Explore further More information: Seth Lloyd, et al. “The quantum mechanics of time travel through post-selected teleportation.” arXiv:1007.2615v2via: The Physics ArXiv Blog and Science News (PhysOrg.com) — The possibility of going back in time only to kill your ancestors and prevent your own birth has posed a serious problem for potential time travelers, not even considering the technical details of building a time machine. But a new theory proposed by physicists at MIT suggests that this grandfather paradox could be avoided by using quantum teleportation and “post-selecting” what a time traveler could and could not do. So while murdering one’s relatives is unfortunately possible in the present time, such actions would be strictly forbidden if you were to try them during a trip to the past. The model of time travel proposed by Seth Lloyd, et al., in a recent paper at arXiv.org arises from their investigation of the quantum mechanics of closed timelike curves (CTCs) and search for a theory of gravity. In simple terms, a CTC is a path of spacetime that returns to its starting point. The existence of CTCs is allowed by Einstein’s general relativity, although it was Gödel who first discovered them. As with other implications of his theories, Einstein was a bit disturbed by CTCs. In the new paper, the scientists explore a particular version of CTCs based on combining quantum teleportation with post-selection, resulting in a theory of post-selected CTCs (P-CTCs). In quantum teleportation, quantum states are entangled so that one state can be transmitted to the other in a different location. The scientists then applied the concept of post-selection, which is the ability to make a computation automatically accept only certain results and disregard others. In this way, post-selection could ensure that only a certain type of state can be teleported. The states that “qualify” to be teleported are those that have been post-selected to be self-consistent prior to being teleported. Only after it has been identified and approved can the state be teleported, so that, in effect, the state is traveling back in time. Under these conditions, time travel could only occur in a self-consistent, non-paradoxical way. “The formalism of P-CTCs shows that such quantum time travel can be thought of as a kind of quantum tunneling backwards in time, which can take place even in the absence of a classical path from future to past,” the researchers write in their paper. “Because the theory of P-CTCs relies on post-selection, it provides self-consistent resolutions to such paradoxes: anything that happens in a P-CTC can also happen in conventional quantum mechanics with some probability.” This figure shows CTCs through (a) conventional and (b) post-selected teleportation. Image credit: Seth Lloyd, et al. 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. However, the scientists note that prohibiting paradoxical events would cause unlikely events to happen more often. These “strange and counterintuitive effects” arise due to the nonlinear nature of P-CTCs. Like a movie hero who always manages to escape seemingly imminent death, the grandfather would always somehow manage to survive his grandchild’s murderous plots. “Some little quantum fluctuation would whisk the bullet away at the last moment,” Lloyd explained. In addition to prohibiting the grandfather paradox, the P-CTC theory also has the advantage that it doesn’t require the distortions of spacetime that traditional time travel theories rely on. These spacetime distortions probably only exist in extreme environments such as inside black holes, making these theories nearly impossible to realize. Although post-selected computations are nonlinear and have not yet been shown to be possible, some studies have shown that quantum mechanics may be nonlinear and allow post-selected computations, which would potentially make quantum computing a very powerful technique. Such a computer could more efficiently solve a complex problem containing lots of variables by running all possible combinations of values and post-selecting only the combinations that solve the problem. This strategy would work much better than the classical strategy of trying different combinations until you get one that works. On the other hand, other studies suggest that quantum mechanics must be linear, in part due to the seemingly impossible things that post-selection allows. Still, the scientists hope that future investigations will reveal whether or not their theory is correct. They explain that the effect of P-CTCs can be tested by performing quantum teleportation experiments, and by post-selecting only the results that correspond to the desired entangled-state output.“P-CTCs might also allow time travel in spacetimes without general-relativistic closed timelike curves,” they conclude. “If nature somehow provides the nonlinear dynamics afforded by final-state projection, then it is possible for particles (and, in principle, people) to tunnel from the future to the past.” © 2010 PhysOrg.com Study Shows Time Traveling May Not Increase Computational Power Citation: Time travel theory avoids grandfather paradox (2010, July 21) retrieved 18 August 2019 from https://phys.org/news/2010-07-theory-grandfather-paradox.html
