Month: August 2019
An image of Chlamydomonas used in the study. Credit: Surzycki, et al. © 2007 PNAS. Now, a team of biologists including Raymond Surzycki and Jean-David Rochaix from the University of Geneva, and Laurent Cournac and Gilles Peltier, both from the Atomic Energy Commission, the National Center for Scientific Research, and the Mediterranean University, have demonstrated a new method for hydrogen production by algae. In a recent issue of PNAS, the team presented a method using copper to block oxygen generation in the cells of Chlamydomonas reinhardtii that could lead to a consistent cycle of hydrogen production.In order to induce hydrogen production in the algae, cells must be placed in an environment without oxygen but with access to light. To completely deplete the algae’s oxygen supply, the researchers turned off part of a chloroplast gene required for oxygen evolution by adding copper to the cells in an enclosed chamber. Specifically, the addition of copper turned off the Cyc6 promoter, which drives the Nac2 gene, which is required for photosystem II (PSII) synthesis. PSII generates oxygen.Within about three hours, nearly all the oxygen was consumed by respiration, and the algae reached an anaerobic state. Without oxygen, the algae began to synthesize hydrogenase and then produce hydrogen.“Hydrogenase is an enzyme that produces hydrogen by combining electrons derived from the photosynthetic electron transport chain with protons,” Rochaix explained to PhysOrg.com. “It is only produced under anaerobic conditions because the photosynthetically produced oxygen is highly toxic to the hydrogenases.”One of the most significant differences between this method and earlier methods is using copper addition rather than sulfur depletion to repress photosynthetic activity. In past experiments, when the cells’ sulfur was depleted, the cells stopped growing and died after a few days. However, when adding copper, the biologists observed that the cells remained healthy. The rate of hydrogen production in the plants with copper was slightly lower than that of sulfur-depleted plants, but comparable.The scientists also observed that, in healthy cells, the Cyc6 promoter doesn’t stay repressed for long due to “anaerobiosis”—the ability of the cells to survive (and repair) with lack of oxygen. Subsequently, PSII activity is restored, and the cell returns to producing oxygen. What happens when you explode a chemical bond? Citation: Algae could generate hydrogen for fuel cells (2007, November 13) retrieved 18 August 2019 from https://phys.org/news/2007-11-algae-hydrogen-fuel-cells.html Explore further For several decades, scientists have known that certain species of algae can produce hydrogen in anaerobic conditions. More recently, researchers have been trying to take advantage of this ability to produce hydrogen that could be used by fuel cells to generate electricity—without expensive processes like electrolysis required for splitting water into hydrogen and oxygen. However, as the scientists point out, this apparent limitation may turn out to be an advantage, since the procedure could be repeated over and over again. Through the alternate expression and repression of the Nac2 gene, the researchers have opened up the possibility of establishing a cycling hydrogen producing system. “One unique feature of the Cyc6 promoter which we use for driving photosystem II synthesis is that this promoter is turned off in the presence of copper but partially switched on under anaerobic conditions,” Rochaix said. “As explained in our article, it is thus in principle possible to establish a cycling hydrogen production system without changing the growth medium in a single vessel. This is the major advantage.”The development of the Cyc6-Nac2 system for controlling chloroplast gene expression can be applied to any chloroplast gene, as the researchers further demonstrated in the study. The method could therefore help scientists investigate the roles of different plant genes in live cells and genetically modify plants, including modifying Chlamydomonas to increase hydrogen productivity.“We are still at a very early stage,” Rochaix said. “We need more basic research for understanding the complex regulation of photosynthesis, respiration and starch metabolism for establishing a more efficient system.” He explained that one option might be to establish a cycling system in which photosynthesis generates reducing power with starch, which can subsequently be used to feed the hydrogenase once anaerobiosis has been achieved. “Another strategy is to modify the hydrogenase by genetic engineering to make it more tolerant toward oxygen,” he said. “One might screen microorganisms in nature for the presence of oxygen-tolerant hydrogenases. The genes of these enzymes could then be introduced into algal cells and tested for hydrogen production under less stringent anaerobic conditions.” He added that several laboratories are making efforts along these lines.“The final challenge will be to produce bioreactors in which large amounts of algae can be grown with efficient hydrogen production,” he said. “It is too early to say whether we will be successful, but it is clearly important to undertake research on this problem given its great potential impact for clean energy production.”More information: Surzycki, Raymond, Cournac, Laurent, Peltier, Gilles, and Rochaix, Jean-David. “Potential for hydrogen production with inducible chloroplast gene expression in Chlamydomonas.” Proceedings of the National Academy of Sciences, October 30, 2007, vol. 104, no. 44, 17548-17553.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. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
Citation: Toshiba announces chip to boost TransferJet (2011, September 28) retrieved 18 August 2019 from https://phys.org/news/2011-09-toshiba-chip-boost-transferjet.html Explore further Consortium Established to Develop ‘TransferJet’ Wireless Technology (PhysOrg.com) — Toshiba earlier this week announced a wireless chip that can help carry TransferJet forward to wider use. The newly developed chip, “TC35420,” is designed to support the TransferJet near-field wireless transmission technology that has drawn interest over the past several years. Toshiba said that samples will start shipping at the end of January 2012 and mass production will begin around April to June of next year. The chip is the smallest and highest sensitivity TransferJet chip, according to reports.Toshiba’s press announcement notes that the chip’s reduced size makes it ideal for lightweight devices such as phones.TransferJet is a potential enabler of truly mobile, ubiquitous computing. Technology proponents have hoped to see TransferJet