Month: August 2019

  • NASAs NautilusX Reusable deep manned spacecraft

    first_img Mark Holderman and Edward Henderson of NASA JSC listed six technology applications in their latest presentation to the” Future in Space Operations” group. The six technologies include: satellite servicing, ISRU on the Moon, a SBSP demo, solar electric propulsion vehicle, propellant depots, and the Multi-Mission Space Exploration Vehicle (MMSEV).The Nautilus-X (Non-Atmospheric Universal Transport Intended for Lengthy United States eXploration) would be assembled from expandable structures, such as the inflatable living quarters proposed by Bigelow Aerospace. It would also contain a ring centrifuge to provide partial gravity, and radiation-mitigation systems that may also include tanks of water or liquid hydrogen slush, according to an article published on HobbySpace’s website. Other views of the ISS centrifuge: (PhysOrg.com) — NASA is currently examining several key technologies that can advance space exploration. Dubbed Nautilus-X this tubular spacecraft can be used as a reusable vehicle for lunar and deep-space missions, holding a crew of six with enough supplies for a two-year voyage. A ring centrifuge would provide partial gravity for crew’s health. Explore further HobbySpace also mentioned that the centrifuge includes both inflatable and deployed structures and may utilize Hoberman-Sphere expandable structures. The rotational hardware would be derived from Hughes 376 spin-stabilized ComSats. NASA’s dream spacecraft would be assembled from expandable structures and hold a crew of 6 with enough supplies for a 2 year mission. © 2010 PhysOrg.comcenter_img Citation: NASA’s Nautilus-X: Reusable deep manned spacecraft (2011, February 15) retrieved 18 August 2019 from https://phys.org/news/2011-02-nasa-nautilus-x-reusable-deep-spacecraft.html New NASA ‘Tool Set’ Will Simplify Engineers’ Efforts to Better Analyze Space Travel Concepts More information: via HobbySpace According to Edward Henderson of NASA’s Johnson Space Center the Nautilus-X will be designed as a multi-mission space exploration vehicle and could incorporate mission-specific propulsion units. In theory the engines and fuel can be swapped out depending on the mission. This all-purpose system would make it much simpler than using heavy-lift rockets for specific missions to the moon or other planets.It’s estimated that construction would take at least five years and require two or three rocket launches and cost about $3.7 billion. By using existing technologies, like Bigelow’s modules and the adaptability of a multi-purpose crew transporter, could mean a system like Nautilus can play a very important role in NASA’s future. 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. The goal is to deliver the centrifuge to the International Space Station (ISS), using a single Delta-IV/Atlas-V launch, where it will be tested.last_img read more

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  • New experiment helps explain extraordinary optical transmission

