Study of isotopes shows recycling of Earths crust began 3 billion years

center_img 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. ( — New research by a team of British Earth scientists shows that while the Earth’s crust was made up of new material for much of its early life, it later began to recycle material three billion years ago, leading to the development of the continents we know today. The research team came to this conclusion, as they report in their paper published in Science, after studying oxygen isotopes in zircon samples taken from several different points across the globe.last_img read more

Researchers use DNA origami technique to build nanoantennas with docking sites

first_img 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. DNA constructs antenna for solar energy © 2013 DNA scaffolding has in recent years been developed to allow for orienting single molecules in useful ways. One of those has resulted in the creation of what is known as DNA origami—where DNA strands are folded in certain ways to create three dimensional nano-sized objects. In this new effort, the team used the technique to place two gold particles astride a protein pillar creating a hotspot that brightens fluorescent signals in zeptoliter volumes. The result is a tall pillar held erect on a flat surface using DNA strands that can be used to hold single molecules.The flat surface was made of a biotin-binding protein. The pillar (also made of a protein) is 220 nm long and 15 nm in diameter. It was held in place by strands of DNA. Two gold nanoparticles (80 to 100nm diameter) were suspended (again by DNA strands) on each side of the pillar (23 nm apart) and were used as an antenna to focus light on a hotspot between them. A fluorescent dye was placed into that hotspot and was used as an optically active source—its purpose was to report the degree of fluorescent enhancement—which was the purpose of the antenna.The antenna the team built demonstrates one way that DNA origami is being used to build a scaffold for holding molecules in three-dimensional space. The hope is that it will lead to what is known as atomically precise manufacturing—where nano-sized components could be manufactured in bulk. An antenna such as the one built in this new effort, allows for focusing light to a very small volume allowing for investigating molecules in a way that is up to 100 times more precise than conventional lenses. What’s most interesting about the antenna, of course, is that it’s held together by DNA strands that have been “programmed” to spontaneously wrap themselves around the antenna in just the right way to hold everything in place.The researchers next plan to conduct experiments to see if DNA origami structures can also be used to allow for more precise control of chemical reactions. Journal information: Science A team of researchers working at Germany’s Technische Universität Braunschweig has succeeded in using a previously known DNA origami construction technique to build a nanoantenna with a docking site. First published in the journal Science, the paper written by the team has now been made publicly available for open access. More information: Science 338, 506 (2012); DOI: 10.1126/science.1228638 Citation: Researchers use DNA origami technique to build nanoantennas with docking sites (2013, July 22) retrieved 18 August 2019 from read more

New type of Andreev process predicted whereby electron and hole states on

first_imgIllustration of the encapsulated graphene heterostructure with molybdenum rhenium contacts. Credit: (c) Science (2016). DOI: 10.1126/science.aad6203 Citation: New type of Andreev process predicted whereby electron and hole states on opposite sample edges carry supercurrent (2016, May 20) retrieved 18 August 2019 from © 2016 Explore further Electron partitioning process in graphene observed, a world first 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.center_img As Mason notes, the general means for causing current to move between two superconductor materials involves placing a barrier between them and then causing the Cooper pairs to be ferried across via electrons and holes—notably, in situations where the superconductors are connected to a quantum Hall state, only one-way paths along the junction can be traversed. But, the researchers wondered, what might happen if a very strong magnetic field were introduced into the junction, causing the charge carriers to move along only on the edges of the barrier? To find out, they assembled a mechanism that involved two superconducting materials separated by encapsulated graphene samples, and then created magnetic fields as high as two tesla. In such a setup, an entirely new type of Andreev process was predicted to occur in which electrons and hole states that existed on sample edges opposite one another would carry the supercurrent—this was predicted 20 years ago. Prior efforts to create a device capable of verifying the prediction have been hampered, Mason, notes, by the problem of creating an environment where superconducting and quantum Hall states might coexist. In this new effort, graphene samples allowed the team to take a first step toward proving the theory and confirming the new physics that occurs when two correlated states are connected—the work also suggests that a host of hybrid systems could be on the horizon, opening the door to a wide variety of quantum transport behavior which, as Mason also notes, could lead to a range of unique excitations and possibly yet-to-be-imagined devices. Journal information: Science (—A team of researchers affiliated with several institutions in the U.S. and Japan has predicted a new type of process whereby electron and hole states on opposite sample edges can carry supercurrent. In their paper, published in the journal Science, the team describes their technique, which involved using encapsulated graphene samples. Nadya Mason with University of Illinois offers a closer look at the work done by the team in a perspective published in the same journal issue. More information: F. Amet et al. Supercurrent in the quantum Hall regime, Science (2016). DOI: 10.1126/science.aad6203AbstractA promising route for creating topological states and excitations is to combine superconductivity and the quantum Hall (QH) effect. Despite this potential, signatures of superconductivity in the QH regime remain scarce, and a superconducting current through a QH weak link has been challenging to observe. We demonstrate the existence of a distinct supercurrent mechanism in encapsulated graphene samples contacted by superconducting electrodes, in magnetic fields as high as 2 tesla. The observation of a supercurrent in the QH regime marks an important step in the quest for exotic topological excitations, such as Majorana fermions and parafermions, which may find applications in fault-tolerant quantum computing.last_img read more

