Tech gadgets that make travel easier (PhysOrg.com) — The Novatel MiFi portable broadband hotspot card does the job of a 3G modem and wireless router combined. The MiFi can connect to either an EVDO Rev. A or HSPA signal. The connection is then shared via a WiFi connection. 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 Novatel Wireless MiFi creates a WiFi hotspot using a mobile broadband network. MiFi is describe by Novatel as intelligent mobile hotspots which are are basically smart routers the size of a credit card but 3 times as thick. The Novatel MiFi would connect to the internet via a high speed mobile phone network such as the EVDO networks operated by Verizon and Sprint Wireless. It can also connect to the AT&T and T-Mobile Wireless via their UMTS/HSDPA networks.According to Novatel, the internal rechargeable battery can last up to 4 hours of continuous use and 40 hours of standby time. It’s small size also makes it more attractive as a travel companion. Connecting a MiFi to a notebook would be as simple as creating a WiFi profile in your operating system. This would eliminate the need for any special software that would be needed if using a broadband network card. The Novatel MiFi cards will become available in early 2009 and will be distributed by the wireless phone carriers that will provision the broadband access. Novatel estimates the cost around $200, but that’s before any carrier subsidies. © 2008 PhysOrg.com Explore further Citation: Novatel Debuts Their Wireless MiFi Hotspot (2008, December 9) retrieved 18 August 2019 from https://phys.org/news/2008-12-novatel-debuts-wireless-mifi-hotspot.html
Citation: Digital quantum batteries inspired by plasma TVs (2010, January 28) retrieved 18 August 2019 from https://phys.org/news/2010-01-digital-quantum-batteries-plasma-tvs.html (PhysOrg.com) — Plasma TVs are notorious for their excessive use of electricity, but the same principle used to produce high definition pictures in the TVs could result in the development of a new type of battery that would save rather than waste energy. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. © 2010 PhysOrg.com Schematic of an array of four vacuum nano tubes (cross section, side view). The cathode(− − −) is a planar. The anode (+ + +) is a nano tip on a flat electrode. The thin curved lines indicate the electric field lines. Image: Alfred W. Hubler, see link below for further details. Plasma TVs contain millions of microtubes filled with ionized gas that allows an electrical current to flow through, but physicists at the University of Illinois at Urbana-Champaign (UIUC) are developing what they call a “digital quantum battery” that uses billions of even smaller tubes (nanotubes). By removing the ionized gas from the tiny tubes, the UIUC team, led by Associate Professor Alfred W. Hubler, wants to take advantage of the strong electrical fields to store electricity. When the gas is removed the vacuum inside the nanotubes acts as an insulator to store the electrical field. Professor Hubler says the device could store twice as much electricity as conventional batteries, and it could store digital information at the same time.The battery is termed the digital quantum battery because it operates on the quantum scale, trapping the strong electrical field generated when negatively charge electrons encircle positively charged protons inside an atom. The device harnesses the most effective way to store energy, which is in the bonds between atoms. (The energy in gasoline and kerosene is held in the same way.)The battery’s reverse-bias nanotubes are much stronger and smaller than plasma tubes and they contain little or no gas. Hubler said the tubes would be five nanometers long and billions of them would be packed together to provide enough power for most 15 V electronic devices. Each nanotube could also represent a bit of information (0 or 1, depending on whether the tube is electrically charged or not). This means the device could be used to store digital information like a flash drive. Hubler said a flash drive uses the smallest amount of energy to store the charge, while the UIUC device would aim for the maximum possible amount of energy.The state of the vacuum tube can be determined without discharging or charging it because a MOSFET (metal-oxide-semiconductor field-effect transistor) is inserted in the wall of the tube to detect the state inside the tube. Each tube has an energy gate and an information gate, which is a similar arrangement to the floating and control gates in a flash drive. The gates allow the nanotubes to be used to store information and energy.Professor Hubler is the Director of the Center for Complex Systems Research at UIUC. The research paper will be published in the journal Complexity, for which Professor Hubler is an executive editor. The work was supported by a National Science Foundation Grant. Digital Quantum Battery Could Boost Energy Density Tenfold More information: Paper: netfiles.uiuc.edu/a-hubler/www … quantumbatteries.pdf 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. (Phys.org) — Finding new connections between different disciplines leads to new – and sometimes useful – ideas. That’s exactly what happened when scientists in the Department of Physics, Queens College, City University of New York (CUNY), in collaboration with City College of CUNY, Purdue University and University of