Searching for a singleelectron source of standard quantized current

first_img Citation: Searching for a single-electron source of standard quantized current (2008, August 14) retrieved 18 August 2019 from https://phys.org/news/2008-08-single-electron-source-standard-quantized-current.html Some, though, believe that it is possible to revive the idea of a standard quantized current. Averin, a scientist at Stony Brook University, in Stony Brook, New York, worked with a team led by Jukka Pekola at the Helsinki University of Technology in Finland to develop a new source of quantized current based on a hybrid single-electron transistor. “Using a simple structure that has been overlooked, we are revising an old discussion,” Averin says.Single-electron devices remain popular subjects of study as science and technology continues to shrink ever smaller. Understanding current quantization is an important step in the development of single-electron devices for metrology. In the work reported in Physical Review Letters: “Nonadiabatic Charge Pumping in a Hybrid Single-Electron Transistor,” Averin and Pekola present a theory of a pumped hybrid single-electron transistor which they hope will further the development of the quantum standard for electric current.Already, there are standards for quantized (limited by quantum mechanical rules) voltage and resistance. “But there is not an explicit quantum standard of current,” Averin explains. “A standard on quantized current would help us close the metrological triangle: Current is related to voltage, which is related to resistance, which is related back to current. This is important from a fundamental physics point of view.”Averin and Pekola speculate in their paper that a controlled manipulation of individual electrons in a hybrid transistor could be the key to a quantized current that is up to metrological standards. The hybrid single-electron transistor is one that involves tunnel junctions between normal metal and superconductor, and can be operated as charge turnstile. “We pump electrons for a certain time, and count how many are pumped. It is a simple structure, and there is hope of a larger amount of current from such structure.”Right now, the pumping idea for the hybrid transistor device has been tested only in a few first experiments. “Pekola’s team in Finland is working on this,” Averin says. “Developing such a transistor as a metrological device would take some time, but there is a basis for trying to improve the accuracy of current quantization.”“The point of this particular paper was to see whether, in principle, this device would be capable of reaching a level of precision sufficient from a metrology point of view,” Averin continues. “And, in principle, this pumped hybrid transistor should be capable.”In the end, Averin hopes that this work will lead to a single-electron quantum current standard, and one that can contribute to the understanding of fundamental physics. “With a metrological current standard, it would allow us to see whether the definitions of electric quantities we have in physics are consistent.”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. (PhysOrg.com) — “More than fifteen years ago, efforts were made to come to some kind of practical and standard realization of single-electron sources of quantized current. However, it was too difficult to combine the wanted magnitude of current with its accuracy,” Dmitri Averin tells PhysOrg.com. “The higher the current, the lower the accuracy.”center_img This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

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Crows demonstrate their cleverness with tools w Video