at work on a wide range of mobile devices such as notebook PCs, tablets, smartphones, along with digital cameras. Just last year, a report noted that short-range, high-speed TransferJet wireless data technology is represented by a lot of well-known companies, but so far its impact in the market has been limited.TransferJet provides high-speed data transfer with low power consumption simply by selecting on the screen of a mobile device the data file to be transferred and touching the receiving device with the mobile device.TransferJet is described as a Close Proximity Wireless Transfer technology. Touching two devices together brings about the transfer of files. Benefits are said to be a short transmission distance which minimizes risks of data theft and high-speed transfer of large data files. With such a device, it is possible to transfer data at a rate of 560Mbps maximum, but typically averaging 375Mbps. The TransferJet system can select the transmission rate depending on the wireless environment.Scenarios of what a consumer digital marketplace might be like with TransferJet as part of a lot of mobile gadgets are instantly fetching photo printouts, swapping online data with a friend, and hearing and buying music, with a tap-touch of your mobile device. This would work with kiosks, digital boards, and digital signs.The TransferJet Consortium was established in 2008 by companies wanting to grow an ecosystem of technology, products and services based on TransferJet wireless technology. The consortium focuses on specifications, compliance testing processes and tools, and promoting TransferJet. Along with Toshiba, companies in the group include Hitachi, Sony, Murata Manufacturing, and others. The TransferJet Consortium will show its latest developments in TransferJet technologies at CEATEC JAPAN 2011, from October 4 to 8. The group hopes to show applications such as sending photos to printers, and future concepts, such as downloading content from kiosks to smartphones and making use of book stores’ cyber shelves handling electronic versions of books for purchase. © 2011 PhysOrg.com More information: Press release 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 researchers who designed the transistor, led by Walter M. Weber at Namlab gGmbH in Dresden, Germany, have published the new concept in a recent issue of Nano Letters.“Synthetic nanowires are used to realize the proof-of-principle,” Weber told PhysOrg.com. “However, the concept is fully transferable to state-of-the-art CMOS silicon technology and can make use of self-aligned processes.”The new transistor’s core consists of a single nanowire made of a metal-semiconductor-metal structure, which is embedded in a silicon dioxide shell. Electrons or holes flow from the source at one end of the nanowire through two gates to the drain at the other end of the nanowire. The two gates control the flow of electrons or holes in different ways. One gate selects the transistor type by choosing to use either electrons or holes, while the other gate controls the electrons or holes by tuning the nanowire’s conductance.Using a gate to select p- or n-type configuration is quite different from conventional transistors. In conventional transistors, p- or n-type operation results from doping that occurs during the fabrication process, and cannot be changed once the transistor is made. In contrast, the reconfigurable transistor doesn’t use any doping. Instead, an external voltage applied to one gate can reconfigure the transistor type even during operation. The voltage causes the Schottky junction near the gate to block either electrons or holes from flowing through the device. So if electrons are blocked, holes can flow and the transistor is p-type. By applying a slightly different voltage, the reconfiguration can be switched again, without interfering with the flow.The scientists explain that the key to making this reconfiguration work is the ability to tune the electronic transport across each of the two junctions (one per gate) separately. Their simulations showed that the current is dominated by tunneling, suggesting that the nanowire geometry plays an important role in the ability for independent junction control. Because the reconfigurable transistor can perform the logic functions of both p- and n-type FETs, a single transistor could replace both a p- and n-type FET in a circuit, which would significantly reduce the size of the circuit without reducing functionality. Even at this early stage, the reconfigurable transistor shows very good electrical characteristics, including a record on/off ratio and reduced leakage current compared to conventional nanowire FETs. In the future, the researchers plan to further improve the transistor’s performance.“We are varying the material combinations to further boost device performance,” Weber said. “Further on, first circuits implementing these devices are being built. … The biggest challenge will be to incorporate the extra gate signals in the cell layout allowing flexible interconnection to the other transistors.” The reconfigurable transistor’s core consists of a nanowire structure embedded in a silicon dioxide shell. Electrons or holes flow from the source at one end of the nanowire through two gates to the drain at the other end of the nanowire. One gate is used to program the p- or n-polarity, whereas the other gate tunes the conductance through the nanowire. Image credit: ©Namlab gGmbH (PhysOrg.com) — Most of today’s electronics devices contain two different types of field-effect transistors (FETs): n-type (which use electrons as the charge carrier) and p-type (which use holes). Generally, a transistor can only be one type or the other, but not both. Now in a new study, researchers have designed a transistor that can reconfigure itself as either n-type or p-type when programmed by an electric signal. A set of these “universal transistors” can, in principle, perform any Boolean logic operation, meaning circuits could perform the same number of logic functions with fewer transistors. This advantage could lead to more compact hardware and novel circuit designs. Explore further Journal information: Nano Letters More information: André Heinzig, et al. “Reconfigurable Silicon Nanowire Transistors.” Nano Letters. DOI: 10.1021/nl203094h Panasonic Develops New Gallium Nitride Power Transistor with Normally-off Operation Copyright 2011 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. Citation: Universal transistor serves as a basis to perform any logic function (2011, December 20) retrieved 18 August 2019 from https://phys.org/news/2011-12-universal-transistor-basis-logic-function.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.