Alberta, leveraged mathematical topology to create an artificially nanostructured anisotropic (exhibiting properties with different values when measured along axes in different directions) metamaterial that can be switched from a non-conductive dielectric state to a medium that behaves like metal in one direction and like a dielectric another. The metamaterial’s optical properties was mapped onto a topological transformation of an ellipsoidal surface into an hyperboloid – and transitioning from one to the other dramatically increases the photon density, resulting in dramatic increase in the light intensity inside the material. The researchers state that by allowing topologically-based manipulation of light-matter interactions, these types of metamaterials could lead to a wide range of photonic applications in solar cells, light emitting diodes, displays, and quantum computing and communications. Citation: The shape of things, illuminated: Metamaterials, surface topology and light-matter interactions (2012, April 28) retrieved 18 August 2019 from https://phys.org/news/2012-04-illuminated-metamaterials-surface-topology-light-matter.html Copyright 2012 Phys.Org All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. Explore further More information: Topological Transitions in Metamaterials, Science 13 April 2012: Vol. 336 no. 6078 pp. 205-209, doi: 10.1126/science.1219171Related:1Optical black hole: Broadband omnidirectional light absorber, Applied Physics Letters 95, 041106 (2009), doi: 10.1063/1.31845942Metric Signature Transitions in Optical Metamaterials, Physics Review Letters 105, 067402 (2010), doi: 10.1103/PhysRevLett.105.067402 Swimming upstream: Flux flow reverses for lattice bosons in a magnetic field Associate Professor Vinod M. Menon recalls that the project started out with theoretical predication and computational modeling. “Our subsequent experimental work was based on computational modeling of the structures and the anticipated effects,” he relates to Phys.org. “At that point, the main challenge in describing the ellipsoid-to-hyperboloid transition was the design of the structure that will show the transition in the relevant spectral range. Relatedly,” Menon continues, “showing that this topological transition manifests itself in increased rates of spontaneous emission of emitters positioned near the metamaterial required the identification of a suitable light emitting material. In our case, that material was quantum dots.” This critical choice of emissive material allowed the researchers to study the enhancement in spontaneous emission in both the elliptical and hyperbolic ranges. Play Artist’s interpretation of the optical topological transition occurring in metamaterials. Here the transformation from an ellipsoid to a hyperboloid (left) is associated with a huge increase in the light intensity inside the metamaterial (right). Courtesy Vinod Menon | Animation created by Vladimir Shuvayev / Queens College – CUNY. Menon is equally to-the-point when describing the key insights, innovations and techniques the team used to address the above challenges. “In addition to the right photon emission source and a suitable material system for metamaterial fabrication, it was necessary to come up with an appropriate control sample to isolate the effect that we were looking for.”Menon adds that the team’s next steps are to reduce optical losses, improve the quality of silver films, and look into new material systems that will show similar effects. “Silver is the metallic component in the metamaterial that allows us to realize the anisotropy. Theoretically one could use any metal or even doped oxides and semiconductors. In our case silver was used because of the lower optical losses in the visible wavelength range, but the roughness of silver layers used in the present structure is an issue. This will have to be addressed in the next round of experiments,” Menon cautions. “Additionally, the optical losses in the material need to be alleviated. Finally, approaches to enhance the transmission properties need to be addressed for light emitting applications.” 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 According to Menon, the team’s findings impact the development of new routes to manipulating light-matter interactions through using metamaterials and controlling the topology of the iso-frequency surface – that is, one having a constant frequency. “The structure that we demonstrated shows a large increase in the light intensity over a wide spectral range,” he explains. “Such structures can help in enhanced light harvesting, which could result in more efficient solar cells. One could also envision using these to develop single photon sources necessary for quantum communication protocols and quantum computers. Finally, through engineering of transmission properties of these systems, and by combining them with light emitters, one may also realize super bright LEDs that would be useful for display applications.”Venturing further afield, Menon descries more exotic possibilities. “Ideas of light manipulation used here could be extended for control of thermal properties as well. More esoteric are the proposed ideas of realizing a table top optical black hole and manipulation of space-time curvature – and in fact, these proposals have been recently made1,2 by one of my co-authors, Evgenii Narimanov, and his collaborators.”
