Ultrasonic vibrations force a polymer to be a semiconductor

first_img © 2017 Phys.org This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Journal information: Science Explore further Design of mechanochemically generated conjugated polymer. (A) Insulating CBE mechanophores connected with π systems, designed to rearrange to continuously extended conjugation under force. (B) Thermally unstable CBEs with sp2 carbon substituents at the 3 and 4 positions. (C) Ladderene-based mechanophore, which would undergo tandem mechano-cycloreversions to give conjugated oligoene. (D) Natural [5]-ladderane fatty acid (5) from anammox bacteria. (E) Design of mechanically active polyladderene via ROMP of ladderene. Credit: (c) Science (2017). DOI: 10.1126/science.aan2797 (Phys.org)—A team of researchers at Stanford University has used mechanical force to transform a molecule from one form to another—from a nonconductive state into a semiconductor. In their paper published in the journal Science, the group describes the process they developed and possible applications.center_img As the researchers note, using mechanical force to change a molecule from one form to another (by prying open their bonds) has been a popular research subject over the past decade, leading to a new field now known as mechanochemistry. In this new effort, the researchers used a physical force to “unzip” a nonconducting polymer, transforming it into a semiconductor.In their work, the team studied chunks of cyclobutanes to learn more about their structure. In their natural state, they exist as a polyladderene molecule with the appearance of stairs leading from a low point to a high point, and walls holding them in place. The team thought that if they could pull the walls apart, effectively unzipping the staircase, they could transform it into a zig-zag-looking polymer known as a polyacetylene, which is a semiconductor.The cyclobutanes were placed in a solution and subjected to sonic waves exerting opposing forces on the molecule, causing it to unzip and stretch out into nearly a flat structure (into alternating C=C double bonds). The group reports that the solution, which was initially clear, slowly changed to blue, and eventually became dark as it was filled with a mesh of nanowires. The researchers note that the material could be used as a means for measuring stresses in other materials. It could also be used to mimic human senses in a robot because it is able to use a mechanical force to convert a material into a wire capable of carrying an electronic signal. But before that can happen, the team acknowledges that more work needs to be done to make the structures simpler, as they are now they are too complex for industrial applications. Citation: Ultrasonic vibrations force a polymer to be a semiconductor (2017, August 4) retrieved 18 August 2019 from https://phys.org/news/2017-08-ultrasonic-vibrations-polymer-semiconductor.html More information: Zhixing Chen et al. Mechanochemical unzipping of insulating polyladderene to semiconducting polyacetylene, Science (2017). DOI: 10.1126/science.aan2797AbstractBiological systems sense and respond to mechanical stimuli in a complex manner. In an effort to develop synthetic materials that transduce mechanical force into multifold changes in their intrinsic properties, we report on a mechanochemically responsive nonconjugated polymer that converts to a conjugated polymer via an extensive rearrangement of the macromolecular structure in response to force. Our design is based on the facile mechanochemical unzipping of polyladderene, a polymer inspired by a lipid natural product structure and prepared via direct metathesis polymerization. The resultant polyacetylene block copolymers exhibit long conjugation length and uniform trans-configuration and self-assemble into semiconducting nanowires. Calculations support a tandem unzipping mechanism of the ladderene units. New algorithm finds the optimal bond breaking point for single moleculeslast_img read more

Evenings and couplets for Mirza Ghalib

first_imgA two-day event will be organised on the 144th death anniversary of Mirza Ghalib to showcase his rich legacy, an organisation dedicated to the legendary Urdu poet announced. Yadgar-e-Ghalib will be held on 26-27 April, the Ghalib Memorial Movement (GMM) said.The event will feature the release and screening of a film on Ghalib produced by Kathak dancer Uma Sharma. In addition recital of couplets of the poet by author Pawan K. Verma, and a mushaira will create the atmosphere of a bygone era. ‘While the couplets have been specially selected for the occasion that will leave the listeners spellbound, the dancers will capture moods befitting the death anniversary,’ GMM said.last_img