Safe and generalizable catalyst for carbonylolefin metathesis reaction

first_imgScope of the iron(III)-catalysed carbonyl–olefin metathesis reaction. Credit: (c) 2016 Jacob R. Ludwig, Paul M. Zimmerman, Joseph B. Gianino & Corinna S. Schindler, Nature 533, 374–379 (19 May 2016) doi:10.1038/nature17432 More information: Jacob R. Ludwig et al. Iron(III)-catalysed carbonyl–olefin metathesis, Nature (2016). DOI: 10.1038/nature17432AbstractThe olefin metathesis reaction of two unsaturated substrates is one of the most powerful carbon–carbon-bond-forming reactions in organic chemistry. Specifically, the catalytic olefin metathesis reaction has led to profound developments in the synthesis of molecules relevant to the petroleum, materials, agricultural and pharmaceutical industries1. These reactions are characterized by their use of discrete metal alkylidene catalysts that operate via a well-established mechanism2. While the corresponding carbonyl–olefin metathesis reaction can also be used to construct carbon–carbon bonds, currently available methods are scarce and severely hampered by either harsh reaction conditions or the required use of stoichiometric transition metals as reagents. To date, no general protocol for catalytic carbonyl–olefin metathesis has been reported. Here we demonstrate a catalytic carbonyl–olefin ring-closing metathesis reaction that uses iron, an Earth-abundant and environmentally benign transition metal, as a catalyst. This transformation accommodates a variety of substrates and is distinguished by its operational simplicity, mild reaction conditions, high functional-group tolerance, and amenability to gram-scale synthesis. We anticipate that these characteristics, coupled with the efficiency of this reaction, will allow for further advances in areas that have historically been enhanced by olefin metathesis. (—Olefin metathesis reactions where two allyls switch substituent groups, has proved to be a useful carbon-carbon bond forming reaction for drug discovery and other industrial processes. The carbonyl-olefin metathesis reaction was discovered around the same time as the olefin metathesis reaction, but has had limited applicability due to harsh reaction conditions and stringent reactant requirements. Until now, there have been no examples of catalysts for this reaction that are generalizable. 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 In a report in Nature, Jacob R. Ludwig, Paul M. Zimmerman, Joseph B. Gianino & Corinna S. Schindler of the University of Michigan have successfully found a Lewis acid catalyst that successfully exacts a carbonyl-olefin ring-closing metathesis reaction for the direct synthesis of functionalized carbocycles. Furthermore, the catalyst uses iron, which is abundant and environmentally safe, and works under mild conditions for a variety of functional groups and at gram-level scales.The olefin reaction mechanism involves a metal-catalyzed [2+2] cycloaddition of two allyls to form a four-member cyclic intermediate in which the metal is one of the members of the four-member ring. This is followed by a [2+2] cycloreversion resulting in products that have exchanged substituents. Carbonyl olefin metathesis reactions operate similarly. There are three carbonyl olefin metathesis reactions have been observed, but each has its limitations. One involves a two-step photochemical cycloaddition followed by a thermolysis cycloreversion. Another involves a stoichiometric amount of transition-metal catalyst. Another reaction involves an organocatalyst that requires a cyclopropene reactant. All of these are limited in scope and, in the case of the photochemical reaction, require prohibitively harsh conditions. The reaction involving a stoichiometric amount of transition-metal catalyst is the most versatile, but it produces a metal-oxo complex that consumes the catalyst.Ludwing, et al. wanted to look for ways to form an in situ oxetane intermediate, a four-member cyclic intermediate with the oxygen as one of the atoms instead of a metal. This would avoid the formation of products that consume the catalyst. In general, they needed a catalyst that promotes [2+2] cycloaddition and [2+2] cyclorevrsion, does not promote side reactions such as polymerization or reforming reactants, and is chemoselective. They decided to investigate metal-derived Lewis acids.To test various Lewis acid catalysts, they reacted a β-ketoester with a pendant isoprenyl group with MClx Lewis acids. They tested AlCl3, TiCl4, SnCl4, FeCl2, ZnCl2, SnCl2, and FeCl3. They found that FeCl3 formed the desired products and that optimal reaction conditions were 5 mol% FeCl3 in dicholorethane at room temperature for one-to-twelve hours. Once a catalyst was determined and reaction conditions were optimized, the next step was to test the generalizability of the reaction. Ludwig, et al. looked at various arene groups. Their reaction conditions worked with electron withdrawing and donating groups producing products in good yield. They then changed the β-substitution on the β-ketoesters and found the reaction worked with a variety of substituents. They also looked at the effects of incorporating a heteroatom, changing structural motifs, and changing the pendant isoprenyl group. Overall, the FeCl3 catalyst showed remarkable versatility in the variety of reactions that were successfully completed.These reactions provided insight into the carbonyl-olefin reaction mechanism. The reaction either proceeds via a carbocation intermediate or in a concerted fashion that involves metal coordination to FeCl3. Subsequent studies using a mechanistic probe to trap the product that would be formed from a carbocation intermediate showed no results, thus demonstrating that a concerted and metal coordinated mechanism is likely. Computational studies indicate that the reaction mechanism is likely a concerted carbon-oxygen bond breakage and carbon-carbon bond formation mechanism that occurs asynchronously.Carbonyl-olefin metathesis reactions had been limited in scope, but this study demonstrates a catalyst and optimal reaction conditions that are generalizable for a variety of reactants opening the door for the synthesis of complex compounds. The reaction is practically useful as iron is an earth-abundant metal and is environmentally safe, and the reactions are scalable.last_img read more