Explore further This new research came about as the chemists collaborated with neuroscientist Anne Andrews, who suggested that perhaps a way could be found to print materials onto surfaces in much the same way that neurotransmitters are “stamped” with biomolecules.The down side is that despite achieving a resolution of 40nm, it still isn’t enough for neurological work, so the team is looking into other ways to create the original stamp rather than using conventional photolithography, which at the nano level, causes some diffusion, and resultant blurring of the original image that is to be reproduced.This new stamping technique is cheaper than conventional methods due to its subtractive, rather than additive nature, which means less waste and also appears to be easier to pull off, thus, it might lead to uses in other fields as well. © 2012 Phys.org Reactive stamps remove molecules from surfaces to create precise nanoscale patterns. Credit: Kei Meguro, Sarawut Cheunkar, Paul Weiss, Anne Andrews, UCLA (Phys.org)—The normal process for printing is centuries old, a piece of material such as wood is fashioned to look like the desired output, a letter of the alphabet, for example resulting in a stamp. Ink is then applied to the stamp and then the stamp is pressed on to something else, such as a piece of paper, resulting in the printing of the letter as the ink is left behind. Modern lithography is based on much the same principle, but now a new way has been found that appears to be cheaper. Instead of inking the stamp, the researchers from the University of California, as they describe in their paper published in the journal Science, ink the “paper” then have the stamp remove the parts of the ink that don’t belong. More information: Subtractive Patterning via Chemical Lift-Off Lithography, Science, 21 September 2012: Vol. 337 no. 6101 pp. 1517-1521. DOI: 10.1126/science.1221774ABSTRACTConventional soft-lithography methods involving the transfer of molecular “inks” from polymeric stamps to substrates often encounter micrometer-scale resolution limits due to diffusion of the transferred molecules during printing. We report a “subtractive” stamping process in which silicone rubber stamps, activated by oxygen plasma, selectively remove hydroxyl-terminated alkanethiols from self-assembled monolayers (SAMs) on gold surfaces with high pattern fidelity. The covalent interactions formed at the stamp-substrate interface are sufficiently strong to remove not only alkanethiol molecules but also gold atoms from the substrate. A variety of high-resolution patterned features were fabricated, and stamps were cleaned and reused many times without feature deterioration. The remaining SAM acted as a resist for etching exposed gold features. Monolayer backfilling into the lift-off areas enabled patterned protein capture, and 40-nanometer chemical patterns were achieved.Press release Credit: Sarawut Cheunkar, Paul Weiss, Anne Andrews, UCLA] The researchers aren’t using ink and paper, of course, instead they are using polydimethylsiloxane, gold and alkanethiols. A pattern was made in a piece of polydimethylsiloxane (a type of rubber), using an electron beam, i.e. photolithography, to create the stamp. They then covered a base of alkanethiols with gold, which served as the material to be printed on. Then to print the desired pattern, the stamp was applied to the base material, then removed, pulling with it (due to a reaction of the materials) not only the gold top layer, but the alkanethiols beneath, resulting in a pattern being left behind which could serve as either the end product itself or a receptacle for filling by another substance, such as protein molecules. Either way the result is a process that results in what the researchers describe as a high degree of resolution, because the material removed is molecule sized. Journal information: Science Universal ink for microcontact printing 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 devise new ‘subtractive’ type of nanoscale printing (2012, September 21) retrieved 18 August 2019 from https://phys.org/news/2012-09-nanoscale.html
