Month: August 2019

Ultrafast quantum computer uses optically controlled electrons

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first_img 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 loop-qubus quantum computer involves a semiconductor chip with a loop of cavities containing quantum dots. By focusing optical pulses at individual quantum dots, the electron spins within the dots rotate, changing the state of the bit. Credit: Clark, et al. “The second limitation on speed is the time it takes for the phase of one qubit to change the phase of another,” he continued. “This must be done with pulses that are slower than the rate light moves in and out of each optical cavity, so this brings the speed down to more like 10 GHz. Finally, as the computer gets bigger, the amount of time it takes for light to propagate around the system will also limit speed, perhaps bringing the speed of physical qubits down to GHz compared to classical computers.” However, Ladd added that the proposed architecture, with its speedy physical operations, non-local couplings, potential for monolithic semiconductor implementation, and non-reliance on single photon sources or detectors, is still much faster than other schemes for quantum computing, such as ion traps.“As opposed to classical computers, quantum computers critically depend on error correcting schemes,” Clark said, explaining the complexity of calculating a quantum computer’s speed. “Techniques for correcting errors can get complicated; however, in general, they require many physical qubits and qubit operations to represent one fault-tolerant logical operation (and therefore more time). The speed of the physical qubit manipulation makes the computer appear faster than it is. Proper error correction may reduce the speed of the quantum computer to 1-10 MHz.”Besides speed, the proposed scheme also has benefits in terms of scalability and manufacturing potential. Because the system can create two-qubit gates between distant qubits, the scheme favors scalability compared with systems that rely on adjacent qubit interactions. Also, the system doesn’t require the two qubits to have the same frequency, which matches other proposals in its potential for large-scale fabrication.“In terms of building this computer, we are working on that one step at a time,” Clark said. “We are starting by putting the quantum dot qubits in cavities, performing rotations on those qubits, and then coupling them via qubus. But a complete, scalable device remains many years away.”Citation: Clark, Susan M., Fu, Kai-Mei C., Ladd, Thaddeus D., and Yamamoto, Yoshihisa. “Quantum Computers Based on Electron Spins Controlled by Ultrafast Off-Resonant Single Optical Pulses.” Physical Review Letters, 99, 04051 (2007).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. Scientists have designed a scheme to create one of the fastest quantum computers to date using light pulses to rotate electron spins, which serve as quantum bits. This technique improves the overall clock rate of the quantum computer, which could lead to the fastest potentially scalable quantum computing scheme of which the scientists are aware. Susan Clark and Kai-Mei Fu, both of Stanford University, and Thaddeus Ladd and Yoshihisa Yamamoto, both with Stanford University as well as the National Institute of Informatics in Tokyo, have published their results on the new scheme in a recent issue of Physical Review Letters. “We still don’t know what a final quantum computer will look like,” Ladd explained to PhysOrg.com. “Large scale quantum computation is a technology that is still very far away from being implemented, and will probably incorporate many new ideas that have not been imagined yet. The important development in this paper is finding a physical implementation of an existing theoretical idea [using phase gates to couple non-local spins] and estimating the speed.”On a single semiconductor chip, the researchers combine fast single-bit rotations and fast two-qubit gates, both of which are optically controlled. In quantum computing, the orientation and phase of the electron spin serve as the bit state, and the gates are responsible for performing reversible operations on input data to produce output data.The semiconductor chip is a square millimeter in size, and consists of a loop of cavities—together, this apparatus is called a “loop-qubus.” Each cavity holds a quantum dot, which is a small piece of semiconductor that contains, in this scheme, a single electron. By focusing optical pulses at individual quantum dots, the electron spins rotate, changing the state of the bit. The architecture is built on the idea of using phase gates to couple non-local spins. The optical pulses can provide a means to couple distant electron spins, or qubits, so that the phase of one qubit can depend on the phase of another qubit. When coupled, the qubits’ spin states form a “qu-bus,” which is the basis of a two-qubit gate. The operating speed of a quantum computer is measured by its clock signal, which could take many different forms. In the optical control scheme, the pulses, which could be supplied by a laser, provide a clock rate for the system. Ladd explained that there are several limitations on speed for quantum computers.“In quantum computing, not only is the state of the bit (0 or 1) important, but also the phase of the bit,” he said. “How quickly we can control the phase of the qubit, in our scheme, depends on the magnetic field. Increasing the magnetic field increases how fast the phase for any single qubit changes in time and ultimately sets the limit of how fast we can control our qubits. In the article, we give the limit of about 100 GHz, which is assuming a very high magnetic field, which would require superconducting magnets to achieve.center_img Citation: Ultrafast quantum computer uses optically controlled electrons (2007, August 15) retrieved 18 August 2019 from https://phys.org/news/2007-08-ultrafast-quantum-optically-electrons.html Explore further Tiny supersonic jet injector accelerates nanoscale additive manufacturinglast_img read more

