Wake cloaking simulated in lab objects move through water without leaving a

first_img Explore further More information: Fluid flow control with transformation media, Yaroslav A. Urzhumov, David R. Smith, arXiv:1106.2282v1 [physics.flu-dyn] arxiv.org/abs/1106.2282AbstractWe introduce a new concept for the manipulation of fluid flow around three-dimensional bodies. Inspired by transformation optics, the concept is based on a mathematical idea of coordinate transformations, and physically implemented with anisotropic porous media permeable to the flow of fluids. In two different situations – for an impermeable object situated either in a free-flowing fluid or in a fluid-filled porous medium – we show that the object can be coated with a properly chosen inhomogeneous, anisotropic permeable medium, such as to preserve the streamlines of flow and the pressure distribution that would have existed in the absence of the object. The proposed fluid flow cloak completely eliminates any disturbance of the flow by the object, including the downstream wake. Consequently, the structure helps prevent the onset of turbulence by keeping the flow laminar even above the typical critical Reynolds number for the object of the same shape and size. The cloak also cancels the viscous drag force. This concept paves the way to energy-efficient, wake-free propulsion systems, which control and prevent wake formation through a smart spatial distribution of propulsion forces.via PhysicsWorld Citation: Wake cloaking simulated in lab – objects move through water without leaving a trace (2011, July 25) retrieved 18 August 2019 from https://phys.org/news/2011-07-cloaking-simulated-lab-.html Velocity pro le and streamlines of flow around and through the porous spherical shell surrounded by a viscous fluid. (See ref. below for details). Image credit: arXiv:1106.2282v1 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. © 2010 PhysOrg.com (PhysOrg.com) — Metamaterials researchers Yaroslav Urzhumov and David Smith, working at Duke University have built a simulation of an object that can move through water without leaving a trace and claim it’s a concept that could be built and used in the real world provided more research is done. In their paper, published on arXiv, the two describe how they programmed the use of metamaterials applied to an object, along with tiny water pumps, into a model to simulate an actual object moving through water without dragging some of the water with it that would normally cause turbulence. The two show, by use of a sphere, how an object could be covered with several layers of a mesh of wire or blades, from large ones nearest the object, too much smaller ones farthest away. The idea is to make up for the difference in movement between the object, and the stillness of the water it’s moving through, all while parting the water in ways gentle enough to cause cloaking and then allowing it to reseal after the object passes. The metamaterials provide the cloaking, while pumps are used to move the water at differing speeds in the different layers to keep the water from being dragged along as the object moves through it.The paper comes after what seems like one announcement after another in new cloaking technologies; first an invisibility cloak, then ones that cloaked sound, electric and ocean waves and even a time cloaking device; all are based on new so-called metamateriasl (materials with properties not found in nature).The advantages of the use of such technology are obvious; without drag, boats or submarines could go farther and faster while using less fuel, and if they ran nearly silent in doing so, it would herald the age of new stealth boats and ships that would be difficult if not impossible to detect by enemies looking for them. In the model created, the object was bullet sized and moves just a few millimeters per second, but the authors suggest that if an actual boat was to be made, it might make more sense to try to reduce just the drag, rather than try to hide the wake as well, as that would likely be much easier to actually make. The authors do not plan to try to build a real world boat, due they say, to lab constraints, but suggest a collaboration with another facility might be feasible. Next generation cloaking device demonstratedlast_img read more

Multinational effort underway to build synthetic yeast using artificial chromosomes