Satellite image of the island of Borneo on August 19, 2002, showing smoke from burning peat swamp forests. Image: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC Malaysian peatswamps obliterated for palm oil: study Explore further Peat-swamp forests contain huge amounts of stored carbon both in the biomass above the ground in composting organic matter slowly breaking down in the soils, and much of this is released in the form of carbon dioxide (CO2) and methane when the forests are cleared and the swamps are drained.The new study published in Proceedings of the National Academy of Sciences (PNAS) used satellite images with 250 meter resolution to produce maps of the closed canopy plantations in Peninsular Malaysia, Borneo and Sumatra.They found the oil-palm plantations covered an area of 2 million hectares in Peninsular Malaysia, 2.4 million in Borneo, and 3.9 million in Sumatra. These figures do not include the smaller open canopy plantations, which are difficult to identify from the images, or plantations planted after 2002.The study showed that around 880,000 hectares of peatlands (around six percent) had been converted to oil-palm plantations by the early 2000s. The researchers also looked at the effects of clearing the forests in the region on wildlife, and found that 12.1 percent of species face probable extinction in Peninsular Malaysia (equivalent to 46 species of forest birds), 3.4 percent in Sumatra and 1 percent in Borneo. Among the species at risk are orang-utans, pygmy elephants and Sumatran tigers and rhinos.The researchers calculated that clearing the peatlands released around 140 million tonnes of carbon from above-ground biomass and 4.6 million from oxidation of peat in the ground. Clearing also reduces the carbon sequestration previously provided by the forest..Dr Koh said by 2010 around 2.3 million hectares of peat-swamp forests had been cleared that are currently degraded land and not yet developed as plantations. He said if the clearings were planted with palm for oil species losses could be exacerbated by as much as 12 percent, while if they were re-forested biodiversity would be enhanced by up to 20 percent.The study recommended the remaining peat-swamp forests in Southeast Asia should be conserved to protect biodiversity and safeguard carbon stocks, with most effort being concentrated in Central and West Kalimantan, Sarawak and Riau in Indonesia, which hold 75 percent of the remaining forests, or around 3.9 million hectares, and much of the cleared but not yet developed peat-swamp forest.Indonesia is accelerating its production of palm oil and is planning to double its production by 2020. Palm oil is used to make biodiesel and is also used in soaps, cosmetics and in many processed foods. It can also be used as a fuel for cooking. More information: Remotely sensed evidence of tropical peatland conversion to oil palm, Proceedings of the National Academy of Sciences, Published online before print March 7, 2011, doi:10.1073/pnas.1018776108 (PhysOrg.com) — Peat-swamp forests in Southeast Asia are being cleared to make way for food production and for oil-palm plantations for biofuel, but now a new study has quantified the resultant carbon emissions for the first time. © 2010 PhysOrg.com Citation: Carbon emissions from peat-swamp forest clearing quantified (2011, March 8) retrieved 18 August 2019 from https://phys.org/news/2011-03-carbon-emissions-peat-swamp-forest-quantified.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.
Explore further More information: Greg J. Stephens, et al. “Statistical Thermodynamics of Natural Images.” PRL 110, 018701 (2013). DOI: 10.1103/PhysRevLett.110.018701 (a) A grayscale image of a forest. Photo by Dan Ruderman. (b) The same image after it is quantized into two equally populated levels of black and white. The researchers found that small patches within this quantized image retain substantial local structure. This finding led them to discover that the photo is scale-invariant—its structure stays the same as its scale changes. Credit: Greg J. Stephens, et al. ©2013 American Physical Society (a) 4 x 4 patches from the quantized forest image with the lowest energy states, starting with the lowest energy states of all: solid black and white blocks. The other patches are local minima, and many of them can be interpreted as lines and edges. The scientists speculate that the visual system might build neurons that identify these local minima in order to build a representation of the world. In part (b), the researchers computed the average light-intensity images that correspond to those in part (a). These average images resemble those that trigger neuron responses in the primary visual cortex. Credit: Greg J. Stephens, et al. ©2013 American Physical Society 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. Copyright 2013 Phys.org All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of Phys.org. The scientists saw this scale invariance as a hint that natural images may have something in common with a physical system at a critical point. In physical systems, scale invariance emerges only when the temperature reaches a critical value, at which point a phase transition occurs between two phases characterized by different forms of order.To examine whether the ensemble of natural images has