Month: August 2019

Scientists solve mystery of the eye

first_img How the drug isotretinoin zaps acne ( — Scientists have a good overall understanding of human vision: when light enters our eyes, it is focused by the lens and strikes the retina in the back of the eye. The light causes some of the millions of photoreceptor cells that line the retina to undergo a chemical change, which send a message through the optic nerve fiber to the brain, which creates a picture. However, there are still a few unresolved questions in the details of the vision process, one of which is why the eye evolved to use a certain light-absorbing chromophore called 11-cis-retinal instead of one of its isomers (i.e., molecules with the same atoms but in different arrangements), such as 7-cis, 9-cis, or 13-cis. More information: Sivakumar Sekharan and Keiji Morokuma. “Why 11-cis-Retinal? Why Not 7-cis-, 9-cis-, or 13-cis-Retinal in the Eye?” Journal of the American Chemical Society. DOI:10.1021/ja208789h A schematic representation of 7-cis- (PSB7, green), 9-cis- (PSB9, blue), 11-cis- (PSB11, black), 13-cis- (PSB13, purple), and all-trans-retinal (PSBT, red). PSB stands for “protonated Schiff base,” the linkage between the retinal chromophore and the opsin protein. Image credit: Sekharan and Morokuma. ©2011 American Chemical Society Journal information: Journal of the American Chemical Society Chemists Sivakumar Sekharan from Emory University in Atlanta, Georgia, and Keiji Morokuma from Emory University and Kyoto University in Kyoto, Japan, describe the eye’s use of 11-cis-retinal as “one of the basic and unresolved puzzles in the chemistry of vision.” But by taking advantage of the rapid advances in hybrid quantum mechanics/molecular mechanics (QM/MM) computational modeling, the researchers have found that the answer to this puzzle lies in electrostatic interactions in the retina. Their study is published in a recent issue of the Journal of the American Chemical Society.The retina contains light-sensitive photoreceptor cells known as rods and cones, which convert incoming light into electrical impulses that are sent to the brain. On the top of every rod and cone is a region that contains opsin proteins bound to 11-cis-retinal chromophores, which together are called rhodopsin. When light strikes the retina, the 11-cis-retinal chromophores absorb the light, which causes them to undergo an isomerization and change their molecular configuration from 11-cis-retinal to all-trans-retinal in a matter of picoseconds. The difference between these two isomers involves the positions of the hydrogen atoms, a shape change that causes the opsin protein to change shape in response. The opsin shape change, in turn, leads to a cascade of biochemical reactions in the photoreceptor cell that ultimately generate an electrical impulse.Since the 11-cis-retinal is the retina’s first responder to incoming light, its unique geometric configuration clearly plays an important role in the vision process. However, theoretically there are a handful of other retinal isomers that seem capable of performing this task, yet for some reason photoreceptor cells only function with 11-cis-retinal (and the corresponding 11-cis-rhodopsin). Explore further Citation: Scientists solve mystery of the eye (2011, November 17) retrieved 18 August 2019 from Copyright 2011 All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of “Because the primary event in vision involves no breaking of chemical bonds but only a conformational change in the shape of the molecule from bent cis to the distorted all-trans form, scientists wondered why 7-cis-, 9-cis- or 13-cis- isomers could not achieve this goal,” Sekharan told answer this question, the researchers built computational models of the rhodopsin found in the eyes of cows, monkeys, and squids. While all known animals’ eyes use 11-cis-retinal, the opsin in different animals contains different numbers and positions of amino acids. Using a cutting-edge QM/MM modeling method called ONIOM (Our own N-layered Integrated Molecular Orbital), the researchers prepared models that matched different animals’ opsins with 7-cis, 9-cis, 11-cis, and 13-cis molecules serving as chromophores. In these artificial rhodopsins, the researchers analyzed the structure, stability, energetics, and spectroscopy to try to find out what makes 11-cis-retinal nature’s preferred isomer.The results of the modeling showed that differences in the electrostatic interactions between the opsin protein and the retinal chromophore played the biggest factor in the natural selection of 11-cis-retinal over the other cis isomers. Due to electric charges, the link between 11-cis-retinal and opsin has a higher stability than the links between other cis isomers and opsin, making it the most favorable choice. “Our results show that the strong electrostatic interaction between retinal and opsin favors the natural selection of 11-cis- over other cis-isomers and arguably prepares the chromophore for the upcoming photochemical event,” Sekharan said. “This indeed is very surprising given the fact that, outside the protein environment, 11-cis-retinal is one of the least stable isomers. Apparently, our results on cow, monkey and squid demonstrate that organisms everywhere may tend to gravitate towards common selection.”Sekharan added that the results not only provide a better understanding of the eyes on a molecular level, but could also have applications for artificial retinas.“Because rhodopsin serves as a decisive crossing point between an organism and its environment, we have been always impressed with this interesting interface by seeing it, say, from the outside and not from the inside,” he said. “Using the ONIOM-QM/MM method we developed, we can ‘enter’ deep into the dark side of this fascinating molecule. One of interesting findings to emerge out of our investigation is that 9-cis-retinal is only slightly higher in energy compared to 11-cis-retinal. This provides strong evidence for the presence of 9-cis-rhodopsin in nature, which in turn may well aid in optimizing the parameters required for designing artificial retinas.” 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