The new thermometer developed by the team follows work by other researchers who have found that single atom impurities in diamond crystals (which typically are replaced with a nitrogen atom and a vacancy gap) can be ultrasensitive to changes in temperature—such fluctuations can be seen as a hindrance when attempting to use such material to hold quantum bits, but in the biological world, they can be used to very precisely measure temperature.In their research the team at Harvard injected a single nanodiamond (a diamond just 100 nm in size) into a human cell. Once in place a green laser was shone onto the nanodiamond. Because it altered the spin state of an electron in the impurity, the light that was emitted was changed to red. The degree to which it was changed was then used to calculate the temperature of the interior of the cell. Following that experiment, the team injected two nanodiamonds into a single cell, then focused two separate green lasers onto them, then measured the red light that was emitted. This allowed them to measure the temperature difference between two locations in the same cell. Next, the team injected a nanodiamond and a gold particle into the cell. Once in place a green laser was shone onto the nanodiamond while another laser was shined onto the gold particle causing it to heat up. That heat was transferred to the rest of the cell and was subsequently measured by the nanodiamond.Using this technique the researchers report being able to measure temperature fluctuations as small as 0.05 Kelvin—they expect to achieve better results in the future as temperature fluctuations as small as 0.0018 Kelvin have been recorded using the device outside of a cell. A thermometer with such precision could conceivably be used for both research purposes and in practical applications such as helping to distinguish (or kill) individual cancer cells inside the body. Researchers stop and store light for 60 seconds © 2013 Phys.org Citation: Researchers develop nanodiamond thermometer to take temperature of individual cells (2013, August 1) retrieved 18 August 2019 from https://phys.org/news/2013-08-nanodiamond-thermometer-temperature-individual-cells.html More information: Nanometre-scale thermometry in a living cell, Nature 500, 54–58 (01 August 2013) doi:10.1038/nature12373AbstractSensitive probing of temperature variations on nanometre scales is an outstanding challenge in many areas of modern science and technology. In particular, a thermometer capable of subdegree temperature resolution over a large range of temperatures as well as integration within a living system could provide a powerful new tool in many areas of biological, physical and chemical research. Possibilities range from the temperature-induced control of gene expression and tumour metabolism6 to the cell-selective treatment of disease7, 8 and the study of heat dissipation in integrated circuits1. By combining local light-induced heat sources with sensitive nanoscale thermometry, it may also be possible to engineer biological processes at the subcellular level. Here we demonstrate a new approach to nanoscale thermometry that uses coherent manipulation of the electronic spin associated with nitrogen–vacancy colour centres in diamond. Our technique makes it possible to detect temperature variations as small as 1.8?mK (a sensitivity of 9?mK?Hz?1/2) in an ultrapure bulk diamond sample. Using nitrogen–vacancy centres in diamond nanocrystals (nanodiamonds), we directly measure the local thermal environment on length scales as short as 200?nanometres. Finally, by introducing both nanodiamonds and gold nanoparticles into a single human embryonic fibroblast, we demonstrate temperature-gradient control and mapping at the subcellular level, enabling unique potential applications in life sciences. (Phys.org) —Researchers working at a lab at Harvard University have developed a technique that allows for taking the temperature of individual living cells. In their paper published in the journal Nature, the team describes their technique and just how precise temperature measurements taken with it can be. Journal information: Nature 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. The image shows an artistic representation of a novel technique for nanoscale temperature control inside of a living cell using techniques from quantum optics. The image depicts a rendering of a cell containing nanodiamonds and gold nanoparticles. A gold nanoparticle is heated by an external laser beam and nanodiamonds are used to probe the local temperature. Credit: Georg Kucsko
, Nature Communications Explore further The researchers highlight several examples of how artificial cells may play a role in controlling cellular behavior. One application is using bacteria to search for and clean up environmental contaminants. Instead of genetically engineering bacteria to do this, artificial cells could be constructed to sense the contaminant molecules and release chemoattractants that lure natural bacteria capable of feeding on the contaminants to the site. Artificial cells could also be used for medical applications, such as to destroy tumors and bacterial infections. For example, rather than spraying engineered bacteria into the lungs of cystic fibrosis patients, artificial cells could be built to detect the presence of specific biofilms, and then release small molecules to disperse the biofilms and thus clear the infection. Similar