Explore further Citation: Can silver nanoparticles be the key to a more compact laser? (2008, June 9) retrieved 18 August 2019 from https://phys.org/news/2008-06-silver-nanoparticles-key-compact-laser.html Holographic imaging of electromagnetic fields using electron-light quantum interference “In random media, multiple scattering and interference reduce the diffusion of light, and in case of extremely strong scattering, photon localization, or Anderson localization of light, is predicted like electrons in glasses,” Katsuhisa Tanaka, a scientist in Kyoto University, tells PhysOrg.com. He and his colleagues are interested in using so-called disordered material to create lasers that could increase our understanding of physics – as well as make the laser creation process simpler. 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. Tanaka points out that silver nanoparticles make a difference: “First, localized optical modes near silver nanoparticle surface provide high optical gain for lasing. Second, scattering properties can be flexibly controlled by the size and shape of nanoparticles, and significantly contribute to light transport in random systems compared to that in dielectric nanoparticles.”In terms of application, Tanaka sees possibilities for fundamental physics knowledge, as well as practical uses for this set-up. “Since the phenomena of random laser are reported for systems having very different scattering strength from nearly transparent to highly-scattering media, it is possible that the laser mechanism — or dominating laser mode — is different depending on the scattering strength. Thus the primal importance is to clarify the mechanism, which is beneficial to the progress of the physics.”As far as practical applications, he says that there is a strong possibility of a compact laser. Plus, Tanaka continues, “Since this type of lasers does not require rigorous alignment of reflectors to form cavity in contrast to the conventional Fabry-Perot type ones, the making process is much simpler.”The team at Kyoto continues to work on this project. Tanaka and his coworkers say that more needs to be known with regard to how the distribution of the silver nanoparticles within the polymer affects the laser. Additionally, they feel that this work could lead to advances in lasers that are based on organic semiconductors. Copyright 2007 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. With Xiangeng Meng, Koji Fujita (also doing work at PRESTO in Saitama, Japan), Yanhua Zong and Shunsuke Murai at Kyoto University, Tanaka has been working on using transparent films embedded with nanoparticles of silver to study the feedback coherence from certain random lasers. Their work can be seen in Applied Physics Letters: “Random lasers with coherent feedback from highly transparent polymer films embedded with silver nanoparticles.”“Random lasers are laser sources that arise from multiple scattering events in random systems so that the strength of light scattering is of large importance in determining the feedback type of laser oscillation, Tanaka explains. “We are interested in such lasers because their fabrication process is technically simple while high gain is involved. At present, researchers are focusing on random lasers based on dielectrics with high refractive index, while little attention has been paid to metal nanostructures-based amplifying random media.” He continues: “Actually, metal nanostructures are rather potential materials in laser devices. The use of surface plasmon resonance of metal nanostructures is extremely attractive because they bring about surface enhanced Raman scattering, enhancement of spontaneous emission, and amplified spontaneous emission, and so on. What we have consisdered for a long time is whether laser actions with high gain could be achieved by combining metal nanostructures and laser working medium.”Indeed, this led Tanaka and his peers to wonder if surface plasmon resonance can help random lasing. The answer, in their minds, is yes: “We found that the presence of silver nanoparticles results in the coherent output even though the scattering strength of the system is very weak. We believe that surface plasmon plays an important role in the laser operation.”In order to make the demonstration work, the Kyoto team embedded silver nanoparticles on highly transparent polymer films. The process was made possible through the in situ method, in which heat is used to create the hybrid material, combining polymer with metal in a way that is useful in terms of lasing. “We have calculated the transport mean free path of our sample and found that it is far larger than the sample size. The light propagates in such systems nearly freely without resistance,” Tanaks says. “Then, the issue that puzzles us is this: What on earth induces laser oscillation?”
