A Cotton-top tamarin at Schwerin Zoo. Credit: Harald Hoyer / Wikipedia. Citation: Research duo discover first instance of non-human primates whispering to each other (2013, September 25) retrieved 18 August 2019 from https://phys.org/news/2013-09-duo-instance-non-human-primates.html (Phys.org) —Psychology researchers Rachel Morrison and Diana Reiss of The City University of New York have discovered the first instance of non-human primates whispering to one another. In their paper published in Zoo Biology, the two describe how they recorded vocalizations of captive tamarin monkeys and found that when threatened they sometimes revert to whispering to one another to avoid being overheard. Explore further More information: Morrison, R. and Reiss, D. (2013), Whisper-like behavior in a non-human primate. Zoo Biol.. DOI: 10.1002/zoo.21099AbstractIn humans, whispering has evolved as a counteractive strategy against eavesdropping. Some evidence for whisper-like behavior exists in a few other species, but has not been reported in non-human primates. We discovered the first evidence of whisper-like behavior in a non-human primate, the cotton-top tamarin (Saguinus oedipus), in the course of investigating their use of human-directed mobbing calls. We exposed a family of captive cotton-top tamarins to a supervisor who previously elicited a strong mobbing response. Simultaneous audio–video recordings documented the animals’ behavioral and vocal responses in the supervisor’s presence and absence. Rather than exhibiting a mobbing response and producing loud human-directed mobbing calls, the tamarins exhibited other anti-predator behaviors and produced low amplitude vocalizations that initially eluded our detection. A post-hoc analysis of the data was conducted to test a new hypothesis—the tamarins were reducing the amplitude of their vocalizations in the context of exposure to a potential threat. Consistent with whisper-like behavior, the amplitude of the tamarins’ vocalizations was significantly reduced only in the presence of the supervisor. Due to its subtle properties, this phenomenon may have eluded detection in this species. Increasing evidence of whisper-like behavior in non-human species suggests that such low amplitude signaling may represent a convergence in a communication strategy amongst highly social and cooperative species. © 2013 Phys.org Whispering is a common strategy used by people to communicate with one or more people while simultaneously trying to avoid having others hear. Other animals have been found to lower the volume of their communications as well under certain circumstances, but never before has any primate other than humans been found to do so. In this new effort, the discovery was inadvertent.The two researchers were studying cotton-top tamarins at New York’s Central Park zoo, hoping to learn more about the kinds of calls the monkeys make to one another under different circumstances. Prior research had found that tamarins are capable of vocalizing a wide range of noises. Morrison and Reiss were most interested in what are known as mobbing calls—sounds members of a group make to confuse or intimidate predators.To better understand how the tiny monkeys use mobbing calls, the researchers recorded sounds a group made when a known threat entered the vicinity—a supervisor that had been part of the team that had captured them in the wild. Prior to the study, the monkeys had used mob calls whenever the supervisor came into their view. Neither of the researchers noticed anything unusual as recordings were made, but later during playback analysis they discovered the monkeys were engaging in vocalizations that were at such low amplitude that people in the area couldn’t hear them—they were whispering to one another.The researchers acknowledge that it’s impossible to know for sure what exactly the monkeys were saying to each other, but it seems pretty clear from observation that they were reminding one another of the threat the man posed and were doing it in a way that wouldn’t alert the threat to the calls they were making to each other. The discovery of whispering by a non-human primate, Morrison and Reiss suggest likely means that it occurs in other species as well—researchers just haven’t heard them yet. Field study shows titi monkeys convey both location and predator type with vocal alarms 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: Researchers design plasmonic cavity-free nanolaser (2014, September 22) retrieved 18 August 2019 from https://phys.org/news/2014-09-plasmonic-cavity-free-nanolaser.html (Phys.org) —A team of researchers at Imperial College in London has designed a new type of laser, one that could be made much smaller than today’s models because it would be cavity-free. In their paper published in the journal Nature Communications, the team describes their idea and offer possible uses for such a laser should they be able to build one. 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. © 2014 Tech Xplore Journal information: Nature Communications As most that have dabbled in the sciences are well aware, conventional lasers work by bouncing light between mirrors inside of a chamber, also known as a cavity, causing a buildup of photons of a certain type that are eventually released as a beam. While this method has worked extraordinarily well for a host of applications, there is still one area where it is lacking—applications at the nanoscale. This is because, the researchers note, the need for the cavity. In this new effort, the researchers have created a design for a very tiny laser that works without a cavity and is able to do so by taking advantage of prior research into stopping light.The envisioned laser (the team hasn’t actually built one yet) would be made by pressing two metals together, with an insulating material between them, resulting in a sandwich of sorts. Pulses of light sent through the middle part of the sandwich would reverse direction upon encountering the metal part, causing the light to become trapped in a vortex, which means it would be stopped. The researchers have found that in testing their idea, light sent into the laser would get trapped in the vortex for approximately 10 trillionths of a second before breaking free in the form of a beam of light. In addition to being cavity-free, the laser would also be able to emit laser beams with a range of frequencies.With the design created and tested, the team is now moving towards building a prototype of the new type of laser—they believe it could be used in optics applications, perhaps as part of a computer. Others have suggested that if such a laser could be built, it could be used in such diverse applications as signaling, or even prosthetics, because it could be embedded in synthetic tissue. More information: Cavity-free plasmonic nanolasing enabled by dispersionless stopped light , Nature Communications 5, Article number: 4972 DOI: 10.1038/ncomms5972AbstractWhen light is brought to a standstill, its interaction with gain media increases dramatically due to a singularity in the density of optical states. Concurrently, stopped light engenders an inherent and cavity-free feedback mechanism, similar in effect to the feedback that has been demonstrated and exploited in large-scale disordered media and random lasers. Here we study the spatial, temporal and spectral signatures of lasing in planar gain-enhanced nanoplasmonic structures at near-infrared frequencies and show that the stopped-light feedback mechanism allows for nanolasing without a cavity. We reveal that in the absence of cavity-induced feedback, the subwavelength lasing mode forms dynamically as a phase-locked superposition of quasi dispersion-free waveguide modes. This mechanism proves remarkably robust against