    first_img More information: Quasi-cylindrical wave contribution in experiments on extraordinary optical transmission, Nature, 492, 411–414 (20 December 2012) doi:10.1038/nature11669AbstractA metal film perforated by a regular array of subwavelength holes shows unexpectedly large transmission at particular wavelengths, a phenomenon known as the extraordinary optical transmission (EOT) of metal hole arrays. EOT was first attributed to surface plasmon polaritons, stimulating a renewed interest in plasmonics and metallic surfaces with subwavelength features. Experiments soon revealed that the field diffracted at a hole or slit is not a surface plasmon polariton mode alone. Further theoretical analysis predicted that the extra contribution, from quasi-cylindrical waves, also affects EOT. Here we report the experimental demonstration of the relative importance of surface plasmon polaritons and quasi-cylindrical waves in EOT by considering hole arrays of different hole densities. From the measured transmission spectra, we determine microscopic scattering parameters which allow us to show that quasi-cylindrical waves affect EOT only for high densities, when the hole spacing is roughly one wavelength. Apart from providing a deeper understanding of EOT, the determination of microscopic scattering parameters from the measurement of macroscopic optical properties paves the way to novel design strategies. Explore further Photon-plasmon coupling: Dye guides light through perforated metal foil Citation: New experiment helps explain extraordinary optical transmission (2012, December 20) retrieved 18 August 2019 from https://phys.org/news/2012-12-extraordinary-optical-transmission.html (Phys.org)—An international team of researchers working in the Netherlands has conducted an experiment that sheds new light on the phenomenon known as Extraordinary Optical Transmission (EOP) – where light is able to shine through a metal with holes in it that are smaller than the light waves themselves. In their paper published in the journal Nature, the team describes how they adjusted the distance between the holes while keeping the wavelength of light constant and in so doing discovered the degree to which two different waveforms impact the metal’s transmission properties. © 2012 Phys.orgcenter_img Sample design. Credit: Nature, 492, 411–414 (20 December 2012) doi:10.1038/nature11669 EOP occurs when researchers drill very small holes in a very thin metal plate and then shine a light on it. Despite the fact that the holes should be too small to allow light to pass through, they appear to do so anyway. Scientists attributed this phenomenon to plasmonics – a strong paring between the incident light field and the motion of free electrons along the surface of the metal. What happens, they say, is that light striking free electrons on the surface of the metal cause a stream of electron motion that moves along the surface. When a hole is encountered, the plasmons move through the hole causing glowing to occur on the other side, which is perceived as the original light.Subsequent research showed however, that plasmonics alone could not explain the phenomenon. Drilling a single hole with the same volume as the total of all the little ones resulted in less light being emitted on the other side, for example; making the metal thinner did the same (it was later discovered that the thinner metal was not actually allowing more light through, but instead was allowing electrons on the opposite of the metal to be excited by the photons directly). This led to the idea that another waveform was involved – quasi-cylindrical waves (QCW) – which is where electrons behave differently near the holes, because they are there. What was not well understood however, was the degree to which each impacted the overall properties of EOP.To find out, the researchers drilled holes in several identical metal plates. The holes were spaced the same vertically but varied by very small amounts horizontally. By flashing light of the same wavelength on each of the plates and noting how much light passed through the holes compared to the other plates, the researchers were able to measure the degree to which each type of waveform was impacting the amount of light that was emitted out the other side.Besides increasing understanding of how EOP works in general, this new work will likely result in improvements in the development of devices that rely on its unique properties. Journal information: Nature 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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  • Human hearing beats the Fourier uncertainty principle