Recently, Jaap Flokstra and colleagues from the University of Twente in Enschede, the Netherlands, have designed a miniature gravity gradiometer that can map a planet’s gravity field. The device is a much smaller version of a gravity gradiometer called GOCE (Gravity field and steady-state Ocean Circulation Explorer), which is a European Space Agency satellite that is currently orbiting and measuring Earth’s gravity field. While GOCE has a mass of several hundred kilograms, the new mini gradiometer weighs just one kilogram. As the scientists explain, the mini gravity gradiometer is made of a single wafer of silicon. The design consists of two masses, each hanging on a spring a few centimeters part (compared with half a meter in GOCE). Whichever mass is slightly closer to a planet’s surface will feel a stronger pull on its spring compared to the other mass, allowing researchers to determine the gravity gradient. In the new design, the position of the masses is measured to within 1 picometer by a device whose capacitance changes as the masses move up and down. Flokstra and his colleagues hope that the new lightweight design would be more practical and cheaper to send into outer space for investigating the gravity fields of other planets in our solar system. For instance, such a device could search for the subterranean ocean suspected to exist near the South Pole of Saturn’s moon Enceladus. The researchers calculate that the device could have a high sensitivity, with the ability to sense changes in a planet’s gravity field due to geological features of about 200 kilometers across or more. The researchers plan to build and demonstrate the device to use on Earth in the next few months.via: New Scientist© 2009 PhysOrg.com 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: Mini Gradiometer Could Map Other Planets’ Gravity Fields (2009, August 10) retrieved 18 August 2019 from https://phys.org/news/2009-08-mini-gradiometer-planets-gravity-fields.html (PhysOrg.com) — Although it may seem like gravity is the same everywhere on the Earth, it actually varies a small amount from place to place. Factors such as mountains, ocean trenches, and interior density variations can all cause gravity differences. By measuring the gravity field of Earth or another planet, scientists can gain insight into that planet’s otherwise hidden geological features. GOCE’s ‘heart’ starts beating Explore further A mini gravity gradiometer could search for the subterranean ocean suspected to exist near the South Pole of Saturn’s moon Enceladus. Image credit: NASA.
How Time-Traveling Could Affect Quantum Computing Explore further (PhysOrg.com) — For more than 50 years, physicists have been intrigued by the concept of closed time-like curves (CTCs). Because a CTC returns to its starting point, it raises the possibility of traveling backward in time. More recently, physicists have theorized that CTC-assisted computers could enable ideal quantum state discrimination, and even make classical computers (with CTCs) equally as powerful as quantum computers. However, a new study argues that CTCs, if they exist, might actually provide much less computational benefit than previously thought. Citation: Study Shows Time Traveling May Not Increase Computational Power (2009, October 22) retrieved 18 August 2019 from https://phys.org/news/2009-10-power.html As the scientists note, one of the motivating factors for their investigation is the previous finding that CTCs can distinguish between two nonorthogonal pure states, which is impossible in standard quantum mechanics. Further, the previous results seemed to imply that CTCs could be used to distinguish between two identical states, which should be impossible no matter how you look at it. To investigate this problem, the scientists considered what would happen if they prepared and evolved quantum states according to a specific physical process. They found that two output states can be distinguished even without using a CTC, eliminating any advantage the CTC may have offered. In addition to quantum state discrimination, the physicists also investigated the alleged computational power of CTCs, where they found that the output is often not correlated with the input. The scientists argue that the root of the problem seems to lie in the definition of the CTC-assisted computational class, which is not physically or computationally meaningful, and does not produce correctly correlated mixtures of input-output pairs. The scientists proposed an alternate CTC-assisted computational class that allows them to correctly evaluate the system’s abilities, but it also shows that CTC-assisted systems do not seem to increase computational power.Not all scientists agree with the new results. Scott Aaronson of MIT, who has also investigated the possible computation benefits of CTCs, said that he has been aware of the issues of nonlinearity, but does not consider it as important as the scientists do in the current study. Further, he explains that, even in the new model, CTCs would still increase the power of quantum computers.“The underlying reason for the disagreement is this: in the actual universe, CTCs almost certainly don’t exist,” Aaronson said. “So, in asking what the right model of computation ‘would be’ if they did exist, one is inherently asking a strange and somewhat ill-defined question.”Aaronson agreed with the new study that requiring the input to be a pure state (as he and coauthor John Watrous do in a previous study) is a problem. But, he said, the new model requires the input to be nothing, which is an even bigger problem.