interface roughness and offers a new route towards nanolasing, the experimental realization of ultra-thin surface emitting lasers, and cavity-free active quantum plasmonics. Explore further An off-center waveguide enables light to be efficiently extracted from nanoscale lasers (a) The core layer of the metal-dielectric (SL) multilayer structure is filled with gain material (blue). (b) Spatially selective excitation of the homogeneous gain layer using a near-field tip leads to the formation of a subwavelength spot of inverted gain, in which the stimulated emission processes take place (inset). Photons are trapped locally in a closed-loop energy vortex (red curved arrows), enabled by an SL point, SL1, at (ω1, k1) that aligns with the peak gain. (c) A second SL point, SL2, at (ω2, k2) enforces a monotonous behaviour of the dispersion over a range of wavevectors with an average slope of (ω2−ω1)/(k2−k1). Bringing the frequencies of the SL points close together while maintaining a large distance in k-space flattens the dispersion to within the bandwidth of the gain (blue), allowing for the formation of highly localized, SL wave packets during lasing operation. Credit: Nature Communications 5, Article number: 4972 doi:10.1038/ncomms5972
Optical images of two types of MoTe2 monolayer samples: (a) MoTe2 flakes that were highly luminescent to begin with maintain their brightness over the 8-day observation period; (b) MoTe2 flakes that were weakly luminescent at the start fade within a few days, and parts of them seem to disappear altogether. Credit: Bin Chen, et al. ©2015 American Chemical Society Defects in 2D semiconductors could lead to multi-colored light-emitting devices The researchers, led by Sefaattin Tongay, Assistant Professor at Arizona State University, have published a paper on the changing luminescence in a recent issue of ACS Nano.”Currently, many researchers throughout the world are demonstrating very impressive and promising proof-of-concept applications using 2D material systems, but we still do not know their material stability over long periods of time,” Tongay told Phys.org. “This research presents the unique case of MoTe2, the only infrared-range TMD, where monolayers visually disappear but are physically still there.”Like other TMDs, MoTe2 stands out for its interesting optical properties. In bulk form, TMDs are not luminescent, but when one-atom-layer-thick flakes are exfoliated from the bulk, the 2D flakes become semiconductors and emit light rather strongly. For this reason, 2D semiconducting TMDs could have applications in optoelectronics and solar energy conversion technologies. As the only TMD that has an infrared-range band gap, MoTe2 is particularly suitable for infrared detectors and tunnel field-effect transistors.Because 2D materials have a large surface-to-volume ratio, their properties can be affected by interactions between their surface and the environment. Noting that tellurium compounds are particularly sensitive to oxygen, the researchers here wanted to investigate what happens when monolayer MoTe2 is exposed to oxygen for several days. The researchers propose that the reason why the weakly luminescent flakes seem to disappear is that they have a large number of defects, particularly vacancies due to missing atoms. These vacancies are why the flakes have a low starting luminescence, and also explain why they lose their luminescence when exposed to oxygen. Oxygen molecules (O2) from the air become embedded in these defects and bind to Mo and Te, forming “deep states” that basically trap electrons and holes, effectively prohibiting luminescence. On the other hand, flakes that are highly luminescent to begin with have a small number of defects, so they don’t absorb nearly as many oxygen molecules, don’t suffer loss of luminescence, and their optical properties remain close to their properties under vacuum conditions.”This work shows that a slim amount of defects in MoTe2 can have a great impact on their material properties, such as optical, electrical, and vibrational, and these changes occur gradually over time similar to aging wine: depending on the defect concentration, MoTe2 monolayers can spoil over time (or might get better),” Tongay explained.The results here show that the defects play a significant role in the optical properties and stability of MoTe2, and could also reveal insight into the environmental stability of other 2D materials, such as silicene (2D silicon), phosphorene (2D phosphorous), and other TMDs. It could also lead to ways to control these materials’ properties. (Phys.org)—When exposed to air, a luminescent 2D material called molybdenum telluride (MoTe2) appears to decompose within a couple days, losing its optical contrast and becoming virtually transparent. But when scientists probed further, they found that the disappearance is an illusion: the material remains structurally stable, and only its material properties change. The results reveal insight into the environmental stability and unusual properties of a newer class of 2D materials called transition metal dichalcogenides (TMDs). Citation: Two-dimensional material seems to disappear, but doesn’t (2015, May 5) retrieved 18 August 2019 from https://phys.org/news/2015-05-two-dimensional-material-doesnt.html Explore further © 2015 Phys.org More information: Bin Chen, Hasan Sahin, et al. “Environmental Changes in MoTe2 Excitonic Dynamics by Defects-Activated Molecular Interaction.” ACS Nano. DOI: 10.1021/acsnano.5b00985 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 (Left to right) Postdoc Aslihan Suslu, PhD student Bin Chen, and Assistant Professor Sefaattin Tongay have investigated the material stability and optical properties of 2D transition metal dichalcogenides (TMDs), which have potential applications in optoelectronics and other areas. Credit: Sefaattin Tongay Journal information: ACS Nano Play Monolayer MoTe2 is visually disappearing in this video recorded over a 7-day period. However, atomic force microscopy measurements reveal that the material is indeed still there; it physically exists, and only its optical properties change. Credit: Sefaattin Tongay The researchers began by observing the material under an optical microscope with an infrared lens. They found that MoTe2 flakes that were highly luminescent to begin with maintained their brightness over the 8-day observation period. On the other hand, weakly luminescent flakes unexpectedly appeared to fade within 1-3 days, and parts of them disappeared altogether. However, when viewing the “vanishing” flakes using an atomic force microscope (AFM), which scans samples mechanically rather than optically, the researchers saw the flakes “reappear.” The flakes had never disappeared in the first place, but their optical properties had changed while their chemical structure was maintained. 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. “This is an important discovery in that it practically implies that we are able to tune the optical properties of 2D MoTe2 by manipulating the defect density in the material and preventing the material from losing its intrinsic attributes by improving the quality of crystal,” said Bin Chen, PhD student at Arizona State University and lead author of the paper.In the future, the researchers plan to explore and establish the stability of other 2D material systems, as well as boost their properties by molecular functionalization through existing or intentionally created defect points. “Despite encouraging results and impressive applications, our results point toward environmental instability over a time period of a month,” Chen said. “We hope to understand this and ideally overcome these challenges using our knowledge and expertise in materials science and engineering.”
