Korean researchers use graphene to create transparent loudspeakers Dark ﬁeld optical micrograph of inkjet printed drops on a) plasma cleaned, b) pristine and c) HMDS treated substrate. Scale: 20µm. d) SEM micrograph of printed pattern. Image from arXiv:1111.4970v1 [cond-mat.mtrl-sci] © 2011 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. (PhysOrg.com) — A group of UK scientists has created a graphene ink that can be used to ink-jet print electronic devices such as thin film transistors. Citation: Graphene ink created for ink-jet printing of electronic components (2011, November 25) retrieved 18 August 2019 from https://phys.org/news/2011-11-graphene-ink-ink-jet-electronic-components.html More information: Ink-Jet Printed Graphene Electronics, arXiv:1111.4970v1 [cond-mat.mtrl-sci] arxiv.org/abs/1111.4970AbstractWe demonstrate ink-jet printing as a viable method for large area fabrication of graphene devices. We produce a graphene-based ink by liquid phase exfoliation of graphite in N-Methylpyrrolidone. We use it to print thin-film transistors, with mobilities up to~95cm^2V^(-1)s(-1), as well as transparent and conductive patterns, with~80 % transmittance and~30kOhm/sq sheet resistance. This paves the way to all-printed, flexible and transparent graphene devices on arbitrary substrates. Professor of Nanotechnology, Andrea Ferrari, and colleagues from the Engineering Department at the University of Cambridge have developed a method of creating a graphene ink that can be used with a modified ink-jet printer. Graphene consists of a hexagonal lattice of carbon only one atom thick, and has great advantages over polymer inks because of its greater electron mobility and electrical conductivity. Electronic components such as thin film transistors (TFTs) can already be created using ink-jet printing with ferro-electric polymer inks, but the performance of such components is poor and they are too slow for many applications.Beginning with flakes of pure graphite, the team exfoliated layers of graphene using liquid phase exfoliation (LPE), which consists of sonication of the graphite in the presence of a solvent, N-Methylpyrrolidone (NMP). The graphene layers were ultracentrifuged and then filtered to remove any particles large enough (>1μm in diameter) to block the ink-jet printer heads. The graphene flakes were then used as the basis for a graphene-polymer ink, which was printed, using a modified ink-jet printer, onto Si/SiO2 substrates and the transparent substrate borosilicate glass. The final step in the process was annealing at high temperature to remove the solvent.They demonstrated the new transparent graphene ink by using it to ink-jet print thin-film transistors, which they made by printing the graphene ink on Si/SiO2 wafers. They used chromium-gold pads to define the source and drain contacts, and they then printed a layer of an organic polymer, PQT-12, on top.The team achieved promising results at least comparable to current inks. They achieved mobilities of up to around 95cm2V−1s−1, about 80% transmittance and 30kohm sheet resistance. Non-graphene polymer inks typically achieve mobilities of less than 0.5cm2V−1s−1, while adding carbon nanotubes can increase this to around 50cm2V−1s−1.The results should improve as the method is refined and enhanced. Their successful first demonstration paves the way for the development of flexible and cheap electronics that can be printed on a wide variety of substrates. Devices printed using graphene inks could include wearable computers, electrical paper, sensors, electronic tags, and flexible touch screens.The paper is available online from arXiv.org.
Explore further (Phys.org)—Physicists in the Department of Mechanical Engineering at MIT have developed a new theory derived from calculations that suggest it should be possible to construct an electron cloaking device, similar in principle to invisibility cloaks that other researchers have created using metamaterials. The team, whose study was recently published in Physical Review Letters, suggests that such a cloaking device could be useful in making semiconductors that optimize electron mobility. 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. © 2012 Phys.org Credit: B. Liao et al., Phys. Rev. Lett. (2012) More information: Cloaking Core-Shell Nanoparticles from Conducting Electrons in Solids, Phys. Rev. Lett. 109, 126806 (2012) DOI:10.1103/PhysRevLett.109.126806AbstractIn this Letter, we aim at making nanoparticles embedded in a host semiconductor with a size comparable to electronic wavelengths “invisible” to the electron transport. Inspired by the recent progress made in optics and working within the framework of the expansion of partial waves, we demonstrate that the opposite effects imposed by potential barriers and wells of a core-shell nanoparticle on the phase shifts associated with the scattered electron wave could make the scattering cross section of the first two partial waves vanish simultaneously. We show that this is sufficient to cloak the nanoparticle from being detected by electrons with specific energy in the sense that a total scattering cross section smaller than 0.01% of the physical cross section can be obtained and a 4 orders of magnitude difference in the total scattering cross section can be presented within an energy range of only 40 meV, indicating possible applications of the “electron cloaks” as novel electronic switches and sensors, and in efficient energy harvesting and conversion technologies. New invisibility cloak allows object to ‘see’ out through the cloak Journal information: Physical Review Letters Citation: MIT physicists suggest a means for creating an electron cloaking device (2012, October 3) retrieved 18 August 2019 from https://phys.org/news/2012-10-mit-physicists-electron-cloaking-device.html In the latter method of creating an invisibility cloaking device, metamaterials are configured around an object, causing the light that strikes both to be bent around the object and then bent back toward its initial path, making the object invisible to the observer. Similar configurations have been constructed based on sound waves that cause a noise-emitting object impossible to hear. As delineated in the current study, researchers suggest something similar could be done with electrons as they too travel in waves, at least until they reach their coherent transport length and dissipate due to scattering. In their paper, the team suggests that an electron cloak could be configured with core-shell nanoparticle structures with multiple interfaces around a semiconductor matrix host. This host could be tuned to redirect incoming electrons with the purpose of creating interference in the electrons’ paths: in effect, canceling the total reflection. This would allow the electrons to travel through without being reflected, as if there were nothing in their path. For it to work, the nanoparticle structures would need to be of the same approximate size as the electron wavelength, i.e. about 10 nm. The team suggests that such cloaks would be most useful in electronic devices requiring very high electron mobility, such as semiconductors. They also suggest that hybrid, energy harvesting, and/or conversion thermoelectric devices might be created with new types of switches that make use of the visible-not visible properties of the nanoparticle structures. In an effort to reveal the practical applications of their theories, the researcher team hopes to develop a real-world electron cloak in the future.