its own critical point, the researchers treated the distribution of pixels as the Boltzmann distribution for a physical system, where the patterns of pixels in the small patches are associated with different energy levels according to their probability. Remarkably, as the patch size increased so too did a peak in the specific heat, a thermodynamic variable that characterizes fluctuations in the energy of the ensemble. These results suggest a sharp transition in the thermodynamic limit of large patch sizes, similar to how a physical system reaches this limit at a critical temperature.The researchers found that this approach to the thermodynamics of images also shares similarities with Zipf-like distributions. According to Zipf’s law, elements in a group (for example, words in a book) that are sorted from most common to least common will follow a pattern where the second most common element is 1/2 as common as the first, the third most common element is 1/3 as common as the first, etc. Zipf-like distributions have been found to hold for many different situations, and here the scientists found that they also closely describe the distribution of the size of pixel patches ranked by the structure as determined by their black and white pixels.Perhaps the most interesting implication of viewing natural images from a thermodynamics perspective is what it reveals about the nature of image patches that correspond to the low energy states. The patches with the absolute lowest energy states are those that are either all black or all white. However, a small number of patches have pixels in both states yet are considered local minima, since flipping any single pixel would increase the energy. Looking closer at these patches, the researchers found that many of them have distinct patterns, such as edges between dark and light regions.The researchers speculate that the importance of these local minima in natural images may help us and other creatures “see” our surroundings, even when our eyes don’t absorb every pixel. The visual system may build neurons that are tuned to these “basins of attraction.” In other words, these low-energy patches may assist the brain in filling in the details using some kind of error-correcting code based on the thermodynamics of the visual world. A team of researchers at Princeton University has taken a closer look at images of nature and proposed that the scale invariance of images closely resembles the thermodynamics of physical systems at a critical point, with the distribution of pixels in the images analogous to the distribution of particle states in a physical system such as a ferromagnet. The parts of an image that correspond to the low-energy states, or local minima, have surprisingly interpretable structure, and these thermodynamic characteristics may help the brain see.The researchers, Greg J. Stephens, Thierry Mora, Gašper Tkačik, and William Bialek, at Princeton University, have published their study on the thermodynamics of images in a recent issue of Physical Review Letters.In their study, the scientists analyzed an ensemble of photographs taken in a forest at Hacklebarney State Park in New Jersey. The researchers converted the grayscale camera images to binary (black and white) images. Although intensity information was lost in the quantization, many details such as the structure of the trees and a body of water could still be identified. The worlds smallest 3D HD display Journal information: Physical Review Letters The researchers then divided each binary image into much smaller patches composed of 3 x 3 and 4 x 4 pixels and examined the distribution of black and white pixels in these patches. To quantify how much structure is present in these tiny segments of natural images, the researchers measured the entropy of the distribution of pixels. Randomly distributed pixels would give an entropy level of 9 and 16 bits, respectively, for the 3 x 3 and 4 x 4 pixel regions. But the researchers found that the entropy levels of the same-sized regions from the photo were only 6.5 and 11.2 bits, suggesting that substantial local structure remains in the tiny patches.To explore how local image structure changes with scale, the researchers averaged neighboring pixels within each image and repeated their patch analysis. After such “coarse-graining,” the image had lower resolution, but remarkably both the entropy and pixel distribution were unchanged from the original image. Even after repeating this coarse-graining process four times, the pixel distributions in the small square regions remained the same, indicating that the photo is scale-invariant—its structure stays the same as its scale changes. Citation: Thermodynamics of visual images may help us see the world (2013, February 13) retrieved 18 August 2019 from https://phys.org/news/2013-02-thermodynamics-visual-images-world.html (Phys.org)—Although researchers know that a large portion of the brain is devoted to visual processing, exactly how we interpret the complex patterns within natural scenes is far from understood. One question scientists ask is, is there something about the structure of the visual world itself that enables our brains to process and understand our visual surroundings, and is this structure something that can be described quantitatively?