strategies could also be used to replace engineered probiotics in food and supplements with artificial cells that communicate with gut microbiota to prevent disease.Before these applications can be realized, however, artificial cells will need several improvements. One of the most important limitations is the batch-to-batch variability of the artificial cells, which results in varying degrees of activity. More work also needs to be done to protect against degradation of the artificial cells’ membranes, which would result in the release of the encapsulated molecules even in the absence of the environmental molecules. Future work may also include merging non-genetically modified and genetically modified components to tailor specific cellular features.”We’d like to make the artificial cells more robust so that they can survive harsher and more varied conditions,” Mansy said. “Ultimately we’d like to build artificial cells that can function inside of animals or in the environment, but right now they are probably too fragile.” © 2014 Phys.org Changing the conversation: Polymers disrupt bacterial communication But a new study has shown that controlling organisms on the cellular level does not necessarily require genetic modification. Writing in Nature Communications, Roberta Lentini, et al., have demonstrated that Escherichia coli (E. coli) behavior can be controlled by constructing artificial cells that first sense molecules that E. coli alone cannot sense, and then release different molecules that E. coli can sense. In a way, the artificial cells act as translators by converting unrecognized signals into a chemical language that organisms can understand. The translated signal can then potentially trigger a controllable response in the organism.”In my opinion, the greatest significance of our work is that it shows that there’s more than one way to do synthetic biology,” coauthor Sheref Mansy, an assistant professor of biochemistry at the University of Trento in Italy, told Phys.org. “Too often everyone gets excited about one technology or one approach, which sometimes means that solutions to problems get missed because these potential solutions don’t depend on prevalent methods. What we’ve shown is that artificial cells could be used to get around a few of the aspects of living technologies that make people uncomfortable.”In their experiments, the researchers constructed artificial cells that contain a special vesicle which in turn contains several biological components, including a chemical that E. coli can sense (isopropyl b-D-1 thiogalactopyranoside, or IPTG) and DNA that encodes for a riboswitch that responds to an external stimulus. In this case, the external stimulus is the molecule theophylline, commonly found in cocoa beans.When the artificial cell’s riboswitch detects the presence of theophylline, it activates the translation process: a small pore opens in the cell, resulting in the release of IPTG. The E. coli responds to IPTG by exhibiting a green fluorescence, enabling the researchers to easily observe that the new strategy works successfully.Although E. coli does not respond to theophylline on its own, the artificial cells effectively “expand the senses” of the bacteria by allowing it to indirectly respond to theophylline by translating the chemical message. In this way, E. coli’s cellular behavior can be controlled without the need for genetic engineering. The new strategy can potentially overcome the disadvantages of genetic engineering, including the technical difficulties and unintended side effects. (Phys.org) —Genetic engineering is one of the great achievements of modern science, allowing for the insertion or deletion of genes in order to control an organism’s characteristics and behaviors. However, genetic engineering has its drawbacks, including the difficulties involved in engineering living systems and the potential long-term consequences of altering ecosystems with engineered organisms. Journal information: Nature More information: Roberta Lentini, et al. “Integrating artificial with natural cells to translate chemical messages that direct E. coli behavior.” Nature Communications. DOI: 10.1038/ncomms5012 (a) In the absence of artificial cells (circles), E. coli (oblong) cannot sense theophylline. (b) Artificial cells can be engineered to detect theophylline and in response release IPTG, a chemical signal that induces a response in E. coli. Credit: (c) 2014 Nature Citation: Introducing synthetic features to living organisms without genetic modification (2014, June 16) retrieved 18 August 2019 from https://phys.org/news/2014-06-synthetic-features-genetic-modification.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