first_imgNew Caledonian crow. Russell Gray talks about New Caledonian crows and cognition. Wild crows reveal tool skills Sam’s successful first trial Lead author of the research, published in the Proceedings of the Royal Society B, was Dr Alex Taylor. He said finding the birds could solve a problem requiring two new behaviors was “incredibly surprising,” even though crows and related birds have been studied for decades because of their intelligence. The experiments showed the performance of the birds in solving the problem was consistent with a thought process — tools can be used to retrieve unreachable objects — rather than a process of trial and error and learning from mistakes. More information: Complex cognition and behavioural innovation in New Caledonian crows, Alex H. Taylor et al., Proceedings of the Royal Society B, Published online before print April 21, 2010, doi:10.1098/rspb.2010.0285Earlier story: Crows can use ‘up to three tools’ – www.physorg.com/news168701856.html © 2010 PhysOrg.com Investigations into the abilities of the New Caledonian crow (Corvus moneduloides) revealed the birds can create tools out of unfamiliar materials, and they can also use several tools in succession. The scientists, led by Professor Russell Gray from the University of Auckland, captured seven wild crows and placed them in an aviary where they were presented with a complex problem in which meat was placed out of reach. It could be drawn out by a long stick, but the stick was out of reach inside a barred toolbox. The long stick could be retrieved using a short stick, but this was attached to a string tied to a branch. So to win the treat, the birds had to first pull up the string to retrieve the short stick, then use the short stick to pull out the long stick, and then use the long stick to draw out the meat.The crows were split into two groups. Birds in the first group were allowed to try out every step in the problem before being presented with the complete task. All the birds in this group succeeded in the multi-stage task on their first attempt.Birds in the second group were shown situations in which food was attached to a string and where sticks could be used to reach food, but they had never experienced a situation in which one tool was used to collect another. Even so, the birds in this group also succeeded in reaching the food in the multi-stage task, although two of them took three or four attempts before they succeeded. One of the birds (nicknamed Sam) spent the first 110 seconds simply inspecting the parts of the task, and then completed it the first time without error. Another (Casper) found the string puzzling, but also completed the task on the first attempt. 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. Citation: Crows demonstrate their cleverness with tools (w/ Video) (2010, April 22) retrieved 18 August 2019 from https://phys.org/news/2010-04-crows-cleverness-tools-video.html (PhysOrg.com) — New Zealand scientists studying New Caledonian crows have found they can use three different tools in succession to gain a food treat. The crows are known to solve problems and fashion and use tools in the wild, but their clevernes and innovation in the experiments astounded the researchers.last_img read more

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Using DNA to assemble a protein lattice

first_img Journal information: Proceedings of the National Academy of Sciences Biotech materials made simple—crystal structures altered by a single protein © 2015 Phys.org One group has accomplished a proof-of-concept experiment for making a protein superlattice. Jeffrey D. Brodin and Evelyn Auyeung, working with Professor Chad A. Mirkin at Northwestern University have devised a general strategy for making a protein lattice out of one or two different proteins and out of a combination of proteins and gold nanoparticles. Their research is reported in The Proceedings of the National Academy of Sciences.Dr. Mirkin of Northwestern University spearheaded research on spherical nucleic acids (SNAs), a form of DNA his group discovered in 1996, in which a nanoparticle is functionalized with DNA via a covalent bond. The DNA creates a “shell” around the nanoparticle and displays unique properties compared to its linear counterpart. In this current research, Dr. Mirkin’s group developed a new strategy for functionalizing enzymes with DNA. For this proof-of-concept procedure, they used two well-known catalases, bovine catalase and corynebacterium glutamicum (Cg) catalase, to serve as their core particle, analogous to the gold nanoparticle in their SNA gold nanoparticle structures. These proteins catalyze hydrogen peroxide (H2O2) decomposition with a known kinetic profile, so they serve as good model systems for comparison studies. The first step was to attach oligonucleotides onto the surface of the catalases. Both catalases have surface-accessible amines that were converted to azides using a procedure that was optimized to preserve the structure and function of the protein while maximizing the number of functional amines. Oligonucleotides were then added to the azide-modified catalases using copper-free click chemistry, a biologically inert cycloaddition procedure. Ultraviolet-Visible (UV-Vis) spectroscopy showed that the density of oligonucleotides on the catalases was 30 to 50 pmol/cm2. Dynamic light scattering confirmed a shell-like structure of oligonucleotides radiating from the protein core, similar to its nanoparticle counterparts. Characterization with UV-Vis and circular dichroism confirmed that the functionalized catalases maintained their native structures. Reaction studies, monitored with UV-Vis, confirmed that the functionalized catalases had an intact active site that maintained its ability to catalyze H2O2 decomposition. Citation: Using DNA to assemble a protein lattice (2015, April 2) retrieved 18 August 2019 from https://phys.org/news/2015-04-dna-protein-lattice.html Explore further More information: “DNA-Mediated engineering of multicomponent enzyme crystals” Jeffrey D. Brodin, PNAS, DOI: 10.1073/pnas.1503533112 The next step was to see if these functionalized proteins formed lattices similar to the SNA gold nanoparticle body-centered cubic lattice structure. They tested two different types of systems. One system contained both of the functionalized catalases in a 1:1 ratio. The other system had a functionalized catalase and spherical nucleic acids with a gold nanoparticle core similar in size to the catalase.To promote lattice formation, the systems were heated to above the melting point, but below the point of denaturing the catalase. They were allowed to cool at a specific rate that was determined in prior studies in which crystallization was optimized. X-ray scattering revealed that all four possible systems (Cg catalase, Cg and bovine catalase, Cg and functionalized gold nanoparticles, and bovine and functionalized gold nanoparticles) showed CsCl-like lattice packing. While the lattices composed of proteins and gold nanoparticles showed the expected scattering patterns, the CsCl-like packing of lattices composed of identical proteins suggests that each catalase is surrounded by eight neighbors, but that the surface chemistry as well as the shape of the catalase impose distinct orientations of proteins at each lattice position.Importantly, lattice formation was not based on the catalase’s chemical make-up or other non-specific interactions, but on complementary oligonucleotides directing the assembly of the catalases into lattice structures. The final step was to confirm that even in a lattice structure, the catalases maintained their functionality. The Cg lattice was used to catalyze the decomposition of H2O2. Kinetic studies showed that the reaction was still first-order with respect to H2O2 concentration, but that the reaction was slower by a factor of 20. This is most likely due to the molecular diffusion into the lattice structure. Furthermore, the catalytic lattice was recoverable using centrifugation and it was reusable in subsequent reactions.Overall, this procedure provides a viable method for producing lattice structures comprised of various types of enzymes. It also provides a potential mechanism for influencing lattice structure by choosing proteins with particular symmetries or arrangements of functionalizable amino acids. Additionally, one could construct lattice structures from nanoparticles and proteins. Future research might explore bio-engineering applications. From left to right, the structures of A-, B- and Z-DNA. Credit: Wikipedia (Phys.org)—Living systems have ready-made catalysts, known as enzymes, for many types of reactions. What if these enzymes could be snapped together like Lego pieces to make a lattice structure? An ideal procedure for accomplishing this would be versatile enough to work with any protein, regardless of its identity, and would maintain the protein’s native functionality while in the lattice structure. 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.last_img read more