“As it turns out, every answer to the question that people have come up with has had conceptual problems,” he said. “But in (essentially) prohibiting any input whatsoever to the CTC register, it seems to me that Bennett et al. make the conceptual problems worse, not better, than they are in my and Watrous’s model. This is a matter of honest disagreement.”In spite of the new study’s conclusions, Smith also thinks that CTCs are still worth investigating, as they may be useful in ways that are currently unknown.“I think it’s still interesting,” he said. “Our work just highlights some of the subtleties involved that can lead you to inaccurate conclusions. I should point out that we haven’t proven CTCs are no good for computation, we’ve only shown that the existing algorithms that have been proposed don’t work. So, there might be something more out there (though I wouldn’t bet on it).”More information: Charles H. Bennett, Debbie Leung, Graeme Smith, and John A. Smolin. “Can closed timelike curves or nonlinear quantum mechanics improve quantum state discrimination or help solve hard problems?” Physical Review Letters. To be published. arXiv:0908.3023v1 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. A team of scientists consisting of Charles Bennett, Graeme Smith, and John Smolin from IBM, along with Debbie Leung from the University of Waterloo, argues that previous analyses of CTCs have fallen into the so-called “linearity trap,” and have been based on physically irrelevant definitions that have led to incorrect conclusions about CTCs. The new study will be published in an upcoming issue of Physical Review Letters.As the physicists explain, CTCs are difficult to think about because they make quantum evolution nonlinear, whereas standard quantum mechanics systems evolve linearly. (In linear systems, the evolution of a mixture of states is equal to the mixture of the evolutions of individual states; this is not the case in nonlinear systems.) It seems that much of the apparent power of CTCs has come from analyzing the evolution of pure quantum states, and extending these results linearly to find the evolution of mixed states. The physicists call this situation the “linearity trap,” which occurs when nonlinear theories are extended linearly. In the case of CTC computations, Bennett and coauthors found that this problem was causing the output to be uncorrelated with the input, which isn’t a very useful computation.“The trouble with the earlier work is that it didn’t take into account the physical processes by which the inputs to a computation are selected,” Smith told PhysOrg.com. “In a nonlinear theory, the output of a computation depends not only on the input, but also on how it was selected. This is the strange thing about nonlinear theories, and easy to miss.” To overcome these problems, the scientists proposed that the inputs to the system should be selected by an independent referee at the start of the computation, rather than being built deterministically into the structure of the computer. In order to ensure that the proper input is selected, the physicists proposed the “Principle of Universal Inclusion.” The principle states that the evolution of a nonlinearly evolving system may depend on parts of the universe with which it does not interact, ensuring that scientists do not ignore the parts of the universe that need to be used to select the inputs. The physicists hope that these criteria will lead to choosing the correct input, and then to generating the correct corresponding output, rather than simply evolving the system linearly based on incorrect inputs. 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.
Photograph of Mesquite Flat Dunes in Death Valley looking toward the Cottonwood Mountains from the north west arm of Star Dune (the largest dune in the area — Death Valley National Park, California. Credit: Wikipedia © 2013 Phys.org Journal information: Geology Large dunes birth or “calve” smaller dunes. After sand dunes get big enough, they calve off smaller dunes that keep them from blowing up to infinite size. The baby dune travels down one of its parent’s horns and buds off. The team simulated “calving” dunes and recreated real-world barchan patterns for their study. Their findings were published online earlier this month in the journal Geology. The paper, by Stacey Worman and colleagues, is titled “Modeling Emergent Large-Scale Structures of Barchan Dune Fields.” The authors stated that “This work supports the hypothesis that calving exerts a first-order control on field-scale phenomena; it prevents individual dunes from growing without bound, as single-dune analyses suggest, and allows the formation of roughly realistic, persistent dune field patterns.”A different view appears this month, however, in Geophysical Research Letters where Mathieu Génois of Paris Diderot University and coauthors flesh out a picture of clashing, not calving, dunes. Collisions control dune field behavior. Looking at barchan formations, they said colliding and breaking apart keep the fields from growing out of control. If two barchan dunes collide they merge into one crescent or split up into multiple smaller barchans.They