additionally, the material permits making displays with large sizes (at least 4 in. x 4 in.), and in principle is scalable. Also, a single display device is stable for many months to a year or more before a noticeable drop in performance is observed. Photorefractive polymers are also attractive because modifying them with different polymers is relatively easy. If we want to test the effects of a different or new polymer to see if it helps increase speed or efficiency, it is not a significant challenge to make that composite.”Holograms, like photographs, are recordings of reflected light. Here, the researchers created a hologram based on a 3D model of an object on a computer, and no real physical object was required. They then generated 2D perspectives of the object on the computer, which were processed and combined to create about 120 holographic pixels, or “hogels.” To create a single hogel, the researchers modulated a laser beam with that hogel, focused the beam on a thin vertical line, and made the beam interfere with a second, unmodulated laser beam. The entire hologram could be written by repeating this process with all 120 hogels and positioning them next to each other. After all hogels were written, the researchers could illuminate the sample with a simple LED to make the 3D hologram viewable. The sensation of 3D is created due to parallax: each eye is seeing a different perspective of the object. Ideally, a polymer material should have a combination of a fast write-erase rate (required for video applications) and a high efficiency (required for bright images). Getting a high efficiency means adding traps for the charges generated, but traps also take time and slow down the write-erase rate, resulting in a tradeoff between these two features. In their study, the researchers tested two slightly different copolymers, each of which exceeded in one of the two areas. “In looking at both the standard display material composition and one that was slightly different, we were able to study the effects of adding more sensitizer and traps (in the form of C60) to the material,” Christenson said. “The greatest significance of this is a more in-depth understanding of the physics that leads to the formation of the hologram. This understanding gives us a better idea of its potential for use in new applications and will guide future studies as we attempt to improve the material.”The researchers determined that improvements could be made by mechanisms such as pulsed writing and reflection geometry, with the ultimate goal of creating realistic 3D holographic applications.“The primary area for improvement is the sensitivity of the material,” Christenson said. “The media for permanent holograms is more sensitive to light than these photorefractive polymers, which permit better looking holograms. We are trying to find ways of decreasing the light needed to write a hologram, which will make it much easier to expand into the areas mentioned in the paper, such as white-light viewing and writing at video rates.” Copyright 2010 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. Explore further 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.center_img Touchable Hologram Becomes Reality (w/ Video) Citation: Researchers analyze performance of first updatable holographic 3D display (2010, May 26) retrieved 18 August 2019 from https://phys.org/news/2010-05-holographic-3d.html (PhysOrg.com) — In 2008, researchers from the University of Arizona created a holographic 3D display that could write and erase images, making it the first updatable (or rewritable) holographic 3D display ever demonstrated. The key to the display was a photorefractive polymer material, which enabled the researchers to take advantage of the potential of holography to a greater extent than previously allowed. Now, in a follow-up study, the researchers have reported the results of their analysis on the performance of the display, including how the polymer enables display enhancements and what more needs to be done before such displays can be widely used. More information: — Cory W. Christenson, et al. “Materials for an Updatable Holographic 3D Display.” Journal of Display Technology. To be published. Doi: 10.1109/JDT.2010.2046620– Savaş Tay, et al. “An updatable holographic three-dimensional display.” Nature 451, 694-698. Doi:10.1038/nature06596last_img read more

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NASA Roscosmos to discuss nuclear powered rocketry