© 2014 Phys.org (Phys.org) —Optical transistors and switches are fundamental in both classical and quantum optical information processing. A key objective in optics research is determining and developing the structural and performance limits of such all-optical devices, in which a single gate photon modifies the transmission or phase accumulation of multiple source photons – a feature necessitating strong interaction between individual photons. While significant progress has been made – especially in cavity QED experiments, which use resonators to enhance interaction between photons, confined in a reflective enclosure, and natural or artificial atoms – the goal is to achieve high optical gain and high efficiency using a free-space – that is, cavity-free – approach. Recently, scientists at Universität Stuttgart, Germany demonstrated a free-space single-photon transistor based on two-color Rydberg interaction, which they say could lead to a high optical gain, high efficiency optical transistor through further improvements. (In a Rydberg atom a single electron is excited to a state with a large principal quantum number, meaning that it has high potential energy.) Moreover, the researchers state that the finding may lead to advances in quantum information processing, condensed matter physics, single step multi-photon entanglement, and other important areas. In addition, the paper notes that their novel approach could enable a high optical gain, high efficiency optical transistor, which so far has been realized only in a cavity QED setup, in which attenuation of hundreds of source photons has been demonstrated. “Cavity QED experiments employ an optical resonator to increase light-matter interaction,” Gorniaczyk says. “However, resonators come with technological challenges and fundamental limitations, such as limited bandwidth, which free-space experiments do not suffer.””Optical transistors open a wide range of potential optics applications, one of which is the single-shot detection of single photons,” Hofferberth tells Phys.org. “In addition, investigating different state combinations can lead to an increase in optical gain. In particular, the use of so-called Förster resonances1, as well as working with states that are directly coupled, can significantly boost performance. Modification of trap geometry for the cold atomic cloud would also improve our system by leading to a greater optical depth for source photons in the presence of gate photons – and thus to a higher attenuation. Finally, the retrieval of gate photons after the transistor experiment would open up the door to quantum computation.”Furthermore, the paper points out that the combination of two independently controlled Rydberg-EIT (electromagnetically induced transparency) schemes offers high flexibility. With two excitation schemes, the gate photon can efficiently be stored using a detuning to the intermediate state, whereas the source photons can propagate through the medium with reduced group velocity. Additionally, the two-color scheme enables novel fields of study, such as Förster resonances or directly dipole-dipole coupled Rydberg states. “Förster resonances occur when a pair state involving two Rydberg states resonantly couples to another pair state,” Tresp explains. “Using a suitable resonance allows to increase the interaction between gate and source photons, while the interaction among source photons can be kept low. This can lead to an increase in gain.” Theoretically, the researchers say, their optical transistor can be extended such that an imaging system with source photons can determine the position of gate excitations in a single shot. If the interaction between gate and source photons is very high, the exact position of gate excitations cannot be tracked back, so the resolution decreases with increasing interaction, especially if more gate excitations are present. “Moreover, our optical transistor can be seen as a device that entangles the gate photon with many source photons,” Gorniaczyk says. “The presence of source photons, for instance, implies the absence of the gate photon in the first place. Systems with strong many-body correlations are of high interest in quantum information technology, and many ideas could be realized including quantum gate arrays.” Quantum gate arrays are basic quantum circuits that process small numbers of qubits and are combined to construct quantum circuits.Another possible quantum computation application is the experimental embodiment of a two-photon phase gate based on Rydberg-polariton collisions(Polaritons are part matter, part light quasiparticles).) “We currently show that a gate photon efficiently attenuates source photons –or in other words, the gate photon causes absorption of source photons,” Hofferberth tells Phys.org. “It’s also possible, though, to modify the scheme such that the gate photon causes dispersion of the source photons, causing a phase shift of the source photons. The only modification required for this is to send the source photons with a different detuning into the medium. Currently they are tuned exactly onto resonance with an optical transition to cause strong absorption, but by detuning them the effect can be turned into a conditional phase shift.” A two-qubit phase-gate is a universal quantum gate, meaning that if a reliable phase gate is available along with single qubit gates), any quantum computation can be realized. “Our system would be the first purely photonic deterministic two qubit gate,” Hofferberth adds.In addition to the research plans discussed above, Gorniaczyk says since their work demonstrates controlled interaction between individual photons , the scientists can now turn towards realizing long-standing goals such as all-optical quantum computation. “Our explicit next goal is to demonstrate that the transistor can be operated