wrote, “Here we use an agent-based model with elementary rules of sand redistribution during collisions to access the full dynamics of very large barchan fields. We tune the dune field density by changing the sand load/lost ratio and follow the transition between dilute fields, where barchans barely interact, and dense fields, where dune collisions control and stabilize the dune field.”In 2012, there were signs that Genois and research colleagues were interested in examining the nature of crescent-shaped dunes. That year, the paper was published, “When Dunes Move Together, Structure of Deserts Emerges.””In contrast with the layman’s view, ” they wrote, “not all deserts are vast sand seas. Depending on the variability of the local winds, sand dunes can adopt various shapes. When viewed from above, they mimic large stars, long linear ridges or crescent structures. The-crescent shaped dune, called barchan is a prototypical model of sand dune dynamics…” Citation: Do barchans birth or collide? Two papers have different stories (2013, September 2) retrieved 18 August 2019 from https://phys.org/news/2013-09-barchans-birth-collide-papers-stories.html (Phys.org) —Geologists continue to puzzle over the how and why of crescent-shaped sand dunes called barchans, found on Earth and on Mars. Barchans can form on the seafloor and on ice, as well as deserts. How do they happen? Why do they not lose their shape? Scientists seeking to understand what keeps these formations going have two recently published papers that can offer detailed explanations of how barchan dune fields can exist, and why they are arranged the way they are. The hitch is that the two papers disagree. A recently published paper by researchers from Duke University say that this is a birthing process, where large dunes give birth to smaller ones. More information: www.sciencenews.org/view/gener … _dune_fields_somehowarxiv.org/abs/1211.7238v1 , Geophysical Research Letters Explore further Image: Great Sandy Desert, Australia 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 Federal judge rules NSA phone surveillance legal (Update) (Phys.org) —What kind of telephone activity does the NSA collect on people? Metadata. How harmful is it to your privacy health? Nada. It is only metadata. That has been the line drawn in the sand by government supporters of NSA activities in monitoring calls. Now a Stanford study by two researchers at Stanford has its own message: Individuals can be easily identified through phone numbers. Connecting metadata with individual names is not just easy; they found it was “trivial.” Jonathan Mayer along with Patrick Mutchler, the researchers, earlier this week on the blog Web Policy, which covers technology, policy, and law, posted their findings under the headline, “MetaPhone: The NSA’s Got Your Number.” Citation: Experiment shows connecting names with phone metadata is easy (2013, December 28) retrieved 18 August 2019 from https://phys.org/news/2013-12-metadata-easy.html © 2013 Phys.org They described their experiment to find out just how easy it might be through an Android app called MetaPhone, which garnered 5,000 phone numbers. MetaPhone is defined by the researchers as a “crowdsourced study of phone metadata.” In November, as a project of the Stanford Security Lab, the two posted a notice, “We’re studying the National Security Agency, and we need your help.” They referred to the NSA’s confirmation that it collects American phone records, and with little privacy impact. Nonetheless, they noted, “Phone metadata is inherently revealing. We want to rigorously prove it—for the public, for Congress, and for the courts.” In turn they said they sought to crowdsource the data for their study. to measure what can be inferred from phone records.”Participation takes just a few minutes,” they said. “You’re eligible if you’re in the United States, use an Android smartphone, and have a Facebook account.”The results of their MetaPhone trial and other research steps are in. “We randomly sampled 5,000 numbers from our crowdsourced MetaPhone dataset and queried the Yelp, Google Places, and Facebook directories,” they reported. Querying those three sources, they matched 1,356 (27.1%) of the numbers—378 hits (7.6%) on Yelp, 684 (13.7%) on Google Places, and 618 (12.3%) on Facebook.Then they took a next step with a random sample of 100 numbers from the dataset, to run Google searches on each. That effort did not even take an hour, where they were able to associate an individual or a business with 60 of the 100 numbers. Finally, they proceeded to run the numbers using Intelius. “Between Intelius, Google search, and our three initial sources, we associated a name with 91 of the 100 numbers.”The authors commented, “If a few academic researchers can get this far this quickly, it’s difficult to believe the NSA would have any trouble identifying the overwhelming majority of American phone numbers.”Mayer is a PhD student in computer science at Stanford , where he received his J.D. in 2013, Reacting to the report, Gregory Ferenstein in TechCrunch, said, “People may disagree about whether or not government agencies should have private information, but let’s not pretend they can’t learn