Study offers hint at a way to predict blow up fires

first_img Play Structure-to-unstructured transition followed by an unstructured-to-structured transition (1/10 actual speed). A 1-cm triangular bump, positioned 13 cm away from the ignition end of a 2.54-cm-wide strip (small mesh) triggers the first transition (structured-to-unstructured). A second bump, positioned 5 cm away from the first (and 8 cm away from the end of the strip), triggers the second transition (unstructured-to-structured). Credit: PNAS, doi: 10.1073/pnas.1417043112 The research pair acknowledge that real world fires, whether in buildings or forests are far more complex with many more variables at play, but believe what they have found likely has enough in common with real fires to warrant further research—which could lead to offering firefighters a way to better predict when a fire is suddenly going to change. Play Failed structured-to-unstructured transition on a double-layer strip (1/10 actual speed). A flame propagating along a stack of two 2.54-cm-wide strips (large mesh) containing a 1-cm triangular bump. Credit: PNAS, doi: 10.1073/pnas.1417043112 Journal information: Proceedings of the National Academy of Sciences © 2015 Citation: Study offers hint at a way to predict ‘blow up’ fires (2015, February 10) retrieved 18 August 2019 from (—A pair of researchers with Harvard University has found that a simple experiment they conducted in their lab might lead to helping predict when fires in buildings or forests might be on the verge of becoming “blow up” fires. In their paper published in Proceedings of the National Academy of Sciences, Jerome Fox and George Whitesides describe their experiment and why they believe what they have learned might help firefighters at some point in the future. More information: Warning signals for eruptive events in spreading fires, Jerome M. Fox, PNAS, DOI: 10.1073/pnas.1417043112AbstractSpreading fires are noisy (and potentially chaotic) systems in which transitions in dynamics are notoriously difficult to predict. As flames move through spatially heterogeneous environments, sudden shifts in temperature, wind, or topography can generate combustion instabilities, or trigger self-stabilizing feedback loops, that dramatically amplify the intensities and rates with which fires propagate. Such transitions are rarely captured by predictive models of fire behavior and, thus, complicate efforts in fire suppression. This paper describes a simple, remarkably instructive physical model for examining the eruption of small flames into intense, rapidly moving flames stabilized by feedback between wind and fire (i.e., “wind–fire coupling”—a mechanism of feedback particularly relevant to forest fires), and it presents evidence that characteristic patterns in the dynamics of spreading flames indicate when such transitions are likely to occur. In this model system, flames propagate along strips of nitrocellulose with one of two possible modes of propagation: a slow, structured mode, and a fast, unstructured mode sustained by wind–fire coupling. Experimental examination of patterns in dynamics that emerge near bifurcation points suggests that symptoms of critical slowing down (i.e., the slowed recovery of the system from perturbations as it approaches tipping points) warn of impending transitions to the unstructured mode. Findings suggest that slowing responses of spreading flames to sudden changes in environment (e.g., wind, terrain, temperature) may anticipate the onset of intense, feedback-stabilized modes of propagation (e.g., “blowup fires” in forests). Fire season in West expected to get more intense 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. All firefighters are familiar with the term “blow up” fire—it is when a fire suddenly grows in magnitude and intensity creating a very dangerous situation. Unfortunately, there is no way to predict when a blow up is likely to occur, thus those attempting to put out such fires are usually surprised when it occurs. In this new effort, the research pair thought that the behavior of blow up fires showed similarities to phase transitions in other instances and devised a simple experiment to see if they could confirm their suspicions.In the lab, the researchers placed nitrocellulose strips on a wire mesh grid (a piece of window screen) and filmed what occurred when they lit one end of the strip. The strips burn, like a fuse, from one end to the other, and if left alone, generally do so in a slow orderly fashion. But, in the lab, the researchers found that they could cause a blow up by changing the conditions under which the strip was burned, by altering the slope, for example, adding wind, or by introducing a bump by bending the strip prior to lighting. By fine tuning the alterations, they were able to nudge the fire ever closer to a blow up which allowed them to confirm that the blow ups conformed to what is known as “critical slowing down”—where the closer a system is to collapse, the more time it takes to recover from an event. 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 Explore furtherlast_img read more

