Image from Phys. Rev. Lett. 102, 253902 (2009). (c)2009 APS. Reprinted with permission. Explore further Citation: Transform a ball into a rock — or make it invisible — using transformation optics (2009, July 9) retrieved 18 August 2019 from https://phys.org/news/2009-07-ball-invisible-optics.html (PhysOrg.com) — Science fiction and fantasy tales are full of the ability to “cloak” characters with invisibility. Whether it is a spaceship with a cloaking device, or a young wizard with an invisibility cloak, the interest in rendering someone or something invisible captures our fancy. Scientists have succeeded in creating the illusion of invisibility by bending light around a region for concealment. These types of devices have limitations, however; one of these limitation that the device normally has to be touching the object to be rendered invisible – or in very close proximity. Instead of bending light, though, what if transformation optics was used to create invisibility – or even give an object the appearance of a completely different object? A team of theorists at the Hong Kong University of Science and Technology propose a technique that might be able to accomplish just that, with a remote device. The group’s proposal appears in Physical Review Letters: “Illusion Optics: The Optical Transformation of an Object into Another Object.”“Right now, invisibility devices bend light, steering it around an object to make it appear transparent, as if it weren’t there,” Che Ting Chan tells PhysOrg.com. Chan is one of the scientists who proposed the idea of a device that would use illusion optics to transform objects within a confined space. “Our proposed device would have special properties. It would employ a type of illusion that makes an object look exactly like another object.”Metamaterials, which are manmade with special properties, would be used. A “complementary medium” would be employed to optically cancel a specified area. Then, a “restoring medium” would be used to make the cancelled space “reappear” as something else. For invisibility, the restored area would look like air. “If it looks like air,” Chan explains, “then it is transparent. You can see through it. It is like making something invisible.” This method could also, theoretically, be used to “transform” objects. “You could make a ball look like a rock,” Chan says. “You could hide something in plain sight, as something else.”In addition to transforming the way an object looks to others, this device would have another advantage over current invisibility devices. “You wouldn’t have to need the device to touch the object being hidden,” Chan insists. “You could remotely control a particular area to entirely exclude a specific wave without having to be as close.”While the device sounds promising, Chan admits that there are difficulties involved in building such a cloak. “In addition to positive refractive material, which is not a big problem, we would require a negative refractive index.” Positive refractive materials are easily made, but something with a negative refractive index would require special design. “Some sort of structure to create a phase delay would be needed,” Chan says.Chan and the Hong Kong team are working on interesting experimentalists in the concept. “We are dealing with electromagnetic waves,” Chan explains, “but there are those who are doing similar experiments with acoustic waves. Maybe if our idea was applied to acoustic waves first, it would be easier to see how to extend it to include light.”More Information: Yun Lai, Jack Ng, HuanYang Chen, DeZhuan Han, JunJun Xiao, Zhao-Qing Zhang, and C.T. Chan, “Illusion Optics: The Optical Transformation of an Object into Another Object,” Physical Review Letters (2009). Available online: http://link.aps.org/doi/10.1103/PhysRevLett.102.253902 . Copyright 2009 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. New invisibility cloak allows object to ‘see’ out through the cloak 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.
Scientists at Aarhus University in Denmark, led by Peter Madsen, analyzed data gathered in 1977 by scientists working with the US Navy Marine Mammal Program. The researchers, Sam Ridgeway and Don Carder, were studying a trained bottlenose dolphin (Tursiops truncatus). They recorded the sounds made by the dolphin, which they interpreted as whistles, while the animal was breathing air and while breathing Heliox, which is a mixture of helium (80%) and oxygen (20%). The Heliox was delivered to the dolphin via a mask over the animal’s blowhole. The aim of using Heliox was to find out if the dolphin sounds would rise in pitch in the presence of helium, as the human voice does (since the speed of sound in heliox is 1.74 times faster than in air).The scientists at the time thought the dolphin sounds were made by resonance of air in their nasal cavities. If that were true, the pitch of the sounds would change as the dolphin moved deeper, since the increased pressure in the nasal air cavities would also raise the pitch of their sounds.The data gathered by the Navy team could not be fully analyzed because at the time an analysis of a single whistle would have taken several hours. Now, with the benefit of digital technologies, Madsen’s team were able to digitize the old recordings and use advanced computing and visualization scripts to analyze them for the harmonics and frequencies of each recorded whistle. They found that the sounds did not change pitch when the dolphin was breathing Heliox.Dr Madsen said the results of the analysis suggest the sounds were not made as whistles at all (which would be made by expelling air out rapidly) but were the result of “pneumatically induced tissue vibrations,” and this would explain why the sounds did not change in the presence of Heliox. He said this makes sense because using tissue vibrations would allow the dolphins to communicate more effectively at depth. Madsen and the team suggest the most likely tissues for producing the sounds are the “phonic lips” in the nasal air cavities. They also think that toothed whales might communicate in the same way.The paper is published in the Royal Society’s Biology Letters. Citation: New study finds dolphins produce sounds in a similar way to humans (2011, September 9) retrieved 18 August 2019 from https://phys.org/news/2011-09-dolphins-similar-humans.html (PhysOrg.com) — It has long been thought that dolphins produce sounds by means of “whistles,” but a new analysis of a data gathered in the late 1970s has revealed that instead, dolphins make sounds by means of tissue vibrations, in a similar way to the way humans and other mammals use vocal cords (also known as vocal folds) and birds use the syrinx.