with gain greater than 1, and the gate photon retrieved afterwards with all of its quantum properties intact. This will enable multi-photon entanglement in a single step and entangled states of multiple particles – in this case, the latter being photons – which are a key quantum information resource.”Another of their ideas is similar to the non-destructive detection of single atoms: If the gate photon can survive the transistor process, it will enable non-destructive quantum state detection of single photons. “Currently, all photon detection methods are destructive and limited in efficiency – in practice, usually to below 0.3,” Tresp explains. “A non-destructive detector with high fidelity would be an innovation with many applications in optical science.”Addressing other areas of research that might benefit from their study, Hofferberth notes that while their current work focuses on making the Rydberg-mediated interaction between photons useful for quantum applications, more generally it realizes a novel system of strongly interacting particles. “If the number of photons interacting with each other simultaneously can be further increased, such a system could be a novel approach to study many-body physics problems, as encountered in condensed matter physics. In addition,” he concludes, “the enormous flexibility of our system could be the foundation of a photon-based quantum simulator used to investigate systems that cannot easily be studied directly.” A transistor-like amplifier for single photons (a) Level scheme, (b) simplified schematic, and (c) pulse sequence of our all-optical transistor. (d) The absorption spectrum for the source field (dots) over the full intermediate state absorption valley shows the EIT window on resonance; the gate field spectrum (circles) is taken around the two-photon resonance at δg = 40 MHz. The solid lines are fits to the EIT spectra. The linewidth of the source EIT window Δν = 2 MHz and the optical depth OD ¼ 25 of our system are extracted from the brown curve. Credit: H. Gorniaczyk et al., Phys. Rev. Lett., 28 July 2014. Journal information: Physical Review Letters Doctoral students Hannes Gorniaczyk and Christoph Tresp, along with Dr. Sebastian Hofferberth, discussed the paper that they and their co-authors published in Physical Review Letters. They first addressed the challenge of devising a novel approach to implement a free-space single-photon all-optical transistor with an optical gain exceeding a factor of 10. “Photons do not inherently interact,” Gorniaczyk tells Phys.org. “Therefore, one has to think about ways of introducing interaction – and it’s been shown that the interaction of Rydberg atoms in a cold atomic cloud can be mapped onto the photons to create an effective interaction.””Due to the large micrometer size of these atoms,” Tresp points out, “the interaction between them is very strong – and we use this property to create strong interaction between single photons. The new aspect of our transistor scheme is that we use two different Rydberg states at the same time, allowing us to independently address the gate and source photons.” This approach enables the scientists to show that an optical gain G > 10 can be reached with, on average, less than one gate photon.Another challenge was mapping gate and source photons into Rydberg excitations with different principal quantum numbers in an ultra-cold atomic ensemble. “To map the gate and source photons of the optical transistor into Rydberg excitations requires experimental effort.” Gorniaczyk explains. “First, it’s necessary to create a cold and dense cloud of atoms in a favorable geometry; then, four excitation laser beams have to be overlapped and aligned on the atomic cloud; and finally, while the strong interaction between Rydberg atoms is the key to our scheme, they are also very susceptible to any external perturbation, requiring great care in shielding the experiment from external electric fields.”A key result was using the optical transistor to demonstrate the nondestructive detection of a single Rydberg atom. The conventional method is to ionize Rydberg atom and detect the resulting ion on an ion detector, with typical detection efficiencies below 0.5. However, by using their optical transistor the researchers mapped the existence of one Rydberg atom onto a probe light pulse by over 10 photons – which would be impossible if source photons destroyed gate excitations. This makes the new approach well-suited to independent control of gate and source photons. “While this is very similar to how electronic transistors are used to amplify signals,” Tresp notes, “our new approach is a clear improvement: Even with all imperfections taken into account, we achieve fidelity of 0.72 for the single shot detection of a Rydberg atom without destroying it during the process.” Moreover, optical transistors based on the interaction of Rydberg excitations are robust, and photon Interaction can be mediated by interaction between Rydberg states with different principal quantum numbers. Citation: Step lightly: All-optical transistor triggered by single photon promises advances in quantum applications (2014, August 29) retrieved 18 August 2019 from https://phys.org/news/2014-08-lightly-all-optical-transistor-triggered-photon.html More information: Single-Photon Transistor Mediated by Interstate Rydberg Interactions, Physical Review Letters 113, 053601 (28 July 2014), doi:10.1103/PhysRevLett.113.053601Related:1Single-Photon Transistor Using a Förster Resonance, Physical Review Letters 113, 053602 (28 July 2014), doi:10.1103/PhysRevLett.113.053602 Explore further This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