Journal information: Nature Communications 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. First freshwater mosasaur discovered ERMNH HFV 197 reveals, for the first time in a mosasaur, the soft tissue outline of a tail fin, to demonstrate that mosasaurs are convergent with ichthyosaurs and whales in the development of a semilunate propulsive surface for enhanced locomotor efficiency. Credit: (top) Photograph (by Johan Lindgren), (centre) sketch indicating the bones and skin structures preserved (by Johan Lindgren), and (bottom) life reconstruction (by Stefan Sølberg) of Prognathodon sp. Mosasaurs lived approximately 98 to 66 million years ago during a time when ocean levels were much higher. In their early history, they had legs and feet and likely resembled modern monitor lizards—after moving into shallow lakes, streams and eventually the ocean, they adapted by becoming more streamlined and developed fins and tails. Despite scientists unearthing hundreds of mosasaur fossils, until now, it wasn’t known what sort of tail they had developed—none of the specimens found had preserved tail parts. Because they are a part of the lizard family, scientists assumed their tails tapered to a point, which would mean they would have had to swim more like eels, than fish. This new find proves otherwise. Instead of a tapered appendage, mosasaurs developed what looks like upside down shark tail—a development that would have enabled the predators to swim very fast, allowing them to catch most anything in their vicinity.The fossil found was that of a juvenile, approximately six feet long—adults are believed to have grown to an average of 33 feet. Though small it marks the first instance of a mosasaur fossil with fins, including the tail, almost completely intact. The find settles the debate about which kind of tail the air-breathing swimming lizard had and has caused paleontologist to revisit theories regarding what life in the oceans during the late cretaceous period must have looked like. If masasaurs, which scientists already believed dominated the seas during their time, were able to swim much faster than has been previously thought, it means that other swimmers in the sea likely had to develop adaptations to elude them. (Phys.org) —A trio of researchers studying a mosasaur fossil found in Jordan report in their paper published in the journal Nature Communications, that the late cretaceous period reptile clearly had a hypocercal (shark-like) tail fin. The fossil was first discovered in 2008 by workers digging at a quarry—it then sat unstudied in Eternal River Museum of Natural History in Amman for four years before this new team of researchers from Sweden, Jordan and the U.S. discovered its existence and began giving it a closer look. More information: Soft tissue preservation in a fossil marine lizard with a bilobed tail fin, Nature Communications 4, Article number: 2423 DOI: 10.1038/ncomms3423AbstractMosasaurs are secondarily aquatic squamates that became the dominant marine reptiles in the Late Cretaceous about 98–66 million years ago. Although early members of the group possessed body shapes similar to extant monitor lizards, derived forms have traditionally been portrayed as long, sleek animals with broadened, yet ultimately tapering tails. Here we report an extraordinary mosasaur fossil from the Maastrichtian of Harrana in central Jordan, which preserves soft tissues, including high fidelity outlines of a caudal fluke and flippers. This specimen provides the first indisputable evidence that derived mosasaurs were propelled by hypocercal tail fins, a hypothesis that was previously based on comparative skeletal anatomy alone. Ecomorphological comparisons suggest that derived mosasaurs were similar to pelagic sharks in terms of swimming performance, a finding that significantly expands our understanding of the level of aquatic adaptation achieved by these seagoing lizards. The first mosasaur tail on record with a preserved soft tissue outline. In similarity with whales and ichthyosaurs, mosasaurs were equipped with semilunate caudal flukes, and they presumably swam like pelagic sharks. Credit: Johan Lindgren © 2013 Phys.org Explore further Citation: Mosasaur fossil proves the early lizards had tails like sharks (2013, September 11) retrieved 18 August 2019 from https://phys.org/news/2013-09-mosasaur-fossil-early-lizards-tails.html
Structure of the metasurface beam splitter. (a) Schematic diagram. TM light enters the slits in plasmonic waveguide mode and is reflected by the bottom Al layer. The light is strongly negatively reflected, as indicated by the chromatic sector. The reflection includes light corresponding to lateral SPR, as shown by green arrow, and light in the non-diffraction zone shown in Fig. 2(b1) and Fig. 3(b1). TE light cannot enter the slits and is primarily reflected. (b) SEM images of the top and side views (insets) of the fabricated device. The grating pitch is T = 420 nm, the width of the dielectric PMMA is t1 = 170 nm, and the width of the metal Al in the bottom PMMA-Al grating layer is t2 = 250 nm. The thicknesses of the PMMA and Al are h1 = 110 nm and h2 = 30 nm, respectively. The size of the Al on the sidewalls of the PMMA grating lines is t3 ´ h3 = 20 nm ´ 110 nm. The substrate is silicon. Credit: Zheng J et al. Highly anisotropic metasurface: a polarized beam splitter and hologram. Scientific Reports 4, 6491 (29 September 2014). “Our technique is quite different from that generally employed in metamaterials research, where very fine nano-size resonators are often required to achieve a specific function, and where the diffraction effect – while more efficient and robust in either periodical or aperiodical structures – is rarely considered,” Ye points out. Our study gave us the profound perspective that we can gain knowledge by utilizing long-established basic mechanisms to alleviate the difficulty of nano-optical device fabrication, rather than by pursuing very complex metastructures without considering cost and application practicality.”Summarizing their approach to creating a novel polarized beam splitters, Ye says that a dielectric grating was fabricated by nano-imprinting or laser interference on a silicon or glass substrate. “The grating was subsequently coated with ten nanometers of metal film by E-beam evaporation,” he tells Phys.org. “In order to narrow the slits to restrain the TE diffraction, the deposition was optimized to make the metal film conform to the dielectric grating as far as possible. In doing so, the metal deposited on the side walls of the grating lines helped reduce the slit width.”The paper discusses how metasurface beam splitting enables a broad range of useable wavelengths and incident angles with flexible tunability in operation by not relying on a resonant coupling mechanism. “For the metasurface polarized beam splitter with TM negative reflection/TE reflection, the upper limit of the working wavelength is determined by the pitch, and the lower limit is decided by the slit width. Thus,” he explains, “by choosing appropriate grating pitch and slit width, the polarized beam splitting can be achieved. For further improving the extinction ratio, it needs to optimize silt and metal thickness.” Therefore, the