Search for stellar survivor of a supernova explosion PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen Explore further An international team of space scientists has found evidence of what they believe is a remnant of a type Iax supernova—a white dwarf moving in a way that suggests it was blown across part of the universe by the power of a thermonuclear explosion. In their paper published in the journal Science, the team describes their study of the star and why they believe it is the remains of an Iax supernova. © 2017 Phys.org Most space scientists agree that supernovae occur when a white dwarf pulls a certain amount of the outer layer from a nearby star until it reaches a tipping point—when that happens, a thermonuclear explosion occurs, obliterating the white dwarf—at least, most of the time. This so-called normal type of supernova is classified as Ia. But some theories suggest that the explosion is sometimes not strong enough to completely obliterate the white dwarf—some of it is left behind and pushed through space at a very high speed due to the energy of the explosion. Such supernovae are labeled Iax, but until now, none had ever actually been observed. In this new effort, the research team describes a white dwarf that appears to have all the markings of a supernova Iax remnant.The star, called LP 40-365, was actually first spotted back in 2013—it drew attention because it was traveling so fast. The researchers found that the star was spinning faster than expected and that it had a mixed composition, which suggested that it very likely once had a companion star. Play 00.0sec: Initial binary star outside the disk of the Milky Way galaxy. A massive white dwarf accreting material through an accretion disk from its red giant companion star. The stars orbit around the center of mass of the binary system. 14.6sec: The white dwarf reaches the Chandrasekhar mass limit and explodes as a bright Type Ia supernova. However, the explosion is not perfect; a fraction of the white dwarf shoots out like a shrapnel to the left. The binary system disrupts. 18.0sec: The supernova explosion again, at an edge-on view. The shrapnel comes at the viewer and passes by. 20.0sec: After passing by, the remnant flies off towards the disk of the Milky Way towards the spiral arm with the Solar System. 24.0sec: The fast moving remnant from the solar neighborhood as it passes by the stars in our galactic arm, including the Sun. The remnant gets in the reach of our telescopes. Credit: Copyright Sardonicus Pax Journal information: Science Citation: Evidence found of white dwarf remnant after supernova (2017, August 18) retrieved 18 August 2019 from https://phys.org/news/2017-08-evidence-white-dwarf-remnant-supernova.html 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 More information: S. Vennes et al. An unusual white dwarf star may be a surviving remnant of a subluminous Type Ia supernova, Science (2017). DOI: 10.1126/science.aam8378 Play The progenitor of LP40-365 could be a binary star system like the one shown in this animation. Here, an ultra-massive and compact dead star called a white dwarf (shown as a small white star) is accreting matter from its giant companion (the larger red star). The material escapes from the giant and forms an accretion disk around the white dwarf. Once enough material is accreted onto the white dwarf, a violent thermonuclear runaway tears it apart and destroys the entire system. The giant star and the surviving fragment of the white dwarf are flung into space at tremendous speeds. The surviving white dwarf shrapnel hurtles towards our region of the Galaxy, where its radiation is detected by ground based telescopes. Credit: Copyright Russell Kightley The researchers also note that in most cases, stars that move faster than normal are doing so because they were flung across their galaxy after traveling too close to its center. But the trajectory of LP 40-365 showed that it had not approached the center of its galaxy.The team suggests the evidence indicates that the white dwarf is most likely the remnant of a supernova—one that occurred between 5 and 50 million years ago. The team and likely others will continue to study the star to add further proof to their assumption. They believe it will help in better understanding what happens prior to a supernova, regardless of type. 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. Image of the accretion disk: A snapshot of the binary star system before the violent supernova explosion blew it to pieces. Credit: Copyright Russell Kightley
