(Phys.org) —Researchers at the University of California, Berkeley, have discovered that a nanocrystal moving through a nanotube due to an electric charge is able to pass through a portion of the nanotube that is smaller in diameter than the crystal, without melting or undergoing compression. In their paper published in the journal Physical Review Letters, the team describes how they observed an iron nanocrystal move through a narrow channel in a nanotube without its properties being changed in the process. Journal information: Physical Review Letters 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. Scientists have known for some time that if metal crystals are inserted into a nanotube, then the crystals will move through the tube if an electric current is applied. The speed and direction of the crystals can be controlled by modifying the amount and direction of the current. However, that was always done with uniform width nanotubes. In this new effort, the researchers created a nanotube that had a diameter of 20 nm for most of its length—in its middle section however, they caused the nanotube to constrict to a diameter of just 5 nm. The assumption was that when an electric charge was applied to an iron nanocrystal introduced into the nanotube, it would be stopped-up by the constriction until either the crystal melted due to the heat of the current applied, or was squished as it was forced through the smaller space. Instead, the researchers found, by watching through an electron microscope, that the crystal was able to move through the constriction before either occurred, without undergoing any changes at all. Instead, it simply rearranged itself. They noted also that the crystal moved through the constriction at the same speed, regardless of its length, so long as the current remained stable.The researchers aren’t sure exactly how the crystal was able to move through the constriction, but theorize that atoms on the back side of the crystal structure somehow migrated, or diffused to the front—over and over again until the crystal had, in essence, re-formed itself on the other side of the blockage. The discovery of this phenomenon could lead to new ways to synthesize metal crystals or to increase their purity. A transmission electron micrograph image of an iron nanocrystal inside a carbon nanotube and the same section after a current has been applied, causing the iron nanoparticle to squeeze into the adjacent constriction. Credit: S. Coh et al., Phys. Rev. Lett. (2013) Citation: Researchers discover nanocrystals able to squeeze through nanotubes without changing (2013, May 2) retrieved 18 August 2019 from https://phys.org/news/2013-05-nanocrystals-nanotubes.html © 2013 Phys.org Simulation shows it’s possible to move [email protected] using electrical charge More information: Surface Atom Motion to Move Iron Nanocrystals through Constrictions in Carbon Nanotubes under the Action of an Electric Current, Phys. Rev. Lett. 110, 185901 (2013) prl.aps.org/abstract/PRL/v110/i18/e185901AbstractUnder the application of electrical currents, metal nanocrystals inside carbon nanotubes can be bodily transported. We examine experimentally and theoretically how an iron nanocrystal can pass through a constriction in the carbon nanotube with a smaller cross-sectional area than the nanocrystal itself. Remarkably, through in situ transmission electron imaging and diffraction, we find that, while passing through a constriction, the nanocrystal remains largely solid and crystalline and the carbon nanotube is unaffected. We account for this behavior by a pattern of iron atom motion and rearrangement on the surface of the nanocrystal. The nanocrystal motion can be described with a model whose parameters are nearly independent of the nanocrystal length, area, temperature, and electromigration force magnitude. We predict that metal nanocrystals can move through complex geometries and constrictions, with implications for both nanomechanics and tunable synthesis of metal nanoparticles.
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. (Phys.org)—Scientists have found that an intricately beautiful yet poorly understood type of crystal found in soap bubbles follows the same mathematical rules as a much better understood type of crystal called martensite. Due to its extreme hardness, martensite has been used since the Iron Age to make swords and horseshoes. The soap-bubble crystals, on the other hand, which are called smectic liquid crystals (where “smectic” is derived from the Greek word for “soap”), have turned out to be what the scientists describe as “the world’s weirdest martensite.” While all crystals are known for their highly ordered, aesthetically appealing structure, smectic liquid crystals stand out because their microstructure is particularly unusual. Full of beautiful patterns of ellipses and hyperbolas that bend, rotate, and curve around each other, the microstructure of smectic liquid crystals has fascinated researchers since they first turned their microscopes upon them over a century ago. Martensite microstructure, on the other hand, is characterized by a simpler striped pattern.Discovering the connection between the two seemingly different types of crystals required the meeting of two experts in these areas: Randall Kamien, a physicist