Evidence of TBlike infection found in 245millionyearold marine reptile

center_img Journal information: Royal Society Open Science A team of researchers from Poland and the U.S. has found possible evidence of tuberculosis in a 245-million-year-old marine reptile. In their paper published in the journal Royal Society Open Science, the group describes their study of the fossilized remains of a Proneusticosaurus silesiacus specimen and why they believe the creature had a TB-like disease. More information: Dawid Surmik et al. Tuberculosis-like respiratory infection in 245-million-year-old marine reptile suggested by bone pathologies, Royal Society Open Science (2018). DOI: 10.1098/rsos.180225AbstractAn absence of ancient archaeological and palaeontological evidence of pneumonia contrasts with its recognition in the more recent archaeological record. We document an apparent infection-mediated periosteal reaction affecting the dorsal ribs in a Middle Triassic eosauropterygian historically referred to as ‘Proneusticosaurus’ silesiacus. High-resolution X-ray microtomography and histological studies of the pathologically altered ribs revealed the presence of a continuous solid periosteal reaction with multiple superficial blebs (protrusions) on the visceral surfaces of several ribs. Increased vascularization and uneven lines of arrested growth document that the pathology was the result of a multi-seasonal disease. While visceral surface localization of this periosteal reaction represents the earliest identified evidence for pneumonia, the blebs may have an additional implication: they have only been previously recognized in humans with tuberculosis (TB). Along with this diagnosis is the presence of focal vertebral erosions, parsimoniously compared to vertebral manifestation of TB in humans. TB is an infection caused by the virus Mycobacterium tuberculosis. It mainly infects the lungs, but can on occasion infect other body parts such as the spine, brain or kidneys. It is also known for causing anomalies to appear on the ribs of people with infected lungs. Such anomalies generally take the form of blebs, or small bumpy protrusions.The researchers were studying a specimen uncovered at the Gogolin quarry, a dig site on the border between Poland and the Czech Republic, over a century ago. Prior research had shown it to be a member of the sauropterygian family—they were aquatic reptiles that lived during the Mesozoic. The specimen under study had a long neck, flat skull and long, rounded teeth. But it was the creature’s rib bones that caught the attention of the researchers—they had blebs very similar to those seen in modern creatures infected with TB.Intrigued by their find, the researchers immediately began searching for all possible causes of the bumps, such as fractures, scurvy, fungal infections or even cancer. But one by one, each was ruled out, leaving TB as the likely cause. In their paper, the researchers also suggest the bumps may have been caused by pneumonia, which, they note, can be caused by TB. They note also that Proneusticosaurus have been referred to as the seal of ancient times, and coincidentally or not, modern seals are the marine animals that are most susceptible to TB infections.The finding pushes back the date of the first evidence of TB by quite a long stretch—prior to this discovery, the record holder was a marsupial from 3 million years ago. The researchers acknowledge that they have no way to verify their findings, but suggest the rib bumps offer reasonably strong evidence of TB.last_img read more