After bypoll drubbing BJP not too upbeat on prospects

first_imgThe civic polls, including in Kolkata, will be followed by elections to 92 other civic bodies across the state on April 25. The party said it will be concentrating more on the 2016 Assembly polls.Trinamool Congress had retained both Bongaon Lok Sabha and Krishnaganj Assembly seats with huge margins in the by-polls held in the month of February. Though the BJP is banking on the excuse that the civic polls will be a state show (with a fact that it will organized by the State Election Commission and managed by local administration), ground realties suggest that the saffron party’s base in the state is in shambles, with its support base declining.Speaking to the Millennium Post, BJP national secretary and in charge of West Bengal, Siddharth Nath Singh said: “The civic election will be highly rigged as it is controlled by the state administration. We recently had a meeting with the state leadership in Delhi and our main focus is to concentrate on 2016 Assembly poll.”On the context of whether the party is happy with the functioning of West Bengal unit of the party with amid rumours like BJP president Rahul Sinha might be removed with party MP Babul Supriya, he said: “We are extremely happy with Sinha and there is no question of removing him.”However, sources said that there is infighting between the state BJP and the central leadership and it has a taken a serious turn in the recent past. It was learnt that BJP president Amit Shah had a detailed meeting with the state leadership and reportedly expressed unhappiness over the party’s West Bengal leaders failing to take advantage of the political situation that was created in favour of the party after the Lok Sabha polls.last_img read more

Dos and donts for running a marathon

first_imgRunning a marathon is never easy but with the right training and following the dos and don’ts, one can not only avoid serious injuries but also enjoy the run, says an expert.Before the run:* Ensure that a part of your longest run (full marathon – 32 to 38 km, half marathon – 21 to 24 km) has about 60-70 per cent distance being run at your goal/race pace. For example, if you intend to finish the half marathon in one hour 59 minutes, the goal pace is 5:40 per km. Also Read – Add new books to your shelf* Also, you need to get familiar with the running course so that you don’t get bothered with unexpected inclines. Practice your long runs with some inclines added so you know how much to slow down on such inclines on the day of the run.* A day before the marathon, it is recommended to stay off one’s feet, and drink a lot of fluids to stay well hydrated.* One also needs to ensure that you don’t skip food, nor go on any kind of diet just before the race. Taking meals that are high (65-75 per cent) in carbohydrates is recommended. There should also be adequate protein intake. Also Read – Over 2 hours screen time daily will make your kids impulsive* Lastly, mentally preparing for your race by visualising the course and your race plan is an integral part of the final preparation. A night before the big run, lay out your gear, have an early dinner and go to bed early.* On the big day, it is critical to take an easily digestible meal two hours prior to the race start time. Additionally, drinking adequate water to digest this meal is also important.On the start line and during the run:* Just before one starts running for the big race, it is important to do a light warm up. Also, sipping water every now and then until the start, is recommended. * For the first half of your race in a half marathon, do not run faster than your goal pace as it might lead to cramps. If the sun isn’t being too nice, use a sponge to cool your head and back of the neck. Also, it is vital that one keeps sipping on water in order to avoid dehydration because once this sets in it becomes difficult for one to keep up to the goal pace.After the run:* On finishing the race no matter how tempted one is to sit down on the grass and stretch the muscles, don’t. This is because the muscles are inflamed and to ensure that one recovers fast, they need to move around to facilitate smooth blood circulation.* Having a meal which comprises of carbohydrates and proteins as early as possible will replenish ones glycogen levels. The proteins will help in repairing the damaged tissue.* For quick post marathon recovery, getting a good night’s sleep, drinking lots of fluids throughout the day and eating food which is high in proteins and carbohydrates is the key to repair and refuel yourselves.* Stretching and ice baths are other ways to boost one’s running recovery. This will help in increasing blood flow to the muscles while an ice bath will help in reducing post marathon soreness by reducing inflammation.last_img read more