anything they want from what information they have.”Meanwhile, a federal judge ruled on Friday that the National Security Agency’s collection of telephone records is lawful. Federal Judge William Pauley said there was no evidence that the Government has used any of the bulk metadata for any purpose other than investigating and disrupting terrorist attacks. More information: webpolicy.org/2013/12/23/metap … sas-got-your-number/ 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 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. Female comb-footed spider (family Theridiidae), Enoplognatha ovata. Photographed in the wild at DuPage County, Illinois, USA. Size = 15mm. Credit: Bruce Marlin/Wikipedia/CC BY 3.0 , Cognition Some dangerous spider species may have been common during our evolutionary history. A number of species with potent venoms populated Africa before hominoids and have co-existed there for tens of millions of years. A black widow spider bite in the ancestral world even if not fatal could leave one incapacitated for days or weeks.Joshua New, Department of Psychology, Barnard College and colleague Tamsin German, wrote “Spiders at the cocktail party: an ancestral threat that surmounts inattentional blindness,” which has been published in Evolution and Human Behavior. The paper stated that the human visual system may retain ancestral mechanisms uniquely dedicated to the rapid detection of immediate and specific threats, such as spiders and snakes, which persistently recurred throughout evolutionary time. The authors concluded that “Spiders may be one of a very few evolutionarily-persistent threats that are inherently specified for visual detection and uniquely ‘prepared’ to capture attention and awareness irrespective of any foreknowledge, personal importance, or task-relevance.”New and German asked their participants to look at abstract shapes and data on computer screens. Among those images were needles and flies. Results, as reported in the Daily Sun: “Of the 252 people reviewed in the study, most recognized the spiders much quicker than other images known to induce fear, such as flies and needles.” Spider images got more attention; the viewers spotted them and knew what they were. The authors reported that, “Despite their highly marginalized presentation, iconic spiders were nonetheless detected, localized, and identified by a very large proportion of observers.” Their test, said the authors, made use of the “inattentional blindness paradigm” in which an unexpected, peripheral stimulus is presented coincidentally with a central task-relevant display. Last year, Inside Science turned to the spider study which had been published online. Inside Science described how the study was designed: “To see if there is something special about spiders, the researchers showed people a cross shape that flashed in the middle of a screen for an eighth of a second. The participants’ task, as far as they knew, was to judge which of the two bars on the cross was longer. During the first three trials, only the cross appeared. On the fourth trial, another image appeared at the same time. The possible images included a spider, a hypodermic needle, a housefly, and abstract shapes made by rearranging the lines of the spider.” People were asked if they saw anything other than just the cross and, if so, in which part of the screen. They also tried to identify the image by selecting it from a lineup.New’s study reflects a question that scientists have posed before about human reactions to spiders: In 2008, the study “Do infants possess an evolved spider-detection mechanism?” appeared in Cognition. Babies looked at spiders longer than they looked at other images. Authors David Rakison and Jaime Derringer talked about “an evolved predator recognition mechanism that specifies the appearance of recurring threats.”The results, they said, supported the hypothesis that humans “may possess a cognitive mechanism for detecting specific animals that were potentially harmful throughout evolutionary history.”Rakison said in Inside Science that “At least with children, there’s very little conflicting evidence that spiders and snakes have some kind of privileged nature in human visual processing.” More information: Spiders at the cocktail party: an ancestral threat that surmounts inattentional blindness, Evolution and Human Behavior, dx.doi.org/10.1016/j.evolhumbehav.2014.08.004 A fear of spiders, arachnophobia, is in our DNA. You don’t learn to freeze at the site of these creatures; you’re born with the fear. Even the sight of hypodermic needles and houseflies does not trigger a similar response. Scientists pin that fear on survival instinct. The theory goes like this: Humans evolved in Africa where being able to spot a spider was of necessity. Spiders found able to custom build webs to trap best food source Explore further Journal information: Evolution and Human Behavior © 2015 Phys.org Citation: Human fear of spiders draws scientific focus (2015, April 6) retrieved 18 August 2019 from https://phys.org/news/2015-04-human-spiders-scientific-focus.