Decomposed body of 3yrold girl recovered from manhole

first_imgKolkata: The decomposed body of a three-year-old girl was recovered from inside a manhole at Shyamlal Street on Friday night. Locals said that the child was missing since Wednesday and according to the primary autopsy report, the child was strangulated to death.Local sources informed that the child used to live with her family members on the pavement opposite to Shyamlal Street in front of Deshbandhu Park. On Wednesday night, her family members all of a sudden noticed that she was missing. Also Read – Rain batters Kolkata, cripples normal lifePrimarily, they tried to search the area, but failed to locate her. Later, with the help of other locals, a search was conducted but in vain.On Thursday, the child’s father lodged a complaint with Ultadanga police station. After commencing the probe to locate the missing child, police could not gather any clues that might have led them to her. On Friday night, a few locals saw a manhole inside a compound of a four-storeyed building was partly open. When some of them peeped in and looked into the manhole, they saw the girl. Also Read – Speeding Jaguar crashes into Mercedes car in Kolkata, 2 pedestrians killedImmediately, the owner of the building was informed. At around 11:10 pm, the police recovered the decomposed body of the missing child. After getting the primary autopsy report, investigators are now trying to understand if there was any enmity with the girl’s family members. Also, the police have tracked a few CCTV cameras on the main road just outside Shyamlal Street and inside a nearby school compound. Sources informed that the footage from the CCTV cameras installed has been viewed but nothing suspicious could be traced. The investigators are yet to look into the footage of the CCTV camera inside the nearby school campus. It is also not clear whether the girl has been sexually harassed or not.last_img read more

BJP gloats over articles slamming Jawaharlal Nehru Sonia Gandhi

first_imgThe BJP on Monday gloated over Congress’ embarrassment following publication of articles critical of Jawaharlal Nehru and Sonia Gandhi in its mouthpiece, saying the “truth” it had been “hiding” has come out. Rubbing salt in the wound of ex-Congress MP Sanjay Nirupam, who is the editor of the journal, Union Minister Prakash Javadekar “congratulated” him and quipped he was known for such write-ups when he was the editor of the Hindi edition Shiv Sena mouthpiece ‘Dopahar Ka Saamana’. Nirupam, who was in Sena before he joined Congress, is also the president of Mumbai Regional Congress Committee, which publishes the magazine ‘Congress Darshan’. Though initially Nirupam sought to wash his hands off the controversy by claiming he had nothing to do with the articles, he later admitted the “mistake” and sacked the editorial content in-charge.  Also Read – Punjab on alert after release of excess water from Bhakra dam“The Congress journal which is named Congress Darshan should be called ‘Satyarth Darshan’ (sight of truth). It is significant that it has come on the 131st foundation day of the party. Sardar Patel had maximum support in Congress to become the prime minister but Gandhiji proposed Nehru and kept Patel at a bay. “Patel merged 562 provinces into India and Nehru was in charge of only Kashmir and it remains a problem. Patel had warned about China’s betrayal on Tibet… This is not BJP or Javadekar saying so but the mouthpiece of Congress. What Congress had been hiding has come out. I congratulate Nirupam,” Javadekar said.last_img read more