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Energyharvesting bracelet could power wearable electronics

first_img(Left) Broken-out sectional view of the energy-harvesting bracelet, in which magnets moving through copper coils generate a voltage. (Right) Photo of the bracelet. Credit: Wu et al. ©2017 American Institute of Physics More information: Zhiyi Wu et al. “An energy harvesting bracelet.” Applied Physics Letters. DOI: 10.1063/1.4991666ABSTRACTAn energy harvesting bracelet (EHB) based on two mutually exclusive circular motion permanent magnetic movers is demonstrated, which is able to capture energy through the natural motions of the wearer’s wrist. The EHB can transform the translational motion in any orientation except the axial into the rotational motion of the movers, which passes through four coil transducers and induces significantly large electro-motive forces across the coils. A prototype EHB is shown to produce power that can charge a capacitor with 470 μF 25 V up to more than 0.81 V during at most 132 ms from any single excitations. © 2017 Phys.org Journal information: Applied Physics Letters Explore further (Phys.org)—Researchers have designed a bracelet that harvests biomechanical energy from the wearer’s wrist movements, which can then be converted into electricity and used to extend the battery lifetime of personal electronics or even fully power some of these devices.center_img Ring and bracelet system designed to help the hearing-impaired The researchers, Zhiyi Wu and coauthors at Chongqing University of Technology and the China Academy of Engineering Physics in Sichuan, have published a paper on the energy-harvesting bracelet in a recent issue of Applied Physics Letters.”The energy-harvesting bracelet could potentially be used to help power activity trackers, smartwatches, and even some health-monitoring applications,” Wu told Phys.org.The bracelet works due to electromagnetic induction, in which the interaction between a moving magnetic field and an electrical conductor generates a voltage. Inside the bracelet’s outer shell, electrically conductive copper coils wind around an inner shell. Inside this inner shell are two moving magnets that rotate around the bracelet in response to the wearer’s wrist movements. As the magnets move through the copper coils, they generate a voltage due to electromagnetic induction. The researchers explain that, according to Faraday’s Law, the amount of voltage generated is proportional to the number of times the magnets rotate around the bracelet. So the faster the motion, the greater the power generated by the bracelet. Tests showed that the magnets can move with an average rotational velocity of between 100 and 300 revolutions per minute, depending on the type and intensity of the wrist movements. The researchers also demonstrated that, from a single shake of the wrist, the bracelet can charge a small capacitor to approximately 1 volt in a fraction of a second and generate an average power of more than 1 milliwatt.One of the advantages of the bracelet design is its symmetry, which allows it to transform motion in any orientation into the rotational motion of the moving magnets, and also does not require the magnets to be in any particular initial position. Other types of electromagnetic energy harvesters, such as those in the shape of tubes or flat objects, have limited degrees of freedom and only work in certain orientations. “The greatest advantage of the bracelet is that it can transform translational motion in any orientation into rotational motion, starting from any initial position of the magnets,” Wu said.In the future, the researchers plan to investigate several different areas. One idea is to use a circular magnetization magnet to fabricate the magnets. They also want to further reduce friction in the bracelet and introduce triboelectric energy-harvesting technology to utilize the remaining friction. Citation: Energy-harvesting bracelet could power wearable electronics (2017, July 25) retrieved 18 August 2019 from https://phys.org/news/2017-07-energy-harvesting-bracelet-power-wearable-electronics.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.last_img read more