device is flexible tunability in a wide range of spectra which is more robust than those beam splitters using resonant mechanism in which grating height, refractive index, pitch and duty circle must be precisely designed.”Relatedly, our metasurface holograph – decodable only by transverse-magnetic polarized light –consists of a bilayer metal grating which ensures that only TM light can be diffracted. This means that the metasurface hologram can only be decodable by TM light, and the real image is reconstructed in the reflection side with the negative first order refraction.” Periodically constructed metamaterials, in which permittivity (a measure of how an electric field affects, and is affected by, a dielectric medium) and permeability (the degree of magnetization that a material obtains in response to an applied magnetic field) have simultaneous negative values, creating negative refraction (a dimensionless number that much light is bent when entering a material. More information: Highly anisotropic metasurface: a polarized beam splitter and hologram, Scientific Reports 4, 6491 (29 September 2014), doi:10.1038/srep06491 © 2014 Phys.org Improving terahertz optics with efficient broadband antireflection coatings Journal information: Scientific Reports In addition to the 1-D metasurface applications discussed in the paper – displays, holograms, and laser optics – Ye mentions several others:Compact reflective mirrors for laser cavities where the polarized output is required to meet the coherence for optical communication or laser interferenceDiffractive gratings in optical spectrometers, where the TM diffraction efficiency is stably high in a wide waveband with high angle resolution since the pith is only several hundred nanometers, which has several advantages: as a reflection element it provides a range of benefits, such as allowing the controlling circuit to be placed below the reflective surface, and more advanced integrated circuit technology becomes available when the substrate materials are not limited by their opaqueness; and a folded light path wherein the input and output light beam share the same physical space, which offers a desirable compact arrangementAs a novel plasmonic beam splitter, it can also be implemented in integrated optics devices for communication: TM light is diffracted into one waveguide and TE light is reflected into the other, allowing the two beams to be manipulated for further useThere are also long-term implications of a higher-security anti-counterfeit plasmonic hologram produced by adding the additional criterion of what Ye refers to as the “simple example” of polarization dependence demonstrated in the paper. “The greater enlightenment is that plasmonic effects can be used for higher-security anti-counterfeits,” he confirms. “In fact, not only the polarized diffraction-change of the brightness but also the polarized reflection-change of the color can be utilized as new criterions to judge a hologram.” Yet another advantage of the plasmonic anti-counter faking is that optical resonance can be well-engineered by the thickness of metal films, slit width and grating pitch, substantially increasing the cost and difficulty of fakery – especially for a complex pattern with several values of pitch, metal thickness and direction of the metallic nanowire grating. “In a word,” Ye notes, “we open a new door for the application of metasurface devices in anti-counter faking.”Moving forward, in the near future the scientists are planning to create a theoretical 1-D metasurface model that presents a quantitative effective refractive index to analyze structural properties, thus facilitating further device design. “In the long-term,” he adds, “for polarized beam splitting we plan to increase the waveband and extinction ratio for both reflection and negative reflection simultaneously by using a more delicate nanowire arrangement. Moreover, in addition to our current emphasis in anti-counter faking, we’ll be looking at other applications, including integrated optics, spectrometers and laser cavities.” Another important innovation that the researchers might consider developing is combining actively tunable metasurfaces with other techniques, such as liquid crystals and electrowetting. “Tunability will enable metasurfaces to be applied to displays, optical storage and communications,” Ye tells Phys.org. “Also, we’re considering if the optical properties we’ve observed can be extended to other frequency spectra – for example, the terahertz range, since doing so may help us to build terahertz devices. In closing, Ye says that other areas of research, such as high-field laser physics, might also benefit from their study. Citation: Flatland, we hardly knew ye: Unique 1-D metasurface acts as polarized beam splitter, allows novel form of holography (2014, October 24) retrieved 18 August 2019 from https://phys.org/news/2014-10-flatland-knew-ye-unique-d.html (Phys.org) —Traditional three-dimensional (3-D) plasmonic metamaterials with metallic structures – artificial materials that exploit coherent delocalized electron oscillations known as surface plasmons produced from the interaction of light with metal-dielectric materials – exhibit unique electromagnetic properties not found in natural materials, such as extraordinary transmission beyond the diffraction limit, efficient light-harvesting ability, plasmonic color filtering, and the ability to control the reflection or transmission direction of a light beam. However, they are difficult to fabricate, have a narrow usable bandwidth due to their resonant character, and exhibit low optical efficiency due to the inherent metal absorption. While two-dimensional metasurface structures have been proposed in an attempt to address these functional limitations, they still require complex designs and sophisticated fabrication procedures. Spectra and photos of a 280-nm-pitch grating. (a) Measured (solid lines) and simulated (dashed lines) NR (blue and cyan lines) and reflection (red and magenta lines) spectra for TM (blue and red lines) and TE (cyan and magenta lines) light with an incident angle of 60o. The inset is the simulated extinction ratio of NRTM/NRTE. (b) Photos of the device irradiated by un-polarized white light with an incident angle of approximately 60o and filtered by a polyvinyl alcohol (PVA) plastic polarizer (extinction ratio of 300). The yellow dotted line indicates the direction of the grating lines. The white dashed lines illustrate the electric field direction of the light passing through the polarizer. An SEM image of the device is also presented. The dielectric grating in the device was fabricated by laser interference, with an Al thickness of 50 nm. Credit: Zheng J et al. Highly anisotropic metasurface: a polarized beam splitter and hologram. Scientific Reports 4, 6491 (29 September 2014). Optical performance is not the only issue the scientists faced: The fabrication challenge is that in order to obtain high extinction ratio for both negative reflection and reflection, the ratio between the silt-width and pitch is always smaller than ½ – that is, the exposure condition for laser interference lithography (LIL) should be optimized. “The issue will be more challenging