(Phys.org) — The computer and subsequent Internet age have brought all manner of change to modern society, one of which is easy access to published scientific research papers; where before it would typically take months for a paper to be published, now it can be done almost instantly and accessed just as quickly. But with such change comes resistance as established entities seek to hold on to their position, even as others push for change. Today, most serious research papers are published by just a handful of journals, who then charge a fee for people to access them. One problem with this system is that it leads some to ask why the public should have to pay to access research papers that came about as the result of public funding. To address this issue in Britain, the government there has asked a working group of individuals to look into the problem and then to make some recommendations. Their report, headed by Dame Janet Finch, has been published online and is available without cost to anyone who wishes to read it. Citation: British group outlines plan for open-access publishing for publicly funded research papers (2012, June 19) retrieved 18 August 2019 from https://phys.org/news/2012-06-british-group-outlines-open-access-publishing.html Open access logo, originally designed by Public Library of Science Explore further In short, the working group is recommending that open-access sites be set up and that publicly funded papers be published on them. In their opinion, the best option is to have those that submit the papers (or their funding group) pay a fee to have the paper peer reviewed and edited before it goes online allowing free access for all.Not everyone agrees with these recommendations, of course, most specifically those well respected journals such as Nature, The Royal Society, Science, etc. They contend that the process they have set up adds value to paper publishing and that moving to an environment where researchers pay for publication, rather than charging readers an access fee would lead to diminishing product quality.As it stands now, when a research team writes a paper for publication, they submit it to one of the respected journals. There an editor reads it to determine if the research has scientific value and to check to see if it was carried out in proper fashion. The editor then either accepts the paper as is, sends it back for fixing or rejects it outright. Once the editor accepts a paper, it is sent to a group of unpaid academic professionals in the field who read it and sometimes try to recreate the results. If it passes peer-review, the journal edits the paper and adds it to its list of online content behind a paywall. All of this costs the journal money of course, which is why it needs to charge so much for access to the published work.What’s still not clear is how changing to an open-access system would impact costs; for those that wish to publish, open-access publishers and those that continue to publish non-publicly financed research projects. Nor is it clear whether the peer-review process or the litmus test of whether the paper has any real value could be maintained by an open-access system.The British government is apparently behind the move towards open-access, though it’s not clear how far they might go to ensure open-access publication of all publicly funded documents. Even so, papers by British individuals or institutions account for just 6% of all such papers published. On the other hand, British publishers account for some 20% of all published research papers in the world, which means if things change in Britain, they might cause a change throughout the rest of the research paper publishing world as well. Ten-fold increase in Open Access publishing during the last decade This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. © 2012 Phys.Org
Passing through. A handful of magnetometers on Earth (stars) could detect the passage of cosmic domain walls, if those walls exist and are abundant enough to affect the balance of dark matter or dark energy in the Universe. Credit: (c) APS/Alan Stonebraker (Phys.org)—An international team of physics researchers is looking to add credence to a theory that might help explain the nature of dark matter and dark energy – using magnetometers placed strategically around the globe. As they describe in their paper published in Physical Review Letters, the aim is to measure the energy in the walls of theoretic domains that control both dark matter and dark energy. More information: Detecting Domain Walls of Axionlike Models Using Terrestrial Experiments, Phys. Rev. Lett. 110, 021803 (2013) prl.aps.org/abstract/PRL/v110/i2/e021803AbstractStable topological defects of light (pseudo)scalar fields can contribute to the Universe’s dark energy and dark matter. Currently, the combination of gravitational and cosmological constraints provides the best limits on such a possibility. We take an example of domain walls generated by an axionlike field with a coupling to the spins of standard-model particles and show that, if the galactic environment contains a network of such walls, terrestrial experiments aimed at the detection of wall-crossing events are realistic. In particular, a geographically separated but time-synchronized network of sensitive atomic magnetometers can detect a wall crossing and probe a range of model parameters currently unconstrained by astrophysical observations and gravitational experiments.Physics Focus For several years, physicists have searched in vain for an explanation of dark matter – the invisible “stuff” that makes up what is believed to be approximately 86 percent of all matter, and dark energy – the mysterious force believed to be responsible for the accelerating expansion of the universe. Because thus far no evidence has been found to support any theory that explains either, new theories continue to develop. One is the theory of cosmic domain