    first_img More information: Jacob N. Oppenheim and Marcelo O. Magnasco. “Human Time-Frequency Acuity Beats the Fourier Uncertainty Principle.” PRL 110, 044301 (2013). DOI: 10.1103/PhysRevLett.110.044301 Play A Gaussian note, characterized by a rise and fall that follows a bell curve shape PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen (Phys.org)—For the first time, physicists have found that humans can discriminate a sound’s frequency (related to a note’s pitch) and timing (whether a note comes before or after another note) more than 10 times better than the limit imposed by the Fourier uncertainty principle. Not surprisingly, some of the subjects with the best listening precision were musicians, but even non-musicians could exceed the uncertainty limit. The results rule out the majority of auditory processing brain algorithms that have been proposed, since only a few models can match this impressive human performance. Journal information: Physical Review Letters But as it turns out, the subjects could discriminate both types of sounds with equally impressive performance. While some subjects excelled at discriminating frequency, most did much better at discriminating timing. The top score, achieved by a professional musician, violated the uncertainty principle by a factor of about 13, due to equally high precision in frequency acuity and timing acuity. The score with the top timing acuity (3 milliseconds) was achieved by an electronic musician who works in precision sound editing. The researchers tested the subjects with two different types of sounds: Gaussian, characterized by a rise and fall that follows a bell curve shape; and note-like, characterized by a rapid rise and a slow exponential decay. According to the uncertainty principle, note-like sounds are more difficult to measure with high precision than Gaussian sounds. The researchers, Jacob Oppenheim and Marcelo Magnasco at Rockefeller University in New York, have published their study on the first direct test of the Fourier uncertainty principle in human hearing in a recent issue of Physical Review Letters.The Fourier uncertainty principle states that a time-frequency tradeoff exists for sound signals, so that the shorter the duration of a sound, the larger the spread of different types of frequencies is required to represent the sound. Conversely, sounds with tight clusters of frequencies must have longer durations. The uncertainty principle limits the precision of the simultaneous measurement of the duration and frequency of a sound.To investigate human hearing in this context, the researchers turned to psychophysics, an area of study that uses various techniques to reveal how physical stimuli affect human sensation. Using physics, these techniques can establish tight bounds on the performance of the senses.An ear for precisionTo test how precisely humans can simultaneously measure the duration and frequency of a sound, the researchers asked 12 subjects to perform a series of listening tasks leading up to a final task. In the final task, the subjects were asked to discriminate simultaneously whether a test note was higher or lower in frequency than a leading note that was played before it, and whether the test note appeared before or after a third note, which was discernible due to its much higher frequency. When a subject correctly discriminated the frequency and timing of a note twice in a row, the difficulty level would increase so that both the difference in frequency between the notes and the time between the notes decreased. When a subject responded incorrectly, the variance would increase to make the task easier. PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen Explore further PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen Play An example of the simultaneous time-frequency discrimination task for note-like notes Copyright 2013 Phys.org All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of Phys.org. Rewired visual input to sound-processing part of the brain leads to compromised hearing Play An example of the simultaneous time-frequency discrimination task for reversed note-like notes. All samples: Credit: Oppenheim and Magnasco The researchers think that this superior human listening ability is partly due to the spiral structure and nonlinearities in the cochlea. Previously, scientists have proven that linear systems cannot exceed the time-frequency uncertainty limit. Although most nonlinear systems do not perform any better, any system that exceeds the uncertainty limit must be nonlinear. For this reason, the nonlinearities in the cochlea are likely integral to the precision of human auditory processing. Since researchers have known for a long time about the cochlea’s nonlinearities, the current results are not quite as surprising as they would otherwise be.”It is and it is not [surprising],” Magnasco told Phys.org. “We were surprised, yet we expected this to happen. The thing is, mathematically the possibility existed all along. There’s a theorem that asserts uncertainty is only obeyed by linear operators (like the linear operators of quantum mechanics). Now there’s five decades of careful documentation of just how nastily nonlinear the cochlea is, but it is not evident how any of the cochlea’s nonlinearities contributes to enhancing time-frequency acuity. We now know our results imply that some of those nonlinearities have the purpose of sharpening acuity beyond the naïve linear limits.”We were still extremely surprised by how well our subjects did, and particularly surprised by the fact that the biggest gains appear to have been, by and large, in timing. You see, physicists tend to think hearing is spectrum. But spectrum is time-independent, and hearing is about rapid transients. We were just told, by the data, that our brains care a great deal about timing.” Play A famous excerpt from Casablanca with the characters Ilsa and Sam. Play An example of the simultaneous time-frequency discrimination task for Gaussian notes PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen Play A