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. © 2012 Phys.Org Image (c) PNAS, doi: 10.1073/pnas.1121596109 Packing it all in for the holidays: Scientists see how many polyhedrons can fit into a box More information: Electrostatic precursors to granular slip events, PNAS, Published online before print June 11, 2012, doi: 10.1073/pnas.1121596109AbstractIt has been known for over a century that electrical signals are produced by material failure, for example during crack formation of crystals and glasses, or stick-slip motion of liquid mercury on glass. We describe here new experiments revealing that slip events in cohesive powders also produce electrical signals, and remarkably these signals can appear significantly in advance of slip events. We have confirmed this effect in two different experimental systems and using two common powdered materials, and in a third experiment we have demonstrated that similar voltage signals are produced by crack-like defects in several powdered materials. PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen (Phys.org) — A voltage signal preceding failure of bridges and other structures made of powder has been documented by three researchers in the Department of Biomedical Engineering at Rutgers University. Their findings, published on Monday in Proceedings of the National Academy of Sciences, are an important step forward. Citation: Rutgers granular-slip study documents voltage signals (w/ Video) (2012, June 12) retrieved 18 August 2019 from https://phys.org/news/2012-06-rutgers-granular-slip-documents-voltage-video.html Play Movie showing association between crack formation and voltage production in sheared powder. Video: PNAS, doi: 10.1073/pnas.1121596109 Outside of Rutgers, a doctoral candidate familiar with the electrification of granular systems noted that five seconds might not be meaningful to save people from an earthquake area but would be beneficial in a smart-grid setting in turning off technologies that might cause explosions or fires during a quake.The researchers at Rutgers performed several experiments before reaching their conclusions; they used different containers and different powders. Bleached and unbleached flour, plaster and mortar were tried and the team found the same results. Similar voltage signals are produced by crack-like defects in several powdered materials.Failure of these materials, in turn, may be preceded by telltale electrical signals. They speculate that similar voltage changes could be warning signs of internal defects or of impending catastrophic failures in objects made of consolidated powders.The authors acknowledge that electrical disturbances have been reported in the past to precede major earthquakes and rockbursts, but many of these reports have been anecdotal. At the same time, a growing body of field measurements will help other research efforts to more fully understand these events. “We anticipate that the ability to generate correlated electrical signals and slip events in a controlled setting will enable future research to unveil the mechanisms leading to the curious effects.”Prof. Shinbrot says a better understanding of the particles’ electrical interactions may enable technologies that predict breakages before they cause catastrophic damage. Journal information: Proceedings of the National Academy of Sciences Explore further Play Movie showing association between defect formation and subsequent slip events in tumbled powder bed. Video: PNAS, doi: 10.1073/pnas.1121596109 The authors of the paper, ”Electrostatic precursors to granular slip events,” are Troy Shinbrot, Nam H. Kim, and Nirmal Thyagu, and they discuss their results from lab tests on powders. They documented a voltage signal. They studied how clumps of fine particles emit electrical voltages just before they crack. Pulling powders apart seems to produce a voltage.Shinbrot and his study team studied scoops of finely ground Tylenol in a slowly-spinning cylinder. Powder stuck to the sides, built up, and after reaching a certain height, cracked and tumbled down to the bottom. The “mini avalanches” created voltages higher than 100 volts. They discovered that the voltage spike sometimes preceded the avalanche by as much as five seconds. The authors note that “it has been known for over a century that electrical signals are produced by material failure, for example during crack formation of crystals and glasses, or stick-slip motion of liquid mercury on glass.” They say that slip events in cohesive powders also produce electrical signals, and that these signals can appear significantly in advance of slip events. Key structural materials—ceramics in turbines, chalk in cliffs, and concrete in bridges—are made from powders; a voltage spike might precede cracking in these structures.