The researchers, including lead author Young Duck Kim at Kyung Hee University in South Korea, Professor James Hone at Columbia University, and their coauthors, have published a paper on the graphene-based light emitters in a recent issue of Nano Letters.”Graphene is an important emerging material in nanophotonics: recent work has demonstrated graphene-based high-speed photodetectors and optical modulators,” Kim told Phys.org. “This work adds light emission to the toolbox of ultrafast graphene-based photonic devices.”As the physicists explain, graphene has several properties that make it a promising candidate as an ultrafast light emitter, including a high thermal stability and low heat capacity. Previous research has demonstrated graphene-based devices can emit light in the infrared and visible ranges, although the challenge to enable practical fast on-off modulation still remains. The researchers explain that, in order to do this, a substrate-supported device design with efficient heat conduction is needed to enable rapid cooling between pulses.To address this need, in the new paper the researchers encapsulated graphene in hexagonal boron nitride (hBN). They demonstrated that the encapsulation allows the graphene to reach temperatures that are high enough to emit bright light in the visible and near infrared range, with good stability (estimated device lifetimes of at least 4 years), and fast cooling. As a result, the device generates ultrafast light pulses with a duration as short as 90 picoseconds and a modulation rate that is several orders of magnitude faster than conventional thermal emitters.The physicists explain that the high speed likely occurs because there are two different types of phonons (optical and acoustic), and the electrons in graphene are strongly coupled to the optical phonons but weakly coupled to the acoustic phonons. Other recent work has shown that electrons and optical phonons form hybrid modes at the graphene-hBN interface known as plasmon-phonon polaritons, which provide highly efficient near-field heat transfer. Together, the weak acoustic phonon coupling and direct electronic relaxation into hBN enable cooling at a much faster speed than required to transfer heat out of the system by conduction, which allows for the high modulation speeds. The researchers expect that the ultrafast graphene light emitters have potential applications beyond 100 GHz optical communications, extending to on-chip spectroscopy, photodetectors, and plasmonics. The devices may also be useful as ultrafast heaters for studying phenomena such as chemical reactions and phase transitions. As a next step, the researchers plan to further improve the devices’ light-emitting properties.”We plan to push both the speed and efficiency of these devices,” Hone said. “Our calculations indicate that the fundamental speed of these devices should exceed 100 GHz. Right now the energy efficiency is low, but there are many techniques that can be used to boost light emission and reduce heat flow in order to improve efficiency.” 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. Explore further Journal information: Nano Letters Fast flowing heat in graphene heterostructures One of the key requirements of future optical communications technologies is a nanoscale light source capable of emitting ultrafast light pulses. In a new study, researchers have shown that graphene may be an ideal candidate for such a light source, by demonstrating graphene-based devices that emit light pulses with a bandwidth of up to 10 GHz and pulse durations of less than 100 picoseconds (or 10 billion pulses per second). Citation: Researchers demonstrate graphene as a source of high-speed light pulses (2018, February 5) retrieved 18 August 2019 from https://phys.org/news/2018-02-graphene-source-high-speed-pulses.html © 2018 Phys.org More information: Young Duck Kim et al. “Ultrafast Graphene Light Emitters.” Nano Letters. DOI: 10.1021/acs.nanolett.7b04324 Researchers have demonstrated graphene-based devices that emit ultrafast light pulses with a duration of less than 100 picoseconds (1 picosecond = 1 trillionth of a second). Credit: Kim et al. ©2018 American Chemical Society
Dolphins tear up nets as fish numbers fall Citation: Dolphins who help fishermen found to also hang out together between meals (2019, April 10) retrieved 18 August 2019 from https://phys.org/news/2019-04-dolphins-fishermen-meals.html Journal information: Biology Letters More information: A. M. S. Machado et al. Homophily around specialized foraging underlies dolphin social preferences, Biology Letters (2019). DOI: 10.1098/rsbl.2018.0909 Credit: CC0 Public Domain In Laguna, Brazil, there are fishermen who have formed an alliance with wild bottlenose dolphins living just offshore, both of whom target mullets, a type of fish. The dolphins have found that if they herd groups of the fish toward the shore where the fishermen are waiting with nets, they make it easier on themselves to catch fish. The dolphins slap their heads or tails on the water when the fish