Pamper your skin with chocolates strawberries

first_imgDuring the monsoon, women often complain of skin dryness and painful pimples and try to cure them by using beauty products.Makeup expert Ishika Taneja shares quick tips and essential natural remedies  for different skin types.Dry Skin: During monsoon, people experience skin dryness mainly because of dehydration caused by lack of skin repairing vitamins.Clean your face with soap-free cleanser as it doesn’t makes your skin dry but keeps it soft. You can make your own toner by mixing a few drops of honey and two tablespoons of milk. It not only tones but also hydrates the skin. You can also use a sunscreen lotion with SPF 30. It protects and hydrates the skin. Also Read – ‘Playing Jojo was emotionally exhausting’Natural remedies: Pomegranate seeds are loaded with anti-ageing compounds like antioxidants and vitamin C and nourish dry skin. Blend two tablespoons of pomegranate seeds and one cup uncooked oatmeal. Add two tablespoons of honey and buttermilk. Apply on your face for a few minutes, then rinse. It helps remove dead skin cells.Recommended facial: Chocolate facialOily skin: Monsoon increases skin problems for those who have oily skin. It makes the sebaceous glands, which are responsible for oil secretion, hyperactive. Also Read – Leslie doing new comedy special with NetflixThe oil secretion and sweat are deposited on the skin and trap dirt and bacteria. This gives rise to blackheads, whiteheads, breakouts and sometimes painful pimples.An oil-controlling cleanser that cleans the pores and controls the oil secretion is good for oily skin. Use an alcohol-free toner to retain the skin’s pH balance. For sun protection, pick a gel-based sunscreen lotion with SPF 30 that adds moisture but isn’t too creamy.Natural remedies: Take two tablespoons of papaya pulp, one tablespoon of curd and an ounce of aloe vera gel. Mix it well. Add a few drops of lavender oil. Papaya works as a great de-tanner, the curd clears blemishes, the aloe vera soothes the skin and the lavender boosts rejuvenation.Recommended facial: Aloe vera facial.Combination skin: This skin type is a mix of oily and dry skin. Cheeks usually become dry and other parts of the face, specially the nose, get oily because of the excessive humidity during monsoon.Anti-bacterial cleanser is perfect for this skin type. For toning, add two drops of lemon juice to cold water and wash your face with it. Lemon is not only refreshing but also works as a cleanser.Before stepping out, apply a hydrating sunscreen lotion with SPF 30 as the skin loses moisture due to sweating. Monsoon also aggravates the problem of dandruff, which can further lead to hair fall, breakouts or acne outburst. So it’s equally important to keep your hair clean.Natural remedies: A strawberry face pack is perfect for this skin type. Blend half a cup of frozen or fresh strawberries with one cup of yogurt and one-and-a-half tablespoons of honey. Apply it on your face for a soft and smooth skin.Recommended facial: Fruit facial with milk.last_img read more