reverse note-like note, characterized by a slow exponential rise and a rapid decay Play In a “surrogated” version, an identical copy of the spectrum is retained, but all phase information is destroyed, destroying all the timing information and rendering the time series statistically stationary. Play A note-like note, characterized by a rapid rise and a slow exponential decay Each dot represents a subject’s performance on Task 5 (simultaneously measuring the duration and frequency of a sound), with temporal acuity on the x-axis and frequency acuity on the y-axis. All dots within the black rectangle beat the Fourier uncertainty principle. Credit: Oppenheim and Magnasco ©2013 American Physical Society (a) In task 5, subjects are asked to discriminate simultaneously whether the test note (red) is higher or lower in frequency than the leading note (green), and whether the test note appears before or after the high note (blue). (b) Tasks 1 through 4 lead up to task 5: task 1 is frequency only, task 2 is timing only, task 3 is frequency only but with the high note (blue) as a distractor, and task 4 is timing only, but with the leading (green) note as a distractor. Credit: Oppenheim and Magnasco ©2013 American Physical Society Play In a “whitened” version, the spectrum is destroyed, but all phases are preserved, creating a time series which is spectrally perfectly white and statistically uncorrelated. The whitened version sounds like a bad-quality and noisier copy of the original, but everything is clearly recognizable. All samples: Credit: Oppenheim and Magnasco New sound modelsThe results have implications for how we understand the way that the brain processes sound, a question that has interested scientists for a long time. In the early 1970s, scientists found hints that human hearing could violate the uncertainty principle, but the scientific understanding and technical capabilities were not advanced enough to enable a thorough investigation. As a result, most of today’s sound analysis models are based on old theories that may now be revisited in order to capture the precision of human hearing.”In seminars, I like demonstrating how much information is conveyed in sound by playing the sound from the scene in Casablanca where Ilsa pleads, “Play it once, Sam,” Sam feigns ignorance, Ilsa insists,” Magnasco said. “You can recognize the text being spoken, but you can also recognize the volume of the utterance, the emotional stance of both speakers, the identity of the speakers including the speaker’s accent (Ingrid’s faint Swedish, though her character is Norwegian, which I am told Norwegians can distinguish; Sam’s AAVE [African American Vernacular English]), the distance to the speaker (Ilsa whispers but she’s closer, Sam loudly feigns ignorance but he’s in the back), the position of the speaker (in your house you know when someone’s calling you from another room, in which room they are!), the orientation of the speaker (looking at you or away from you), an impression of the room (large, small, carpeted).”The issue is that many fields, both basic and commercial, in sound analysis try to reconstruct only one of these, and for that they may use crude models of early hearing that transmit enough information for their purposes. But the problem is that when your analysis is a pipeline, whatever information is lost on a given stage can never be recovered later. So if you try to do very fancy analysis of, let’s say, vocal inflections of a lyric soprano, you just cannot do it with cruder models.”By ruling out many of the simpler models of auditory processing, the new results may help guide researchers to identify the true mechanism that underlies human auditory hyperacuity. Understanding this mechanism could have wide-ranging applications in areas such as speech recognition; sound analysis and processing; and radar, sonar, and radio astronomy.”You could use fancier methods in radar or sonar to try to analyze details beyond uncertainty, since you control the pinging waveform; in fact, bats do,” Magnasco said.Building on the current results, the researchers are now investigating how human hearing is more finely tuned toward natural sounds, and also studying the temporal factor in hearing.”Such increases in performance cannot occur in general without some assumptions,” Magnasco said. “For instance, if you’re testing accuracy vs. resolution, you need to assume all signals are well separated. We have indications that the hearing system is highly attuned to the sounds you actually hear in nature, as opposed to abstract time-series; this comes under the rubric of ‘ecological theories of perception’ in which you try to understand the space of natural objects being analyzed in an ecologically relevant setting, and has been hugely successful in vision. Many sounds in nature are produced by an abrupt transfer of energy followed by slow, damped decay, and hence have broken time-reversal symmetry. We just tested that subjects do much better in discriminating timing and frequency in the forward version than in the time-reversed version (manuscript submitted). Therefore the nervous system uses specific information on the physics of sound production to extract information from the sensory stream.”We are also studying with these same methods the notion of simultaneity of sounds. If we’re listening to a flute-piano piece, we will have a distinct perception if the flute ‘arrives late’ into a phrase and lags the piano, even though flute and piano produce extended sounds, much longer than the accuracy with which we perceive their alignment. In general, for many sounds we have a clear idea of one single ‘time’ associated to the sound, many times, in our minds, having to do with what action we would take to generate the sound ourselves (strike, blow, etc).” Citation: Human hearing beats the Fourier uncertainty principle (2013, February 4) retrieved 18 August 2019 from https://phys.org/news/2013-02-human-fourier-uncertainty-principle.html 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 create blackest material ever made