first_img Explore further Russia hopes nuclear ship will fly humans to Mars Citation: NASA, Roscosmos to discuss nuclear powered rocketry (2011, April 6) retrieved 18 August 2019 from https://phys.org/news/2011-04-nasa-roscosmos-discuss-nuclear-powered.html Cooperation between the Russians and the United States in space exploration, is nothing new of course, dating back to the 1970’s and the Apollo-Soyuz missions, and more recently with astronauts from the U.S. and many other nations riding up to the space station on Russian rockets. What is new is the possibility of not just a rocket powered by nuclear energy, but a joint international project based on a technology that causes people from most any country to feel a little fear. The idea of a nuclear powered rocket exploding in the air shortly after takeoff (Challenger) or burning up upon reentry (Columbia) and spreading radioactive material over thousands of miles below is an issue that won’t go away any time soon.This would not be the first time that a spacecraft has employed the use of nuclear power (Soviet Topaz spy satellites, etc.) but it would be the first time an actual nuclear reactor would be installed onto a rocket and sent into space.Perminov, in his announcement, reiterated that Roscosmos has been working on nuclear powered rocket designs for quite some time and is now ready to move forward on developing an actual rocket, though there seems to be some discrepancies regarding the type of engine the agency has in mind. In earlier reports, it seemed the Russians were considering a reactor heat engine, but of late seem to be more of a mind to use the reactor to produce electricity to drive an ion or plasma type engine.The idea of using nuclear power to drive a rocket is not unique to the Russians, NASA and likely other space agencies have been working on their own designs for a nuclear powered rocket, as most in the field agree that chemical based engines just won’t work for long range space exploration. The sheer weight of the fuel along with the huge amount of cargo space required to hold it, prevent any serious thought of very long missions. Nuclear power on the other hand would require far less of both, plus it would require fewer moving parts.At this point, though not stated specifically, it appears the only thing holding back the Russians is the money to pay for their project, with current estimates at or near $600 million; and it’s the likely reason that the Russians are looking to form a consortium. Whether the United States or any of the other invited guests is willing to sign on to such a partnership though, is anyone’s guess. 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. © 2010 PhysOrg.com (PhysOrg.com) — Anatoly Perminov, director of the Russian Space agency Roscosmos, has announced plans for an upcoming meeting between the Russian space agency, and it’s counterparts in the United States, France, Germany and Japan (countries with a high level of nuclear engineering capability) on April 15. The meeting is being held to discuss the possibility of cooperation between the nations in building a nuclear powered rocket.last_img read more

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62year old man makes car that runs on whisky

first_imgInventor Mickey Nilsson and his bourbon powered car (PhysOrg.com) — Mickey Nilsson, a 62 year old resident of Bardstown Kentucky, has found a way to turn his junk, into a car that runs on Kentucky Bourbon Whiskey. Nilsson, a long time tinkerer, got his inspiration from a character in the film Chitty Chitty Bang Bang. The character in question, one Caractacus Potts was best known for re-purposing junk to create new and more useful machines, which is exactly what Mr. Nilsson has done. Citation: 62-year old man makes car that runs on whisky (2011, April 25) retrieved 18 August 2019 from https://phys.org/news/2011-04-year-car-whisky.html The idea of doing something with an old still came to him last October, after he had some unusual visitors. The cast of a TV show, American Pickers, Mike Wolfe and Frank Fritz, came to try and purchase some of his items for the show. While they did manager to grab an older oil can from Mr. Nilsson, after making a disparaging crack about the use of his still, they were gently encouraged to leave his property, with the help of a fire arm. After a hasty retreat by the crew, Mr. Nilsson began to think about what he could do with that old still. After that, he spent six months in his workshop turning his pile of junk, still included, into a pretty snazzy looking car. According it is creator it will run on almost any bourbon created. Apparently, the engine prefers Maker’s Mark, though some people may find the cost, and the taste, of Maker’s Mark to be a deterrent from putting it into the car. This car has even attracted attention from the White House. President Obama released a statement saying, “the type of ingenuity that makes this country great. With brilliant minds such as Mr. Nilsson at work, we will soon purge our dependence on the middle east for oil”. A commercial version of this car may even come out in the near future. On Wednesday, Nilsson cut a deal with Nissan. who hope to release the vehicle to the public by 2014. More information: via DailyLoad New discovery: Plaice are spotted (on the inside) © 2010 PhysOrg.com Explore further 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