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. Stabilization of the doping profile by counter-ion immobilization in self-compensated doped polymer organic semiconductors. Credit: (c) Nature (2016). DOI: 10.1038/nature20133 To make optoelectronic devices a layering technique is used—a thin film conductor is caused to be in contact with a semiconductor allowing an electric charge to move between them—to facilitate the transfer an IFL is placed between them. But as Facchetti notes, conventional IFLs are considered to be inefficient—improvements would allow greater efficiency in solar cells, for example. In this new effort, the researchers suggest a particular type of polymer, part of a group called π-conjugated polymers—a type of stable polymer with high doping content that has a self-compensation mechanism that involves covalently bonded counter ions that serve to block the migration of dopants—they offer not only improved efficiency but stronger performance and more stability. But, as Facchetti also notes, most such polymers in their native state are not able to transfer large numbers of charged particles—to overcome that problem the researchers used a chemical doping process that caused the charge carriers to become denser which in turn caused the polymer to become much more conductive.To test their ideas, the researchers modified several devices (solar cells, LEDs, photodiodes, etc.), replacing conventional IFLs with ones they had created and then tested their performance. The team reports that the expected improvements in efficiency were realized, which they note, suggests such polymers have the potential to improve the efficiency of a wide variety of optoelectronic devices. More work will need to be done though before that can be proven—first it remains to be seen if such polymers can be scaled up and then it must be shown that they can stand up to the rigors of real-world demands. © 2016 Phys.org New polymer able to store energy at higher temperatures Citation: IFLs created from pi-conjugated polymers improve performance and stability of optoelectronic devices (2016, November 24) retrieved 18 August 2019 from https://phys.org/news/2016-11-ifls-pi-conjugated-polymers-stability-optoelectronic.html More information: Cindy G. Tang et al. Doped polymer semiconductors with ultrahigh and ultralow work functions for ohmic contacts, Nature (2016). DOI: 10.1038/nature20133AbstractTo make high-performance semiconductor devices, a good ohmic contact between the electrode and the semiconductor layer is required to inject the maximum current density across the contact. Achieving ohmic contacts requires electrodes with high and low work functions to inject holes and electrons respectively, where the work function is the minimum energy required to remove an electron from the Fermi level of the electrode to the vacuum level. However, it is challenging to produce electrically conducting films with sufficiently high or low work functions, especially for solution-processed semiconductor devices. Hole-doped polymer organic semiconductors are available in a limited work-function range, but hole-doped materials with ultrahigh work functions and, especially, electron-doped materials with low to ultralow work functions are not yet available. The key challenges are stabilizing the thin films against de-doping and suppressing dopant migration. Here we report a general strategy to overcome these limitations and achieve solution-processed doped films over a wide range of work functions (3.0–5.8 electronvolts), by charge-doping of conjugated polyelectrolytes and then internal ion-exchange to give self-compensated heavily doped polymers. Mobile carriers on the polymer backbone in these materials are compensated by covalently bonded counter-ions. Although our self-compensated doped polymers superficially resemble self-doped polymers, they are generated by separate charge-carrier doping and compensation steps, which enables the use of strong dopants to access extreme work functions. We demonstrate solution-processed ohmic contacts for high-performance organic light-emitting diodes, solar cells, photodiodes and transistors, including ohmic injection of both carrier types into polyfluorene—the benchmark wide-bandgap blue-light-emitting polymer organic semiconductor. We also show that metal electrodes can be transformed into highly efficient hole- and electron-injection contacts via the self-assembly of these doped polyelectrolytes. This consequently allows ambipolar field-effect transistors to be transformed into high-performance p- and n-channel transistors. Our strategy provides a method for producing ohmic contacts not only for organic semiconductors, but potentially for other advanced semiconductors as well, including perovskites, quantum dots, nanotubes and two-dimensional materials. (Phys.org)—A team of researchers from Singapore and the U.K. has found that using a particular type of polymer allowed for creating interfacial layers (IFLs) in optoelectronic devices with improved performance and stability. In their paper published in the journal Nature, the team describes their technique and their results when they made actual devices using the polymer. Antonio Facchetti with Northwestern University offers a News & Views piece on the work done by the team in the same journal issue and outlines some of the benefits of self-compensated polymers as well as some of the hurdles that will need to be overcome before they can be used in commercial products. Explore further Journal information: Nature