Indians seem to be comfortable with Caucasians writing about themselves

first_imgJhinuk Sen chats up Raghu Srinivasan about his The Avatari, the story of a British man’s journey through Ladakh, Pakistan and Afghanistan that is mainly set in 1986, during the height of the Soviet Afghan War. Read on… How did The Avatari happen? How did this story come about?The Avatari owes its origins to a drink I had with an old timer huddled over a stove, in an arctic tent in the shadow of the Karakorum ranges. The old timer had been a mountaineer before he had had a bad fall and had tramped all over the Karakorums, spending much of his time with local porters and guides. It was from them that hewho had picked up a story of a group of Germanswho had formed an expedition to search for Shambhala, and were never heard of again. Also Read – ‘Playing Jojo was emotionally exhausting’What kind of research did you need to do for The Avatari?I am an avid reader, and the one thing I promised myself while writing The Avatari was that I should attempt to make no factual errors. I remember reading San Andreas by Alistair Maclean; where one of the characters is a Pakistani, but the story is set during World War II – when there could have been no Pakistanis. So starting with reading the BardoThodol (The Tibetan Book of the Dead) and everything that has ever been written about the Shambhala myth, to events as they chronologically happened in history in 1296, 1956, 1963 and 1986 has been researched. I had to do a fair bit of reading on Kublai Khan and Marco Polo as also the Afghan War. Likewise I needed to read up on travelogues of people who had visited the enchanting places which Henry Ashton and his team visit in the book. Also Read – Leslie doing new comedy special with NetflixWhat were the toughest times you faced as The Avatari fell into shape?The Avatari actually began as a short story which I gave up after the first 100 pages. Also it was to deal with a mystical journey and then metamorphosed into an action-quest-adventure.  So at times I must confess I was not totally in control, and the story was writing itself. Also I would write parts which I would fall in love with but had no relation to the movement of the story. I think excising those, especially for a first time author, was really tough. The longest time was spent in figuring out how Shambhala would confer immortality; making it believable to the reader. What was also difficult was getting the story to be chronologically correct; both in terms of years and dates. I received a lot of help getting that right from my wife, Sumita. And … what were the best times?The best times were when I was writing about the military action or the mountains. I could sit on the computer the whole night typing away, actually feeling the sweat stinging my eyes, the sound of gunfire and the icy wind on your face. I would sit at the computer long after I had finished writing, and enjoy the emotion as it slowly drained away.How easy or difficult was it to get a story like this figured out in your head and on paper?I think I started out with a beginning and an ending and some marks in between which I had to get to on the way. But then, like I said at times the story would write itself and I would veer away from the mark, having to create a new one. When you have so many characters and so many periods in history to deal with, the difficult part is to decide how much of detail you need to go into. For the last seven years I have always had The Avatari humming in my head – at times I would be unaware of what was happening around me (much to Sumita’s annoyance). There were times when I thought that I wouldn’t be able to make the story stick and I couldn’t resolve the contradictions for many months; and then luckily I would have a ‘eureka’ moment.Why pick a British hero? Just for argument’s sake – why not an Indian?The story involves the hero undertaking a journey through Ladakh, Pakistan and Afghanistan, and is mainly set in 1986, during the height of the Soviet Afghan War. I don’t think an Indian could have gone to those places at that time without arousing tremendous suspicion or being interned at some stage.You don’t really have an Indian character in the book and even the story touches India only briefly in Leh – was this a conscious call?Like I said it was a question of locations and periods of history where an Indian on the group would have stood out like a sore thumb; and the discerning reader would have easily made out that it was a poorly contrived attempt to bring in an Indian character. Here I would like to make a point that Western writers don’t seem to get asked about the same thing – starting from Jungle Book and The Far Pavilions right up to Dalrymple and Patrick French; Indians seem to be comfortable about Caucasians writing with authority and felicity about themselves. It’s just that an Indian writer hasn’t tried the obverse out so far. As far as locations go, it was just that the story found itself happening at these places.How true are the legends of the Avatari and the Shambhala?They are true!  When you live for eight months on the wrong side of the great mountains, with the passes closed – it is an enchanted world which not many people have the privilege to be part of. For Tibetans, Shambhala exists; definitely on the spiritual plane and possibly at the physical level also. Similarly, the Tibetans believe deeply in the concept of an Avatari – and so do I.What’s next in the pipeline?I am mulling over a story set in China in the near future, and like The Avatari it has historical references. So far I have only the broad contours, but I am hopeful that I will be able to write it faster than The Avatari which took seven years!last_img read more

St Xaviers Bcom student found dead

first_imgKolkata: Mystery shrouds the death of Rik Bose (21), a B.Com final year student from St Xavier’s College whose body was found hanging from a ceiling fan inside his residential apartment at Purbachal.Police have started a case of unnatural death in this connection. According to preliminary investigation, police suspect that he might have committed suicide following depression. Victim’s family members found the victim hanging from the ceiling fan inside his room which was locked from inside. The incident took place at around 1.10 pm on Wednesday afternoon. After being informed, police reached the spot and recovered the victim by breaking open the door. He was rushed to MR Bangur Hospital where he was declared brought dead by the doctors. Also Read – Heavy rain hits traffic, flightsNo suicide note was, however, recovered from the place of incident. A resident of Abhisikta I, Bose hanged himself by the help of the power cord of Laptop. The victim was a final year student of B.Com at St Xavier’s College. Police suspect that he was suffering from depression as he was not well prepared for final exam scheduled to start from 18 April.According to police, no external injury marks were found in his body. The circumstantial evidences also suggest that he committed suicide. Police came to know that the victim apprehended that his exam results would not be up to the mark. Also Read – Speeding Jaguar crashes into Merc, 2 B’deshi bystanders killedPolice have collected samples from his room for the sake of investigation. They are also going through his mobile phone and other electronic gadgets of the victim. In the course of investigation, police came to know that Bose was not mixing with his friends for the past few days.Cops are also investigating other possible angles into the incident. They are also probing if the victim was involved in any relationship. The family members of the victim and his friends are being interrogated in this connection so far. A probe has been initiated.last_img read more