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Research pair theorize metamaterials that exhibit negative compressibility transitions

first_img © 2012 Phys.Org Negative compressibility contrasted with other effects. Image (c) Nature Materials (2012) doi:10.1038/nmat3331 (Phys.org) — In the real world of so called “normal” materials, people expect certain things to occur as a result of certain actions. Covering an object with a cloak for example, should hide the object, but the cloak should still be visible (or vice-versa), or if you push or sit on a couch cushion, it should contract. Lately though, new science has been changing our perception of how materials should behave. For example, recent research into metamaterials; materials that aren’t normally found in nature, has been turning some of what we see as normal, on its head. The development of cloaking devices that hide objects and are themselves invisible, is one example. Explore further Improving on the amazing: Scientists seek new conductors for metamaterials More information: Mechanical metamaterials with negative compressibility transitions, Nature Materials (2012) doi:10.1038/nmat3331AbstractWhen tensioned, ordinary materials expand along the direction of the applied force. Here, we explore network concepts to design metamaterials exhibiting negative compressibility transitions, during which a material undergoes contraction when tensioned (or expansion when pressured). Continuous contraction of a material in the same direction of an applied tension, and in response to this tension, is inherently unstable. The conceptually similar effect we demonstrate can be achieved, however, through destabilizations of (meta)stable equilibria of the constituents. These destabilizations give rise to a stress-induced solid–solid phase transition associated with a twisted hysteresis curve for the stress–strain relationship. The strain-driven counterpart of negative compressibility transitions is a force amplification phenomenon, where an increase in deformation induces a discontinuous increase in response force. We suggest that the proposed materials could be useful for the design of actuators, force amplifiers, micromechanical controls, and protective devices.Press releasecenter_img Journal information: Nature Materials Citation: Research pair theorize metamaterials that exhibit negative compressibility transitions (2012, May 23) retrieved 18 August 2019 from https://phys.org/news/2012-05-pair-theorize-metamaterials-negative-compressibility.html Now, two researchers Zachary Nicolaou and Adilson Motter, from Northwestern University have proposed another material that doesn’t behave the way we’ve come to expect. They are proposing a metamaterial that reacts contrary to the expected norm, to pressure. When pushed on, it expands, when pulled, it contracts. The two have written a paper describing how such a matermaterial could be made and have had it published in the journal Nature Materials.While such a material might seem contrary to the laws of nature, the two explain how a metamaterial could be made that actually exploits such laws, rather than changes them. They suggest that if a material were constructed out of a row of four, as yet undetermined elements, where each was made of groups of molecules that are attracted to one another, then, if a force was applied to the inner particles that would be weak enough such that pulling on the metamaterial would cause those bonds to break, then the outer particles would become more strongly attracted to one another, causing compression. If on the other hand the material is squeezed, the inner particles would be brought closer together strengthening those bonds, causing the material to expand.The two have not yet made an actual metamaterial that exhibits such behavior, but it’s not difficult to see how it could be put to practical use if real ones are constructed; in fact, it’s not a far cry from the properties of the shield Captain America uses to ward off violent attacks. Military vehicles with such a material could expand out when driving over an IED, for example, preventing injury to occupants or car cushions could be fashioned creating perhaps, the smoothest ride ever. 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

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Researchers find link between amount of silica in subduction zones and frequency