Exotic Chameleon Spends Most of its Life as an Egg

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first_img The small F. labordi lives in the extremely arid southwest region of Madagascar. The desert-like, spiny-forest area experiences a long dry season from March through November, and a rainy season between December and February. This harsh, variable environment may be one of the reasons for the odd life history of F. labordi.As scientists Kristopher Karsten, et al., describe in a recent issue of PNAS, F. labordi’s eggs hatch in November, at the start of the rainy season. The creatures grow extremely quickly, with males increasing their body mass by more than 4% per day. By January, the juveniles become full-grown adults. The females lay their eggs in February, and then, quite abruptly, the entire F. labordi adult species dies out by the end of March. Between April and October, the species only exists inside well-hidden eggs.Of the nearly 30,000 species of tetrapods (four-limbed vertebrates), none has such a short post-hatching lifespan, such a rapid growth rate, or spends the majority of its life cycle inside an egg like F. labordi. As the scientists explain, the chameleon’s unique characteristics are more reminiscent of ephemeral insects or aquatic vertebrates than terrestrial tetrapods.“I think the most exciting thing to come out of this paper is that we’ve identified this really bizarre system, a short-lived chameleon, that is closely related to other species that have life histories more like what we expect from a typical tetrapod,” Karsten, of Oklahoma State University, told PhysOrg.com. “This presents an ideal system to explore evolutionary questions in a comparative framework.”Despite data from five seasons of field studies, the researchers say that it’s still unclear as to why the chameleon lives this way. One hypothesis is that the high climatic variability and unpredictability forces the animals to shorten their life histories. They point out that many Malagasy mammals (those that live on the island of Madagascar) differ from their close relatives in more stable environments by exhibiting extremely short-lived or long-lived life histories to cope. As part of a possible coping mechanism, the F. labordi embryos are presumed to exist in a state of diapause for their first several months, a dormant condition where the embryos delay growth. Up until the rainy season, the embryos grow extremely slowly during cool temperatures, and only resume normal development when the warm rainy season approaches before they hatch. 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 Malagasy chameleon F. labordi has the shortest lifespan and most rapid growth rate of any known four-legged animal, and is also the only such species to spend the majority of its life as an egg. Credit: Chris Raxworthy, AMNH. As prolonged as their embryonic growth is, the adult chameleons appear to quickly age and die just as naturally. The scientists observed that, by February, adults exhibited typical age-related deterioration, such as reduced mass, slower locomotion, and reduced strength, which caused several radio-tracked chameleons to fall from trees. The researchers also discovered three- and four-month-old individuals that were dead of unknown causes, with no signs of predation or mutilation. Another explanation of such an odd life history suggests a hormonal – and, likewise, behavioral – influence. F. labordi may have high levels of androgens, which are associated with aggression, and may also participate in physically intense combat and agonistic courtship. If its androgens are high (due to a physically intense social system), this could lead to immune suppression, which might increase adult mortality relative to juveniles. As the scientists note, high adult mortality often leads to the evolution of short life spans and early age of reproduction. But despite its unique life history, F. labordi still conforms to standard theory: it has the normal combination of small size, rapid growth, early reproductive age, and high adult mortality. It just exhibits these characteristics in a very extreme way. The scientists hope that the discovery of this unique creature will offer researchers a new method for testing how various chameleon species, which in some ways are very similar, can evolve so differently. Such future studies may also help explain the ecological and hormonal factors of aging and longevity.“We can not only start to explore why this type of life history evolved in this species, but also what the proximate mechanisms are of how these organisms grow, age, and reach senescence so quickly; things like genetics, hormones, environment, and the interactions between those variables,” Karsten said.He added that the study may influence conservation strategies, too: “I think this study points out that, at least for some species, conservation efforts that utilize captive breeding propagation may not be beneficial. For several chameleon species, namely the perennial ones that we know about already, perhaps captive propagation would be a viable alternative. But for species like F. labordi, it would be wasted effort and resources. For this species, a conservation management plan for natural populations would be a better idea.”More information: Karsten, Kristopher B.; Andriamandimbiarisoa, Laza N.; Fox, Stanley F.; and Raxworthy, Christopher J. “A unique life history among tetrapods: An annual chameleon living mostly as an egg.” 8980-8984, Proceedings of the National Academy of Sciences, July 1, 2008, vol. 1, no. 26.Copyright 2008 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.center_img (PhysOrg.com) — Scientists have discovered a chameleon species that spends a good two-thirds of its life inside an egg: Furcifer labordi lives about 8-9 months as an embryo, and has a post-hatching lifespan of just 4-5 months. As far as the scientists know, this strange life history is unique among all land vertebrates, and may help researchers better understand how certain ecological and hormonal factors influence life history evolution. Citation: Exotic Chameleon Spends Most of its Life as an Egg (2008, July 11) retrieved 18 August 2019 from https://phys.org/news/2008-07-exotic-chameleon-life-egg.htmllast_img read more