    first_img Material inspired by nature could turn water into fuel More information: Jianfeng Huang et al. Harnessing structural darkness in the visible and infrared wavelengths for a new source of light, Nature Nanotechnology (2015). DOI: 10.1038/nnano.2015.228AbstractEngineering broadband light absorbers is crucial to many applications, including energy-harvesting devices and optical interconnects. The performances of an ideal absorber are that of a black body, a dark material that absorbs radiation at all angles and polarizations. Despite advances in micrometre-thick films, the absorbers available to date are still far from an ideal black body. Here, we describe a disordered nanostructured material that shows an almost ideal black-body absorption of 98–99% between 400 and 1,400 nm that is insensitive to the angle and polarization of the incident light. The material comprises nanoparticles composed of a nanorod with a nanosphere of 30 nm diameter attached. When diluted into liquids, a small concentration of nanoparticles absorbs on average 26% more than carbon nanotubes, the darkest material available to date. By pumping a dye optical amplifier with nanosecond pulses of ∼100 mW power, we harness the structural darkness of the material and create a new type of light source, which generates monochromatic emission (∼5 nm wide) without the need for any resonance. This is achieved through the dynamics of light condensation in which all absorbed electromagnetic energy spontaneously generates single-colour energy pulses. As the researches also note, it is likely impossible to create the perfect black material that absorbs all of the energy that strikes it, and then emits it without any loss of energy. Still, scientists would like to come closer because it is believed that such materials could help in creating better or more efficient devices, such as solar collectors. In this new effort, the team bested the blackness of previous materials using carbon nanotubes by emulating what they found when studying the all-white cyphochilus beetle. The result was a an extremely tiny nanoparticle rod resting on an equally tiny nanoparticle sphere (30 nm diameter), which was able to absorb approximately 98 to 99 percent of the light in the spectrum between 400 and 1,400 nm, which meant that it is able to absorb approximately 26 percent more light than any other known material—and it does so from all angles and polarizations.The researchers noted that the scales on the cyphochilus beetle—a photonic crystal structure—caused the beetle’s shell to reflect light very efficiently. They took that idea and turned it on its head by inverting the structure and used the idea of chaotic energy harvesting to create the extremely black material—the surface of the structure is disordered, which creates a pattern of random pits, each consisting of infinitely long metallic waveguides. As a bonus, the material can be easily created and applied and used both in and out of liquids. Also, by firing a laser at it, they created a new type of light source that generated monochromatic emissions without the necessity of resonance.The team notes that devices using such an application might be used for desalination projects, and, of course, in solar energy collecting systems, and perhaps in optical interconnects. They also suggest the material might even lead to using a wholly new approach in the design of such devices. Explore further © 2015 Phys.org 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 Journal information: Nature Nanotechnology (Phys.org)—A team of researchers at King Abdulla University of Science and Technology in Saudi Arabia has made the blackest material ever created by human beings. As they note in their paper published in Nature Nanotechnology, the idea for the material came from the all-white cyphochilus beetle. Optical black body, the fabrication of which occurs via seeded growth of Au nanospheres from Au nanorods. a, Low-magnification TEM image of a realized sample. b, TEM image of a single nanostructure. c, HRTEM image near the kissing point between the nanosphere and the nanorod. Credit: (c) 2015 Nature Nanotechnology (2015) doi:10.1038/nnano.2015.228 Citation: Researchers create blackest material ever made (2015, October 23) retrieved 18 August 2019 from https://phys.org/news/2015-10-blackest-material.htmllast_img read more