Citation: Towards a global quantum network: Photoelectron trapping in double quantum dots (2013, July 31) retrieved 18 August 2019 from https://phys.org/news/2013-07-global-quantum-network-photoelectron-dots.html Journal information: Physical Review Letters © 2013 Phys.org. All rights reserved. More information: Nondestructive Real-Time Measurement of Charge and Spin Dynamics of Photoelectrons in a Double Quantum Dot, Physical Review Letters 110, 266803 (2013), doi:10.1103/PhysRevLett.110.266803 Researchers entangle a single electron spin to a single photon in a quantum dot Explore further (color online). (a) A scanning electron micrograph of the typical lateral DQD device. The surface gates for dot formation have Tið10 nmÞ=Auð20 nmÞ metal thickness. A 60 nm thick Al2O3 insulating layer was formed on top of them by atomic layer deposition. (b) A Tið30 nmÞ=Auð220 nmÞ mask was fabricated on the surface above the DQD with an aperture of 400 nm diameter. (c) Band profile of the HEMT structure. The excitation laser energy is tuned just above the GaAs band gap. The excited electron-hole pair is separated due to the intrinsic electric field. Copyright © doi:10.1103/PhysRevLett.110.266803 To successfully address these challenges, Fujita explains, the scientists relied on a small number of key insights and innovations. “A significant innovation was to introduce an additional infrared laser beam so that persistent photoconductivity would be erased. This was an innovative scheme because it made it possible to continuously experiment with photon irradiation single-shot single photon detection and obtain series of data.” Another technique, he continues, was to form different kinds of charge sensors to improve the signals in DC measurements.Several other interesting results were achieved in this study, one being that the researchers’ approach offers a novel method to study the multielectron dynamics which are strongly affected by the Coulomb interaction in a multidot system. “Photoexcitation can create multiple electrons within the pulse duration, and the excited spins depend thoroughly upon the incident polarization,” Fujita points out. “This allows initialization of multiple spins and multiple coupled dot experiments.”The demonstrated results can also be regarded as excited state spectroscopy, in that they correspond to a spin excitation over the ground state of the dot, which is an excited state. “Excited states reflect the configuration of the quantum dot which could be modified by tuning the gate voltages,” Fujita notes. “Using our scheme we can investigate energy and spin correlations of excited states using photoelectrons through interdot interactions.”The paper also reports that fast initialization of the excited states can be realized by controlling the incident photon number, energy, and polarization. “Photon number could be tuned with the laser power, energy with the wavelength, and spin polarization with the photon polarization,” Fujita explains. “The photon configurations are tuned in the optics and excitation could be realized fast within the laser pulse width. If we compare this with electrical initialization by tunneling from the leads, the initialization time is limited by the tunneling rate and exact spins are currently difficult to inject.”Using the resonant interdot tunneling in the DQDs, the researchers’ technique would also open a way to high fidelity photon counting. “Our technique to keep the photoelectrons from escaping is an advantage for counting multiple photoelectrons,” Fujita says. “We’ve shown that tunneling rates could be properly tuned in a desired range. This enables us to tune the tunneling of each electron number to a good tunneling rate so that every electron tunneling could be resolved and give us a higher fidelity.”Fujita also comments on the relationship between their findings and the no-cloning theorem, which he points out holds that quantum communication becomes perfectly safe – but on the other hand, there’s also no way to amplify a quantum state to extend the communication length. This therefore restricts the length of quantum information transfer with a single photon. “Quantum repeaters would shorten each photon propagation,” Fujita notes, “thus making it possible to connect between more distant places – and we’ve demonstrated a scheme that brings us closer to the realization of a quantum repeater.”More specifically, in the current study a quantum repeater is shown as a solution for extending the quantum communication length. “We think our demonstrated nondestructive single-shot single photon detection in lateral quantum dots is a good candidate for one of the ingredients of this repeater,” Fujita tells Phys.org. “In the future it could realize determination and storage of the arrived photons to immediately create entanglement at its convenience to raise the entanglement creation rate. Further integration of quantum operations in our quantum dot would possibly move the establishment of information network forward, and thereby impact the establishment of a global quantum information network.””We’ve demonstrated the detection of photoelectron spin configuration using two electron spin correlation, namely the spin blockade, so next we’ll detect single photoelectron spin by correctly initializing the prepared spin.” Fujita adds. “Our next step is to combine our photoelectron spin detection scheme with heavy hole excitations to verify angular momentum transfer,” In terms their continued research, Fujita says that the researchers would like to verify the angular momentum transfer to the electron spins. “This requires selective excitation of electron hole spin states, so a wavelength-tunable single shot irradiation setup is needed. Another development,” he continues, “would be to increase the photon absorption rate at a scale that would permit realizing sufficient entanglement