Study Rules Out Fröhlich Condensates in Quantum Consciousness Model

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first_img Citation: Study Rules Out Fröhlich Condensates in Quantum Consciousness Model (2009, March 10) retrieved 18 August 2019 from https://phys.org/news/2009-03-frhlich-condensates-quantum-consciousness.html “The Penrose-Hamerhoff model is very good in that it provides a comprehensive proposal involving physics and biology, but this falls short in the area of the chemistry – the precise nature of the atomic motions involved in forming the basic quantum qubit,” lead author Jeffrey Reimers, a chemistry professor at The University of Sydney, told PhysOrg.com. “Our original intention was to take their proposal and run full simulations of the protein motion and hence provide a significantly enhanced and better justified model that would form the core of subsequent research.”Instead, the researchers found that the Penrose-Hamerhoff model runs into problems due to the nature of Fröhlich condensation. In their study, the researchers show that, unlike Bose-Einstein condensation, Fröhlich condensation is a classical process that does not guarantee coherent motion. Fröhlich condensates are classified into three types (weak, strong, and coherent), with each type arising in different circumstances. In weak and strong condensates, the vibrations are incoherent but can still have profound observable effects on various systems by redistributing energy. In coherent condensates (the kind used in the Orch OR model), all the vibrational energy is in a single quantum state. In calculations and simulations, the researchers showed that coherent Fröhlich condensates are very fragile and the coherence lasts a very short time – shorter than a single vibrational period. This finding agrees with the criticism of Orch OR that quantum coherence should decohere too quickly for it to have a significant impact on cognitive function. Also, the scientists showed that the formation of coherent Fröhlich condensates requires high energy and extremely high temperatures – up to 100 million Kelvin, which is not possible in any biological environment.“Strictly, we show that Fröhlich condensation cannot cause quantum consciousness, so the challenge is then to find a way of implementing Orch OR in which coherence is guaranteed by some other process so that Fröhlich condensation is no longer required,” Reimers said.However, as the researchers elaborate in an upcoming paper, the involvement of a process other than Fröhlich condensation appears unlikely. As Reimers explained, coherence is known to exist in many analogous chemical and biological systems, including masers and photosynthesis, the latter of which is one of the most optimized quantum systems in biology. However, the coherence lifetime for these systems is only a few picoseconds, while Orch OR requires coherence on a timescale that is at least six orders of magnitude longer. Nevertheless, weak and strong Fröhlich condensates may have realistic applications, though not in theories of quantum consciousness. The researchers found that weak condensates could have significant effects on proteins, and could possibly help explain enzyme actions in terms of excitation of vibrational modes, as Fröhlich originally proposed. The researchers also suggested methods to observe the three types of condensates. In the past, researchers have attempted to observe coherent Fröhlich condensates by channeling a large amount of mechanical energy into a specific vibrational mode of a system. The current study shows that no amount of mechanical energy can produce a coherent Fröhlich condensate. Instead, the most likely ways to produce coherent condensates is by exposing systems to terahertz radiation or using microwave reactors. Observing strong and weak Fröhlich condensates may be easier than observing coherent condensates, the researchers showed. For instance, mechanical energy sources might be able to produce strong condensates, and the interaction of radiation with biological systems could produce weak condensates.More information: Jeffrey R. Reimers; Laura K. McKemmish; Ross H. McKenzie; Alan E. Mark; and Noel S. Hush. “Weak, strong, and coherent regimes of Fröhlich condensation and their applications to terahertz medicine and quantum consciousness.” PNAS. To be published. 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. Explore further This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. (PhysOrg.com) — Scientists don’t fully understand how consciousness works, and, so far, no classical theories can explain consciousness in the brain. In light of this lack of understanding, some researchers suggest that quantum mechanics may play a significant role in the workings of the mind and the brain. Quantum consciousness theories have always been controversial, and now a recent study has undercut one more component of these proposals.center_img One quantum mind theory, proposed by physicist Roger Penrose and anesthesiologist Stuart Hamerhoff, is called “orchestrated objective reduction” (Orch OR). The theory suggests that microtubules, which are structural components inside cells, might function as cellular quantum computing elements. Inside the microtubules, coherence among quantum superpositions is maintained until the wave function collapses. Normally, a wave function collapses due to a measurement (i.e., interaction of the system and its environment), but here the collapse is postulated not to occur until the quantum superpositions become physically separated within spacetime geometry, called “objective reduction.” When an area of quantum coherence collapses, an instant of consciousness occurs. The physical cause of the coherent activity within the microtubules, as Penrose and Hamerhoff suggest, could be Fröhlich condensates. Proposed by physicist Herbert Fröhlich in 1968, Fröhlich condensates are similar to Bose-Einstein condensates in that both are systems with the unique collective property of macroscopic quantum coherence. In Fröhlich condensation, several vibrating oscillators can achieve a highly ordered condensed state, vibrating in resonance. Specifically, nearly all the vibrations occur in-phase at the Fröhlich condensate’s lowest frequency. However, Fröhlich condensates have never been unambiguously observed in experiments, despite intense research during the past 40 years. In a recent study in PNAS, researchers from The University of Sydney and The University of Queensland in Australia have investigated the basic properties of Fröhlich condensates in an attempt to determine the most likely methods to experimentally observe them. The researchers showed that extremely high energies and temperatures are required to form coherent Fröhlich condensates and hence they cannot exist in biological systems, as proposed by the Orch OR theory. Still, Fröhlich condensates could exist outside a biological environment, such as in terahertz radiation, which could have medical applications, and in microwave reactors used in “green” chemistry applications. Researchers have found that the formation of coherent Fröhlich condensates requires high temperatures, making them incompatible with biological systems, and thus an unlikely component in the Penrose-Hamerhoff model of quantum consciousness. Physicists show coherence of Bose-Einstein condensates extends to spin state of atomslast_img read more