More information: Evidence for a Dusty Dark Dwarf Galaxy in the Quadruple Lens MG0414+0534, arXiv:1701.05283 [astro-ph.GA] arxiv.org/abs/1701.05283AbstractWe report the 4σ detection of a faint object with a flux of ~ 0.3 mJy, in the vicinity of the quadruply lensed QSO MG0414+0534 using the Atacama Large Millimeter/submillimeter array (ALMA) Band 7. The object is most probably a dusty dark dwarf galaxy, which has not been detected in either the optical, near-infrared (NIR) or radio (cm) bands. An anomaly in the flux ratio of the lensed images observed in Band 7 and the mid-infrared (MIR) band and the reddening of the QSO light color can be simultaneously explained if we consider the object as a lensing substructure with an ellipticity ~ 0.7 at a redshift of 0.5≲z≲1. Using the best-fit lens models with three lenses, we find that the dark matter plus baryon mass associated with the object is ∼109M⊙, the dust mass is ∼107M⊙ and the linear size is ≳5kpc. Thus our findings suggest that the object is a dusty dark dwarf galaxy. A substantial portion of faint submillimeter galaxies (SMGs) in the universe may be attributed to such dark objects. ALMA 0.88 mm (Band 7) dust continuum images of MG 0414+0534. A faint spot inside a red circle (left) is the “object Y”. Credit: Inoue et al., 2017. Dozens of new ultra-diffuse galaxies discovered in Abell 2744 MG 0414+0534 is a quadruply lensed, radio-loud quasar that showcases a strong sign of anomaly in the flux ratio and reddening in the optical and near-infrared band. This anomaly baffles scientists as its origin is not fully understood yet.In order to reveal more insights into this mysterious anomaly, a team of researchers led by Kaiki Taro Inoue of Kindai University in Japan conducted continuum observations of MG 0414+0534 with ALMA. The observational campaign, which was carried out in June and August 2015, resulted in the discovery of a faint object with a flux of about 0.3 mJy in the vicinity of the quasar. For the purpose of the research, this newly found object was designated “object Y.”According to the paper, “object Y” has an ellipticity of about 0.7 at a redshift between 0.5 and 1.0 and its linear size is at least 16,300 light years. The scientists estimate that the dark matter plus baryon mass associated with the object is about one billion solar masses, while its dust mass is approximately 10 million times greater than that of the sun.The images obtained by ALMA allowed the researchers to draw conclusions that the newly detected object is most likely a dusty dark dwarf galaxy, previously undetected in either optical, near-infrared or radio bands.”Our findings suggest that the object is a dusty dark dwarf galaxy,” the paper reads.However, the astronomers also explore the possibility that “object Y” could be an UDG. With stellar masses typical of dwarf galaxies, UDGs are extremely-low-density galaxies. The largest UDGs have sizes comparable to the Milky Way but contain only about one percent as many stars as our home galaxy. Notably, the phenomenon of UDGs still puzzles scientists as they try explain why these faint but large galaxies are not ripped apart by the tidal fields of their host clusters.The researchers explain that if “object Y” is a UDG, then its stellar components may have been expanded due to outflow caused by starburst or active galactic nucleus (AGN) activity. Therefore, the surface brightness in the optical and near-infrared band can be extremely small despite being gas-rich, which makes this object difficult to spot.The team concluded that more detailed analysis of the newly found object could provide important information about the origin of past starburst activity. They also noted that if “object Y” is residing in the intervening line of sight, many faint submillimeter galaxies may be classified in the future as gas-rich dusty dark dwarf galaxies.”A substantial portion of faint submillimeter galaxies (SMGs) in the universe may be attributed to such dark objects,” the researchers wrote in the paper. Citation: Mysterious faint object detected in the vicinity of a quadruply lensed quasar (2017, January 25) retrieved 18 August 2019 from https://phys.org/news/2017-01-mysterious-faint-vicinity-quadruply-lensed.html (Phys.org)—Astronomers have spotted a mysterious faint object in the vicinity of a quadruply lensed quasar designated MG 0414+0534. The object, which was discovered using the Atacama Large Millimeter/submillimeter Array (ALMA), appears to be a dusty, dark dwarf galaxy or an ultra-diffuse galaxy (UDG). The findings were presented January 19 in a paper published on arXiv.org. © 2017 Phys.org 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.