Photo fest on sustainable development kicksoff

first_imgThe second edition of ‘Habitat Photosphere’, a year-long photography festival conceptualised and curated by Dr Alka Pande and initiated by India Habitat Centre, New Delhi, has finally kicked off. The event – which revolves around the theme of sustainable development, commenced with the announcement of this edition’s four awardees of the Photosphere fellowship. Selected through an open call for application process, the four photographers – Juhi Saklani (New Delhi), Thulasi Kakkat (Kochi), Zishaan Akhbar Latif (Mumbai) and Syed Adnan Ahmed (Rajasthan) – have been given a Rs 2 lakh grant to produce a significant body of work that will be exhibited during the grand finale of the festival, slated for February – March, 2019. The awardees will be mentored throughout the year by an eminent panel of photographers including Aditya Arya, Bandeep Singh, Parthiv Shah and Prabir Purkayastha. Also Read – Add new books to your shelfHabitat Photosphere will bring together the spheres of photography and sustainability, through fellowship and mentorship, followed by a month-long grand finale of exhibitions, workshops, talks and screenings at India Habitat Centre. In addition, there will also be curated events and exhibitions on the theme of sustainability. The festival is followed up with a photo-book titled ‘Visual Arts Journal 2018 Photography: Art, Archive, Document’ that aims to position itself as a handbook of diverse scholarly works on photography from prominent authors, curators, and art practitioners. Also Read – Over 2 hours screen time daily will make your kids impulsiveDr. Alka Pande, Festival Director, Habitat Photosphere stated: “We are a festival with a green conscience. While the first edition dealt with the subject of Panchtattvas (five elements) under the meta-narrative of sustainable development, this year’s focus will be on cultural sustainability, which is as relevant and pertinent as ecology and environment, and in fact, impact it as well. Also this year, there was a shortlist round where eight candidates were first shortlisted, and from which the final four were then selected.” Delhi-based Juhi Saklani’s photographs will be of trees and roots that grow out of the old walls and buildings, out of unexpected spaces. The idea is to emphasise the synergy and interconnectedness of life. The performative silhouette of the artist placed amongst these surroundings explores this interconnection. Thulasi Kakkat focuses on the eco-cultural significance of Theyyam, a ritualistic form of worship from Kerala. An unmistakable umbilical link existed between Theyyam, with its organic accouterments drawn from nature, and the biodiversity-rich wilderness of the sacred groves (Kaavus) home to Malabar’s pantheistic deities. A government report published in 1956 had identified some 10,000 Kaavus in various parts of Kerala. Fifty years hence, in 2015, just about 1,200 of them survived. Development has ushered most Theyyams out of what remained of the groves to built structures with open spaces engirdled by high compound walls.Speaking about the work, Kakkat said: “My aim is to document the surviving Kaavus with their integral Theyyam deities. I seek to explore the strong underpinning of eco-feminism that remains embedded in Theyyam, with its subaltern ecological identity that is at war with its own opportunistic transformation.”Syed Adnan Ahmed is dealing with the culturally and socially sensitive subject of rooster combat where animals are pitted against each other resulting in fatal injuries and pain.Zishaan Akhbar Latif is developing work around the “withering” away of the river Majuli in Assam, with an aim to speak to about larger consequence of climate change and those who continue to deny its ​existence. The primary sponsor for Habitat Photosphere 2018-19 is Dalmia Bharat.last_img read more