first_img Scientists have only known about slow earthquakes for a few years—since they can’t be felt, there was no real indication that they were occurring. They happen when silica rich sediment is pushed from below when one plate pushes beneath another. The fluid is trapped causing pressure to build—eventually that pressure is released by slow sliding (due to lubrication provided by the silica), rather than the jolt associated with surface quakes. After the sliding stops, the pressure begins to build up again and the whole process is repeated. Such quakes can occur over days or even weeks, releasing energy equivalent to large surface quakes. Scientists now know that such quakes occur off the coast of Japan, New Zealand, the United States and Canada, but, they all have a different frequency rate. They happen every two years in New Zealand, every six months in Japan and every 14 months beneath Canada’s Vancouver Island. The difference in rates, the researchers have found, is due to the amount of silica in the fluid—there more there is, the faster faults knit together after the sliding has stopped.The pair of researchers note that much more study needs to be done before it can be determined if slow earthquakes can be used to help predict surface quakes. In their experiments, they found the crust to be 5 to 15 percent quartz above the plates in the Cascadia subduction zone, an area that experienced a magnitude 9 quake in 1700. Scientists believe a major quake will likely occur again there sometime over the next 200 years. If slow earthquakes are found to portend larger ones, perhaps enough warning time can be given to save lives in the heavily populated area. (Phys.org) —A pair of researchers, Pascal Audet and Roland Burgmann of the Universities of Ottawa and California, respectively, has found a connection between the amount of silica rich quartz above subduction zones and the frequency rate of “slow” earthquakes. In their paper published in the journal Nature, the two describe how they measured quartz amounts in the Cascadia subduction zone using seismic waves, and how it relates to slow earthquakes. Journal information: Nature Pair of seismologists publicly wonder if it might be possible to predict largest earthquakes Aerial photo of the San Andreas Fault in the Carrizo Plain, northwest of Los Angeles. Credit: Wikipedia. © 2014 Phys.orgcenter_img Citation: Researchers find link between amount of silica in subduction zones and frequency of ‘slow’ earthquakes (2014, June 19) retrieved 18 August 2019 from https://phys.org/news/2014-06-link-amount-silica-subduction-zones.html Explore further More information: Possible control of subduction zone slow-earthquake periodicity by silica enrichment, Nature 510, 389–392 (19 June 2014) DOI: 10.1038/nature13391AbstractSeismic and geodetic observations in subduction zone forearcs indicate that slow earthquakes, including episodic tremor and slip, recur at intervals of less than six months to more than two years. In Cascadia, slow slip is segmented along strike and tremor data show a gradation from large, infrequent slip episodes to small, frequent slip events with increasing depth of the plate interface. Observations and models of slow slip and tremor require the presence of near-lithostatic pore-fluid pressures in slow-earthquake source regions; however, direct evidence of factors controlling the variability in recurrence times is elusive. Here we compile seismic data from subduction zone forearcs exhibiting recurring slow earthquakes and show that the average ratio of compressional (P)-wave velocity to shear (S)-wave velocity (vP/vS) of the overlying forearc crust ranges between 1.6 and 2.0 and is linearly related to the average recurrence time of slow earthquakes. In northern Cascadia, forearc vP/vS values decrease with increasing depth of the plate interface and with decreasing tremor-episode recurrence intervals. Low vP/vS values require a large addition of quartz in a mostly mafic forearc environment. We propose that silica enrichment varying from 5 per cent to 15 per cent by volume from slab-derived fluids and upward mineralization in quartz veins can explain the range of observed vP/vS values as well as the downdip decrease in vP/vS. The solubility of silica depends on temperature, and deposition prevails near the base of the forearc crust. We further propose that the strong temperature dependence of healing and permeability reduction in silica-rich fault gouge via dissolution–precipitation creep can explain the reduction in tremor recurrence time with progressive silica enrichment. Lower gouge permeability at higher temperatures leads to faster fluid overpressure development and low effective fault-normal stress, and therefore shorter recurrence times. Our results also agree with numerical models of slip stabilization under fault zone dilatancy strengthening15 caused by decreasing fluid pressure as pore space increases. This implies that temperature-dependent silica deposition, permeability reduction and fluid overpressure development control dilatancy and slow-earthquake behaviour. 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