Bar Association lifts ceasework in Calcutta HC

first_imgKolkata: The Bar Association of the Calcutta High Court on Saturday lifted its two-month-long ceasework following the Centre’s notification to appoint four more judges and a permanent chief justice, an official said. The lawyers will resume work in the high court from Monday, Bar Association President Uttam Majumder said at a press conference here.The ceasework at the high court, which had 2.22 lakh cases pending before it at the end of January, had commenced on February 19 to press for the appointment of more judges and a chief justice for the high court which had been headed by acting chief justices for over three years with the exception of only three months. The Bar Association, which commands the support of majority of the lawyers, said the decision to lift the ceasework was taken unanimously in consultation with other striking lawyers’ bodies. Also Read – Heavy rain hits traffic, flights”Today (Saturday) we got the notification from the Centre about the appointment of four new judges who will take over from next week. The high court will also have a permanent chief justice from next week. In the wake of these developments, we are lifting the ceasework,” Majumder said.He said three judges had been appointed by the Centre in March and with four new appointments on Saturday, the high court now has 37 judges which is a little over 50 percent of the sanctioned strength of 72 judges. To a question about the Bar Association’s earlier decision that the ceasework will continue till May 11, Majumder said: “We had asserted that the ceasework will automatically stand withdrawn if the appointment of new judges is notified in the meantime.”last_img read more

Jagaddal SI hangs self inside quarter

first_imgKolkata: Mystery shrouds the death of a sub-inspector of Jagaddal police station whose body was found hanging inside his quarter on Monday night. According to preliminary investigation, police suspect that the victim might have committed suicide. The victim, Arindam Kundu was assigned in Panchayat poll duty on Monday. After the duty was over, Kundu went to his quarter on Monday evening. Some of his colleagues on Tuesday morning found the door was locked from the inside. Police later broke open the door and found the victim hanging from Also Read – Heavy rain hits traffic, flightsthe ceiling fan. The body was later sent to a hospital for post-mortem. The victim’s wife and two children live at a house in Dum Dum. After starting an investigation, police came to know that Kundu had a quarrel with his wife over an issue. It was also learnt that his wife wanted to work somewhere to which Kundu had objected. The couple had some war of words over the issue.After going through WhatsApp messages, police came to know that the victim was mentally depressed over certain issues. The circumstantial evidence suggests that he committed suicide following depression from family related issues. Police have started a detailed probe in this regard. They are looking into all possible angles which might have prompted the victim to commit suicide. The family members of the victim demanded an independent probe into Kundu’s death. The victim’s wife, however, told police that the incident came to her like a shock. She had a discussion with her husband and could never imagine he could take such a drastic step. The investigators are waiting for the post-mortem report.last_img read more