as the slit-refractive index increases, because the slit width should be further reduced to achieve the cut-off effect,” Ye notes. “Smarter design of the grating structures is needed for the high extinction ratio of both reflection and negative reflection, especially for a very wide waveband device.”The third challenge was combining the intrinsically fringed structure of a hologram and the anisotropic character of metasurface beam splitter. “In a hologram, the interference fringes usually have random direction, pitch, duty cycle, and depth,” Ye points out. “Therefore, to combine the hologram and beam splitter, photoresist processing and recording parameters should be well-designed in order to get deep and narrow slits for guaranteeing high-efficiency of TM light and inhibiting TE diffraction simultaneously. Otherwise, extinction ratios for both negative reflection and reflection will be lowered.” Moreover, since a laser hologram is usually recorded on photoresist film in the form of fringes caused by two-beam interference, the patterns are typically fringed structure with pitch decided by the wavelength and angle between the interference beams. “To obtain maximum diffraction efficiency,” Ye explains, “the fringes should be deep enough – but the contradiction is that deepening photoresist fringes causes slit width to increase, which in turn weakens anisotropy.”The researchers leveraged a range insights and techniques to address these challenges. “In our one-dimensional metasurface, the key point was fully combining the intrinsic properties of dielectric-metal-dielectric slit and the diffraction characteristics of grating, and finding the proper parameters to meet the required waveband,” Ye recounts. “At the same time, the starting point of our research is physically as simple and fundamental as the description in classic optics textbooks that for diffraction to exist in a grating, the light should be able to enter into the slits. Therefore,” he explains, “by considering the fact that in metal-insulator-metal waveguides TM mode is always supported while TE mode is dissipative in sub-wavelength size, we intuited that TM diffraction can be made to break the diffraction limit – corresponding to vector diffraction optics – while for TE light the diffraction should disappear without ‘sensing’ the slits, corresponding to geometrical optics.” The demonstration of the hypothesis not only convincingly reveals a new way to control photons, but also gives a very clearly physical image for the transition between scalar optics (where the optical phenomena can be described by scalar diffraction) and nano-optics (where the wavelengths are much larger than the size and pitch of the resonant units so the diffraction is therefore absent.) Recently, scientists at Shanghai Jiao Tong University proposed a unique method for controlling photons with a 1-D metasurface that, by integrating diffraction, waveguide, and plasmonic effects, is fundamentally distinct from 2-D or 3-D methods. The 1-D metasurface they presented, based on bilayered metallic nanowire gratings, behaves as an ideal polarized beam splitter that produces highly anisotropic strong negative reflection for transverse-magnetic (TM) light and efficient reflection for transverse-electric (TE) light. (Anisotropy is the property of being directionally dependent, as opposed to isotropy, which implies identical properties in all directions.) Moreover, by combining this feature with the fringed structure of a hologram, the researchers demonstrated a higher-security anti-counterfeit metasurface holograph, that can be decoded only by TM light.Dr. Zhicheng Ye discussed the paper that he, Dr. Jun Zheng and their co-authors published in Scientific Reports with Phys.org. A key factor is simplifying the metastructure to a one-dimensional metasurface using a bilayer metallic nanowire grating. “Designing three- or two-dimensional nanoantenna arrays can modify the optical wavefront with spatially-varying phase response,” Ye tells Phys.org. “However, complex designs and sophisticated fabrication procedures are required. Simplifying the metastructure to one dimension is preferred for applications and large-scale production, but the structure that allows tunable parameters is limited. Therefore, the main challenges to achieve specific functions using bilayer metallic nanowire grating involve exploring and utilizing the intrinsic properties of surface plasmon waveguide, combining these with the diffraction characteristics of grating, and finding proper parameters.”Relatedly, Ye continues, using bilayer metallic nanowire gratings with nano-slits as 1-D metamaterials to realize both polarized negative reflection and reflection carries its own challenges. “Thus far, the dielectric or metal beam splitters based on gratings usually have narrow working spectrum and angle range. On the other hand, these studies have typically focused only on transmission and reflection properties – but polarized diffraction has not been considered,” he explains. “We proposed the bilayer metallic nanowire gratings with nano-slits as 1-D metamaterials to realize polarized negative reflection for transverse-magnetic light and reflection for transverse-electric light, with a broad range of useable wavelengths and incident angles.” The key point is that metasurface beam splitting does not rely on a resonant coupling mechanism, thereby enabling a broad range of useable wavelengths and incident angles, with flexible tunability in operation. “The main challenge was determining how to simultaneously realize broadband, angle-insensitivity and high polarization extinction ratios. Our research shows that, the grating pitch should be large enough to ensure a broad working spectrum; the slit should be wide enough to insure that transverse-magnetic light can be refracted strongly, but also thin enough to suppress TE refraction efficiently; and the proper slit height should significantly enhance the polarization extinction ratio.” Metasurface hologram. (a) Photoresist hologram fabrication scheme: The badge was placed perpendicularly to the photoresist film, and both were illuminated by a large cross-section collimated laser beam with an incident angle of 49o to the photoresist film. (b) Microscopy and SEM images of the top views of the metasurface hologram film at different scales. The film consists of randomly distributed B-MNGs with a pitch of 300 nm. The width of the dielectric PMMA is t1 = 150 nm, and the thicknesses of the PMMA and Al are h1 = 110 nm and h2 = 50 nm, respectively. (c) Real images reconstructed using TM and TE laser light, respectively. The metasurface hologram was illuminated by a TM or TE laser with a wavelength of 532 nm and an incident angle of 75o. The reconstructed real 3-D image was formed by the negative first-order diffraction mode with a diffractive angle of 55o and was imaged onto a black screen, as presented in the bottom left pictures. The image was also viewed with a camera, as presented in the top right pictures, or directly by eye. Credit: Zheng J et al. Highly anisotropic metasurface: a polarized beam splitter and hologram. Scientific Reports 4, 6491 (29 September 2014). 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.