at the University of Pennsylvania who studies smectic liquid crystals, and Cornell University physicist James Sethna, who specializes in martensites.In a new paper published in Physical Review Letters, Kamien, Sethna, and their coauthors have modified the mathematical theory of martensites so that it also explains the unusual features of smectic microstructure. It turns out that the rules that describe how all of the ellipses and hyperbolas fill 3D space in the smectic microstructure are very similar to the rules that describe the relatively simpler patterns in martensitic crystals.”I’m excited because a weird, anomalous scientific backwater with beautiful phenomena has now been fit into a standard framework,” Sethna told Phys.org. “The mathematically beautiful theory of martensites, which until now mostly predicted layered structures, now has an amazingly rich example, smectic liquid crystals.”The resulting new theory of smectic microstructure captures observations made as far back as 1922, when the French mineralogist Georges Friedel discovered that smectic layers bend in a very specific way, into so-called “cyclides of Dupin.” These layers of curved surfaces have centers of curvature that all lie along another single curve. As the curved surfaces somewhat resemble flower petals curving around the center of a flower, the cyclides of Dupin give the crystals a “flower texture.” All of this highly ordered curvature also enables the complex surfaces to pack together very tightly. (Left) Simulations of smectic liquid crystals and (right) experimental martensites, which have a characteristic striped pattern. Small images of smectic liquid crystals in the middle show close-ups of ellipses and hyperbolas, which form curved patterns known as cyclides of Dupin. The microstructure also exhibits Apollonian packing, where the small gaps between ellipses are filled with smaller and smaller ellipses. The concentric circles can be described by the same mathematics used to describe light cones in special relativity. Credit for smectic liquid crystals: Liarte, et al. ©2016 American Physical Society. Credit for martensites: Chu and James. Besides the connection between the two crystals, there is another mathematical connection in this work, which is that to special relativity. In smectic liquid crystals, the cyclides of Dupin form concentric circles of increasing size that form cones which look like the “light cones” in special relativity. Light cones represent the path of light as it broadens in all directions, like light emerging from a flashlight. Since the crystal and light models are geometrically identical, the same math used in special relativity, such as manipulating the shapes with Lorentz transformations, can be used to describe these crystals.”The links to Einstein’s relativity are both real and theoretically cool,” Sethna said.Although the new theory of smectic liquid crystals and martensites describes many characteristics of both crystals, questions still remain regarding some of the unique geometrical features, and the researchers hope to continue to investigate these tiny structures in future work.”We’re hoping to extend our tools to analyze experimental smectic microstructures,” Sethna said. “There are some new imaging methods that should allow the layer orientations to be understood in three dimensions, and we should be able to use our numerical methods to figure out how the cyclides of Dupin (each with an ellipse and a hyperbola) fit together to fill the volume, adapt to changing boundary conditions, and evolve as the smectic flows.” More information: Danilo B. Liarte, et al. “Weirdest Martensite: Smectic Liquid Crystal Microstructure and Weyl-Poincaré Invariance.” Physical Review Letters. DOI: 10.1103/PhysRevLett.116.147802 Another characteristic that results in tight packing in the smectic microstructure is called “Apollonian packing.” Since there are small gaps between the ellipses, these regions are filled with smaller ellipses, and the gaps between them are likewise filled with even smaller ellipses, all the way down to the molecular scale. Both the Apollonian packing and cyclides of Dupin occur for the same reason: they offer the most energetically favorable arrangement for this crystal. Citation: Two different crystals can be described by the same mathematical rules (2016, April 19) retrieved 18 August 2019 from https://phys.org/news/2016-04-crystals-mathematical.html © 2016 Phys.org Simulations of the “topography” of smectic liquid crystals. The concentric circles on the bottom form “light cones” analogous to those in special relativity. Credit: Liarte, et al. ©2016 American Physical Society ‘Weirdest martensite’: Century-old smectic riddle finally solved Journal information: Physical Review Letters
Kansas well owners, non-well owners have different watering routines during droughts Credit: CC0 Public Domain © 2017 Phys.org 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. (Phys.org)—A team of researchers from several institutions in Australia has developed a model that sheds light on the social factors involved in getting users to cooperate on water conservation efforts. In their paper published in the journal Nature Human Behavior, the group describes the factors they used to build their model and what it revealed.