Oxford Questions seek to pull back the curtain on the foundations of

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first_img 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 Oxford Questions were developed by theorists, experimentalists, and philosophers of physics in order to elucidate the areas of physics in which genuine progress may be made in the foreseeable future. Credit: G. A. D. Briggs, et al. Explore further (Phys.org) —Relativity and quantum theory form the backbone of modern physics, but a group of physicists stresses that daily use of these theories can numb the sense of wonder at their immense empirical success. At the same time, fundamental questions on the foundations of these two theories remain. In 2010, experimentalists, theorists, and philosophers of physics convened at a conference at the University of Oxford called Quantum Physics and the Nature of Reality. They produced a set of “Oxford Questions” aimed at identifying some specific open problems about the nature of quantum reality in order to stimulate and guide future research. Citation: Oxford Questions seek to pull back the curtain on the foundations of quantum physics (2013, July 18) retrieved 18 August 2019 from https://phys.org/news/2013-07-oxford-curtain-foundations-quantum-physics.html More information: G. A. D. Briggs, et al. “The Oxford Questions on the foundations of quantum physics.” Proceedings of The Royal Society A. DOI: 10.1098/rspa.2013.0299 (free) Journal information: Proceedings of the Royal Society A Physicists publish solution to the quantum measurement problem The Oxford Questions are presented in a new Perspective Paper published by physicists G. A. D. Briggs at the University of Oxford, J. N. Butterfield at the University of Cambridge, and A. Zeilinger at the University of Vienna in a recent issue of Proceedings of the Royal Society A.At the conference, the scientists emphasized that they wanted to “avoid rehashing various aspects of the status quo in debates about the foundations of quantum physics.” Instead, their set of questions focuses on issues that can be specifically investigated with current methods and theories. The five broad categories of questions are (1) time, irreversibility, entropy, and information; (2) the quantum-classical relationships; (3) experiments to probe the foundations of quantum physics; (4) quantum physics in the landscape of theories; and (5) interactions with questions in philosophy. (See accompanying figure for details.)”The Oxford Questions seek to take problems which would be widely recognized by the academic community, and to articulate topics on which there is a prospect of making genuine progress in the foreseeable future,” Briggs told Phys.org. “In this way, we hope that the Oxford Questions will provide an agenda for successful research by philosophers, theorists, and experimentalists. Some of this will require the expertise of more than one discipline. The Oxford Questions include issues on which there is currently a divergence of views even among experts.”Taking a broader perspective, the physicists explain that the Oxford Questions can be thought of as addressing two larger “clouds” on the horizon that may threaten the success of 20th century physics, just like the anomalies confronting classical physics did at the end of the 19th century. The first cloud is the quantum measurement problem: “the difficulty of explaining completely, in terms of quantum theory, the emergence of a classical world, i.e., a world so accurately described by classical physics with its definite values—a world free of superposition and entanglement.” The scientists call this cloud “the cat in the room,” and explain how several of the Oxford Questions probe the measurement problem more deeply. The analogous “elephant in the room” is the search for a quantum theory of gravity, which is the second cloud. The physicists think there are several reasons why reconciling general relativity and quantum theory is so elusive. One reason is that, whereas relativity theory is grounded on reasonable physical principles, it’s unclear whether quantum theory is based on comparable principles. Another reason is the dire lack of experimental data. Testable characteristics of quantum gravity arise only under conditions of such high energy, short distances, and short times that they are inaccessible to researchers. For example, the physicists note