Why chameleon tongues work in the cold (w/ Video) Citation: Mathematicians propose model for the dynamics of the chameleon tongue (2016, April 20) retrieved 18 August 2019 from https://phys.org/news/2016-04-mathematicians-dynamics-chameleon-tongue.html Explore further More information: Derek E. Moulton et al. The elastic secrets of the chameleon tongue, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science (2016). DOI: 10.1098/rspa.2016.0030AbstractThe ballistic projection of the chameleon tongue is an extreme example of quick energy release in the animal kingdom. It relies on a complicated physiological structure and an elaborate balance between tissue elasticity, collagen fibre anisotropy, active muscular contraction, stress release and geometry. A general biophysical model for the dynamics of the chameleon tongue based on large deformation elasticity is proposed. The model involves three distinct coupled subsystems: the energetics of the intralingual sheaths, the mechanics of the activating accelerator muscle and the dynamics of tongue extension. Together, these three systems elucidate the key physical principles of prey-catching among chameleonides. (Phys.org)—A small team of mathematicians with Oxford University and an engineer with Tufts University has together proposed a model to explain the dynamics of the chameleon tongue. In their paper published in Proceedings of the Royal Society A, the team describes their study of chameleon tongues, their findings and a description of the math used to model the sequence of events that lead up to a very fast tongue strike. The chameleon tongue strike is well documented, most people have seen examples of it in action in nature documentaries—generally in slow motion. What sets it apart is its speed—a chameleon can push its tongue out at a target at speeds up to 100 kilometers per hour. But how it does so, has not been well understood. In this new effort, the researchers have found that in order to reach such incredible speeds so quickly, the chameleon relies on three main parts: the sticky pad that is situated on the end of its tongue which adheres to prey, coils of acceleration muscles and retractor muscles that pull prey back in before they have a chance to escape. They also note that both types of muscles coil around a tiny bone in the mouth—the hyoid. In order for a chameleon to catch prey, all of its systems must work in near perfect unison.It all starts, the researchers report, with the accelerator muscles contracting, which squeezes tube shaped segments inside of the tongue, pushing them to the far end in what they team calls a loaded position. As the accelerator muscles contract, the tongue is forced outward while at the same time, the tube shaped segments are pushed outwards telescopically, like an old fashioned car radio antenna. The sheets are made of collagen which is of course very elastic, which means they are stretched out as the tongue is pushed away from the mouth, but then naturally recoil once the target has been reached. Retraction is assisted by retractor muscles.The researchers have put all these actions into a mathematical model which allows them to manipulate various factors, such as how big around the sheets can be. They noted that such changes to the system could be destructive—if the radius of the inner sheath was more than 1.4 millimeters, they found, the tongue would rip loose from its base as it was launched causing the loss of the tongue. © 2016 Phys.org Journal information: Proceedings of the Royal Society A Oustalet’s Chameleon, Ambalavao, Madagascar. Credit: Bernard Gagnon/Wikipedia. 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.