first_img ‘Synthetic’ chromosome permits repid, on-demand ‘evolution’ of yeast (Phys.org) —A multinational effort to replicate the genome of brewer’s yeast has been launched. Led by Professor Jef Boeke of John Hopkins University in Baltimore, and with teams in China, India, Great Britain and other countries, the goal of the effort is to build artificial chromosomes to replace the 16 normally found in yeast cells. If successful, the effort will mark the first time the entire genome of an organism with a nucleus has been artificially replicated. © 2013 Phys.org Sacharomyces cerevisiae cells in DIC microscopy. Credit: Wikipedia. Citation: Multinational effort underway to build synthetic yeast using artificial chromosomes (2013, July 12) retrieved 18 August 2019 from https://phys.org/news/2013-07-multinational-effort-underway-synthetic-yeast.htmlcenter_img This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Explore further Besides the possibility of providing new insights into how chromosomes work, the project hopes to also serve as a means of learning how to program an organism by altering its genetic functions. Yeast with artificial chromosomes, for example, could be programmed to serve as an engine to manufacture antibiotics, vaccines, biofuels, etc., instead of alcohol.A team of scientists successfully replaced the DNA of a bacteria cell back in 2010, but it had no nucleus, meaning it was a much simpler organism. Replicating all of the chromosomes in a yeast cell will require far more effort. For that reason, the work has been split between teams working at various facilities around the world. Each team will design one chromosome on a computer, which will then be sent to a central facility for its actual creation. Once all of the teams have built their chromosomes, a single yeast cell will be stripped of its natural chromosomes to be replaced by their artificial counterparts—giving it an entirely artificial genome. The project is expected to be expensive—the British team alone has received £1m from the U.K government to fulfill its part in the project which is expected to be completed by 2017.The yeast cell was picked for the project because it is a relatively simple organism—it’s one celled and has only 6000 genes. One the other hand, it’s sufficiently complex to further the science of bioengineering. Another plus is that yeast, because of its ability to convert sugars to alcohol, is seen as a becoming a more useful organism if its DNA could be controlled directly by creating new chromosomes in the lab and replacing the ones that nature gave it.last_img read more

Testing proves giant eyes of netcasting spider help with nocturnal foraging

first_img The net-casting spider is shown holding the band of wooly silk that it uses to engulf and capture prey. UNL doctoral student Jay Stafstrom spent two months in a Florida state park observing the spider’s hunting behavior. Credit: Courtesy Jay Stafstrom Journal information: Biology Letters © 2016 Phys.org Many visitors to Florida have been alarmed by the sight of a small spider with humongous eyes—the net casting spider, so named because of the unusual shape of the webs it creates—fortunately, the spiders are harmless to humans. Interestingly, until now, no one has gone to the trouble of actual testing the spiders to fully understand why they have such big eyes—the largest proportionally, for any arachnid.To prove the theory that the big eyes evolved to help with night foraging, the researchers started by video-taping several of them as they went about their activities in their natural environment. Then, they captured some samples and applied dental silicone over the single pair of big eyes (net-casters, like other spiders have eight eyes altogether, the others eyes are much smaller) temporarily blinding those eyes. The research pair then recorded the activities of the spiders as they tried to survive without benefit of their huge eyes.In studying the results, the researchers found that the blinded spiders were much weaker hunters when their big eyes were covered. Removing the eye covers allowed the spiders to regain their former skill levels.In a second test, the researchers conducted a similar experiment, except they did it in a controlled environment in their lab. In studying the results, the researchers found almost identical results. Citation: Testing proves giant eyes of net-casting spider help with nocturnal foraging (2016, May 18) retrieved 18 August 2019 from https://phys.org/news/2016-05-giant-eyes-net-casting-spider-nocturnal.html Explore further Jumping spiders are masters of miniature color visionlast_img read more

Astronomers observe outburst of comet 15PFinlay

center_img Scientists investigate change in activity of comet 17P/Holmes Explore further More information: 2014-2015 Multiple Outbursts of 15P/Finlay, arXiv:1609.00792 [astro-ph.EP] arxiv.org/abs/1609.00792AbstractMultiple outbursts of a Jupiter-family comet, 15P/Finlay, occurred from late 2014 to early 2015. We conducted an observation of the comet after the first outburst and subsequently witnessed another outburst on 2015 January 15.6-15.7. The gas, consisting mostly of C2 and CN, and dust particles expanded at speeds of 1,110 +/- 180 m/s and 570 +/- 40 m/s at a heliocentric distance of 1.0 AU. We estimated the maximum ratio of solar radiation pressure with respect to the solar gravity beta_max = 1.6 +/- 0.2, which is consistent with porous dust particles composed of silicates and organics. We found that 10^8-10^9 kg of dust particles (assumed to be 0.3 micron – 1 mm) were ejected through each outburst. Although the total mass is three orders of magnitude smaller than that of the 17P/Holmes event observed in 2007, the kinetic energy per unit mass (104 J/kg) is equivalent to the estimated values of 17P/Holmes and 332P/2010 V1 (Ikeya-Murakami), suggesting that the outbursts were caused by a similar physical mechanism. From a survey of cometary outbursts on the basis of voluntary reports, we conjecture that 15P/Finlay-class outbursts occur >1.5 times annually and inject dust particles from Jupiter-family comets and Encke-type comets into interplanetary space at a rate of ~10 kg/s or more. 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