that the Planck length (10-35 m) is as many orders of magnitude from the diameter of a quark (10-18 m) as that diameter is from the familiar scale of a centimeter.Although these two clouds highlight the problems with quantum physics, the physicists also point out that the Oxford Questions arise in large part from empirical work from the last 100 years that has shown the immense success of the basic postulates of relativity and quantum theory. They give many examples in which these postulates have proven to be successful in domains far beyond their original ones:”Why should the new chronogeometry, introduced by Einstein’s special relativity in 1905 for electromagnetism, be extendible to mechanics, thermodynamics and other fields of physics? And why should the quantum theory devised for systems of atomic dimensions (10?10 m) be good for scales both much smaller (cf. high-energy experiments 10?17 to 10?20 m) and vastly larger (cf. superconductivity and superfluidity, or even a neutron interferometer, involving scales of a fraction of a metre or more)? Is there an upper limit to the scale on which quantum theory should be expected to work? There is a sense in which all properties of matter are quantum mechanical. Topics as diverse as phase changes of alloys and conduction in semiconductors have all yielded to quantum theory. New quantum mechanical models are being developed for a growing range of superconductors, magnets, multiferroics and topological insulators. “The point applies equally well when we look beyond terrestrial physics. General relativity makes a wonderful story: the theory was created principally by one person, motivated by conceptual, in part genuinely philosophical, considerations—yet, it has proved experimentally accurate in all kinds of astronomical situations. They range from weak gravitational fields such as occur in the solar system, where it famously explains the minuscule precession of the perihelion of Mercury (43″ of arc per century) that was unaccounted for by Newtonian theory, to fields 10 000 times stronger in a distant binary pulsar, which in the last 30 years has given us compelling evidence for a phenomenon (gravitational radiation) that was predicted by general relativity and long searched for.”Overall, the aim of the Oxford Questions is to continue expanding these applications and unifying these concepts of quantum physics, just as scientists have been doing for the past several decades. To describe the present state of physics, the physicists here use an analogy by the theoretical physicist Carlo Rovelli. He compares the present situation in physics to that of the early 17th century when Galileo and Kepler were working on the mechanics of early modern science. Looking back at that time, today’s scientists view Galileo’s and Kepler’s ideas as a mixed bag of insight and error; future scientists may see the ideas of today’s brightest researchers in much the same way.In the meantime, the physicists are using the Oxford Questions to guide their own research. For Briggs, this has led to digging deeper into the philosophical aspects of quantum theory.”In my own laboratory at Oxford, we benefit from a ‘Philosopher in Residence’ who is distinguished for his contributions both to physics and to philosophy,” Briggs said. “He has already contributed to elucidation of how interpretations of quantum reality can be tested theoretically and experimentally, and he has contributed to the design of practical experiments. We have formulated a new research program entitled ‘Experimental Tests of Quantum Reality.’ This will address the three topics in the third category of the Oxford Questions. The program has been funded in full and will start on 1 October 2013.”The physicists also plan to follow up on the Oxford Questions as they make progress in searching for answers.”The grant for ‘Experimental Tests of Quantum Reality’ will organize a conference in 2014, which will be similar in format to the 2010 conference ‘Quantum Physics and the Nature of Reality’ at which the Oxford Questions were formulated,” Briggs said. “This will provide an opportunity to formulate new questions in the light of progress made. In the following year we shall organize a smaller conference specifically for theologians and church leaders, with the aim of enabling them to benefit from the advances in understanding.” © 2013 Phys.org. All rights reserved.last_img read more