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. (Phys.org)—Stephen Hawking, along with Malcolm Perry and Andrew Strominger has updated his ideas regarding solving the black hole information paradox. In their new paper published in the journal Physical Review Letters, the trio outlines their ideas regarding soft hair and black holes and why they believe it may hold the key to resolving a problem that has been causing issues for physicists for over forty years. © 2016 Phys.org The black hole information paradox is relatively easy to understand—black holes theoretically suck in everything around them, including light, causing information to be lost, forever. But back in the 70’s Hawking and colleagues discovered that some information escapes—it is now known as Hawking radiation—but the information that escapes is not enough to describe everything that was eaten by a given black hole, so, the question remains, what happens to the rest of the information when the black hole dies? Trying to solve this paradox has proven to be much more difficult. But, this past January, progress was made, Hawking, Perry and Strominger proposed a possible solution to the paradox, a theory based on what they called soft hair—but not everyone was convinced. The idea behind the theory is that quantum excitations known as soft hairs form a halo around a black hole, holding the information for the things that were consumed. The team came to conclude this was possible by identifying two problems with the assumptions that were made back in the 70’s, namely that the vacuum around black holes is unique and that black holes had no “hair.”After posting their paper on the preprint server arXiv, in January, critics were wary of the theory because it failed to explain how it was that information could be exchanged between the black hole and the soft hair. In this new paper, the trio still has not addressed this problem completely, but they have reworked the math and have found stronger evidence for the existence of soft hairs—if they can do the same for gravity, and show that all of the information is held in the soft hairs, rather than just some, it should greatly increase the chances that one day the paradox will be solved once and for, offering relief for those who feared that the paradox might one day lead to having to toss out some of the most cherished theories in physics. Journal information: Physical Review Letters More information: Stephen W. Hawking et al. Soft Hair on Black Holes, Physical Review Letters (2016). DOI: 10.1103/PhysRevLett.116.231301ABSTRACTIt has recently been shown that Bondi–van der Burg–Metzner–Sachs supertranslation symmetries imply an infinite number of conservation laws for all gravitational theories in asymptotically Minkowskian spacetimes. These laws require black holes to carry a large amount of soft (i.e., zero-energy) supertranslation hair. The presence of a Maxwell field similarly implies soft electric hair. This Letter gives an explicit description of soft hair in terms of soft gravitons or photons on the black hole horizon, and shows that complete information about their quantum state is stored on a holographic plate at the future boundary of the horizon. Charge conservation is used to give an infinite number of exact relations between the evaporation products of black holes which have different soft hair but are otherwise identical. It is further argued that soft hair which is spatially localized to much less than a Planck length cannot be excited in a physically realizable process, giving an effective number of soft degrees of freedom proportional to the horizon area in Planck units. Citation: Hawking team updates soft hair theory to help solve black hole information paradox (2016, June 9) retrieved 18 August 2019 from https://phys.org/news/2016-06-hawking-team-soft-hair-theory.html Physicists split on ideas expressed in Hawking’s latest black hole paper Hawking, Perry, and Strominger suggest that black holes might have “soft hair,” low-energy quantum excitations that release information when the black hole evaporates. Credit: APS/Alan Stonebraker Explore further , arXiv
Credit: CC0 Public Domain © 2018 Phys.org NASA is taking a new look at searching for life beyond Earth Explore further Journal information: arXiv Citation: A model that computes the fraction of the ‘haystack’ that SETI programs have collectively examined (2018, September 28) retrieved 18 August 2019 from https://phys.org/news/2018-09-fraction-haystack-seti.html More information: How Much SETI Has Been Done? Finding Needles in the n-Dimensional Cosmic Haystack, arXiv:1809.07252 [astro-ph.IM] arxiv.org/abs/1809.07252 While it might seem to people who are not space scientists that humans have done an awful lot of work searching for signs of life on other worlds, the truth is quite the opposite. Back in 2010, well-known space scientist Jill Tarter compared the search thus far to peering at a glass of water looking for fish while standing next to the still unexplored ocean. In their new effort, Wright, Kanodia and Lubar have created a model that they believe better frames the effort to date. Their model uses inputs such as the number of searches conducted and amount of space covered, and compares them to estimates of the size and intricacy of the galaxy and universe beyond.In their work, the researchers focus on the more traditional types of searching methods—using telescopes and other advanced equipment to study signals that arrive here on Earth from other places. This, of course, rules out the possibility of extraterrestrial life already residing here on Earth or unexplained phenomena such as UFOs.The researchers have found Tarter’s analogy to be quite close to reality, though they would bump the sample size from a glass to a swimming pool. But they also note that another famous analogy might need modification. They suggest the search for extraterrestrial life might be more akin to searching for any one of multiple needles in a proverbial haystack, rather than just one. But they also note that all we really need to find is just the one. Why haven’t we found evidence of life anywhere but Earth? A trio of astrophysicists has revisited this question by taking a closer look at the “needle in a haystack” analogy. Their analysis involved creating a model to assess the amount of work that has been done searching for extraterrestrial life, the Search for Extra-terrestrial Intelligence (SETI) project, compared to how much is required before scientists can rule out the possibility that there is none. Jason Wright, Shubham Kanodia and Emily Lubar have written a paper describing their efforts and uploaded it to the arXiv preprint server. 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.