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  • Criteria to predict experimentally stable allotropes

    first_img(A) “Willow tree” pattern of different C60 isomers, with the lower points of each vertical bar representing the calculated formation enthalpy relative to Ih-C60, and bar heights representing the calculated barrier to transformation. This shows that Ih-C60 is significantly more stable than other isomers and lies at the center of an “energetic funnel.” Adapted from ref. 7, with permission from Macmillan Publishers Ltd.: Nature, copyright 1998. (B) Calculated formation enthalpies of B40, showing the D2d cage structure is significantly more stable than alternative isomers. Reproduced from ref. 12, with permission from Macmillan Publishers: Nature Chemistry, copyright 2014. Credit: (c) 2015 Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1520402112 (Phys.org)—A group of researchers from France, the U.K. and Florida proposes criteria to determine whether an allotrope is experimentally feasible. They use theoretical carbon allotropes, penta-graphene and Haeckelites, as examples and demonstrate why penta-graphene, contrary to recent research, is not experimentally practical while Haeckelites could be isolated in the presence of charge transfer ions. Their study appears in The Proceedings of the National Academy of Science. Christopher P. Ewels, Xavier Rocquefelte, Harold W. Kroto, Mark J. Rayson, Patrick R. Briddon, and Malcolm I. Heggie’s work responds to Zhang, et al.’s February 2015 article in The Proceedings of the National Academy of Sciences reporting that penta-graphene is a new allotrope of carbon based on calculations that confirm its dynamical, thermal, and mechanical stability. Ewels, et al. disagree that this is an experimentally possible allotrope and believe that, while penta-graphene may exhibit properties that place it within a local energy minimum, it will tend toward spontaneous formation of graphene.Graphene is made of a network of hexagonal carbon rings, characterized by carbon atoms that are sp2 hybridized. Fullerenes, C60, are a network of hexagonal and pentagonal carbons and are a mixture of sp2 and sp3 hybridized carbons. Zhang, et al. conducted molecular studies to demonstrate that carbon should also be able to form a network of pentagonal carbon rings in the form of Cairo pentagonal tiling. This structure consists of out-of-plane distorted ethylene units connected via sp3carbon linkers.However, Ewels, et al. show that while Cairo pentagonal tiling is geometrically enticing, it is not experimentally feasible to form a carbon allotrope due to several criteria that are based largely on the potential energy landscape of possible carbon allotropes. They summarize their criteria as: Stable allotropes must reside in a potential energy minimum; surrounding “wells” must be higher in energy such that a kind of “funneling” toward an energy minimum can occur; and theoretical carbon allotropes must have some kind of energy barrier to keep them from readily converting into a more stable structure. Penta-graphene, while it may sit in a relative energy minimum, is a high-energy structure. It is significantly less stable than graphene, amorphous carbon, most nanotubes, and C60.First, rather than being the center of a “funnel” in an energy landscape of isomers, penta-graphene is part of the “funnel” that leads to graphene as the most stable structure. Their studies showed that transformation from penta-graphene to graphene via bond rotations is thermodynamically favored at each step. Importantly, their studies of the energy landscapes for crystalline carbon allotropes predict these structures will “funnel” toward fully sp2 or sp3 hybridized carbons. Secondly, penta-graphene is not kinetically or chemically stable. Upon heating, notably in the presence of structural defects, penta-graphene does not maintain its structure for an appreciable timeframe. And, theoretical studies with O2 indicate that penta-graphene would likely undergo exothermic spontaneous oxidation upon exposure to air.Ewels, et al. then subjected another theoretical carbon structure, called Haeckelites, to their model. These carbon allotropes were proposed fifteen years ago, and while much research has been done on Haeckelites, they have never been experimentally isolated. They were proposed as a type of graphite-like planar sp2-carbon structure made predominantly of pentagonal and heptagonal carbons. Using their criteria for determining feasible carbon allotropes, Ewels, et al. found that three theoretical Haeckelite structures that would be less stable than graphene become more stable when doped with a metal cation. This is based on experimentally isolated structural analogs of metal borocarbides, and indicates that Haeckelites containing a charge transfer ion are experimentally feasible. This theoretical work calls into question some conclusions on whether penta-graphene is a viable candidate as a stable carbon allotrope and proposes criteria that could be generally applied to evaluate future isomeric structures. 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. Penta-graphene, a new structural variant of carbon, discovered More information: Christopher P. Ewels et al. Predicting experimentally stable allotropes: Instability of penta-graphene, Proceedings of the National Academy of Sciences (2015). DOI: 10.1073/pnas.1520402112AbstractIn recent years, a plethora of theoretical carbon allotropes have been proposed, none of which has been experimentally isolated. We discuss here criteria that should be met for a new phase to be potentially experimentally viable. We take as examples Haeckelites, 2D networks of sp2-carbon–containing pentagons and heptagons, and “penta-graphene,” consisting of a layer of pentagons constructed from a mixture of sp2- and sp3-coordinated carbon atoms. In 2D projection appearing as the “Cairo pattern,” penta-graphene is elegant and aesthetically pleasing. However, we dispute the author’s claims of its potential stability and experimental relevance. Explore furthercenter_img , Proceedings of the National Academy of Sciences , Nature Chemistry © 2016 Phys.org Citation: Criteria to predict experimentally stable allotropes (2016, January 5) retrieved 18 August 2019 from https://phys.org/news/2016-01-criteria-experimentally-stable-allotropes.html Journal information: Naturelast_img read more

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  • Possible second Viking site discovered in North America

    first_img 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. © 2016 Phys.org A team of archeologists has found what may be the remains of a previously unknown Viking settlement on a south west shore of the Island of Newfoundland. If the remains can be confirmed, the site would make it just the second ever discovered that has given proof of Vikings inhabiting parts of North America. The team has been videotaping their work and a documentary of their efforts will be presented this month on PBS. Explore further The “Lofotr” viking ship and the smaller “femkeiping”. Both recosntructions based on excavations from the Gokstad find. Credit: Geir Are Johansen/Wikipediacenter_img Leading the research is archeologist and National Geographic fellow, Sarah Parcak, who has been described as a “space archaeologist” because of her groundbreaking use of satellite technology to uncover Egyptian ruins. In this latest effort, she and her team have altered their methods to uncover what appears to be evidence of Viking iron smelting.To find hidden artifacts, especially those that have been buried by some amount of dirt, using a satellite, the researchers used computer tools to help them scan images, looking for human-like angles or long straight, unnatural lines. In the case of the newly discovered Newfoundland site, called Point Rosee, the team looked for changes in the richness of the grasses that grow near the sea—those that grow over stone, or other material are less robust, and can be made out from a distant satellite. The team also used magnetometer surveys to help isolate images below the ground once they were on site. That led to an initial excavation which revealed an iron-working hearth (with 28 pounds of slag in it) and what appeared to be the remains of turf walls. Radiocarbon testing has dated the site to between 800 and 1300 AD, which would coincide with the time of the Vikings.Prior to this possible discovery, the only site ever officially designated as evidence of Norse activity in the New World was L’Anse aux Meadows, hundreds of miles north, on the tip of the same island. Archeologists do not have much to go on when attempting to prove that a settlement was made by Norsemen, rather than Basque fisherman or Native Americans—the one true hallmark of Norse travelers was the use of iron nails to build their boats, thus the discovery of an iron-smelting oven would be strong evidence of Viking activity.If additional excavation and testing indicate that the site was indeed made by Vikings, it will likely lead to changes being made to the history books—it would mean they found and settled North America five centuries before Christopher Columbus arrived. Evidence of Viking/Norse metalworking in Arctic Canada Citation: Possible second Viking site discovered in North America (2016, April 4) retrieved 18 August 2019 from https://phys.org/news/2016-04-viking-site-north-america.htmllast_img read more