Modelindependent measurement of dark matter mass could lead to future discoveries

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first_imgHere, the physicists have presented an approach that allows the WIMP mass to be measured without any prior assumptions, using only data that will be available soon from upcoming experiments. To demonstrate the approach, the physicists generated three mock data sets and used them to reconstruct the WIMP mass in different scenarios. They showed that, although the method does lead to an unavoidable uncertainty in the cross section (a factor that involves particle interaction), it can still accurately recover the WIMP mass.”Prior to this work, it has been necessary to make at least some assumptions about the velocity distribution in order to extract information on the dark matter mass,” Kavanagh told Phys.org. “However, with no way of knowing how accurate these assumptions are, we would have no way of knowing whether the dark matter mass we extract is correct. We have shown for the first time that in a variety of scenarios, we can analyze data without making such assumptions and therefore that the dark matter mass can be recovered reliably from direct detection experiments.As the physicists explain, this ability to measure the WIMP mass without making assumptions of the velocity distribution will be very useful when analyzing data from many other dark matter experiments.”Dark matter cannot be accounted for by any of the known particles in the Standard Model of particle physics,” Kavanagh said. “This means that dark matter must be in the form of a new species of particle, governed by new physics beyond the Standard Model. Knowing the dark matter particle’s mass can give us an insight into this new physics, for example allowing us to rule out theories which do not predict the correct value.”At present, no confirmed dark matter signal has been observed in any direct detection experiments. This allows us to place bounds on how weakly dark matter particles interact with ordinary nuclei. However, with larger detectors and longer exposure times, we can probe weaker and weaker interactions and it is hoped that a signal will be observed sometime in the near future at current and upcoming detectors. Once this happens, our method will allow us to combine data from several direct detection experiments in order to reliably extract both the dark matter mass and velocity distribution.”In the future, the physicists plan to further text and extend their method, and are hoping to see a dark matter signal in the near future.”We are currently working on testing the method using even more mock data sets, representing a wider variety of underlying velocity distributions and WIMP masses,” Kavanagh said. “We also hope to extend the method to the analysis of directional data. Directional detectors measure both the energy and direction of nuclear recoils and therefore allow us to probe the full three-dimensional velocity distribution, rather than the one-dimensional speed distribution. This in turn will allow us to probe the dynamics of the Milky Way halo using directional experiments.”Unfortunately, we do not know how strongly (or weakly) dark matter interacts with ordinary nuclei, so we do not know when a WIMP signal will be observed. With the advent of ton-scale detectors in the next few years, we should be able to test dark matter interactions 100 times weaker that what can currently be probed. If we’re lucky, this means we could see a dark matter signal within the next few years.” The scientists, Bradley J. Kavanagh and Anne M. Green at the University of Notthingham, have published their paper on the model-independent measurement of dark matter mass in a recent issue of Physical Review Letters.Although physicists don’t know exactly what dark matter is, one promising candidate is weakly interacting massive particles (WIMPs). Scientists can detect WIMPs in the lab, both directly and indirectly through their annihilation products. In one type of direct detection experiment, scientists can measure the nuclear recoils produced by WIMPs when they interact with atomic nuclei, and this data can provide a way to measure the WIMP mass. In order to extract the mass data, however, scientists must make assumptions about the velocity distribution of the dark matter particles within the Milky Way halo. This velocity distribution encodes the speeds of the dark matter particles and determines the recoil energies observed in experiments. Usually, scientists use the simplest model of the Milky Way halo, called the standard halo model, to make assumptions about the velocity distribution. But as the physicists point out, some recent simulations suggest that this model is incorrect. For one thing, the standard halo model does not account for the effect of baryons, which is not fully understood. The differences can lead to uncertainties in the velocity distribution that cause significant bias in measurements of the WIMP mass. Although several different approaches have been proposed to account for this uncertainty, they all still have significant shortcomings, and some of them make other assumptions. A massive cluster of yellowish galaxies, seemingly caught in a red and blue spider web of eerily distorted background galaxies, makes for a spellbinding picture from the new Advanced Camera for Surveys aboard NASA’s Hubble Space Telescope. To make this unprecedented image of the cosmos, Hubble peered straight through the center of one of the most massive galaxy clusters known, called Abell 1689. The gravity of the cluster’s trillion stars — plus dark matter — acts as a 2-million-light-year-wide lens in space. This gravitational lens bends and magnifies the light of the galaxies located far behind it. Some of the faintest objects in the picture are probably over 13 billion light-years away (redshift value 6). Strong gravitational lensing as observed by the Hubble Space Telescope in Abell 1689 indicates the presence of dark matter. Credit: NASA, N. Benitez (JHU), T. Broadhurst (Racah Institute of Physics/The Hebrew University), H. Ford (JHU), M. Clampin (STScI),G. Hartig (STScI), G. Illingworth (UCO/Lick Observatory), the ACS Science Team and ESA Journal information: Physical Review Letters © 2013 Phys.org. All rights reserved. Citation: Model-independent measurement of dark matter mass could lead to future discoveries (2013, July 29) retrieved 18 August 2019 from https://phys.org/news/2013-07-model-independent-dark-mass-future-discoveries.html Theorists weigh in on where to hunt dark matter 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) —Determining the mass of dark matter particles requires accounting for several factors, one of which is the velocity distribution of the particles. Most current estimates of dark matter mass involve assumptions regarding the velocity distribution, since this distribution involves a high degree of uncertainty. In a new paper, physicists have presented a model-independent method for determining the dark matter mass that doesn’t require any assumptions about the velocity distribution, marking the first time that the dark matter mass can be accurately measured in an unbiased way. The physicists predict that this tool will be invaluable for the analysis of future experimental data. Explore further More information: Bradley J. Kavanagh and Anne M. Green. “Model Independent Determination of the Dark Matter Mass from Direct Detection Experiments.” PRL 111, 031302 (2013). DOI: 10.1103/PhysRevLett.111.031302last_img read more