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Investigative report shines light on philanthropic foundations use of offshore investments to

first_img Corporate links of global health foundations may conflict with philanthropic interest Explore further Charles Piller, an investigative reporter for the journal Science, has published a News Feature piece in the latest issue of the journal outlining his findings surrounding the practice by philanthropic foundations of putting money in offshore investment accounts. More information: Charles Piller. At arm’s length, Science (2018). DOI: 10.1126/science.362.6419.1100 Philanthropic foundations by their very nature are not money-making ventures. Their purpose is to accept donations from individuals, groups or other entities and use the money they receive to support efforts to make the world a better place. But some of these foundations find they are unable to secure as much money in donations as they would like, so they turn to investment strategies. And some also try to maximize their return on such investments by conducting them through off-shore banks and other entities. Such arrangements allow the foundation to forgo paying taxes on investment income and to keep their investment activities private. But Piller wondered what happens when there are conflicts of interest. He found an example of one of the largest philanthropic foundations in the world—one that routinely doles out funds to curb air pollution—investing indirectly in a gas supply company that was clearly not involved in helping to clean the air.Piller came into possession of confidential documents that have become known as the Paradise Papers, leaked documents of investment information from seven of the world’s largest philanthropic foundations, and their investments in offshore accounts. The seven were the Bill & Melinda Gates Foundation, Wellcome Trust, the Howard Hughes Medical Institute, the Robert Wood Johnson Foundation, the William and Flora Hewlett Foundation, the David and Lucille Packard Foundation and the Gordon and Betty Moore Foundation. All except for the Gates Foundation were found to be using offshore accounts.Piller notes that there is also the distasteful nature of investing in offshore accounts even when there are no conflicts of interest. He wonders, for example, if philanthropic organizations should be doing their utmost to avoid paying taxes intended to be used for the public good. And he suggests there is something inherently wrong with such organizations engaging in a practice alongside criminals using the same services to launder their ill-gotten gains. He suggests the time has come for those who support such foundations to demand more transparency. Journal information: Sciencecenter_img This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Citation: Investigative report shines light on philanthropic foundation’s use of offshore investments to raise money (2018, December 7) retrieved 18 August 2019 from https://phys.org/news/2018-12-philanthropic-foundation-offshore-investments-money.html © 2018 Science X Network Credit: CC0 Public Domainlast_img read more