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  • The things left unsaid

    first_imgKanodia explores how ideas flow and  senses come alive when a man becomes one with nature in her latest venture The Great Outdoors. Her body of work shows the close bond man has with nature. A union that helps him regain his lost innocence, enjoying a solace that can be derived from the peace and quiet of nature. There are a number of  paintings set with indoors trees, foliage and birds which are skillfully integrated.    ‘The conversation I hope to create in my work is a certain truth of life and on a deeper level, a well thought philosophy. I construct fantastic versions of accessible scenes, both rural and urban utopias. Also Read – ‘Playing Jojo was emotionally exhausting’Individuals may interpret my paintings in vastly disparate ways and each view will be equally logical and plausible, thought provoking and intriguing’, concedes the artist.There are several layers in Kanodia’s paintings. Her narrative uses colour, intricate patterns and humor to create alluring images. Time plays an integral part in her paintings as she has managed to capture a moment. Her work is a salient artistic combination of a still life composition with a message. Also Read – Leslie doing new comedy special with NetflixShe is a painter of women who are on the cusp of telling their story. The woman on the bicycle  opens up a pastoral picture of married life with a dog that brings a smile to the face. It is an interesting mixture of East and West, the open umbrella accentuating the lure of the woman. Still life compositions of domestic middle class interiors with a collection of flowers are an interesting oddity when put in context of soulful women in saris. It is as if two genres work successfully side by side, a surprise at every turn of the page.When: Till 20 August Where: Art Alive Gallery,  S – 221, Panchsheel ParkTiming:11 am to 7 pmlast_img read more

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  • Kolkata Police mark road to divert small vehicles

    first_imgKolkata: The Kolkata Police have found a new road towards Rabindra Sarobar Metro station to divert small vehicles with a view to lower the vehicular pressure on Durgapur Bridge and Tollygunge Circular Road. According to the police, there is a road through New Alipore, which merges with Deshpran Sasmal Road. It passes through a culvert which is locally called the ‘kaathpool area.’Sources informed that Kolkata Police and the Irrigation department have paid a joint visit to the spot to check the ground reality on whether the area is wide enough for vehicular movement. Also Read – Rain batters Kolkata, cripples normal lifeFollowing the visit, it was found that small vehicles and two-wheelers can be diverted through this area. Only a median needs to be removed which was built in the middle portion of the culvert to prevent vehicles from using it.As per the plan, police along with Irrigation department officials and workers went there to demolish the median on Tuesday. However, the local residents objected to the move. According to them, if any heavy vehicle moves through, the culvert might not be strong enough to support the weight. Later, police informed them that only small vehicles and two-wheelers will be diverted through the area. Also Read – Speeding Jaguar crashes into Mercedes car in Kolkata, 2 pedestrians killedLocal councillor Jui Biswas also agreed with the police. “We need to cooperate with the police. They are well aware of the area. There will be police personnel there to manage traffic,” said Jui.Later, following a chat with the police, the local residents got assurance that no heavy vehicle will ply through the area. Police have also promised to post enough personnel there.According to the officials from Kolkata Police, the road will be used to divert small vehicles. As a result, the pressure on Tollygunge Circular Road will reduce, which will also reduce the travelling time.last_img read more