Components of the classical experiment that produces the same bounds that quantum experiments do. Credit: Frustaglia et al. ©2016 American Physical Society 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. Citation: ‘Quantum’ bounds not so quantum after all (2016, July 1) retrieved 18 August 2019 from https://phys.org/news/2016-07-quantum-bounds.html More information: Diego Frustaglia et al. “Classical Physics and the Bounds of Quantum Correlations.” Physical Review Letters. DOI: 10.1103/PhysRevLett.116.250404. Also at arXiv:1511.08144 [quant-ph] One of the many implications of the study is that it offers new insight into what it means to be quantum. By showing that quantum bounds are not unique to quantum theory, but are universal bounds, the findings show that ongoing attempts to define quantum theory should not focus on these bounds.Instead, the results provide a clue for finding a true quantum feature by revealing an important difference between the way in which the classical and quantum systems produce the same bounds. While the classical systems require some kind of extra resource, such as memory, the quantum systems do not. So a complete description of quantum theory should explain how quantum systems can violate the same bounds that classical systems do, but without using extra resources. As the researchers explain, this approach of investigating classical systems to better understand quantum mechanics tends to be the opposite of most research.”We somehow reverted the strategy followed by the founders of quantum theory,” Frustaglia told Phys.org. “In the early times of quantum mechanics, microscopic systems were subject to an intense questioning naturally biased towards classical physics. The result was a set of oddities interpreted as the paradigmatic features of the quantum realm: the particle-wave duality (is it a particle or a wave?), the Schrödinger’s cat (is it dead or alive?), and the Heisenberg’s uncertainty principle (where and how fast is it?). “As a consequence, it was soon understood that quantum systems should be interrogated in their own specific language, eventually provided by modern quantum theory. It is then pertinent to address the possibility of interrogating classical systems with questions inspired by quantum physics. This is what we did, indeed, finding that classical systems with an underlying wave mechanism answer these questions in the same way truly quantum systems do. But one has to choose your system carefully: one would not be able to make it by using plain balls, for instance.”In the future, the physicists plan to investigate how the universal bounds might emerge in the first place.”Our results show that the ‘quantum’ bounds are common to many physical theories,” said coauthor Adán Cabello at the University of Sevilla. “This suggests that the reason for these bounds is something very simple and arguably inherent to the kind of theories we are interested in: theories in which ‘measurements’ produce repeatable results which are not affected by some other measurements.”Surprisingly, this simple idea singles out many ‘quantum’ bounds. When we adopt this perspective, what is really significant is the fact that these bounds are actually reachable in nature. This shows that no hypothetical physical principle is acting and leads us to the conjecture that one of the physical principles that singles out quantum theory is precisely that one: There is no principle determining the probabilities of the outcomes of these ‘measurements.'”One plan is to prove that this simple idea is responsible for all quantum bounds. Another plan is to test whether it is really true that these bounds can be reached with quantum systems. So far, and only very recently, H. S. Poh et al. have confirmed the so-called Tsirelson bound, 2√2, with four significant digits, but there is absolutely no experimental evidence of whether we can ‘touch’ these bounds in other scenarios. Also, it would be great to derive quantum theory from the assumption that there are no laws of nature determining or limiting the probabilities of measurement outcomes, and that the whole machinery of the theory follows from the aesthetic preference in the way we define ‘measurements.'” Finally, the physicists also plan to investigate potential applications, such as building quantum technologies with the help of classical systems. “Although inefficient in the sense that they require more memory or space, classical systems are sometimes better to produce ‘quantum’ numbers than quantum systems themselves,” Frustaglia said. “In contrast to quantum systems, which are very sensitive to the environment, the wires in our experiment can be bent, moved, heated, etc., and the results are the same. This suggests a future in which quantum technologies are actually built using quantum systems plus classical systems imitating quantum systems. It also raises the question as to whether similar ‘quantum’ features with potential functionalities can emerge in other supports as complex networks of artificial or biological nature. An appropriate answer to this questions requires multidisciplinary efforts that we are presently considering.” (Phys.org)—Quantum bounds are numbers (such as 4, 6, and 2√2) that naturally appear in quantum experiments, similar to how the number π emerges in circles. But just as how π pops up in a wide variety of areas beyond circles, in a new study physicists have found that quantum bounds are not exclusive to quantum theory but also emerge in purely classical experiments. The results suggest that attempts to define quantumness should not be concerned with quantum bounds, since there is nothing inherently quantum about them. Journal information: Physical Review Letters The physicists, Diego Frustaglia et al., at the University of Sevilla in Spain, have published a paper on the emergence of quantum bounds in classical experiments in a recent issue of Physical Review Letters. Different experiments, same boundsIn their study, the researchers performed three classical experiments that correspond to three famous quantum experiments involving quantum bounds. These quantum experiments are a sequential version of the Bell inequality and two other related quantum inequalities, all of which are used to distinguish between quantum and classical phenomena. In order to show that a system exhibits quantum effects, these experiments traditionally attempt to show that a system can violate a quantum inequality. The greater the violation, the more quantum the system. The maximum violation of a quantum inequality is the quantum bound. The quantum bounds arise from probability distributions in the experiments and are specific numbers—for instance, the Bell inequality has a quantum bound of 2√2 (approximately 2.82), which is known as Tsirelson’s bound. The other two inequalities addressed here have quantum bounds of 4 and 6. Both theoretically and experimentally, no violation of a quantum inequality has ever surpassed these bounds.In the new study, the researchers showed that these same quantum bounds emerge in experiments in which classical waves travel along an ordinary transmission line. The researchers found that the probabilities originating from the detection of wave intensities at the end of the transmission line follow the same distribution as the probabilities of detecting violations of the quantum inequalities. Specifically, the classical experiments yield bounds of 2.78, 3.93, and 5.93 for the three analogous experiments. In all three cases, these values are actually slightly closer to their theoretical values mentioned above than the values obtained in quantum experiments are, providing strong evidence that both quantum and classical experiments produce the same bounds. Interpreting the results © 2016 Phys.org Explore further Physicists discover an infinite number of quantum speed limits