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Pedestrians at crosswalks found to follow the Levy walk process

first_img Journal information: Journal of the Royal Society Interface When large groups of people stand on either side of a road waiting for the light to change and then find themselves walking toward one another, they tend to walk in predictable ways. The approach taken is not generally one that typically provides the most direct or the quickest route, but one that takes into account the other people around them. In this new effort, the researchers sought to learn more about the behavior of people in such situations by studying them very closely in action.To learn more about how people behave in crosswalk-type situations, the researchers enlisted the assistance of volunteers and asked them to walk in what they describe as mock corridors. As the volunteers did so, the researchers filmed them in action. They noted directional changes, the number of steps taken and step patterns.The researchers found that individuals tended to deviate from their expected straight-ahead path as a means of most efficiently reaching their destination, and in so doing, faced a trade-off between path length and speed of transit. They noted that each individual made adjustments to their path based on the actions of those traveling in the same and opposite directions. They also found that collective action tended to arise, though the individuals involved did not seek to become participants. The collective action typically involved the formation of streams of people walking in uniform ways in both directions. Thus, rather than people continually meeting face to face, walkers would simply follow a person moving in the same direction, preventing the constant need to shift their path. Doing so increased efficiency both for the individuals and for the crowd as a whole. The researchers also found that streams created by walking individuals followed the Lévy walk process.The Lévy walk process is a mathematical description of a type of walk in which the pedestrian takes small steps, but then takes long steps at regular intervals. Mathematician Paul Lévy showed that it leads to a power-law distribution of step lengths. Citation: Pedestrians at crosswalks found to follow the Levy walk process (2019, April 10) retrieved 18 August 2019 from https://phys.org/news/2019-04-pedestrians-crosswalks-levy.html Explore further © 2019 Science X Network A team of researchers at the University of Tokyo has found that large numbers of pedestrians meeting in crosswalks tend to follow the Lévy walk process. In their paper published in Journal of the Royal Society Interface, the group outlines their work observing crowd movement and what they found.center_img Credit: CC0 Public Domain Escalator etiquette: Should I stand or walk for an efficient ride? 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. More information: Hisashi Murakami et al. Lévy walk process in self-organization of pedestrian crowds, Journal of The Royal Society Interface (2019). DOI: 10.1098/rsif.2018.0939last_img read more

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Donation worth flaunting

first_imgIn the 65 years since its inception, National Museum (NM) for the first time, is hosting an exhibition of a treasure-trove donated by a private individual. Close to a 100 works which C L Bharany and his father collected from across India will be displayed for over a month in a specially designed gallery. Sculptures in stone, bronze, and wood, besides paintings (on paper and cloth), manuscripts and textiles across the past two millennia will be showcased at the month-long show, titled A Passionate Eye. Also Read – ‘Playing Jojo was emotionally exhausting’The exhibition, mounted on 6,000 sq ft carpeted space, brings out select items from a donation of close to a thousand objects Bharany made to the museum in 1976 in memory of his father. ‘It thus acknowledges one of many people who have helped gather items of our cultural heritage,’ says Venu V, Director-General of National Museum. ‘It highlights the role private collectors have played in enriching the nation’s public museums.’Giles Tillotson, one of the curators of the exhibition, notes the Bharanys – starting from Radha Krishna, the late father of Chote Lal (now 87) — are among the most significant collectors of Indian art in the 20th century. ‘What is striking is not just the range and quality of the works they assembled; their contributions to the work of scholars and of the country’s museums are immense,’ he says. Also Read – Leslie doing new comedy special with NetflixThe objects at the show are diverse in terms of social context as well, ranging from courtly art and elite items to rural and folk art. ‘Indeed Bharany’s breadth of vision is a notable feature of his collecting: irrespective of where and when works were made, and for whom, his eye alights on anything of beauty,’ says curator Venkateswaran. Through its design, the exhibition seeks to reflect this variety and eclecticism. Objects are grouped sometimes by material such as textile and sometimes by subject matter or themes such as asceticism – irrespective of provenance and date – to highlight the varied and layered links that inspire collecting. Venu says National Museum is keen to share more of the collections with people, and similar exhibitions will allow visitors to show more than what is on permanent display. ‘This is the first special exhibition National Museum is holding to explore this subject,’ he adds.last_img read more