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  • Treated Water a national challenge

    first_imgThe Council of Scientific & Industrial Research (CSIR), is geared to meet the challenge with focus on its ‘Water’ technological interventions on the ninth day of CSIR Platinum Jubilee Technofest at 36th India International Trade Fair (IITF), at Pragati Maidan in the National Capital. Theme-day seminar highlighted  important aspects of water conservation and water management system in India. Scientists and researchers from the concerned laboratories of CSIR unfolded the means to generate pure and treated water for a large chunk of India’s population. Also Read – Add new books to your shelfAmitava Das, Director, CSIR-Central Salt & Marine Chemicals Research Institute (CSMCRI), said, “CSIR is focused to find out the solutions to minimize the adverse effect of water crisis in India. We are 4% of global water resource. 88% of India’s population has access to different water bodies, out of which only 32% gets treated or pure water. It has become a national challenge to provide access to treated water to a large chunk of India’s population. There is a huge gap that needs to be bridged and CSIR is dedicated in this cause.” Quoting a data he added, “The per capita usable water availability has drastically gone down from 1820 cubic meter in 2001 to 1550 cubic meter in 2011. As expected, till 2025, it will be struggling at 1340 cubic meter.” Also Read – Over 2 hours screen time daily will make your kids impulsiveThe ‘Water’ theme pavilion showcased advancements in water processing technology. ‘Indigenously developed Membranes’ namely Reverse Osmosis Membranes, Ultra Filtration Membrane and Hollow Fiber Membrane, have revolutionized the efforts targets towards water purification. This technology is commercialized now. The lab has provided resins to overcome the lethal effect in the Arsenic and Fluoride prone water states like West Bengal. 65 water sources have been installed in some parts of West Bengal. Nirmal Kumar Saha, Scientist, CSIR-CSMCRI, marked, “People say water is life, but we say clean water is life. CSIR has been working hard to provide safe, hygienic and affordable water to the masses.” Dr. Alok Dhawan, Director, CSIR-Indian Institute of Toxicology Research (IITR), said, “We have developed water filters using membrane. ‘O neer’ is a solar-operated purifier eliminating any hassle of changing filters. This is a breakthrough in providing safe and affordable water in the rural areas. CSIR is working on several pilot projects to manage water crisis in the future.”Dignitaries from other major CSIR labs also attended the seminar and discussed on waste water treatment. Working in the theme area, Mr. Rahul Kesharwani, PMPL (Vadodara) and Mr. Soumendu Porel, MD, Poral Dass Water and Effluent Control Pvt Ltd were amongst the industrial partners of CSIR who attended the seminar.The event day embraced several scientific activities for school students, science quiz and public science talk by CSIR-Center for Cellular & Molecular Biology (CCMB), Hyderabad.last_img read more

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  • 27yearold youth drowns in Hooghly river

    first_imgKolkata: The body of a 27-year-old youth from Belghoria was recovered from Hooghly River on early Sunday morning.He had gone to attend a picnic at Hooghly’s Balagarh and later drowned on Saturday afternoon. The incident triggered chaos in the locality after the body was recovered. Police said Jayanta Chouhan (27) along with his friends had gone to Milandwip area for a picnic on early Saturday morning. It was learnt that in the afternoon the victim along with one of his friends went for a bath in the river. According to the preliminary investigation, police suspect that the duo was competing with each other when Chouhan drowned. Also Read – Speeding Jaguar crashes into Mercedes car in Kolkata, 2 pedestrians killedThe matter was immediately reported to the local police station. Cops reached the spot and divers were called in. After conducting a prolong search operation, the divers finally managed to recover the body. Police have sent the body to Imambara Sadar Hospital in Chinsurah for autopsy. As per the investigation, the police came to know that a team comprising 12 members went for the picnic on the day of Republic Day. It may be mentioned that a large number of people from various parts of the state visit the place for picnic throughout the year. Also Read – Bose & Gandhi: More similar than apart, says Sugata BoseA caretaker who looks after the picnic spot said they had taken the immediate step of reporting the matter to his family members and the police. He also said the youths should have been careful while going for a bath. A detailed probe into the incident has been initiated. According to the preliminary investigation, police suspect that there may not be any foul play behind his death. They are, however, looking into all possible reasons that might have led to the incident. The other members of the group who went to the picnic and the one who accompanied the victim for a bath are being interrogated in this connection. The investigating officers are waiting for the autopsy report of the deceased that might throw some light on the cause of the death.last_img read more

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