Play (1) On the training chair, the trained monkey learned to touch the light spot on the rubber balls (with food reward) by looking at the mirror image of the light spot with 100% success rates. When the laser light was projected to the monkey’s face, the trained monkey failed to touch the face mark point. (2) The rubber ball was substituted by a bigger flat board on each side of the monkey’s head that could be seen only in the mirror. The light spot could be moved rapidly to multiple random positions in two dimensions on the board, and more precise touching was required for obtaining the food reward. On the training chair, the trained monkey could correctly touch the light spot on the board with 100% success rate. When the light spot was projected to the monkey’s face, the trained monkey correctly touched the spot position on his face. Credit: (c) Proceedings of the National Academy of Sciences (2017). DOI: 10.1073/pnas.1620764114 The team then placed a dye mark on each of the monkeys’ faces without them knowing it and then allowed them to look at a mirror—at that point, all of the monkeys individually noticed the mark and directed their hand to it, wiping at it and sniffing it. All of the test monkeys eventually passed the test, even while control monkeys continued to misidentify their own faces in the mirror as belonging to another monkey. This, the team suggests, indicates that the monkeys are clearly capable of passing the self-recognition test, and thus have self-awareness. Their claims were further bolstered by continued monitoring of the trained monkeys as they sat in front of a mirror with no direction. They used the mirror to check out normally unseen body parts, such as their genitals and to preen themselves. This, the team suggests, clearly shows that having learned how a mirror works, the monkeys truly demonstrated that they were aware of themselves. Monkeys can learn to see themselves in the mirror 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)—A team of researchers at the Shanghai Institutes for Biological Sciences has found that rhesus monkeys can pass the mirror self-awareness test if they are first taught how mirrors work. In their paper published in Proceedings of the National Academy of Sciences, the team describes how they taught the monkeys to understand how mirrors work and how the monkeys behaved once they had it down. © 2017 Phys.org Explore further Citation: Monkeys taught to pass mirror self-awareness test (2017, February 14) retrieved 18 August 2019 from https://phys.org/news/2017-02-monkeys-taught-mirror-self-awareness.html More information: Liangtang Chang et al. Spontaneous expression of mirror self-recognition in monkeys after learning precise visual-proprioceptive association for mirror images, Proceedings of the National Academy of Sciences (2017). DOI: 10.1073/pnas.1620764114AbstractMirror self-recognition (MSR) is generally considered to be an intrinsic cognitive ability found only in humans and a few species of great apes. Rhesus monkeys do not spontaneously show MSR, but they have the ability to use a mirror as an instrument to find hidden objects. The mechanism underlying the transition from simple mirror use to MSR remains unclear. Here we show that rhesus monkeys could show MSR after learning precise visual-proprioceptive association for mirror images. We trained head-fixed monkeys on a chair in front of a mirror to touch with spatiotemporal precision a laser pointer light spot on an adjacent board that could only be seen in the mirror. After several weeks of training, when the same laser pointer light was projected to the monkey’s face, a location not used in training, all three trained monkeys successfully touched the face area marked by the light spot in front of a mirror. All trained monkeys passed the standard face mark test for MSR both on the monkey chair and in their home cage. Importantly, distinct from untrained control monkeys, the trained monkeys showed typical mirror-induced self-directed behaviors in their home cage, such as using the mirror to explore normally unseen body parts. Thus, bodily self-consciousness may be a cognitive ability present in many more species than previously thought, and acquisition of precise visual-proprioceptive association for the images in the mirror is critical for revealing the MSR ability of the animal. For many years, cognitive researchers have relied on the mirror self-recognition test as a means for determining if an animal is capable of self-awareness. A dye mark is made on the face of an individual being tested and then that individual is allowed to look at itself in the mirror—if it see the mark and touches it, then it passes the test. But more recently, some in the field have begun to question the validity of the test, suggesting that an inability to pass the test might be more of an indication that an animal simply does not understand how a mirror works. In this new effort, the researchers sought to see if that might be the case by training a group of male rhesus monkeys on how a mirror works before giving it the test.The training involved placing a monkey in front of a mirror and rewarding him each time he correctly placed his hand on a spot in its cage lit up by a laser pointer on the wall behind the animal. Over time, as the monkeys got the idea, the pointer was eventually directed to its face, at which point, a given monkey would touch its face where the mark was—a close approximation of the self-recognition test. Journal information: Proceedings of the National Academy of Sciences 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.
β Cep stars are massive, non-supergiant variable stars with spectral type O or B, showcasing variations in photometric, radial velocity, and line profile due to low-order pressure and gravity mode pulsations. Observations show that most stars of this class are of early B-type with masses ranging from 8.0 to 17 solar masses, characterized by their relatively high-frequency pulsations (typically between two to seven hours).β Cep stars are perceived as natural laboratories to conduct seismological studies of the interiors of massive stars. Such studies could be crucial in advancing knowledge about the evolution and structure of massive stars. However, given that the list of known β Cep stars is still relatively short, any new detection of a star of this class is of high importance for astronomers.Now, a team of researchers led by Jonathan Labadie-Bartz of University of São Paulo, Brazil, reports the finding of dozens of new stars of this type. The detection was made as part of the KELT exoplanet survey. As a result, the astronomers identified 113 β Cep stars, and 86 objects of this sample turned out to be new discoveries.”We conducted the search by performing a frequency analysis on the optical light curves of known O- and B-type stars with data from the KELT exoplanet survey,” the paper reads.As noted in the paper, the team’s primary goal was to conduct a periodicity analysis of light curves from the KELT survey for O- and B-type stars. Besides the detection of 86 new β Cep pulsators, the astronomers also identified a further number of 96 stars as β Cep candidates. This group likely contains a mix of genuine β Cep stars, plus other O-type and B-type variable stars.On the list of 113 β Cep stars observed by Labadie-Bartz’s team are five new eclipsing binaries and 22 stars with equal frequency spacings, which could be indicative of a rotational splitting of non-radial pulsation modes. Moreover, the average number of pulsation modes detected per star in the sample turned out to be 3.14. This value is higher when compared to other studies reporting new β Cep stars. In addition, the researchers found unusual light curve shapes for some of the identified β Cep stars that are difficult to explain at the moment. Therefore, the scientists propose to perform time-resolved spectroscopy of these stars in order to unveil their true nature.In concluding remarks, the authors of the paper underlined the significance of their discovery, noting that it means a 70 percent increase over the currently known sample of galactic β Cep stars. They added that the newly found stars, together with β Cep stars identified by previous studies, will be a target for observations with NASA’s Transiting Exoplanet Survey Satellite (TESS), which could shed more light on the structure and evolution of massive stars in general.”The high-quality TESS light curves will then be used to perform asteroseismic studies on this population, which will reveal valuable information about the interior structure and evolution of massive stars,” the researchers concluded. Frequency spectrum of the Beta Cephei star TIC 295435513 computed from KELT (top) and TESS (middle) data. Credit: Labadie-Bartz et al., 2019. Explore further Astronomers detect new massive stars in the young cluster VVV CL074 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: New Beta Cephei stars with KELT, arXiv:1907.11666 [astro-ph.SR] arxiv.org/abs/1907.11666 Citation: Astronomers identify dozens of new Beta Cephei stars (2019, August 7) retrieved 18 August 2019 from https://phys.org/news/2019-08-astronomers-dozens-beta-cephei-stars.html © 2019 Science X Network Using the Kilodegree Extremely Little Telescope (KELT), astronomers have detected 86 new Beta Cephei (β Cep) stars in the Milky Way galaxy. The discovery, detailed in a paper published July 26 on the arXiv pre-print repository, greatly improves the number of galactic β Cep stars known to date.