, Advanced Materials 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 work demonstrated the atomic geometry of metallic quantum contacts that could be modulated with light and the ability to reverse switch (on/off, vice versa) their conductance using plasmonic heating. While the atom-by-atom separation of electrodes were clearly observed, they could also adjust the gap size, between the electrodes at sub-angstrom resolution by controlling the intensity of light. Zhang et al. showed that the plasmon can potentially breakthrough the diffraction limit of light to realize nanofocusing, to transfer the plasmon-controlled atomic switch to realize highly integrated nanodevices; opening a new path to engineer nanoelectronic devices. Explore further While generating a nanogap was crucial to fabricate single molecule-based devices, engineering an adjustable atomic-scale gap has remained a significant challenge. Although fixed gap sizes could not be adjusted post-fabrication, the gap-size could be readily and continuously adjusted through plasmonic heating at sub-angstrom resolution, as shown by Zhang and the research team. For this, they used a commercial light-emitting diode (LED) lamp as a light source in the experiments with an AC adaptor to continuously control the intensity of light. The experimental setup did not require special optical hardware or high power laser sources. They used a commercially available gold wire with a constriction in the middle on a spring steel substrate to construct the nano contacts. Then using a ‘mechanically controllable break junction’ (MCBJ), the scientists stretched the constriction by bending the substrate, and observed it with scanning electron microscopy (SEM) images. Thereafter, the scientists reduced the cross-section of the constriction to form two separate electrodes. When they turned the light on, the conductance increased and decreased when the light was turned off; the large conductance resulting from light illumination strongly reconnected the two separated electrodes.The scientists analyzed the phenomenon at the level of atomic arrangement, upon light illumination. They showed that the nanogaps had strong absorption of light in the visible and near infrared regions due to localized surface plasmon resonances (LSPR). When the frequency of the LED light matched the oscillation frequency of the free electrons and the electromagnetic field at the tip of the electrodes, the LSPR around the gap was excited. The absorbed light then converted to thermal energy causing nanoelectrode expansion and their reconnection. The conductance reached its maximum value when the system was at thermal equilibrium. When the light was shut off, the electrons separated once more. Characterization of MCBJ devices and simulation of expansion distribution of the electrodes upon light illumination. a) System for the measurement of optical spectroscopy. b) Measured dark field scattering spectra from the gap area that employs three different samples. The gap size is ~2 nm in sample A and ~0.2 nm in sample B. The electrodes were strongly reconnected, and no nanogap is observed in sample C. Plasmonic resonances are indicated by the arrows. c) Model used in the simulation. Parts of the large metal wire close to the nanotips were considered. The gap size between two nanotips is initially set to 2 nm. The polarization of the incident light is parallel to the x-axis. d) Expansion distribution (in X component) when equilibrium temperature was established. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0144-z. , Light: Science & Applications Zhang et al. also observed how the nanogap size could be precisely modulated by light by showing that the conductance could be modified in the tunneling region, between the gap of the two electrodes, by controlling the LED light. When the light intensity was fixed, they could keep the tunneling current constant for longer. The scientists estimated the distance between the two electrodes using the Simmons equation; used to describe the relationship between the tunneling current and the tunneling gap size. They could thereby precisely control the distance between the two separated electrodes at sub-angstrom accuracy using the light intensity.To confirm that the origin of switching behavior was plasmon-induced heating in the nanoscale plasmonic systems, the scientists investigated the scattering spectrum of the MCBJ samples to reveal the frequency of plasmonic resonance. The results indicated that the conductance change related to the expansion of the electrodes due to plasmonic heating. Zhang et al. also performed finite element method simulations to estimate the expansion of the electrodes and solved the electric field distribution, temperature distribution and thermal expansion on light illumination, using the COMSOL Multiphysics program package. The simulation calculated the maximum displacement of the electrodes as approximating 0.4 nm. Zhang et al. were able to further optimize the switching frequency by optimizing the characteristic dimensions for heat transfer. In this way, the scientists experimentally proved that atomic switches could be rapidly operated via plasmonic heating. Illumination system with different frequencies. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0144-z Dependence of conductance on the incident light. a) Real-time measurement of the conductance upon the LED light illuminations in the tunneling regime. Vbias = 1 mV. b) Schematic of the gap size variation upon light illumination. The dashed lines indicate the new position of the nanoelectrodes upon LED illumination. c) The conductance of the tunneling gap dependent on the laser polarization. When a p-polarized laser (pink) is employed, the conductance is approximately two times larger than the conductance when an s-polarized laser (orange) is employed. The laser central wavelength is 640 nm with a bandwidth of 5.7 nm, and the maximum laser power density is 0.5 mW/mm2. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0144-z. , Nature Nanotechnology © 2019 Science X Network Current modulated by the light illumination. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0144-z. LEFT: a) A metal wire with a notch in the middle is fixed on the substrate. The notch can be stretched until it finally breaks due to the bending of the substrate, which produces two separated electrodes. b SEM images of the notched microwire during the stretching process. Scale bar: 50 μm. c Real-time measurement of the current with the light switched on/off every 50 s–60 s. Zoomed image: conductance decreases in quantum steps at multiples of G0 (=2e2/h) as the light intensity decreases. d Schematic of the atomic arrangement, which corresponds to four conductance states upon light illumination. State 1: the two electrodes are separated by a few angstroms (G ≪ 1 G0). State 2: the two electrodes are reconnected upon light illumination (G ~ 80 G0). State 3: the two electrodes are stretched, and a gold atom chain is formed before the nanocontact breaks when the light intensity is reduced (G ~ 1 G0). State 4: the two electrodes are separated again due to the heat dissipation as the light is completely turned off (G ≪ 1 G0). RIGHT: Fabricating a nanocontact. a) Setup to roundly cut the metal wire. The metal wire was sandwiched between a knife blade and a supporting platform. The platform can move in the vertical (Z) and parallel (X) directions with a resolution of ~5 μm. b) SEM image of the nanogap after breakage of nanocontact. Scale bar: 5 μm. c) Optical micrograph of the metal wire with a notch in the middle. Scale bar: 50 μm (d) SEM image of the metal wire. Scale bar: 20 μm. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0144-z. In the method developed by Zhang et al. light can be used to control electrical conductance at the junction between gold nano-electrodes by heating electrons at the electrode surface, in a technique known as ‘plasmonic heating.’ They validated the experimental mechanisms using simulations. The research team expanded electrodes via plasmonic heating to close the gap and turn the switch on, paving the way to build single-molecule transistors and nanopore-based biosensors at the nanoscale. Molecular junctions were previously investigated as an approach to build nanoswitches by employing photochromic (light sensitive) molecules that switched between two distinct isoforms. The present work by Zhang et al. contrastingly demonstrated conductance switch behavior only with a bare metallic contact, under light illumination, without any molecules. They demonstrated the conductance of bare metallic quantum contacts as reversible switches across eight orders of magnitude to substantially exceed the performance of the previous molecular switches. The scientists were able to adjust the gap size between the two electrodes after the switch process with sub-angstrom accuracy, by controlling the light intensity or polarization. Illumination system with different frequencies. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0144-z More information: Weiqiang Zhang et al. Atomic switches of metallic point contacts by plasmonic heating, Light: Science & Applications (2019). DOI: 10.1038/s41377-019-0144-z K. Terabe et al. Quantized conductance atomic switch, Nature (2005). DOI: 10.1038/nature03190 Kasper Moth-Poulsen et al. Molecular electronics with single molecules in solid-state devices, Nature Nanotechnology (2009). DOI: 10.1038/nnano.2009.176 Tsuyoshi Hasegawa et al. Atomic Switch: Atom/Ion Movement Controlled Devices for Beyond Von-Neumann Computers, Advanced Materials (2011). DOI: 10.1002/adma.201102597 Scientists have recently developed a light controlled nano-switch to lay groundwork for atomic device development in nanotechnology. They engineered the switches at the nanoscale in a first step toward fully integrated electronic device miniaturization. The multidisciplinary research was conducted by Weiqiang Zhang and co-workers, and an international team of collaborators. Results of the study are now published in Light: Science & Applications. Journal information: Nature To understand how conductance depended on the light intensity, the scientists performed experiments where the maximum light intensity within each illuminated circle gradually increased. Zhang et al. showed that the maximum conductance in each circle increased approximately linearly with the intensity of light. They obtained repeatable data of the current as a function of the light intensity and showed how the conductance of quantum contact, could be regulated by the intensity of light. In the present study, Zhang et al. used this principle to show how a metallic, atomic scale contact could be operated reliably as a conductance switch through controlled illumination of light. To engineer the metallic atomic-scale contact they precisely stretched a metal nanowire using the mechanically controllable break junction. When they reduced the cross-section of the metal wire to a few nanometers or a few atoms, the diameter became comparable to the Fermi wavelength of the electrons, allowing quantum-mechanical effects to strongly influence the properties of electron transport. Using these principles, Zhang et al. showed how the conductance of an atomic gold contact could be switched from a few quanta of conductance to hundreds of quanta, and vice versa with light illumination. The scientists were able to reversibly switch the metallic quantum contacts between the open and closed state by controlling the light intensity. They created a nanogap between the quantum contacts within which coherent tunneling governed electron transport. In-plane coherent control of plasmon resonances for plasmonic switching and encoding Citation: Atomic switches by plasmonic heating of metallic contact points (2019, April 3) retrieved 18 August 2019 from https://phys.org/news/2019-04-atomic-plasmonic-metallic-contact.html Engineering electronic devices using functional building blocks at the atomic scale is a major driving force in nanotechnology to form key elements in electronic circuits, which were previously miniaturized using mechanical tunneling, bias voltage/current operation and electrochemistry. Previous studies did not, however, address the concept of atomic switches controlled by plasmonic heating. Surface plasmons are coherent delocalized electron oscillations at the interface between two materials that form metallic nanostructures, which can be concentrated into the subwavelength gaps between the materials. In principle, when the resonance frequency of surface plasmons match the frequency of the incident light, the plasmon resonance is excited to produce strong light absorption and substantial plasmonic heating.