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Backstage diaries

first_imgBollywood actor and theatre personality, Anupam Kher recalled his student days at the National School of Drama (NSD) when he visited the campus last week for the 17th Bharat Rang Mahotsav. He held an interactive session with the students where he talked about a gamut of issues. He addressed a group of students, answered their queries and gave them suggestions to improve their acting skills as well as hone their talent better for the real struggles of the world. Excerpts: Also Read – ‘Playing Jojo was emotionally exhausting’On actingI was not from an acting background. I didn’t even know that they are actually books that can teach you acting when I enrolled in NSD. I realised later on that anyone who can lie can act. After all, that is all you do. If you can lie convincingly, you can act. Acting is the only course where your mind has to do the least work. You don’t have to decide how your limbs will go, how should you react to a situation because all that is predefined for you. So the most important thing is to use your memory. You remember your triggers, what makes you cry or laugh and then use the memory to get that emotion. Also Read – Leslie doing new comedy special with NetflixOn learning Here at NSD, I had classmates like Anant Desai who were immensely talented and even though I was great friends with them, I had always considered them competition.  (To the students) this is the phase in your life where you make new friends, you want to hang out with them, and unfortunately many of you will lose focus because of that. You end up forgetting why you came here; you lose focus and become mediocre. The important thing is to retain your individuality and that is what is crucial when you go to the film industry. As a student, be hungry, lonely and frustrated and that will help you achieve your dreams. Dream big and be uncomfortable with your current situation. Even today, I don’t consider my Bollywood contemporaries my competition; my competitors are Al Pacino and Robert De Niro.  On free speechFreedom of speech comes with responsibility. However much I may want to be funny it is important to follow your own instinct. I haven’t seen the AIB Roast so I can’t comment on it, but what I can say is that it is easy to make someone laugh on abuses. We have to consider the country we live in. If you make fun of women on stage it goes straight to women who are harassed in small towns. I saw this young kid abusing another kid in Hindi when asked about why he was abusing the boy replied ‘I am not abusing you, I am roasting you’. Is that what we want?last_img read more

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Gurgaon to have university schools for girls Khattar

first_imgHe was addressing the people in a function organised in the Government College for Women of Sector 14, Gurgaon. He inaugurated a multi-purpose hall constructed at a cost of Rs 7.26 crore within the college premises and laid foundation stones of three other projects, including the construction of a new science block and teaching block in Government College for Women and DSD Government College and the extension of district library in Gurgaon. All these three projects would cost about Rs 10 crore.The Chief Minister approved almost all the demands put up by the local MLA Umesh Aggarwal. He said that Gurgaon needs a University and the proposal received will be put in the pipe line. On the issue of providing basic amenities to the people residing within 900 meters of Ammunition Depot, he said that the matter is pending with the High Court and the government would plead on grounds of public interest in the High Court.last_img read more

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Woman held after video of beating up motherinlaw goes viral

first_imgKolkata: Kolkata Police arrested a middle-aged woman on charges of beating up her mother-in-law on Wednesday. Police have arrested the woman, Sapna Pal, after a video clip where the woman was found mercilessly beating up her mother-in-law, went viral.The incident comes just a few days after the Mother’s Day. After seeing the vide, police initiated a search for the woman. They finally arrested the woman from her residence. A police officer said the woman beat up her mother-in-law because the latter had picked up some fruits from a garden adjacent to their house without taking permission from the woman. Also Read – Heavy rain hits traffic, flightsA neighbour recorded the entire scene on a mobile phone and posted it on a social networking site. The video went viral by Wednesday morning. Within a few hours, around 25,000 people shared the video and finally it was also viewed by the police. Sergeant Subhro Chakraborty, who is posted with Bansdroni police station, saw the video footage and took up the matter with the officer-in-charge of the police station. They also received several messages to take steps in order to save the elderly woman, Jasodha Pal, who is an amnesia patient. Also Read – Speeding Jaguar crashes into Merc, 2 B’deshi bystanders killedPolice initiated a search for the place where the incident took place and went to the house as soon as they found out the location. They arrested the woman. Police also came to know that the woman often used to beat up her mother-in-law. Police also spoke to the neighbours. It may be mentioned that the Kolkata Police runs a project called Pranam to ensure safety and security of elderly people mainly, who stays all alone in their houses. Police have extend all support to the elderly people and help them in case they face any trouble.last_img read more