Sand, Sunscreen And … Sharks! Cape Cod Beach Towns Do… Sarah Mizes-Tan by NPR News Sarah Mizes-Tan 8.28.19 3:09pm A year after a young man was killed by a shark off Cape Cod — the first such death there in more than 80 years — beach towns full of vacationers are struggling to manage an influx of great whites. Sharks off the coast have become more common in recent years as the seal population they hunt has increased. Scientists point out that sharks do not target humans, though they can mistake them for prey. But many officials believed the attack was only a matter of time.Last year’s death happened while a 26-year-old was boogie boarding. Weeks before that, another man was attacked and fought off a shark while swimming in what he said was 8 to 10 feet of water. Both those incidents have driven home the risk for many. On Newcomb Hollow Beach in Wellfleet, Mass., vacationer Olivia Gattuso says she normally enjoys hourlong swims. She is being more cautious now.”I mean yesterday was a really good swimming day, and I wouldn’t let myself go anywhere above my waist because I was too afraid, she says.In recent months, Outer Cape towns have been making changes to protect beachgoers from sharks. With grant money from the state, many have purchased taller lifeguard chairs to help lifeguards see farther offshore and spot sharks or seals. Beach entrances have updated shark warning signs, which note that sharks hunt seals in shallow water. Some beaches have landline emergency phones and first-aid kits. At Newcomb Hollow Beach, there’s also a new high-tech buoy in the water that alerts lifeguards when it detects a tagged shark in the area. “We actually are just coming off of a closing right now,” says head lifeguard Joey Craven. “We had to close for an hour because the buoy pinged at 10:15.”The buoy sends an alert and a description of the tagged shark to lifeguards, who then call everyone out of the water. This year, these calls have happened a lot, sometimes twice a day. This time, Craven says, “it was a shark named Ben, and he’s about 13.9 feet long. That’s a pretty mature shark.” The buoy was set up by Massachusetts shark researcher Greg Skomal, who began tagging white sharks off Cape Cod four years ago. He says the sharks his organization has logged are just a small slice of the population that exists in these waters. “We know at least 300 individuals are visiting Cape Cod, but we’ll definitely be able to tell you that’s not the actual estimate — it’s going to be much more than that,” he says. Skomal is also working on a study about shark behavior to help advise towns how to best prevent another attack. He is trying to determine whether specific areas around the cape are used for hunting or breeding or something else entirely.”We talk a lot about seeing more and more white sharks from year to year to year,” he says. “Now we’ll be able to tell you, is it increasing?” His study is due out this fall. On Nauset Beach in the town of Orleans, a mobile EMT team patrols the beach front in all-terrain vehicles, part of the town’s initiative to increase emergency response times on the beach in case of another shark attack. After last year’s fatal attack on Arthur Medici, some felt he might have survived if emergency response times had been faster. “We work with lifeguards. We patrol around looking for stuff, make sure everyone’s doing good,” says EMT Henry Rex. Every ATV is equipped with a large plastic box full of first-aid equipment, including new items specifically for treating shark bites. “We have a lot more trauma dressings and hemostatic dressings,” Rex says. Critics worry these measures are reactive, and they want towns to do more to prevent attacks. In Chatham, local official Shareen Davis says there have been “calls for putting shark barriers up, and pingers” that could detect not just tagged sharks but any shark movement in the water. “That would be great,” she says, “but those are costly, and I don’t know if the technology is even there yet.”In lieu of proven prevention tools, town officials believe their most effective approach is education, to make people aware of this new risk.Copyright 2019 WCAI. To see more, visit WCAI.
‘Marks are made by markers, but the marks also define the markers. This show is all about memory and history. Memories are like marks which have been created by a particular time and at the same time, eroded by time too. So “time” is the marker here, a personal/private time and Time as an eternal flow. Marks are then the signs of/for my intrinsic unconscious self and these could be read also as conscious choices from my socio-private experiences, mediated by time,’ says artist Samindranath Majumdar, talking about his work. Also Read – ‘Playing Jojo was emotionally exhausting’Paintings of this Kolkata-based artist will be on exhibition at the Gallerie Ganesha in a show called Marks And Markers. Samindranath Majumdar’s paintings look back to his own experiences, using abstraction and multiple layers of paint to redefine space and memory.His works tread the fine line between completely abstract and representative forms, calling into question the role that narrative threads play in experiencing art. For Majumdar, memory unfolds in a series of unstable visuals. Born in a Kolkata suburb, he grew up among greenery which was slowly being replaced by the growing space of a crowded metropolis. Observing the imposing and, sometime, crumbling buildings on a daily basis left its mark on his memory, to surface many years later in his canvases.