Comparison of measured and time-integrated Th/U in zircon. The panel a is for oldest known terrestrial igneous zircons, whereas panel b is for oldest known terrestrial detrital zircons from Western Australia. Time-integrated means calculated from measured 208Pb/206Pb ratio and 207Pb/206Pb age. Corresponding data can be found in Credit: Nature Communications, doi: 10.1038/s41467-019-10382-y LEFT: Influence of Pb mobility on present-day 207Pb/206Pb ages and time-integrated Th/U. The panel (a) shows the effect of Pb-loss and Pb-addition on determined 207Pb/206Pb ages for a 4430 Ma zircon with original Th/U of 1, whereas the panel (b) presents the effect of Pb-loss and Pb-addition on time-integrated Th/U for the same zircon. Percentages next to the dotted-curves correspond to the degree of Pb-loss or Pb-addition. The age of perturbation refers to the age at which the Pb is lost or added. Note that Pb-addition corresponds to local increase in radiogenic Pb concentration and not addition of common Pb. This figure illustrates the great sensitivity of 207Pb/206Pb ages to Pb mobility whereas it has a limited effect on time-integrated Th/U. RIGHT: Time-integrated Th/U as a function of that measured for Martian zircons. Data are from previous studies. Note the large decoupling between measured and time-integrated Th/U for domains within zircon Z2 from NWA 7533. Measured Th/U are also well outside the common magmatic range, much as what can be seen in Jack Hills zircons. Error bars represent two standard errors on analytical measurements. Corresponding data can be found in Credit: Nature Communications, doi: 10.1038/s41467-019-10382-y Via extensive experiments, Guitreau and Flahaut showed that decoupling between the measured and time-integrated Th/U exhibited by terrestrial zircons as a proxy for zircon alterations by aqueous solutions at low temperatures. Upon comparison, the scientists showed that lunar (moon) zircons exhibited anomalously high Th/U in compliance with the common range for terrestrial larva/magma based igneous (fiery) zircon. This was expected since there is no evidence for liquid water on the moon. Similarly, Martian zircon crystals obtained from the meteorite NWA 7533 and the matrix of NWA 7034 showed consistent measurements and time-integrated Th/U ratios. Based on existing data and the present calculations, Guitreau and Flahaut interpreted the horizontal distribution as evidence for low temperature alterations of Martian zircon grains by aqueous solutions—much like the crystals from Western Australia. The present findings using decoupling between the measured and time-integrated Th/U ratios reinforced the idea of the availability of liquid water in the Martian subsurface. The phenomenon induced advanced weathering of radiation-damaged zircon crystals. Explore further In the present work, Guitreau and Flahaut explored if decoupling between the measured and time-integrated Th/U in Zircon could proxy for low-temperature aqueous alterations and then outlined the principles of their new method. When the scientists applied the method to extraterrestrial zircons on the moon for comparison with Martian zircons, they obtained evidence for low-temperature aqueous weathering on Mars. In this way, Guitreau and Flahaut presented their new data with robust evidence from existing investigations to indicate that the low-temperature alteration event recorded in NWA zircons occurred in the late Amazonian period on Mars. They assume that the availability of water for weathering in the late-Amazonian was likely controlled by impact-induced hydrothermal activity. The observations in the present study were consistent with post-brecciation (rock fragmentation) zircon alteration, and the youngest volcanic activity on Mars could also have played a role due to alterations with the current cryosphere. The recorded alterations of Zircons in the NWA 7533 meteorite represented the youngest episode of persistent aqueous alteration thus far reported on Mars. The results support the concept that Mars may yet be habitable relative to the evidenced availability of liquid water in its recent past. Calculated radiation doses as a function of Th/U in zircon. The panels a, b and c correspond to data from previous studies. Note the general upward-opening fan shape distribution of data above the first percolation point (stage at which amorphous domains become connected). Corresponding data can be found in Credit: Nature Communications, doi: 10.1038/s41467-019-10382-y Many accounts at present support the presence of liquid water on Mars, where hydrated minerals testify to past processes of aqueous weathering in Martian meteorites such as NWA 7533/7034. Planetary scientists aim to estimate the timing of weathering on the Martian crust to help understand its evolution, the availability of liquid water and habitability on Mars. In a recent study, Martin Guitreau and Jessica Flahaut at the University of Manchester, U.K., and the National Center for Scientific Research in France, presented a new method based on U-Th-Pb (Uranium-Thorium-Lead) isotope dating systems. Using the technique, Guitreau and Flahaut investigated if Zircon crystals underwent low-temperature aqueous alteration, similar to observations with Hadean-aged detrital crystals from Western Australia. Results for the two-stage model simulating Martian zircon evolution. Models were run for U enrichment factors of 5 for panels (a) and (b), whereas a factor of 2 was used for the results presented in panels (c) and (d). The pre-alteration Th/U was set to 1 for models shown in panels a and c, and it was set to 0.5 in panels (b) and (d). Th/U ratios increased by alteration were set to 1–27 and 0.5–27, depending on the pre-alteration Th/U. Colored curves correspond to measured Th/U in zircon Z2 domains. The U–Pb resetting age corresponds to the lower intercept of the general Discordia line displayed in a previous study and is represented by a solid vertical line. The horizontal dashed lines, which are the intercepts between the colored curves and the solid vertical line, indicate the time-integrated Th/U deduced