Campaigning ends with CMs roadshow

first_imgKolkata: Trinamool Congress supremo Mamata Banerjee’s three roadshows on Kolkata’s streets on the last day of campaign for the final phase of the ongoing Lok Sabha elections, just hours before the Election Commission’s campaign ban kicks in at 10 pm, witnessed tremendous response from her party workers and the common people alike.Hundreds lined up on both the sides of the streets as the first roadshow hit Diamond Harbour (DH) Road on a hot Thursday afternoon after it kick-started from Thakurpukur 3A bus stand. People tried to get a closer look at the charismatic leader giving her security personnel and police a tough time. Roadshows were conducted in favour of Mala Roy and Mimi Chakraborty contesting with Trinamool Congress’ tickets from South Kolkata and Jadavpur respectively. Also Read – Rs 13,000 crore investment to provide 2 lakh jobs: MamataThe rally grew bigger in size as it marched down DH Road with the joining of thousands of Trinamool Congress supporters. People started congregating as the news of Banerjee taking part in roadshows reached the local residents of Thakurpukur, Behala, Taratala areas and to those living on either side of DH Road. Braving the heat, the roadshow witnessed a sea of people while passing through Behala. Many were found queuing up on both sides of the road while some of whom tried to capture the moment on their mobile cameras. People waved at Banerjee when she passed Behala Chowrasta area and shouted slogans in her support. Banerjee did not disappoint them and reciprocated by waving back at them. People gathered with TMC’s festoons and flags across the entire stretch. The first roadshow concluded at Taratala. Also Read – Lightning kills 8, injures 16 in stateThe second rally began at Sukanta Setu in the evening and ended at Gariahat. It went past all the important locations of South Kolkata. In some areas, women were found blowing conch shells to hail Banerjee who has emerged as the key challenger to Modi and the saffron party and will play a major role in forming the next government at the Centre. As the roadshows touched down the streets, TMC activists and leaders shouted political slogans to oust the Narendra Modi government from the Centre. The slogans resonated in the air as the roadshows crossed various lanes and bylanes of the city. People who came for shopping in Gariahat witnessed the mammoth rally. The third roadshow kicked off at Ballygunj Phari and ended at Harish Chatterjee Street, near her residence, later in the evening. Support for Mamata remains unwavering with the masses chanting anti-BJP slogans as she made her was along the areas for her rallies. Concerns over national issues remain foremost on the voters’ minds, who gathered in hundreds for the final chapter of the campaign before the state goes to polls in the final phase of the Lok Sabha elections on May 19.last_img read more

Monitoring cell advisor visits Raina Jamalpur to interact with beneficiaries

first_imgKolkata: Colonel Diptangshu Chowdhury, advisor of the monitoring Cell constituted by Chief Minister Mamata Banerjee to take stock of various government schemes, visited Raina and Jamalpur to interact with the beneficiaries and to listen to their complaints.Colonel Chowdhury took a detailed stock of the social schemes run by the Mamata Banerjee government. He examined various aspects as to how the schemes were being implemented in the district. This is for the first time in the history of the state that a representative deployed by the Chief Minister is visiting the districts to ensure that beneficiaries in the remote areas can reap the benefit of various government schemes. Also Read – Rs 13,000 crore investment to provide 2 lakh jobs: MamataIt has been a huge success for the monitoring cell as Bankura District Magistrate Umashankar S attended a public interaction program in the name of Sahamarmi Sabha in a remote village of Taldangra Block in Bankura to address a grievance redressal and to perform a social audit on schemes and beneficiaries. The villagers also took active part in the event. The Chief Minister has given a platform where the beneficiaries of various government schemes can directly converse with the Chief Minister’s office, sharing their feedback and suggestions for the improvement of the delivery mechanism. Also Read – Lightning kills 8, injures 16 in stateOnce a beneficiary from the districts raises his/her issue with the Chief Minister’s office through email at [email protected], it will be thoroughly examined and replied to within 10 days. One of the main objectives of the initiative is to bridge the gap between the beneficiaries and the government, thereby ensuring a smooth implementation of all the schemes. The focus of the move is to reach out to the marginalised beneficiaries in particular. The monitoring cell has already addressed many other issues. The grievances of two widows at Purulia’s Bagmundi have been addressed within two days.last_img read more