Japanese companies develop quake damping pendulums for tall buildings

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first_img(Phys.org) —Two Japanese companies, Mitsui Fudosan and Kajima Corp, have announced plans to install quake damping pendulums atop the Shinjuku Mitsui Building in downtown Tokyo by 2015. The building, like many others in the city, was built before new quake dampening technology was developed for skyscrapers. Both old and new anti-quake technology is based on the same idea—heavy pendulums that counter the ground moving action caused by an earthquake. When an earthquake (with long-period seismic motion) begins, it pushes the base of a tall building in the direction of the seismic activity—the top of the building is left motionless for a moment, but then soon catches up, but by then, the bottom has moved back in the opposite direction. Such motions can cause tall buildings to sway violently resulting in damage or even destruction of the building. To counter such motion in newly built skyscrapers, pendulums are installed on the upper floors. They work by automatically swaying counter to the motion created by the earthquake. The result is a reduction in swaying and hopefully, damage to the building and harm to its occupants.Unfortunately, many of Tokyo’s skyscrapers were built long before the new pendulum technology was developed, leaving them at risk when the next quake strikes. In this new effort, engineers working for the two involved companies have devised a means for adding pendulums to the tops of existing skyscrapers. The 55 story Shinjuku Mitsui Building (which was observed to sway approximately 2 meters during the 2009 Great East Japan Earthquake of 2009) will be outfitted with six such pendulums, each hung inside its own frame and weighing 300 tons. Presumably, the size of the pendulums and the number would vary by building based on its size and space available on its top. Also, a thorough analysis of the building would have to be undertaken before adding so much weight—most buildings would likely require reinforcement. Adding the pendulums to the Shinjuku Mitsui Building is expected to cost approximately $51 million. Citation: Japanese companies develop quake damping pendulums for tall buildings (2013, August 2) retrieved 18 August 2019 from https://phys.org/news/2013-08-japanese-companies-quake-damping-pendulums.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. Retrofitting earthquake protection could save livescenter_img In Japanese. Officials for the companies involved told the press at an announcement of the project that they believe the pendulums will reduce the amount of swaying by 60 percent and that they should also reduce the amount of time the building sways. © 2013 Phys.org Explore furtherlast_img read more

Sculpting a conjugated polymer using DNA origami

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first_img Using DNA origami to build nanodevices of the future © 2015 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. (Phys.org)—New research allows scientists to sculpt polymers into two- and three-dimensional shapes, similar to how polypeptides fold into functional three-dimensional shapes. This ability is particularly advantageous for conjugated polymers, polymers that have a networked pi-electron system, because they are conducting. Immobilizing and shaping conducting polymers is an important step in constructing molecular circuits. Journal information: Nature Nanotechnology A group of scientists from Aarhus University in Denmark, the Wyss Institute at Harvard, and Max Plank Institute in Germany, have synthesized, characterized, and immobilized a conjugated polymer using DNA origami. Their polymer was able to be shaped and molded into various two- and three-dimensional shapes while maintaining its physical properties. Their work appears in Nature Nanotechnology.Knudsen, et al. synthesized a conjugated brush polymer, (2,5-dialkoxy) paraphenylene vinylene (APPV) that is functionalized with a nine nucleotide long single stranded DNA (ssDNA) sequences to serve as a linkage to the DNA origami. APPV has hydroxyl groups along its backbone that are attached to phenylene units. These hydroxyl groups are available for functionalization with synthetic ssDNA. The ssDNA annealed to complementary strands that extend from a DNA platform, thus holding the polymer in place. This technique is known as DNA origami because the complementary strands of DNA extending from the DNA origami can be tailored to any shape or design and should guide the polymer with its complementary ssDNA to take that same shape.In this experiment, APPV-DNA was characterized with gel permeation chromatography, UV-Vis spectroscopy, fluorescence spectroscopy, XPS, and AFM. Gel permeation chromatography showed that the polymer size ranged from 340 kDa to 3,300 kDa. This and AFM studies indicated the presence of smaller and longer polymer pieces. XPS showed that less than two-thirds of the phenylene units, containing hydroxyl groups, where functionalized with ssDNA. Additionally, AFM studies provided surface potential information, indicating that the APPV-DNA polymer has a higher charge transfer than the silicon oxide substrate but lower than gold or carbon nanotubes.The polymer was then immobilized on DNA origami into various two and three-dimensional shapes, and charge transfer as well as polymer integrity were tested. The first test involved DNA origami in linear, U-shaped, and at 90o angles. Surface potential studies indicated that the immobilized APPV-DNA polymer displayed similar charge transfer abilities in all conformations. The polymer’s flexibility was verified by subjecting it to DNA origami shapes that would strain the structure: wave, staircase, and circular. Finally, the APPV-DNA polymer was formed into a three-dimensional cylindrical structure made from stacked rings of double helices. The stacked rings are held together using staple strands. TEM studies confirmed the shape of the cylinder, but the polymer does not provide adequate contrast for full characterization using TEM. AFM or any other scanning microscopy techniques will not work for this kind of structure either. The interaction between the tip and the molecule could damage the “soft” three-dimensional structure of the polymer. In order to obtain a three-dimensional rendering of the APPV-DNA cylinder, Knudsen, et al. used DNA-PAINT. Using the excess nine-nucleotide ssDNA that did not bind to the DNA origami structure, Knudsen, et al. made complementary strands with a fluorescent label. They then used DNA-PAINT to visualize the strand pattern and render a three-dimensional image.This research demonstrates the ability to control the two and three-dimensional conformation of a conjugated polymer, which has promising implications for molecular circuit design.center_img The topography and height measurements of poly(APPV-DNA). Credit: Nature Nanotechnology, DOI: 10.1038/NNANO.2015.190 Citation: Sculpting a conjugated polymer using DNA origami (2015, September 15) retrieved 18 August 2019 from https://phys.org/news/2015-09-sculpting-conjugated-polymer-dna-origami.html More information: “Routing of individual polymers in designed patterns” Nature Nanotechnology, DOI: 10.1038/NNANO.2015.190AbstractSynthetic polymers are ubiquitous in the modern world, but our ability to exert control over the molecular conformation of individual polymers is very limited. In particular, although the programmable self-assembly of oligonucleotides and proteins into artificial nanostructures has been demonstrated, we currently lack the tools to handle other types of synthetic polymers individually and thus the ability to utilize and study their single-molecule properties. Here we show that synthetic polymer wires containing short oligonucleotides that extend from each repeat can be made to assemble into arbitrary routings. The wires, which can be more than 200 nm in length, are soft and bendable, and the DNA strands allow individual polymers to self-assemble into predesigned routings on both two- and three-dimensional DNA origami templates. The polymers are conjugated and potentially conducting, and could therefore be used to create molecular-scale electronic or optical wires in arbitrary geometries. Explore furtherlast_img read more