walls. It’s based on the idea that shortly after the Big Band, the universe had random energy fields, but as things cooled, different energy regions began to form dominated by an energy factor, with walls between the different regions – and that’s how things stand today. A model might look like a bunch of soap bubbles that have been pushed together. The flat walls that exist at the juncture points would represent the cosmic domain walls.In this new research effort, the aim is to measure the energy in these walls, to hopefully learn more about them and by extension, more about the nature of dark matter and dark energy. The team members believe that it should be possible to test for the energy they are looking for using simple magnetometers. But it would have to be more than one of course, because there are so many things that can be recorded by such devices – it would be difficult to attribute any readings found from just one or even two, to cosmic domain walls. To get around that problem, they propose setting up five of the devices at various locations around the globe, and then correlating them together to rule out interference and other noise.The team isn’t suggesting that if they find what they believe to be the existence of cosmic domain walls, that answers regarding dark matter and dark energy will follow soon thereafter – instead, they are simply hoping to add credence to a theory that many currently consider far outside of the domain of mainstream science. Journal information: Physical Review Letters Citation: Physicists looking to test theory of ‘cosmic domain walls’ (2013, January 21) retrieved 18 August 2019 from https://phys.org/news/2013-01-physicists-theory-cosmic-domain-walls.html © 2013 Phys.org How do you know if you ran through a wall? Testing the nature of dark energy and dark matter 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 artistic concept of Kepler-186f is the result of scientists and artists collaborating to help imagine the appearance of these distant worlds. Credit: Credit: NASA Ames/SETI Institute/JPL-CalTech. © 2014 Phys.org This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
Explore further © 2015 Phys.org Knowing who the first person to be infected was, when an epidemic occurs, can be very helpful to health workers trying to figure out how to combat the disease (by noting how and from which other animal it jumped from, for example) unfortunately, there are few tools available that are able to help. In this new effort, the team in Croatia used statistical tools and real data to create and test an algorithm that appears to offer a way to get closer to an original source, which they claim, can be quite accurate in some cases.To address the problem, the researchers built a network of connected nodes to represent both infected and non-infected people in an epidemic. They then applied exact analytic calculations and Monty Carlo estimations to determine the probability of any one node on a network being patient zero. Once all the calculations have been made, the likelihood for each node is noted, if just one shows a hundred percent certainty, than the task has been completed. If there is more than one, relative certainties for each are generated.To test their network, the researchers used real data from a web site where patrons of sex-workers could offer reviews on their experience. They found that there were able to pinpoint a single individual (or one that was just one hop away) with a 60 percent accuracy rate.The team notes that their algorithm is more accurate when used with fast spreading diseases, and of course does better the sooner it is applied. They also note that it does not do very well when used for a small population after a period of time has passed because it can lead to every node having an equal chance of being patient zero.The researchers also point out that their network and algorithm can be used in other areas as well, such as with assisting in finding patient zero in a computer virus epidemic, or with incidents that occur on social networks. Journal information: Physical Review Letters (Phys.org)—A team of researchers affiliated with several institutions in Croatia has developed an algorithm that is able to help pinpoint the first person who became ill when an epidemic occurred. In their paper published in the journal Physical Review Letters, the team describes how they built their algorithm, how it was tested and how accurate they believe it is. Researchers develop method to predict source of network diffusion , arXiv More information: Identification of Patient Zero in Static and Temporal Networks: Robustness and Limitations, Nino Antulov-Fantulin, Alen Lančić, Tomislav Šmuc, Hrvoje Štefančić, and Mile Šikić, Phys. Rev. Lett. 114, 248701 – Published 16 June 2015. journals.aps.org/prl/abstract/ … ysRevLett.114.248701 . On Arxiv: arxiv.org/abs/1406.2909ABSTRACTDetection of patient zero can give new insights to epidemiologists about the nature of first transmissions into a population. In this Letter, we study the statistical inference problem of detecting the source of epidemics from a snapshot of spreading on an arbitrary network structure. By using exact analytic calculations and Monte Carlo estimators, we demonstrate the detectability limits for the susceptible-infected-recovered model, which primarily depend on the spreading process characteristics. Finally, we demonstrate the applicability of the approach in a case of a simulated sexually transmitted infection spreading over an empirical temporal network of sexual interactions. Citation: Researchers develop algorithm to help identify patient zero in an epidemic (2015, June 29) retrieved 18 August 2019 from https://phys.org/news/2015-06-algorithm-patient-epidemic.html Visualization of a part of the aggregated empirical temporal network of sexual contacts in Brazil. Credit: 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.