Astronomers uncover properties of a molecular outflow feature in a nearby starburst

first_imgALMA CO(1–0) observations of NGC 253. Credit: Walter et al., 2017. © 2017 Phys.org More information: Dense Molecular Gas Tracers in the Outflow of the Starburst Galaxy NGC 253, arXiv:1701.05040 [astro-ph.GA] arxiv.org/abs/1701.05040AbstractWe present a detailed study of a molecular outflow feature in the nearby starburst galaxy NGC 253 using ALMA. We find that this feature is clearly associated with the edge of NGC 253’s prominent ionized outflow, has a projected length of ~300 pc, with a width of ~50 pc and a velocity dispersion of ~40 km s^-1, consistent with an ejection from the disk about 1 Myr ago. The kinematics of the molecular gas in this feature can be interpreted (albeit not uniquely) as accelerating at a rate of 1 km s^-1 pc^-1. In this scenario, the gas is approaching escape velocity at the last measured point. Strikingly, bright tracers of dense molecular gas (HCN, CN, HCO+, CS) are also detected in the molecular outflow: We measure an HCN(1-0)/CO(1-0) line ratio of ~1/10 in the outflow, similar to that in the central starburst region of NGC 253 and other starburst galaxies. By contrast, the HCN/CO line ratio in the NGC 253 disk is significantly lower (~1/30), similar to other nearby galaxy disks. This strongly suggests that the streamer gas originates from the starburst, and that its physical state does not change significantly over timescales of ~1 Myr during its entrainment in the outflow. Simple calculations indicate that radiation pressure is not the main mechanism for driving the outflow. The presence of such dense material in molecular outflows needs to be accounted for in simulations of galactic outflows. Explore further (Phys.org)—An international team of astronomers led by Fabian Walter of the Max Planck Institute for Astronomy in Germany has revealed essential properties of a molecular outflow feature in the nearby starburst galaxy designated NGC253. The findings were presented in a paper published Jan. 18 on the arXiv pre-print repository. NGC 253, also known as the Sculptor Galaxy, is an intermediate spiral starburst galaxy in the constellation Sculptor some 11 million light years away. The galaxy is one of the brightest spiral galaxies visible and also one of the dustiest. Due to its proximity and the fact that it is currently undergoing a period of intense star formation, it serves as one of the best laboratories to study starburst–driven galactic–scale winds in detail.NGC 253 is known for the galactic wind emerging from its central area, which carries significant amounts of molecular gas. In order to better characterize this emission, Walter and his team carried out a series of observations between November 2013 and August 2014 utilizing the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. This observational campaign allowed the researchers to uncover crucial properties of the studied molecular outflow.”We present a detailed study of a molecular outflow feature in the nearby starburst galaxy NGC 253 using ALMA,” the paper reads.According to the study, NGC 253’s most prominent outflow feature towards the south has a projected length of about 978 light years, a width of approximately 163 light years, and a velocity dispersion of 40 km s−1. The scientists note that its extent and dispersion are consistent with an ejection from the galaxy’s disk starting about 1 million years ago.The kinematics of the molecular gas in this feature show that the material is approaching us and is also accelerating. However, the astronomers were unable to determine whether or not the molecular mass entrained in the outflow will escape the galaxy, or be recycled to fuel later episodes of star formation. More observations are required to draw final conclusions.”The kinematics of the molecular gas are consistent with accelerating with a velocity gradient of 1 km s−1 pc−1, and at its last measurable point it approaches the escape velocity. (…) More sensitive ALMA observations will trace the outflow even further out, and will shed light on whether or not part of the ejected molecular material will escape the galaxy,” the researchers wrote in the paper.The team also discovered bright tracers of dense molecular gas like HCN, CN, HCO+, CS in the molecular outflow. Moreover, they found that line ratios HCN/CO measured in the outflow are high and consistent with ratios observed in the central starburst region of NGC253 and in other starbursts, while the HCN/CO line ratio in the galaxy’s disk is significantly lower, which is typical for gas in the disks of nearby galaxies. The researchers concluded that this indicates that the dense molecular gas is retaining its properties in the process of its ejection from the central regions into the outflow. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Citation: Astronomers uncover properties of a molecular outflow feature in a nearby starburst galaxy (2017, January 24) retrieved 18 August 2019 from https://phys.org/news/2017-01-astronomers-uncover-properties-molecular-outflow.html Starburst to star bust: Astronomers ID suspect behind dearth of high-mass galaxieslast_img read more