The energy harvester consists of a carbon fiber beam with a piezoelectric sensor and stepper motor to adjust the angle of attack of the airflow in the wind tunnel. Unlike previous designs, the system does not require a secondary vibrating structure because the beam itself vibrates, reducing the volume of the harvester and increasing its efficiency. Credit: Zakaria, et al. ©2015 AIP Publishing UK scientists develop optimum piezoelectric energy harvesters Citation: Scientists harvest energy from beam’s self-induced, self-sustaining vibrations in airflow (2015, July 27) retrieved 18 August 2019 from https://phys.org/news/2015-07-scientists-harvest-energy-self-induced-self-sustaining.html More information: Mohamed Y. Zakaria, et al. “Experimental analysis of energy harvesting from self-induced flutter of a composite beam.” Applied Physics Letters. DOI: 10.1063/1.4926876 Journal information: Applied Physics Letters © 2015 Phys.org The researchers, Mohamed Y. Zakaria, Mohammad Y. Al-Haik, and Muhammad R. Hajj from the Center for Energy Harvesting Materials and Systems at Virginia Tech, have published a paper on the new energy-harvesting method in a recent issue of Applied Physics Letters.”The greatest significance of the work is the reduction of the volume of the harvester, which translates to an increase in the power density, by eliminating the need for a secondary structure to be attached to the beam,” Zakaria said. “This reduction is important in the design of very small harvesters that can be used to develop self-powered sensors.”The research shows that subjecting a flexible beam to wind at the right angle of attack can cause the beam to bend so much that the beam’s “flutter speed” is significantly reduced. A large degree of bending also induces a change in the beam’s natural frequencies that basically results in a synchronization of the beam’s bending and twisting frequencies. Specifically, the beam’s second bending frequency and torsional frequency coalesce, resulting in “self-induced flutter” of the beam. Complex aerodynamic effects ensure that the vibrations are self-sustaining, allowing for continuous energy harvesting.The researchers demonstrated the design using a flexible cantilever beam with a piezoelectric transducer, which they hung from the ceiling in a wind tunnel. They found that the amount of energy harvested depends on a combination of factors, including the wind speed and the angle at which the wind hits the beam. At a wind speed of 10 m/s and 5.4° angle, the method can harvest approximately 0.3 mW of power. Although the researchers plan to improve the power levels, even this small value can be used to power individual sensors, which, as Zakaria explained, have a wide variety of applications.”Future monitoring of different systems and platforms such as air and water systems, structures, vehicles, infrastructure, etc., as well as secure data transmission and reception from these sensors, will require the use of hundreds or thousands of sensors, data loggers and hardware components,” Zakaria said. “The ability to integrate energy harvesters within these sensors or data loggers to develop such self-powered instruments is very much needed to enable their use without the need to replace batteries on a regular basis.”In the future, the researchers plan to design even smaller beams with specific geometries and capabilities, as well as to improve the performance of the piezoelectric elements. 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)—In an attempt to harvest the kinetic energy of airflow, researchers have demonstrated the ability to harvest energy directly from the vibrations of a flexible, piezoelectric beam placed in a wind tunnel. While the general approach to harvesting energy from these “aeroelastic” vibrations is to attach the beam to a secondary vibrating structure, such as a wing section, the new design eliminates the need for the secondary vibrating structure because the beam is designed so that it produces self-induced and self-sustaining vibrations. As a result, the new system can be made very small, which increases its efficiency and makes it more practical for applications, such as self-powered sensors. Explore further
Bats in Sweden are generally welcomed because they eat destructive insects and tend to hide at night. But bats have a unique history in the country, as well, because Sweden does not have many caves—instead, most of the bats live in the warm towers and belfries of rural churches. But, the researchers suggest, a recent lighting trend has put the bats at risk, and their numbers are falling.Rydell has been interested in bats for many years—back in the 1980s, he conducted surveys of specimens living in 61 churches in southwest Sweden, making population charts. In this new effort, he and his colleagues revisited those churches along with 50 others, counting the number of brown long-eared bats.The researchers concluded that bat populations had remained stable in churches that lacked floodlighting. But in churches with such lighting, populations dwindled depending on how much lighting had been installed. In churches where floodlights were installed on all four sides of a building, there were no bats left at all.Installing floodlights, the researchers note, became popular over the past few decades as church staff sought to show off the unique architecture at night. The contrast of the usually stark white buildings lit against a deep black sky offers an inspiring visage, but, it also makes resident bats much more vulnerable to predation by owls, hawks and cats.The researchers note that bats are protected in Sweden—it is against the law to harm them, or even to disturb them. They suggest it is likely that most of the people involved in installing church lighting do not know that their efforts have caused problems for the bats. They suggest a partial solution—instead of installing lighting all the way around a church, leaving at least one side dark, preferably the side closest to trees. The bats will adjust and only roost on that side. 