between photons and electron spins.” The scientists are also thinking of embedding Bragg reflectors inside the wafer.Over the next decade, Fujita continues, their research would lead to the entanglement between distant solid state qubits by trapping entangled photon pairs. “After the verification of coherent angular momentum transfer, experiments on trapping entangled photon pairs will be demonstrated to verify the entanglement between photons and electron spins. The advantage of our lateral quantum dot is that 2-spin qubit operations could be done,” Fujita concludes. “This will be then demonstrated in two trapped photons to create entanglement between distant entangled photon pairs.” Recently, however, scientists at The University of Tokyo, Princeton University, Ruhr-Universität Bochum, and RIKEN found that nondestructive measurement is feasible using gallium arsenide double quantum dots (DQDs), thereby taking a significant step towards long distance entanglement distribution. Moreover, the importance of using a lateral dot is that these have a possibility to store and manipulate the photoelectrons – and while previous studies show detection of photocurrents or photoelectron signals, the scientists state that to their knowledge, none of them performed experiments demonstrating the possibility of further photoelectron storage or manipulation. Lastly, although the researchers have not yet demonstrated the spin manipulation of photoelectrons, their double dot structure shows repetitive tunneling of single photoelectrons, and so satisfies the photoelectron spin manipulation condition.Researcher Takafumi Fujita discussed the research he, Prof. Seigo Tarucha, and their colleagues conducted with Phys.org. “The main challenge in demonstrating the trapping of single photons and interdot tunneling of the photogenerated electrons in a nondestructive manner using double quantum dots was to stabilize our quantum dot while performing single-shot single photon detection experiments,” Fujita tells Phys.org. “Conventional lateral quantum dot devices can change their condition upon irradiation. We had to fine-tune and maintain the resonant interdot tunneling condition while performing irradiation experiments. The photon responses do not recover immediately so repetition of the irradiation sequence also had to be tuned to wait for photoconductivity to relax.”Regarding the use of resonant tunneling, Fujita explains, the idea of using a double dot was to use spin blockade, but the researchers also had to clearly distinguish photoelectron trapping signals from the noise. Rather than using a single-step signal – which can be difficult to distinguish in photon irradiation measurements – they decided to use iterative bi-stable charge tunneling signals in the double dot to clearly discriminate single photoelectron trapping events from noise. “With iterative bi-stable charge tunneling to determine the number of trapped photoelectrons,” Fujita adds, “we had to wait in order to be certain that there were no other electrons left in the dot. However, we found that the resonant interdot tunneling would give us an immediate response of the last remaining electron.” In addition, says Fujita, to infer photoelectron spin states, the scientists thought that they needed a large number of data samples – but once again, interdot resonance proved to be an advantage. (Phys.org) —While the journey from today’s fledgling quantum computers to a global quantum information network may seem daunting, researchers are continually, and at an accelerating pace, making progress towards that goal. One key element essential to that progress is the transfer of quantum information between single photons and solid-state quanta – and the properties of semiconductor quantum dots (QDs) make them excellent candidates for photon-electron quantum coupling. One historical stumbling block has been that although quantum circuits require nondestructive transfer between separate dots, using single QDs usually fails due to destructive transfer in which photoelectrons are immediately lost upon measurement. 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.
Although an increasing number of transient astronomical events in the centers of galaxies are being discovered by surveys like the Optical Gravitational Lensing Experiment (OGLE), such phenomena are challenging to detect and study. Given that transients could be explained by various violent deep-sky events, including supernovae, gamma-ray bursts, or tidal disruption events (TDEs), finding new ones is important to better understand their origin.In a recently published paper, astronomers led by Mariusz Gromadzki of Warsaw University Astronomical Observatory in Warsaw, Poland, reports the finding of a peculiar nuclear transient event in the nucleus of the galaxy GALEXASC J015624.70-710415.8, some 680 light years away from the center of the host. OGLE17aaj was detected by the OGLE-IV Transient Detection System in January 2017 and follow-up observations of this transient were performed subsequently using various ground-based and space telescopes.”We report on the discovery and follow-up of a peculiar transient, OGLE17aaj, which occurred in the nucleus of a weakly active galaxy,” the paper reads.The researchers revealed that OGLE17aaj was detected at a host-subtracted I-band magnitude of about 21.0 and reached an I-band maximum magnitude of 20.0 in about 60 days. Afterward, the transient declined for about 200 days and appears to have reached a plateau. The estimated peak absolute magnitude of OGLE17aaj in the I-band was found to be 18.8.Results from ultraviolet measurements of OGLE17aaj follow the trend seen in optical observations. The astronomers noted that at maximum, the transient reached a magnitude of 19.06, and 18.52 on galaxy-subtracted images from NASA’s Swift space telescope.Moreover, the scientists calculated