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A spicy affair

first_imgDakshin, WelcomHotel Sheraton brings you its October special menu that celebrates the Chettinad cuisine, one of the spiciest and aromatic cuisines in South India. The food is prepared with a variety of exotic spices.The main attraction of this cuisine is its variety, nutritional balance, and the sudden surprises that spring on you.  Although the Chettiyars are well known for their delicious vegetarian; fish, meats, delicate noodles preparation is also exhaustive. Delicate curries using sun dried berries and legumes cooked with a liberal use of spices, like peppercorn, bay leaves, cinnamon, nutmeg green and red chilies is the speciality of the cuisine.Some of the popular dishes in Chettinad menu are ‘Varuval – Pepper gravy, poriyal and ‘Kozhumbu’, which has the ingredients stewed in gravy of coconut milk and spices.  Special mention must be made of their ‘Kola Kozhumbu, (kofta gravies) and savory ‘Paniyarams’ (dumplings).last_img read more

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26yearold youth stabbed to death

first_imgKOLKATA: A 26-year-old youth was stabbed to death at Tangra on Sunday.Locals found the body lying beside the railway tracks at Tangra on Monday morning and informed the police. Police sent the body for an autopsy and initiated a probe in this connection. Though the investigating officers are yet to ascertain the exact reason behind the murder, they are suspecting that the crime is an outcome of an old rivalry. There were deep injury marks on the victim’s body and head. Also Read – Heavy rain hits traffic, flightsPolice are suspecting that someone “very close” to the victim, Sunny, is behind the murder. After preliminary investigation, they are suspecting that the victim had trouble with one of his friends on Saturday night when they had assembled near the railway tracks.Sunny often used to meet some of his friends at the spot and he went to the same place on Saturday night as well. Police are now trying to ascertain what led to the heated altercation between Sunny and one of his friends. The investigating officers Also Read – Speeding Jaguar crashes into Merc, 2 B’deshi bystanders killedare going through the footages of the CCTV cameras in the area.Meanwhile, police have arrested one person in connection with the murder of another youth at Tangra on Sunday. The victim, Babu Sarkar, was stabbed to death on late Friday night. Acting on a tip off, police conducted a raid and arrested one Joydeb Halder in connection with the murder.It may be recalled that Babu was attacked when he was returning home on Friday night. He was declared brought dead when taken to NRS Medical College and Hospital.Police have come to know about two more persons who are also suspected to be involved in the murder. Preliminary investigation further revealed that a business rivalry had led to the crime. He was also involved in to the business of real estate development. Police are, however, trying to find out if there is any other reason behind the murder.last_img read more

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Youth dies after touching train overhead wire at Sealdah Station

first_imgKolkata: An unidentified youth, who is suspected to be mental challenged, died after he came in contact with an overhead wire of train.Locals spotted the victim on the roof of UP Canning local after it arrived at Sealdah station on Tuesday morning. According to the railway police, the victim was electrocuted when the train was about the enter platform at Sealdah station. The incident triggered tension among the commuters at the station at around 7 am. The incident also led to the disruption of train services in the Sealdah South section for sometime. Also Read – Heavy rain hits traffic, flightsThe railway police later recovered the body from the roof of the train after switching off the power connection in the overhead wire. According to police, the victim, whose identity is yet to be confirmed, climbed up to the roof after the train reached Ballygunge station. He was walking on the roof of the moving train. When the train arrived at the Park Circus station, some of the passengers urged the victim to get down from the roof. But he did not pay any attention to their appeal. Also Read – Speeding Jaguar crashes into Merc, 2 B’deshi bystanders killedHe sat on the roof of the moving train. He was alive when the train then left Park Circus station. As the train was about to enter Sealdah station, the victim came in contact with the overhead wire and got electrocuted.The victim was brought down and sent to NRS Medical College and Hospital where he was declared brought dead. Police have started a probe to ascertain the identity of the victim. According to the preliminary investigation, police suspect that the victim was mentally challenged.last_img read more

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