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Swine flu claimed 66 lives in JuneJuly Nadda

first_imgAs many as 66 people have lost their lives due to swine flu (Influenza-A H1NI) in the last two months, which was more than the toll during the same period last year, Lok Sabha was informed on Friday. Union Health Minister JP Nadda said that the June-July period also saw 740 swine flu cases being detected across the country, adding that during the same period last year, 45 people had lost their lives out of 220 detected cases of swine flu. “All the reported deaths may not have occurred only due to Influenza A H1N1 infection but may also be due to co-morbid conditions and the patients being immuno-compromised,” Nadda said during Question Hour. The minister said the recent cases were being reported from few states which have informed that they have sufficient stock of drug ‘Oseltamivir’. The Ministry has also kept an emergency stock of Oseltamivir.last_img read more

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Modi woos US investment promises to remove bottlenecks

first_imgKicking off his second visit to the US in one year with a meeting with eight of the top 10 financial entities in the US, including JP Morgan and Blackstone, Modi outlined efforts made during the last 15 months to increase investment in key areas like infrastructure. He outlined the government’s reform agenda as well as improving economic climate and said: “Any bottleneck  which should not be there, will not be there.” Also Read – Punjab on alert after release of excess water from Bhakra damThe GDP growth last year was 7.3 per cent – among the highest in large economies world over, he said. Also, there has been a 40 per cent jump in foreign direct investment (FDI).World Bank, International Monetary Fund and Moody’s say the economic climate is bound to improve further, MEA spokesperson Vikas Swarup quoted the Prime Minister as telling the one-hour-long roundtable. CEOs, he said, shared their concerns as well as experiences of doing business in India. Also Read – Union Min doubts ‘vote count’ in Bareilly, seeks probeThe Prime Minister “took on board” suggestions made by the executives as he outlined the sheer scale of development that will happen in India and the “tremendous opportunities” it offers to foreign institutional investors and for FDI.Swarup said the Prime Minister assured the investors that “work is already underway” to resolve concerns of doing business and investing in India.Swarup said some of the concerns raised by investors are that there is still some bureaucracy left, deregulation has not been as fast as they had expected. On the REIT side, they had some concerns about taxation policies, bankruptcy laws and deregulation and wanted faster pace of infrastructure development. He added that these were not new issues and the Prime Minister is fully aware of them. Modi has asked the CEOs to give him a detailed note on all the points and concerns raised by them. “Prime Minister Modi appreciated the fact that they had aired these issues and he was very committed to working to resolve them,” Swarup said.He said the companies manage billions of dollars and most of them have exposure to India. “This was a very good opportunity for the Prime Minister to listen to their experience of dong business in India, see what concerns they have and how we could work to remove those,” he said.Swarup added that the CEOs voiced their appreciation over the steps taken by the government on ease of doing business, economic growth and reforms and “were very bullish on India.” On concerns over land acquisition, Swarup said the Prime Minister has set a target of constructing 30km roads per day, increasing it from the current 13km. This, he said, will be possible only when there is land available and “we are trying to get political consensus on the issue.”The CEOs noted that India has a lot of potential for investment and acknowledged that financial market reforms have already started and more reforms would happen in the days to come. PM Modi to meet Obama, leaders of other nations Prime Minister Narendra Modi will meet US President Barack Obama and top leaders of a dozen other countries during his stay in the American city over the next several days, officials said. In his meeting with Obama – the third bilateral between the two leaders in about on eyear – the Prime Minister will discuss bilateral, regional and global issues and decisions taken by the two governments during the recently concluded inaugural Strategic and Commercial Dialogue in Washington DC. “They (Modi and Obama) will discuss a range of bilateral, regional and global issues. Economic engagement will certainly be a part of things being discussed,” Indian Ambassador to the US Arun K Singh told reporters. “There would be discussion also on the political, bilateral, regional and global issues,” he said.last_img read more

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