the lower limit on the total energy emitted by OGLE17aaj until now. This value is at a level of approximately 7.0 sexdecillion ergs, what corresponds to a lower limit of the accreted mass of about 0.04 solar masses.The authors of the paper suppose that OGLE17aaj may be a TDE, taking into account its properties, such as: a long rise time, lack of color-temperature evolution, and high black-body temperature. In general, TDEs occur when a star passes fatally close to a supermassive black hole, and is pulled apart by the black hole’s tidal forces.However, narrow emission lines and slow post-peak evolution of the transient, disfavor this hypothesis.”We investigated it as a potential TDE candidate based on its high black-body temperature and on the similarity of its spectrum to that of the recently reported nuclear event in F01004-2237, which was interpreted as a TDE. (…) OGLE17aaj showed a well-covered 60-day-long rise and a slow 200-day decline, followed by a plateau until day 300. This is unlike any TDE reported so far,” the astronomers concluded. Upper panel: Host-subtracted photometry of OGLE17aaj in the OGLE-IV I and V bands and the Swift UVW1 and UVW2 bands in absolute magnitudes as a function of days since maximum. Lower panel: Temperature evolution derived from Swift ultraviolet data over the same period. Credit: Gromadzki et al., 2019. More information: M. Gromadzki et al. Discovery and Follow-up of the Unusual Nuclear Transient OGLE17aaj. arXiv:1901.03718 [astro-ph.HE]. arxiv.org/abs/1901.03718 © 2019 Science X Network Rapid ‘turn-on’ of a nuclear transient observed by astronomers Explore further Citation: Astronomers discover an unusual nuclear transient (2019, January 23) retrieved 18 August 2019 from https://phys.org/news/2019-01-astronomers-unusual-nuclear-transient.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. An international group of astronomers has detected an unusual nuclear transient in the nucleus of a weakly active galaxy. The new transient was identified by the OGLE-IV Transient Detection System and received designation OGLE17aaj. The finding is reported in a paper published January 11 on the arXiv pre-print repository.
More information: Yashpal Bhulla et al. AstroSat observation of GX 5-1: Spectral and timing evolution. arXiv:1903.11986 [astro-ph.HE]. arxiv.org/abs/1903.11986 X-ray binaries consist of a normal star or a white dwarf transferring mass onto a compact a neutron star or a black hole. Based on the mass of the companion star, astronomers divide them into low-mass X-ray binaries (LMXB) and high-mass X-ray binaries (HMXB). When X-ray light from these objects flickers about certain frequencies, such behavior is known as quasi-periodic oscillations (QPOs). Although many questions about the phenomenon of QPOs remain unanswered, it is believed that they occur when X-rays are emitted near the inner edge of an accretion disk in which gas swirls onto a compact object, for instance, a neutron star or a black hole. Astronomers hope that these oscillations could advance our knowledge the innermost regions of accretion disks.Located near the center of the Milky Way galaxy, some 29,300 light years away from the Earth, GX 5-1 is the second brightest persistent LMXB harboring a neutron star. In February 2017, the binary was observed by the AstroSAT spacecraft – India’s first dedicated multi-wavelength observatory.These observations, using AstroSAT’s Large Area X-ray Proportional Counters (LAXPC) and Soft X-ray imaging Telescope (SXT), allowed a group of astronomers led by Yashpal Bhulla of Pacific Academy of Higher Education and Research University in Udaipur, India, to detect QPOs in GX 5-1 and to collect important data regarding this object.”We present the analysis of an AstroSAT observation of the Z-track source GX 5-1. We used the strictly simultaneous SXT and LAXPC data to track the spectrum of a neutron star source as it moves along its Hardness intensity diagram (HID) and at the same time quantify the rapid temporal variability of the source,” the astronomers wrote in the paper.The observations found that the power spectra of GX 5-1 show a strong QPO whose frequency changes from around 30 to 50 Hz. It was also found that time-lags between high and low energy photons are less than a few milliseconds, and that the QPO frequency increases, while its root mean square (r.m.s) decreases with disk flux ratio.According to the study, these results suggests that the detected QPO originates in the thermal Comptonized component and it weakens when the component is less dominant.”The results suggest that the spectral properties of the source are characterized by the disk flux ratio and that the QPO has its origin in the corona producing the thermal Comptonized component,” the paper reads.The researchers concluded that more studies of GX 5-1, especially a detailed radiative modeling of its energy could be much helpful providing more details about the origin of QPOs in this system. Using the AstroSAT spacecraft, Indian astronomers have observed the low-mass X-ray binary designated GX 5-1. The observations were published March 28 on the arXiv pre-print repository. The authors report the detection of quasi-periodic oscillations in this binary and discuss its nature. © 2019 Science X Network Background subtracted light curve of the GX 5-1. The time bin is 2.3778 seconds at the SXT time resolution. The vertical lines mark the regions from which strict simultaneous spectra were obtained. Credit: Bhulla et al., 2019. Citation: AstroSAT observations reveal quasi-periodic oscillations in the X-ray binary GX 5-1 (2019, April 4) retrieved 18 August 2019 from https://phys.org/news/2019-04-astrosat-reveal-quasi-periodic-oscillations-x-ray.html Millisecond pulsar PSR J0740+6620 has a white dwarf companion with helium atmosphere, study suggests 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.