are close enough for the fishermen to catch them. Upon seeing the signal from the dolphins, the fishermen cast their nets. When they do so, the fish begin to break away from their school, making it easier for the dolphins to catch them. But it was not the relationship the dolphins established with humans that the researchers were studying—they wanted to know if working together resulted in the formation of social relationships in dolphins.To find out, the researchers focused on a particular group of dolphins that were known to assist in helping the fishermen—they followed them with cameras, capturing details of their activities both during fishing expeditions and the times between them.The researchers report that the same individual dolphins that fished with humans hung out together even when they were not fishing. They would swim around and play together, clearly preferring the company of one another over the company of other dolphins in the area. They were even seen taking naps together.The researchers claim the behavior they observed in the dolphins was an example of homophily, which sociologists define as behavior by individuals in a group who associate in a social manner with those who engage in that behavior with them—in this case, fishing with humans. They suspect that the fishing behavior they engage in is likely learned by watching others in their group as they grow up—a behavior that could be part of a cultural tradition. Explore further © 2019 Science X Network 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. A team of researchers with members from Brazil, South Africa and the U.S. has found an example of homophily among dolphins who work together with fishermen in Brazil for the mutual benefit of both. In their paper published in the journal Biology Letters, the group describes their study of the dolphins and what they found.
I’m going through a divorce. I have had some casual one-night-stands. It seems I need sex but I cannot commit. Am I abnormal?Tejas, HaryanaThere is nothing abnormal in it! The body needs sex and that is normal. But, a marriage not working out shouldn’t change your perception towards the institution as a whole! Take time, live life on your own terms but don’t block your mind to love or commitment. Once bitten, it’s fine, don’t be forever shy!My wife is having an affair with her boss. I have seen some personal Facebook interactions between the two. My wife tells me that she loves me but I can’t trust her anymore. Also Read – ‘Playing Jojo was emotionally exhausting’Rajesh, Madhya PradeshBe alert, but not overtly suspicious. Sometimes we read too much into things that can be avoided or taken casually. Do talk with your wife whenever you feel a pang of suspicion, but trust her as well. It could be just casual, friendly closeness with her boss and not a romantic relationship! Trust yourself and ensure you show your love and faith to her too.My mother-in-law is very possessive about my husband, her only son. She hardly allows us to have any personal space. She gets upset if we plan trips or movies without her! This is annoying me a lot. Also Read – Leslie doing new comedy special with NetflixReva, New DelhiSpeak to your husband about this. Be transparent and let him know your feelings about the small, little things that are worrying you. The situation is bound to improve if he takes a stand and explains things to his mother. Don’t let these unwanted pressure of in-laws seep into your marital life. Play intelligently and you will be the winner!I live with my brother and his wife. One night I saw them having sex and since then I fantasise my ‘bhabi’ while masturbating. I feel guilty but can’t help it! Tanveer, Uttar PradeshWell, it’s all in your mind and you have to control it! She is your ‘bhabi’ who is supposed to be your ‘sister’. Tell yourself everyday — this is wrong. If need be, start living separately. These attractions are fatal as it will break the trust between your brother and you! There are millions of faces, bodies to watch and fantasise about. Spare your brother’s wife please!I lost my virginity when I was 15-year-old. I had sex with my cousin who lives in the UK. We stay in touch and he insists that I send him sexy, nude snaps! I’m extremely worried as he might reveal the secret to the family, if I don’t listen to him!Name withheld, PunjabWhat’s done cannot be undone! But, the ‘secret’ is a part of his life too! He surely will not risk his own reputation by doing something stupid. Don’t give into any pressure and don’t send any snaps/mails that might complicate things further. Just ignore him and his temptations completely and he will get the message loud and clear.Have a love or life query you cannot find an answer to? Send your questions to – email@example.com