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)—A trio of researchers, two from Sweden and one from Spain has found that installing floodlighting around rural churches drives away roosting bats. In their paper published in Royal Society Open Science, Jens Rydell, with Lund University, Johan Eklöf, with Graptolit Ord och Natur and Sonia Sánchez-Navarro with Estación Biológica de Doñana-CSIC describe their comparison of church bat populations over the course of several decades. Winging it: How do bats out-maneuver their prey? Explore further Journal information: Royal Society Open Science Citation: Increased floodlighting reducing bat populations in Sweden’s churches (2017, August 9) retrieved 18 August 2019 from https://phys.org/news/2017-08-floodlighting-populations-sweden-churches.html Credit: CC0 Public Domain More information: Jens Rydell et al. Age of enlightenment: long-term effects of outdoor aesthetic lights on bats in churches, Royal Society Open Science (2017). DOI: 10.1098/rsos.161077AbstractWe surveyed 110 country churches in south-western Sweden for presence of brown long-eared bats Plecotus auritus in summer 2016 by visual inspection and/or evening emergence counts. Each church was also classified according to the presence and amount of aesthetic directional lights (flood-lights) aimed on its walls and tower from the outside. Sixty-one of the churches had previously been surveyed by one of us (J.R.) between 1980 and 1990, before lights were installed on Swedish churches, using the same methods. Churches with bat colonies had decreased significantly in frequency from 61% in 1980s to 38% by 2016. All abandoned churches had been fitted with flood-lights in the period between the two surveys. The loss of bat colonies from lit churches was highly significant and most obvious when lights were applied from all directions, leaving no dark corridor for the bats to leave and return to the roost. In contrast, in churches that were not lit, all of 13 bat colonies remained after 25+ years between the surveys. Lighting of churches and other historical buildings is a serious threat to the long-term survival and reproduction of light-averse bats such as Plecotus spp. and other slow-flying species. Bat roosts are strictly protected according to the EU Habitats Directive and the EUROBATS agreement. Lighting of buildings for aesthetic purposes is becoming a serious environmental issue, because important bat roosts are destroyed in large numbers, and the problem should be handled accordingly. As a start, installation of flood-lights on historical buildings should at least require an environmental impact assessment (EIA). © 2017 Phys.org
Citation: An example of plasmons directly impacting molecules (2018, May 10) retrieved 18 August 2019 from https://phys.org/news/2018-05-plasmons-impacting-molecules.html Excitation mechanisms for plasmon-induced chemical reactions. (A) Indirect hot-electron transfer mechanism. Hot electrons (e−) generated via nonradiative decay of an LSP transferred to form the TNI states of the molecule. (B) Direct intramolecular excitation mechanism. The LSP induces direct excitation from the occupied state to the unoccupied state of the adsorbate. (C) Charge transfer mechanism. The electrons are resonantly transferred from the metal to the molecule. Credit: Science (2018). DOI: 10.1126/science.aao0872 Plasmonics chips through better control of the directional excitation of plasmons in a gold grating Explore further Scientists continue to look for ways to make solar energy more efficient, such as photocatalytic devices based on plasmon resonance. Plasmons are, of course, oscillations of electrons near the surface of a material. They are relevant to solar energy applications because they can be triggered by photons. But how this process works is still under investigation. Prior research has suggested plasmon-excited reactions are due to high-energy electrons that are generated as plasmons decay. But in this new effort, the researchers found that it is possible to impact molecules directly using plasmons.The technique involved using a scanning tunneling microscope to observe a reaction caused by plasmon excitation. They pointed the tip of the microscope’s probe at a single molecule of dimethyl disulfide atop a metal base. The researchers noted that the molecule formed an elliptical protrusion as it sat in a plasmonic field. The team then shone light of different wavelengths on the molecule, which caused changes to the plasmons around it. Those changes, in turn, caused a change in the dimethyl disulfide molecule. It separated into two round protrusions. This, the researchers suggest, occurred because the plasmons had broken the bond holding the components together. They note that their technique is not consistent with the high-energy theory and suggest that the plasmons were actually absorbed by the molecule, which led to weakening the bonds that held it together.The team has plans to test their technique using other molecules to learn more about which sorts of reactions might occur. Their hope is that, unlike with their example, other reactions will not be constrained by special temperature and pressure requirements. Such conditions are assumed to be necessary for use in manufactured applications. A team of researchers from Japan, Korea and the U.S. has found a way to demonstrate an example of plasmons directly causing changes to a molecule. In their paper published in the journal Science, the group describes their technique and what they learned from it. Journal information: Science © 2018 Phys.org More information: Emiko Kazuma et al. Real-space and real-time observation of a plasmon-induced chemical reaction of a single molecule, Science (2018). DOI: 10.1126/science.aao0872 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.