Man lynched to death for protecting wife from eveteasers

first_imgKolkata: A husband was lynched to death after he protested against some local youths who had allegedly assaulted his wife.The incident took place at Arsa village in Purulia on Saturday evening. The victim, Dharani Singh Sardar went to a village fair with his wife and younger sister on Saturday afternoon. They were returning home on his motorcycle when some miscreants stopped their way. Some of the accused touched his wife inappropriately and abused her. Also Read – Rain batters Kolkata, cripples normal lifeSardar protested against the incident but the accused threatened him of dire consequences if he raised an alarm. The victim later tried to prevent them from assaulting his wife. A scuffle broke out between Sardar and the accused youths. The victim’s wife and sister told police that the miscreants beat up Sardar indiscriminately. He fell on the ground after receiving several punches on his chest. After hearing the screams of the two women, some of the locals reached there. The miscreants managed to flee the spot before locals arrived. Also Read – Speeding Jaguar crashes into Mercedes car in Kolkata, 2 pedestrians killedThe locals rushed the victim to a nearby hospital where Sardar was declared brought dead by the doctors. The family members of the victim alleged that the local police station initially refused to lodge a complaint from them. They also alleged that the local police station also cooked up a story to establish that it was a road accident. The family members of the victim also alleged that there were several injury marks on the body of the victim. The motorcycle that the deceased was riding on had gone missing since the incident occurred. It is yet to be confirmed if the victim had any past rivalry with the accused who are at large since the incident took place on Saturday evening.last_img read more

Get your hair skin ready for monsoon

first_imgHeat, humidity and rain come together to create havoc for hair, skin and make-up during the monsoon. It can get difficult to keep up with a beauty regimen, but taking care of a few basic things like never leaving the skin wet for long or keeping it moist can be helpful, say experts.TIGI Educator Audrey D’ Souza, Sushma Khan, National Creative Director – Makeup, Lakmé Salon and Disha Meher, National Expert – Skin and Nails, Lakmé Salon, share tips on how you can keep hair frizz, make-up mess and skin breakouts at bay, especially when the monsoon gets going! Also Read – Add new books to your shelf* Skin tips by Disha Meher:Rainy rituals:* During the day, cleansing, toning, moisturising and applying sunscreen should be your facial ritual. Remember to reapply moisturiser and sunscreen if the skin is exposed to rain.* During the night, stick to cleansing, toning and applying a good night cream.No-nos for the monsoon:* Never leave the skin wet for a long time. Fungal infections are very common. Always keep your feet and toes dry to avoid infections. Also Read – Over 2 hours screen time daily will make your kids impulsive* Do not wear synthetic clothes and allow your skin to breathe.* Avoid cold water for bathing. Lukewarm water is best for the skin during monsoon.* Just dab and dry the face and avoid rubbing it with a towel.Absolute monsoon musts:* Keep the skin moist by using soap-free cleansers and scrubs. Go for clean-ups which help in unclogging pores and reducing dead skin and dryness.* Use an alcohol-free toner to prevent dryness of the skin.* Moisturising is key. Make sure to select a moisturiser as per your skin type. * Sunscreen lotion must be used even if the sun is not visible.* Go for regular manicures and pedicures to keep your feet clean.* Keep your skin smooth and clean by opting for waxing services regularly. Chocolate and Fruit waxes are good options for sensitive skin.-*-Monsoon make-up hacks by Sushma Khan* To build a smear-proof base skip the foundation and start with a concealer. Choose a waterproof, matte product followed by a compact powder. When you apply the combination of setting powder and primer on your skin, it dissolves giving you light and flawless coverage. * The best bet for your lips are matte tints. Instead of choosing gloss, head straight to ultra-matte and dry-finish lip liquids.* When it comes to liners, ensure to hydrate your lids before application. For a flawless matte finish, use a felt-pen liner because it dries quickly and stays put throughout the day. Experiment and use coloured liners like olives, pinks and blues to add a ‘pop’ to your look. Opt for a waterproof and volumising mascara for your lashes.* Contrary to using creamy formulations for the lips, eyes or the face — using it for your cheeks is perfect. Cream-based cheek tints glide on the skin, giving your cheeks a natural flush.* Seal your look with a make-up setting spray. It features a patented Temperature Control Technology that lowers the temperature of the make-up, keeping it in place.-*-TIGI Educator Audrey D’ Souza’s monsoon mane hacks:* Don’t wash your hair too often: You might feel the need to shampoo often to rid yourself of the dirt and rainwater, but that also means stripping your hair of its natural oils (sebum), leaving it dry and limp.* Mask it: Deep conditioning helps smoothen out your hair and provides heavy nourishment. Be sure to leave on your mask for at least ten minutes. Intense formulaes in masks help coat the strands with strong conditioning and shine.* Stay away from heat: Stick with air drying, finger drying or use a blow dryer on low or medium heat on damp hair to control the frizz for better finish.* Dodge friction: Your hair is prone to damage in the rains, so be as gentle as possible. No vigorous towel drying and squeezing harsh brushing.last_img read more