from our model. The gray-shaded zones between Th/U values of 1 and 2 correspond to the time-integrated Th/U exhibited by zircon Z2 domains. These results show that time-integrated Th/U derived from the current model are higher than those exhibited by zircon Z2 domains, and, hence, alteration at 1700 Ma (or 1500 Ma) cannot account for the observed decoupling between measured and time-integrated Th/U in the study. Credit: Nature Communications, doi: 10.1038/s41467-019-10382-y More information: Martin Guitreau et al. Record of low-temperature aqueous alteration of Martian zircon during the late Amazonian, Nature Communications (2019). DOI: 10.1038/s41467-019-10382-y A. A. Nemchin et al. Record of the ancient martian hydrosphere and atmosphere preserved in zircon from a martian meteorite, Nature Geoscience (2014). DOI: 10.1038/ngeo2231 Michael H. Carr et al. Geologic history of Mars, Earth and Planetary Science Letters (2009). DOI: 10.1016/j.epsl.2009.06.042 William J. Weber et al. The radiation-induced crystalline-to-amorphous transition in zircon, Journal of Materials Research (2007). DOI: 10.1557/JMR.1994.0688 Timeframe for Martian crust evolution. Displayed are details of knowledge about the history of NWA 7034/7533 and paired stones. The igneous crystallization of NWA7034/7533 zircons and clasts are derived from previous studies. Metamorphism and alteration ages are from additional studies. Brecciation age range is also from previous investigations, and so is the age of ejection. Corresponding data can be found in Credit: Nature Communications, doi: 10.1038/s41467-019-10382-y Moon rock recovered by astronauts likely originated on Earth Journal information: Nature Communications The data for NWA 7533 Zircons showed evidence for aqueous alteration, and modeling the evolving U-Th-Pb isotope system indicated the latest alteration to have occurred in the late Amazonian period (227-56 Ma). The finding largely expands the time duration in which liquid water was available near the Martian surface—suggesting that Mars may still be habitable, based on the evidence. Results of the study are now published on Nature Communications. Zircon is a robust time capsule extensively used in U-Pb geochronology and in the study of magmatic/metamorphic processes on Earth. Planetary scientists have testified this process using terrestrial detrital Zircon predating to 4378 million years. Nevertheless, the alpha-particle emission and α-recoil cascades due to U and Th decay can damage the crystal lattice, causing radiation to accumulate in zirconium at different rates based on the concentrations (ratio) of U and Th. This stage is defined as the “first percolation point” after which chemical elements can be more readily mobilized than in pristine crystals. The progressive amorphization can induce crystal lattice expansion and crack formation in Zircon to enhance the crystal’s sensitivity to thermal events as observed with ancient Zircons from Jack Hills, Western Australia. When they modeled the evolution of the U-Th-Pb isotope systems of zircon to determine the development of decoupling between the measured and time-integrated Th/U, they discovered the alteration occurred at 1500-1700 Ma; as a much younger event. The event corresponded to the late Amazonian period, which is generally considered cold and dry on Mars. As a result, the present work demonstrated the availability of water near the Martian surface in the recent past, suggesting its presence in the present day. To investigate the sensitivity of Zircon, the scientists considered chemical modifications as well as isotopic resetting during preservation of the lattice. To assess these conditions, they used macroscopic visual criteria and microscopic methods including transmission electron microscopy, Raman spectroscopy, X-ray diffraction, nuclear magnetic resonance and atom probe tomography. A simpler, indirect approach is to also calculate the radiation dose that a zircon sample underwent (alpha decay events per gram of sample) using chronological information provided by U-Pb isotype systems and U and Th concentrations. For example, when scientists calculated the radiation doses of Jack Hills zircon datasets, they showed decoupling between the measured and time-integrated Th/U ratios in zircon domains. In this instance, radiation doses appeared to accumulate beyond the first percolation point, however the process required verification prior to its use on aqueous alterations beyond Earth. To understand the timing of Marian aqueous weathering, Guitreau and Flahaut developed a two-stage model of the U-Th-Pb isotope evolution in the present work. They tested if an aberration event (deviation) at 1500 or 1700 Ma could have accounted for the observed decoupling between the measured and time-controlled Th/U and the zircon alteration in NWA 7533. In the first stage of the model, Guitreau and Flahaut investigated zircon formation at 4430 Ma, followed by the second stage as an alteration event on increasing U and Th concentrations to alter zircon in the NWA 7533 meteorite. Using the two-stage model, they showed that uranium could be enriched by 2-5 times the original concentration to match both Jack Hills and Martian Zircon data. The results indicated that the observed levels of Th/U could have occurred at 1700 Ma or 1500 Ma. The scientists further implemented the model with an additional stage to form a three-stage model, using the same Th/U ratios and Uranium enrichment factors as in the two-stage model. The results showed that while the determined alteration ages remained very young, the specific alterations recorded by the scientists occurred during the late Amazonian period. 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. , Earth and Planetary Science Letters Citation: Low-temperature aqueous alteration of Martian zircon during the late Amazonian period (2019, June 26) retrieved 18 August 2019 from https://phys.org/news/2019-06-low-temperature-aqueous-martian-zircon-late.html © 2019 Science X Network , Nature Geoscience