Modis trusted lieutenants to stay put in battleground Bihar

first_imgThe Central Government has come to a standstill with nearly half of the Cabinet colleagues of Prime Minister Narendra Modi campaigning in Bihar for the upcoming Assembly polls, which are being seen as a close contest between the ruling NDA and the regional alliance.Besides PM Narendra Modi, who will remain in Bihar during his political rallies, Home Minister Rajnath Singh, Finance Minister Arun Jaitley, Foreign Affairs Minister Sushma Swaraj, Transport Minister Nitin Gadkari, Steel Minister Narendra Singh Tomar, Health Minister JP Nadda, Agriculture Minister Radha Mohan Singh, HRD Minister Smriti Irani, Telecom Minister Ravi Shankar Prasad, Chemical and Fertilisers Minister Ananth Kumar, Food and Consumers Minister Ram Vilas Paswan, and MSME Minister Kalraj Mishra are camping in the state. Also Read – Punjab on alert after release of excess water from Bhakra damApart from Cabinet Ministers, the ten Ministers of State, including four MoS with independent charge have been deployed to win the crucial state poll. The Ministers of state include Power Minister Piyush Goyal, Skill Development Minister Rajiv Pratap Rudy, Petroleum Minister Dharmendra Pradhan, Textile Minister Santosh Gangwar, MoS Rural Development Ram Kripal Yadav, MoS Railways Manoj Sinha, MoS HRD Upendra Kushwaha, MoS Finance Jayant Sinha, and MoS Food Processing Sadhvi Niranjan Jyoti.Central Ministers Radha Mohan Singh, Ravi Shankar Prasad, Ananth Kumar, Ram Vilas Paswan, Dharmendra Pradhan, Rajiv Pratap Rudy, and Ram Kripal Yadav have been deployed on permanent basis till the last phase of the polls. Prime Minister Modi, who started his campaign with four rallies on Thursday, will stay in Patna for two days to have a real-time assessment of the electioneering process.last_img read more

You need 27 seconds to regain attention after phone use

first_imgIf you thought it is okay to talk to your car infotainment system or smartphone while driving then think again. New research has found that it takes up to 27 seconds to regain full attention after issuing voice commands.University of Utah researchers conducted two studies for the traffic safety charity AAA Foundation for Traffic Safety.One of the studies showed that it is highly distracting to use hands-free voice commands to dial phone numbers, call contacts, change music and send texts with Microsoft Cortana, Apple Siri and Google Now smartphone personal assistants.  Also Read – ‘Playing Jojo was emotionally exhausting’In another study, they examined voice-dialing, voice-contact calling and music selection using in-vehicle information or “infotainment” systems in 10 model-year 2015 vehicles. Three were rated as moderately distracting, six as highly distracting and one as very highly distracting, the US-based traffic safety non-profit said in a report.“Just because these systems are in the car doesn’t mean it’s a good idea to use them while you are driving,” said senior author of the two studies David Strayer, psychology professor at University of Utah.“It is better not to use them when you are driving,” Strayer said. The research also found that, contrary to what some may believe, practice with voice-recognition systems does not eliminate distraction.last_img read more

Steps to check arbitrary fare hike by auto drivers around Behala

first_imgKolkata: The state Transport department is going to hold a meeting next week to bring an end to the menace of arbitrary fare hike by auto-rickshaw drivers in and around Behala after the caving-in of the Majerhat bridge.Suvendu Adhikari, the state Transport minister, said: “The matter has come to our notice and necessary steps would be taken up in this connection. It is true that some auto-rickshaws are charging arbitrary fare whenever they get the opportunity in Taratala and Behala area.” Also Read – Rain batters Kolkata, cripples normal lifeHe further said that there will be a meeting in this connection next week after Viswakarma Puja. People’s representatives from the area, officers of the Kolkata Police, personnel from the depot at Thakurpukur and Taratala will be present in the meeting. “The matter will be sorted out soon as it has been done for the Ultadanga to Sector V route. There are no more complaints in connection with the Ultadanga to Sector V route. Similarly, the issue at Behala and Thakurpukur will also be resolved,” he said. Also Read – Speeding Jaguar crashes into Mercedes car in Kolkata, 2 pedestrians killedAdhikari further added that similar to the “Pathadisha” app that helps to check real-time movement of buses, an app to check the same for vessels that operate through inland waterways will also be introduced. While speaking about the surge fare in app-based cabs, the minister added: “As of now the role of Ola in this connection is satisfactory contradictory to that of Uber. Ola is complying with the advisory of the state Transport department and our officials went to the Ola centre and found that they are maintaining the advisory. But Uber is delaying the process and has not taken out officials to its centre. So I have said that the role of Ola is satisfactory while it is not so in the case of Uber in terms of surge fare.” Moreover, in the programme that was held on Thursday, around 50 cars were handed over to driver partners as per the Memorandum of Understanding (MoU) signed between the West Bengal Transport Infrastructure Development Corporation Limited (WBTIDCL) and Ola in the Bengal Global Business Summit 2018 to create 5,000 employment opportunities.last_img read more