She loves her Italian, she’s loved it since she was a child and that is exactly what super-chef Ritu Dalmia makes her Diva restaurant in GK 2 all about. ‘I serve what I like to eat,’ she says simply and one of the first questions she throws at me when I sit down in – ‘Do you cook?”I don’t,’ I say with a little hesitation, wondering if I will be pulled up for not trying one of the recipes from her latest book Diva Green. Surprisingly, she is elated! ‘I have great respect for people who don’t cook,’ says Dalmia. ‘I am a restaurateur, people who don’t cook help me run my business,’ she explains. Also Read – ‘Playing Jojo was emotionally exhausting’ ‘I am going to take a break from television for now,’ she puts in as she moves on to talk about what made her love Italian food. Her show Travelling Diva is all set to air it’s last season. A school trip to Italy is what changed the world for her. The homemade pasta in fresh tomato sauces and the bruschettas is what made her fall in love hook, line and sinker. And a few years later, that passion took form of a restaurant in Hauz Khas. Further down the line, she sits happily in Diva and surveys her other restaurants in the city ( Also Read – Leslie doing new comedy special with NetflixLatitude 28 and cafe at the Italian Embassy, clearly there’s no looking back. She chats happily about Bengali cuisine – ‘They don’t eat like we do,’ she says, ‘Bengalis know how to eat, they take their time with food,’ she adds giving a slow-eater like me an excellent excuse. Dalmia has big plans for 2013. From a book that will bring together different cuisines from households that have inter-cultural marriages to another that is about Asian food. Another restaurant is also on the list. ‘The research for the book has already begun and I am going to give it two years…all my books roughly took two years to get into shape, this one might take longer,’ she says adding that she has already singled out families who are going to be a part of her pet project. Diva Green explores vegetarian food, Dalmia says that vegetarian food is very close to her heart. Born in a Marwari family, she took to cooking early, ‘My mother cannot cook,’ she says. ‘I learned more outside school, hands on, than I did from classrooms,’ she says and that in the trade of being an ace-restaurateur, is perhaps the best thing. From opening up the minds of Delhiites to the pleasures of Italian food to witnessing the culture of eating out changing over time, Dalmia has come a long way and she is in no mood to stop. And we shall gladly tuck in!
Bollywood music is an intrinsic part of every Indian’s life. Combining it the larger than life production values, special effects, graphics, dancers, singers, and DJ’s will give it a complete new twist and create unique live entertainment experience for the massive bollywood music fans across the globe. The BollyBoom festival is a scintillating blend of music, dance and entertainment. scheduled to be held in the capital on 24 November. One out of every 6 people on the planet is an Indian, and bollywood music is an integral part of his life. Bollywood music has also grown in popularity and acceptance beyond the Indian population. There is a huge untapped market out there for ‘bollywood dance music’. Also Read – ‘Playing Jojo was emotionally exhausting’Sonu Nigam, Salim Suleiman, and Talat Aziz have been working relentlessly to create this new magic and will present their creations to the world at the first edition of BollyBoom at Delhi.’The Indian music scene has undergone a huge change in the past few years and electronic dance music has emerged as one of the most popular genre of music in India courtesy properties like Sunburn which have contributed immensely in bringing in this change. EDM has a huge fan following and appeal to the youth population globally. Also Read – Leslie doing new comedy special with NetflixBollyBoom will set a new benchmark in live entertainment event industry and will appeal to a larger section of people in India as well as globally,’ concluded Sonu Nigam. The music will be a blend of Trance,House,Synthetic, Pop, Club Music,Techno, Trance, Hardstyle and Dubstep, among others. The concerts will have state of the art technology which will play an important factor in enhancing the music lovers experience and making them sway away to the tunes. There will be an infusion of electronic beats that will take the Bollywood music to yet another level.