No longer soaring high

first_imgJitender Bhargava’s book The Descent of Air India, was launched at the India Habitat Centre ( IHC) on Friday by TN Ninan, an eminent journalist and chairman of Business Standard along with PC Sen, former chairman and managing director of Indian Airlines.The book gives a detailed account of the manner in which the airline, Air India, was brought down.  It is an insider’s tale of how an airline was allowed to fall apart by the very people who had been entrusted with its care.  Also Read – ‘Playing Jojo was emotionally exhausting’Bhargav, former executive director of Air India for 13 years, has not spared anyone in his indictment as he goes on to explain the details of the controversial aircraft acquisition deal, the botched up merger between Air India and Indian Airlines and the financial mismanagement which proved to be the airline’s doing. He brings out the role played by several of the airline’s leaders, ministers and other interested parties in the downfall. During the launch, Bhargav, said that he actually wanted to name the book ’Who destroyed Air India?’. However, he hasn’t shied from naming the people responsible for initiating the downfall of the airline. Several questions about the airlines were addressed by the author during the event.last_img read more

The choice of mind

first_imgUnseen Passages, an art show that exhibits the works from the studios of two young and discerning women is on in the Capital that started off on 13 October. Delhi based artist Pallavi Singh’s series Desire to be Desired explores her observations of male vanity and the conditions that feed it. Punctuating the generation of the millennial is easier and faster access to information resulting in renewed socialisation and an increased interest in one’s self-image. Singh breaks away from the stereotype by focusing on the urban male to whom fashion and grooming are an important norm. A middle–aged potbellied bald man is her choice of protagonist, comically represented fussing over his physical appearance. The comment is intended to be both realistic and ironic, with Singh ensuring that the viewer steps aside from the work wearing a smile. Also Read – ‘Playing Jojo was emotionally exhausting’Soghra Khurasani’s from Baroda work is about freedom of thought and draws from a deep angst against unjust social and religious prescriptions. Her large-scale prints are compositions dominated by red: a colour that she feels expresses her rage and despair at the redundant injunctions imposed on common people. By morphing cells of blood into roses through valleys and volcanoes, her art posits the bittersweet moments. Khurasani’s current series Silent Landscapes reveals a resistance to violence and the telling impact of its trauma in rows, swirls and circles that inform the viewer of a never-ending cycle of repression and defiance.last_img read more

Gupta alleges AAP has scant regard for Assembly rules

first_imgThe Leader of Opposition in Delhi Assembly Vijender Gupta on Monday alleged that the AAP government is violating all rules and traditions in conducting the sessions of the Assembly and is running away from discussions.“This is the smallest session of the House. The government has confined the question hours to the last two days only. How can the budget be discussed in two days? The members will not get time to put their views,” said Vijender Gupta on Monday.  Also Read – Company director arrested for swindling Rs 345 croreHe alleged that the budget is scheduled to be presented on Friday, which was reserved for private member’s bills. “All the members should have been informed 12 days in advance about the session but it was not done,” added Gupta.As per the schedule of the Speaker the budget is likely to be presented in the House on Thursday, June 25.The Speaker, however, in a press conference informed that he had relaxed the norms for the question hour. “The question hours have been fixed for the last two days of the session. I have relaxed the norms to allow members to ask questions by relaxing the minimum limit of 12 days. So far 67 questions have been received,” said Ram Niwas Goel, the Speaker. Goel also informed that Friday is reserved for private member’s bill and three bills are scheduled to be introduced in the Assembly.last_img read more