Art set go

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first_imgQuad Set Go, presented by TAD arts is a group exhibition with Rajan Krishnan, Shubhra Das, Hindol Brahmbhatt and Nupur Kundu at the Visual Arts Gallery in IHC. Highlighting the aesthetic brilliance of each of the four artists Quad Set Go – gives an insight into their individual styles of paintings. Each artist in this show represents a different and unique treatment and genre of art. Bringing their individualistic styles together and watching it all together gives an adrenaline rush to any art lover – thus Quad Set Go. Also Read – ‘Playing Jojo was emotionally exhausting’Rajan, known for his Kerela inspired artworks with the topography and surroundings displayed so gorgeously on his canvases. Shubhra captures the beauty, sensuality and grace of women with her depiction of women in beautiful canvases. Hindol plays with the medium and also with the subject – doing full justice to the term contemporary. Nupur’s artworks have this calming yet invigorating effect on its viewers with her bold colors and textures, her works almost depicting the complexities of human life in an abstract form.A must go for art lovers – head over!last_img read more

Delhi gets state wise

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first_imgNorth East Design Fest – a mega four day festival comprising of Fashion shows, Cultural program and Exhibitions of Handloom, Handicrafts, Jute, MSME sector of the North East Region kicked off  in the Capital on Thursday. The aim of the festival is to create an interaction of ideas, provide an international standard marketing forum and a unique platform to showcase NE India’s textiles and artisans and their handloom and handicrafts.  The opening day witnessed three fashion shows highlighting Handloom and Handicrafts Ensemble by designers Meghna Rai Medhi, Aji Semy Rengma and Mona Pali. The inaugural performance of the festival was a Sattriya dance performed by Sanjukta Barooah. Rock band group Featherhead performed at the event as well. Also Read – ‘Playing Jojo was emotionally exhausting’North East Region of the country with the eight beautiful, exotic and to an extent unexplored states of Assam, Arunachal Pradesh, Tripura, Meghalaya, Nagaland, Manipur, Mizoram and  Sikkim has a strong history of its traditional textiles and handicrafts which forms an integral element of  its socio-economic structure.The festival will act as a curtain raiser to showcase the talents of artistes from that. People of the Capital will get an opportunity to interact with this wonderful talented young visionaries and this shall create a bridge of understanding and mutual growth of thought process. The North East Design Fest was inaugurated by  Pranatee Phukan, Minister of Handloom and Textiles Government of Assam. Also Read – Leslie doing new comedy special with NetflixTo create a fusion of pan-India and NER, designers Meghna Rai Medhi, Boney Darang, Charlee Lalthlenmawia, Monapali, Agnimitra, Gauranga were roped in to  display their collections along with the NER designers. Bollywood stars Minisha Lamba, Sonal Chauhan walked the ramp for the event. Vikram Rai Medhi, Event Director said, ‘Eighty number of stalls being erected at Select Citywalk which will showcase and create a mini North East for cross section of the society of Delhi and this will create an element of positive awareness and curiosity of our region which will thereby also play a role in the development in the Tourism sector. We appeal to all culture loving people of Delhi and the media to wholeheartedly support this humble and sincere effort closer to the mainstream.’The festival is presented by Ministry of Textiles with the support of Ministry of MSME, Ministry of Home Affairs – departments of Handloom and Textiles of government of Assam and the government of Arunachal Pradesh.last_img read more

Fun with feasting

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first_imgAdding to the festivities of this month, WelcomHotel Sheraton, New Delhi, gives you a reason to savour some exotic flavours offered by it. Discover a dinner buffet, at Baywatch, put together carefully to feature all-time season favourites and decorated to get you in the right spirit on the ocassion of the yearly celebration Halloween.  For November, Baywatch offers you to savour the favourite recipes of Chef Imtiaz Qureshi, crafted in that inimitable style which has made him the icon in the culinary world. After all, very few master chefs go on to become legends. So book you table soon!Where: Baywatch, WelcomHotel Sheraton New DelhiWhen: 31 Oct and 14 – 23 November  Timing : Dinner Price: Rs. 1750 plus taxeslast_img