With the mercury dipping each passing day, the chill can get harmful for your furry friends. Unlike humans, animals have lower immunity levels, hence taking care of them becomes more important during the winters.Change in weather conditions, decreasing temperature and other dangers of winter may pose a number of expected and unexpected health threats to your pets. Therefore, shielding them from diseases and infections becomes a daunting task.‘Some long-haired breeds, such as German Shepherds and Huskies, are better suited to cold winters and love the weather. But other sensitive breeds need protection during this season,’ said Dr KG Umesh, Waltham Scientific Communication Manager, South Asia, Mars India. ‘Older dogs are usually more vulnerable to the adverse effects of winters. Dogs with health conditions like a hormone imbalance, heart problems, kidney disease or diabetes are not able to regulate their body heat appropriately. Ones who are suffering from arthritis can experience considerable discomfort as cold weather can make their stiff joints stiffer. Vaccination, de-worming and regular health check ups are important during winter,’ added Umesh. Also Read – ‘Playing Jojo was emotionally exhausting’By following certain steps, you can ensure that your pets are in pink of health: FEEDING: Give your pet more food during cold weather than you do during the hot months. Dogs, for example, may need upto 25 per cent more energy in the winter than they do in the summer, especially those who exercise outdoors. Pets need extra food because exercising outdoors in cold weather takes up more energy. Ensure that you feed them energy-dense food and give them balanced nutrition. Also Read – Leslie doing new comedy special with NetflixEXERCISE: Take your pets out for walks at frequent intervals. Increasing their physical activity will help keep the metabolism under control and winter ailments at bay.GROOMING: Groom your dog in winters using dry bathing technique by brushing corn starch or baby powder. Your dog probably won’t get very dirty in the winter, and you may not need to bathe them. But if you do, it’s very important that you keep him warm after the shower.HAIR SHEDDING: Hair loss is common for dogs in this season. Every winter, dogs shed their summer coat and grow a nice thick one. However, taking your pet for a visit to the vet for examination of parasites like fleas, ticks, mange or allergy, hormonal imbalance, bacterial or yeast infection that causes hair loss is required.BEDDING: Dogs exposed to extreme cold weather conditions may become hypothermic or even develop frostbite. Dog owners may select from a bedding options such as pads, blankets or quilts and straw or hay. Adding a thick blanket to the bed will help.
It’s only in a work of art can you expect life being breathed into the dying. Shovan Gandhi, a Delhi based photographer, in his work Alang has done just the same. Being a part of the bigger picture – Pix – a photo quarterly, Gandhi has portrayed Habitat through this endeavor along with fifteen other artists. Alang is a journey of ships, starting from the day they are born to the waves they crash and land to their graveyard and even beyond. It tries to encapsulate the experiences the ships go through throughout their life and finally end up in this ship breaking centre in Gujarat. He compares, not the life of a ship to that of a man, but vice-versa. One cannot ignore the idea glaring through his pictures that each man-made thing has to come to an end. Once worn out, nothing can keep the drums rolling, or here, the ships sailing. Though ‘philosophical’, it asks the question of death and birth; of waste from value and conversely. Also Read – ‘Playing Jojo was emotionally exhausting’Alang also portrays the journey, its end and a new beginning. The lines by T. S. Eliot, ‘What we call the beginning is often the end. And to make an end is to make a beginning. The end is where we start from,’ fits Alang beautifully. It shows not only how the once mighty ships sailing the economies of the world come to rest in peace, but also how their end marks a new beginning for scrap collectors. For truly, there never is an end. The project has attracted various view points from various fields of ecology, architecture and finance. Not being faced with a criticism yet, Shovan has tried to highlight the prevailing socio-cultural ecosystem in which, according to him, ‘unimportant men can aggregate and die so that dead ships live.’ Drawing influence from architecture and fine art, Gandhi wishes there would be more platforms in the country for display of photographs and art. He expects to present a new project in the following year.WHERE: Goethe-Institute, Maxmuller Bhawan, New DelhiWHEN: When: 9 to 16 May, 7:00 pm to 9:30 pm
Don’t we all get a craving for some crispy, sizzling, juicy chicken during some part of the day? Well, Thank God it’s Friday (TGI Friday) has a special treat stored in for all the chicken lovers out there this summer! They have featured their new ‘Chicken Sensations- flavours beyond your expectations’ which will flatter your taste buds with a galore of exciting chicken dishes. TGIF’s Chicken Sensations include Crab Crusted Cajun Chicken, Parmesan Crusted Chicken and Wicked Chicken. We tried their Crab Crusted Cajun which was rich and quite juicy with two blackened chicken breasts topped with bruschetta crab blend. The dish was served with a flavourful parmesan mushroom cream sauce and creamed spinach with cheddar potatoes. Also Read – ‘Playing Jojo was emotionally exhausting’Their Parmesan Crusted Chicken was also quite commendable with two nicely sauteed chicken breasts which were brushed with Caesar dressing and then finished with a parmesan-crust. The dish was served with a creamy spinach Alfredo fettuccine pasta and a fresh tomato mozzarella salad which complimented the chicken perfectly.The special menu also offers Wicked Chicken which includes two blackened chicken breast topped with cajun cream sauce over jambalaya rice. The dish is served with butter roasted corn cobs and a side of cajun cream sauce. So head over to TGI Friday’s to satify your chicken mania. A meal for two would cost Rs. 1200 plus taxes.