Amor Fati (love of one’s fate), a show that exhibits digital works by Santosh Jain is being organised in the Capital. The show that opens today at Gallery Pioneer is curated by Niyatee Shindee. Jain’s work encompasses all the various strands of new media technologies. Her artworks display an exceptional degree of conceptual sophistication, hi-tech suave, social relevance and dexterous skills, all born through the computer screen, media technology being its riveting factor. The artiste’s work is strongly invested in the conceptual rather than the craft of making. Like all digital art, the work displays an enchanting etiquette. Also Read – ‘Playing Jojo was emotionally exhausting’All the works are attitudes in which one sees everything that happens in life, including suffering and loss, in a positive light. This philosophy resonates in Jain’s fearless attitude towards her life and her art. Her perceptive nature helps her photograph the often hidden yet honest stories of destiny, fate, despair and hope. Her works are a sensitive and empathetic portrayal of the various stages and seasons of life, with perseverance and hope emerging as an underlying metaphor. Also Read – Leslie doing new comedy special with Netflix‘I’ve always been exploring and experimenting with different art forms. With the camera and digital art, I feel I’ve finally found a language through which I can converse with people. I feel through this medium I’m now able to express what I feel inside with ease’, says the artiste.In the work Feline, the woman protagonist is present in eight roles. Either lounging or squatting or toothlessly grinning at the viewer, or lost in the domesticity of household chores or simply gazing into the distance very poetically, each are unique in their own worlds yet harmoniously bound by the scape with an expectant air. From My Attic series allows the viewer an intimate gaze into the artist’s life and surroundings and nudge him to examine closely held memoirs of stored experiences and feelings left in the recesses of the mind. These works display a meditative and transcendental quality.Choices, Dream Catcher and Chai Boy are chronicles of urban strugglers and survivors. While they showcase the realities of the downtrodden and demoralised, they are all laced with the phenomenon of hope and make the viewer sense the opportunity for the subjects to re-begin and re-build.Where: Gallery Pioneer, Lado SaraiWhen: On till 20 SeptemberTiming: 11 am till 7 pm
Singer Miley Cyrus has been vocal about her take on Taylor Swift’s work and now she has made her choice more clear by denying any chance of joining Swift’s bunch of friends.The Wrecking Ball hitmaker, who recently hosted the VMA’s said while Swift, 25,
No third child after the birth of two daughters and only Re 1 to be taken from the girl’s family by the groom were among a host of rulings given out by a Khap Panchayat in the town to discourage the practices of female foeticide and dowry.In an announcement that comes as a breath of fresh air as khaps are infamous for issuing orthodox diktats, Bura Khap’s head Rajbir Bura said that members in a meeting held on Sunday had decided to felicitate couples, who do not have a third child after the birth of two daughters and those who took no or only Re 1 as dowry from the bride’s family. Also Read – Punjab on alert after release of excess water from Bhakra damThe Khap has also put a limit on the number of members to be part of the bridegroom’s wedding procession at 21.“The decision was much needed as too many people constituting a ‘baraat’ puts unnecessary financial burden on the bride’s family,” the Khap head said.Bura said a decision to shorten the mourning period after a family member’s death from 13 to 7 days was also taken during the meeting. “It was also decided to end the old practice of not having wheat flour, pulses and ghee (clarified butter) during the mourning period.” Felicitating sportsmen, social activists and writers was also proposed during the meeting.