How would you assess the impact of Ebola in the entire African region, particularly the 3 most affected countries?Ebola outbreak was declared in March 2014, but Indian media did not do much at the time, although I tried to reach out. Media around the world put my country or our three countries in the spotlight. Anyway now everyone knows what’s happening in my country. In fact Ebola fever epidemic killed nearly more than 5,000 and infected close to 10,000 in the the countries- Guinea, Sierra Leone and Liberia. And all those three countries are located in the West African region, so that deadly fever has affected the human relationship, and it has affected the country, the trade, it has affected all the activities in the country. Also Read – FM favours cess over additional tax for compensating statesIn West Africa, we belong to the community called Economic Community of West African States (ECOWAS) where there is no requirement of a visa, if you want to travel from one country to another. Therefore, there is free movement of people and free movement of goods as well. So those three countries are neighboring countries and can see how people are willing to move freely from one country to another. We used to do that, it is more or less the same, just that people have been divided into three territories. It is not easy to control the border. Ebola’s impact has been on every single aspect of human life in the country. It has changed even the way people are behaving. For instance in our country we greet people by a handshake. And today due to the Ebola scare, people are not shaking hands, even blood relations. Also Read – Indian eves lose to NZ in four-nation series openerThis disease has changed the way of life in these three countries. Thanks to the international communities including India, I feel that now it is under control and I was reading a report that said that from next week some vaccines will be available and they will start experimenting. We were supposed to organise the African Cup of Nations. A big soccer event that periodically takes place in Africa. Morocco was supposed to host the event but now the soccer authorities in the country are looking for other countries to host the event for Africa. Similarly, many international conferences that were supposed to take place in Africa have been postponed. Even here in India we were supposed to have the third edition of the African India Forum Summit but it has been cancelled due to the breakout of Ebola. So basically this is my assessment, not only it has affected the three countries but the whole sub region as a whole. Tell us about its impact on your country?As far as my country is concerned, the latest statistics which came out yesterday, show that 1,659 people have been infected and 966 have died. The rate of mortality is nearly 58.2 per cent including medical personnel. 94 of the medical staff have been infected and 43 have died. So the rate is nearly 46.23 per cent- which is a lot!What are the steps the government or people are taking to control the disease?Lack of awareness is the main issue. We have to convince the population as a whole that this disease is curable although there is no vaccine yet, to cure. The main steps we have taken is the awareness campaign and which involves all the leadership, all political and religious leaders, the civil servants and the national bodies are involved in the fight. So today, according to statistics, the scope is now decreasing and is stablising. There are no more new infections. This happened because of what the leadership did in the country. They increased the awareness campaign and told people what to do, what not to do, why to wash hands and what to do incase someone is affected- quickly to be taken to a treatment centre. And whoever that person has contact with has to be followed too, medically speaking. So that’s what the country has been doing, and we have received a lot of support from WHO, from France, from USA, from China, from India, from Canada and from so many countries around the world. So in the near future, before the end of the year, we are hoping to receive a good signal from my country. You see for instance, I was reading from the newspaper that Liberia has waved the state of emergency for medical reasons. That state of emergency has been waved to allow people to move freely because they have assessed that the infection rate is stable and people more and more are understanding that yes the disease is curable – if you go early to the treatment centre, but if you stay home, you wont be cured and you will infect the people surrounding you as well. So that is what we have been doing, I feel that the campaign has been successful.You mentioned that your country has received tremendous response from countries all over the world. Please elaborate.Yes. From Asia: China, India and Malaysia ahve contributed trmemdously. India contributed up to 12.5 million USD to WHO and which has directly affected countries. And China did a lot as well- they sent logistics, money and even sent personnel. But even while we are talking about some countries making contribution I can’t call it absolute, it is just an overview. From west, France is on the front line. France is even establishing a hospital in one of the affected areas and the French foreign minister is in Guinea since yesterday as we speak. USA has done a lot, they have sent 3,000 trucks to Monrovia in Liberia. United Kingdom, Germany, Netherlands have sent money. Its a concern for everybody in the world as we have seen some cases in USA and also in Spain. People are travelling. People make contact and we cannot stop that. This deadly disease has to be fought strongly. Developing countries are suffering because the health infrastructure is too poor as compared to the developed countries you. So it is a huge cause for every one. And I really appreciate the contribution made by the whole world to fight the disease. And I am sure that in the near future, we will find the appropriate drug to eradicate it completely.Can you please share with me, how do India and Guinea engage with each other. What kind of relationship do they have with each other?I think that should have been the first question. Of course, India and Guinea are friendly countries. They share lot of things in common. Because they are all independent states and they belong to so many international organisations for instance United Nations, Non Aligned Movement and other organisations around the world, so the relationship has enough strategy and history behind it too. India was the first country to open its diplomatic mission in Guinea. Until 1988, India had an embassy in Conakry but for some reason it was closed down and currently your embassy in Cote D’Ivore, is taking care of Guinea.As far as development is concerned, India has been funding so many projects in Guinea, in the sector of power (energy). India has been providing funding for the transportation sector. We have more than 100 buses from TATA. Since I am here, we will be working together. India will be funding up to $35 million in the sector of strengthening our health system and nearly $60 million in the sector of agriculture. Some projects are on in the sector of food processing, in providing fertilisers for agriculture, in providing machines for agriculture. In the sector of education we have some students here. When it comes to international affairs and international issues, we support each other. So far we have upto 12-15 students studying in universities and high schools in India. And the number will be increasing as India is allocating every year, scholarship platforms for students from the 8th to the 12th standard. Although as countries, we use different languages, it is not a barrier. I feel that basically as a developing country, India, being one of the largest democracies in the world has inspired so many countries in Africa including Guinea.