(Left) Photograph of the flexible IGZO Schottky diodes. (Right) The highest frequency achieved by the flexible diodes is 6.3 GHz, which can accommodate all transmission frequencies of wireless communication. Credit: Zhang, et al. ©2015 Macmillan Publishers Limited More information: Jiawei Zhang, et al. “Flexible indium-gallium-zinc-oxide Schottky diode operating beyond 2.45 GHz.” Nature Communications. DOI: 10.1038/ncomms8561 (Phys.org)—While there are hints that Samsung and LG are developing flexible phones that can fold, roll up, and even be stretched into larger screens, there are still some obstacles to overcome before such bendable phones become a reality. Arguably the largest obstacle is the need for a high-speed flexible diode, which is what detects and modulates the cell phone’s signal. The diode must operate at high speeds in order to match the transmission frequencies used by wireless cellular communication, Bluetooth, Wi-Fi, and GPS signals (which range from 935 MHz to 5 GHz). World-first UHF IGZO Schottky diode presented: Breakthrough achievement towards low-cost passive thin-film RFID tags Citation: Fastest-ever flexible diode provides ‘last missing piece’ needed to realize bendable phones (2015, July 15) retrieved 18 August 2019 from https://phys.org/news/2015-07-fastest-ever-flexible-diode-piece-bendable.html 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. © 2015 Phys.org Journal information: Nature Communications In a new paper published in Nature Communications, a team of researchers led by Professor Aimin Song at the University of Manchester in the UK with collaborators at Shandong University in China have developed a flexible Schottky diode that achieves a speed of 6.3 GHz, which to the best of their knowledge makes the device the fastest of its kind to date. It is also the first flexible diode to reach what is widely considered the “benchmark speed” of 2.45 GHz, which covers the principal frequency bands used in most current wireless communications, with the exception of 4G and the newest 5G Wi-Fi channels.”A flexible GHz diode is the last missing jigsaw piece needed to achieve flexible mobile phones and rapidly growing wearable electronics,” Song told Phys.org. “Thin-film IGZO transistors have already been demonstrated that operate at frequencies beyond 100 MHz, which is enough to construct mobile phone chips for data processing in at least entry-level smart phones. Now having a fast-enough diode for front-end signal receiving and modulation shall bring the flexible mobile phones that were envisaged many years ago much closer to the market.”In the new study, the researchers fabricated the diode using the flexible semiconductor film indium-gallium-zinc-oxide (IGZO). They demonstrated the high-speed operation using low-temperature processing on flexible substrates, which has not been achieved before now. The previous best IGZO Schottky diodes could achieve speeds of up to 3 GHz, but could not be made on flexible plastic substrates because they used high-temperature processing, and so could only be fabricated on glass substrates. The previous best flexible Schottky diodes, which were made of crystalline silicon microparticles, obtained speeds of up to 1.6 GHz but still required complex and expensive processing. One of the keys to achieving the high-speed flexible diode was controlling the IGZO thickness to optimize performance. As the researchers explained, it is very surprising that this could be done at all, as it has been thought that a thick IGZO layer is essential for high-speed operation due to having a low capacitance. Here the researchers found that, in fact, the series resistance increases as IGZO thickness increases, which plays a critical role in determining the diode speed. While the researchers initially expected that the thickest IGZO layer would have the best performance, they found that it actually exhibits the worst performance. By investigating the factors underlying this surprising finding—which include the relationships between resistance, reactance, and capacitance—the researchers could optimize the diode’s performance by using an 80-nm-thick IGZO layer. With a better understanding of the IGZO semiconductor material’s electronic properties, the researchers were able to create a promising component of next-generation phone technology. They expect that post-treatment processes could further improve the diode’s performance—both its speed and its output voltage, which is necessary to maintain a strong signal.”Our future research will focus on integration of the fast diodes and transistors for a range of demo circuits, or even simple systems, in order to demonstrate the amazing potential of flexible thin-film electronics,” Song said.