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. A quartet of researchers from the University of Tokyo in Japan and the University of Reading in the U.K. has found an association between the evolution of foot posture and body size in mammals. In their paper published in Proceedings of the National Academy of Sciences, Tai Kubo, Manabu Sakamoto, Andrew Meade and Chris Venditti describe their study of foot posture in a large variety of extant mammal species and their subsequent development of a phylogenetic tree. Journal information: Proceedings of the National Academy of Sciences Explore further The researchers note that all modern mammals can be classified by one of three types of foot posture: flat-footed, tiptoed and hooved. Flat-footed creatures include species like humans and mice. Tiptoed species include animals such as dogs and cats and hooved species include creatures such as horses and deer. In this new effort, the researchers began by classifying 880 species of extant mammals by their respective foot-posture type. They note that most species were easy to classify, while some, such as elephants (flat-footed) and rhinos (tiptoed) were not.Once the team completed the classifications, they plotted the species under study on a family tree that included all mammalian species—they also added some extinct species with known foot types. They were able to see associations in the tree between species based on foot type. In so doing, they found that foot type could be generally associated with body size. Animals with hooves, for example, tended to be large. They also found that tiptoed animals were, on average, twice as big as flat-footed animals, though there were some notable exceptions. People are generally bigger than dogs and housecats, for example. They also found that hooved animals were actually a lot bigger on average than tiptoed animals—57 times as big. The researchers noted that the association between foot type and size posed the question of which came first—did the development of hooves allow certain species to grow bigger, or did hooves come about because larger animals needed them?The researchers also used their tree to analyze historical specimens and found evidence that suggested the first mammals to evolve likely belonged to the flat-footed category. More information: Tai Kubo et al. Transitions between foot postures are associated with elevated rates of body size evolution in mammals, Proceedings of the National Academy of Sciences (2019). DOI: 10.1073/pnas.1814329116 Citation: Study of foot posture shows association between foot type and body size evolution in mammals (2019, January 29) retrieved 18 August 2019 from https://phys.org/news/2019-01-foot-posture-association-body-size.html Credit: CC0 Public Domain Skull scans tell tale of how world’s first dogs caught their prey © 2019 Science X Network
Winters have set in Delhi and celebrations have begun. It is time to feel the warmth of love and celebration in the air. In a bid to boost tourism in the city, Delhi Tourism will be organizing Winter Carnival and mark the celebration on the season. The festival will be from December 20 to 31 at Dilli Haat INA. The occasion of Christmas spreads joy and laughter and this celebration would heartily bid farewell to 2014 and welcome the new year in great enthusiasm. Also Read – ‘Playing Jojo was emotionally exhausting’An exhibition of ACASH under the Ministry of Textiles-Development Commissioner for Handlooms, which had started on December 16 will be continuing till December 31 at the same venue and it is be an additional attraction for masses. This taana-baana exhibition by ACASH includes sareers and suits of exclusive variety. The exhibition would include attire from places like Kantha, Patola, Chanderi, Banaras, North East, Kangivaram and Gujarat. Shawls from J&K, Himachal Pradesh and Gujarat would be a fashionable attraction for visitors.A unique Christmas bazaar would be the main attraction and Santa Claus would be moving around the venue distributing candies to charm the little ones. Delhi Bible Fellowship would conduct singing of carols, while people dressed as clowns would be entertaining the visitors.
Final year’s master’s students of Convergent Journalism, Jamia Millia Islamia screened their documentaries at the second Ainaa Documentary Film Festival. The festival marks the showcasing of their documentaries that was made during their final year of the course under the guidance of mentors and the Mass Communication Research Centre (MCRC) faculty of Jamia Millia Islamia.Five documentaries from the duration of five minutes to twenty minutes were screened at the spacious M A Ansari Auditorium that was brimming with students, friends, family and alumnus of the course. Teachers and students from other colleges too joined in. The screening was followed by a question answer session where audience asked questions to the directors and team involved in the film making. Also Read – ‘Playing Jojo was emotionally exhausting’The theme of the documentaries covered a range of subjects. The first documentary was on Rohingya Muslims from Burma who have migrated to India in search of safer shelter. The documentary follows Afsa and her family who fled from Burma following violence and it shows their story of survival in a different land. Directed by Muhammad Faisal K, and titled I can’t be mad at Allah, the film talks about the spirit of resilience and faith in God that these refugees show even when facing terrible times. Also Read – Leslie doing new comedy special with NetflixA fun take on dreams, those achieved and those that died in the heart somehow, Malvika Saini’s documentary is aptly called Delhi Dreams. The documentary features many Delhiites’ who talk about what their dreams are/were, what adds music and fun to the story is how each respondent has a xylophone and can create music of their own while recalling their dream. The audience was in splits while watching this very short documentary.Memories of an Autumn was a documentary on Sikh riots of 1984 narrated through the memories. The film talks about memories of people who survived the riots and were witnesses, those who have heard about the riots and are old enough to understand what happened, reflecting selective memory and finally small children who know of the riots like a fable, learnt by heart even when the story is completely flawed, false memory. Three generations tell what they knew of the riots. Many questions followed the screening where the audience asked many question to director Sanat Sinah and his team. Aaqib Raza Khan’s Desi Angrezi was a fun take on the numerous ‘Spoken English’ courses that has sprouted in the country. It follows two characters who are struggling to learn and understand the language and master good English pronunciation so that they can succeed in achieving their dreams. Another film that drew many eyeballs was Sailabnama by Sheikh Saaliq and Qazi Zaid that traced volunteers during their rescue/aid operations during the recent floods in Kashmir. While the filmmakers focused on the feeling of brotherhood the Kashmir floods had invoked in the locals, the discussion after the film discussed the role of the Indian army in the rescue operations. They were numerous questions asked and answered. The documenatries were produced by the course co-ordinator Richa Pant and Simon Chamber, mentor for the students and an independent documenatry filmmaker from London.
Part of the proceeds of the Indian, Himalayan and Southeast Asian Art auction scheduled to be held in New York on September 14, with total estimates of $ 2 million — $ 3 million will be donated to charities engaged in relief and rebuilding operations in the earthquake affected Nepal, auctioneers said in a statement.