A cool breezy evening with rainclouds hovering over Delhi, the narrator started talking about the love story of Leela and Chanesar. With limited knowledge of Hindi and a smattering of Punjabi, I looked around completely bewildered, unable to make any sense of the epic about to be played out on stage at the Sindhi Sufi Music Festival performed by Padmashri Rani Karnaa’s students.A friend’s mother came to my rescue, patiently explaining the entire story for me. Sajan Rahiyo aa Ruha Mein brought to life the lovers from Sindh – Leela and Chanesar. How the epic lovers lose their love forever because of a mistake by Leela which paves the way for her to unite with the divine; for as Karnaa explains, ‘I have always been influenced by the Sufi saints of my native land Sind. For me Sufi means pure being derived from the word safa… there is no union with God without illumination and that can only come from pure soul.’ Also Read – ‘Playing Jojo was emotionally exhausting’Love betrayed is love fulfilled, says Karnaa in her introduction to the performance. Chanesar, the king of Devalkot was devoted to his wife Leela. Leela had all the luxuries in the world but her heart went out to a precious necklace offered to her by a common maid. The maid, Kumro, asks Leela for one night with her king in exchange for the necklace. Leela complies. When Chanesar comes to know of this he gets furious and abandons Leela. The dejection, the agony of separation makes Leela suffer till the end untill she surrenders herself to God for mercy and finally is allowed to transcend her pathos, pain and suffering. Also Read – Leslie doing new comedy special with NetflixHer students recreated the love story on stage ending their riveting performance with a special dedication to the legendary whirling dervishes who are intrinsically tied to Sufism and its celebrations, called Tarana (derived from Tarannum). The qawwals offers prayers that involve continuous singing of a specific composition which brings the singer closer to God in a feel of sublime frenzy or junoon, or the trance that we most associate with sufism. The audience got a chance to witness Karnaa on stage for a brief spell to pay the perfect tribute to her art through the higher being. ‘What fascinated me the most about the sufi path to reach God was the role of dance, music and poetry,’ she says. The evening that had Vice President Hamid Ansari as chief guest ended with the powerful performance of Taj Mastani from Sindh. Mastani is one of Pakistan’s most popular folk singers who presents an eclectic melange of folk and Sufi repertoire with a rustic touch to it, replete with the original favour and dialect.With the Shiv Sena protestors raging outside the venue (which was smoothly handled by the police), the festival was the sign of how art and culture can help bring two nations closer.‘The festival was not only a celebration of the joint Sindhi heritage of India and Pakistan, it was also a tribute to the shared legacy,’ says Sindhu Mishra Bhagia, Secretary of Sindhi Academy. The tie that binds? Why not!
Masters champion Bubba Watson roared back to beat Tim Clark in a playoff after seemingly blowing his chances down the back nine of the WGC-HSBC Champions on a super Sunday in Shanghai. Watson punched the air after holing an outrageous 20-yard bunker shot for eagle at the 18th to get into a playoff with South Africa’s Clark at 11-under. The left-hander then rolled in a lightning quick 20-foot putt down the hill on the same hole for the winning birdie, sparking wild celebrations for his first world golf championships event win and his first victory of any kind outside of US. Leading at 12-under par with three holes to play, Watson had seemingly imploded with a bogey followed by a double-bogey at the 16th and 17th to fall to nine under. At that point five players were a shot ahead of him, until his magic from the sand saw him finish 11-under for the tournament. Clark, playing alongside Watson, holed out for birdie from six feet at 18 to also get to 11 under as Rickie Fowler’s chance disappeared into the greenside water. The final group of overnight leader Graeme McDowell, Martin Kaymer and Japan’s Hiroshi Iwata then all failed to get the birdie they needed to join the extra-holes shootout. Also Read – Khel Ratna for Deepa and Bajrang, Arjuna for JadejaWatson turned up the heat in the front nine with a hat-trick of birdies from the sixth to lead at the turn by one from McDowell and Kaymer. Watson put his drive into the water at 13 and dropped a shot to slip back alongside McDowell, one ahead now of Kaymer who dropped a shot at the 11th after finding sand twice. Watson then birdied the par-five 14th from 15 feet to put himself alone in froant. Iwata, who was hanging on grimly after a two-over par outward half, finally nailed his first birdie at 11th and clawed his way back into contention with a fine back nine before Watson’s stunning finish.