Krill superswarm formation investigated

first_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 (PhysOrg.com) — Scientists have been studying how krill form into superswarms, which are among the largest gatherings of living creatures on Earth. Krill swarm. Photographer: Jamie Hall. Image source: NOAA. via Wikimedia Commons. Antarctic krill provide carbon sink in Southern Ocean Citation: Krill ‘superswarm’ formation investigated (2009, October 13) retrieved 18 August 2019 from https://phys.org/news/2009-10-krill-superswarm-formation.html Juvenile krill (small crustaceans resembling shrimps) gather in their trillions in the Southern Oceans to form superswarms. In the Antarctic, for example, one species of krill (Euphausia superb) forms superswarms that stretch for tens of kilometers. Until recently, no one has understood why or how they do it. So scientists with the British Antarctic Survey (BAS), led by Cambridge (UK) researcher Dr Geraint Tarling, decided to try and find out. The team used echo-sounding equipment to study over 4500 different swarms of krill in the Scotia Sea, a massive area that lies between South Georgia Island and the Antarctic Peninsula. The report, published in the journal Deep Sea Research I, described how the research team discovered there are two types of swarm: small swarms composed of adult krill, and large swarms composed of juveniles. The small swarms may be only around 50 meters long and four meters deep, and are not densely packed (about 10 krill per cubic meter). The large swarms are the “superswarms”, which can stretch for many kilometers and are about 30 meters deep. The superswarms are much denser, with up to 10 times more individual krill per cubic meter.This was the opposite of the result expected by Dr Tarling and his team, who thought the small swarms would be dense and the superswarms more diffuse. Dr Tarling said he was astonished at the density of the superswarms and the concentration into a small area of such a massive amount of biomass.The BAS team also discovered that the large swarms tended to form when there was less food available, but the reasons for the formations of superswarms were unclear. Dr Tarling said a likely explanation is that a large swarm gives an individual protection from predators such as seals and whales, and a large swarm can confuse predators. It can also be more energy efficient, which could help juveniles grow more quickly.The trade-off in forming large swarms is much greater competition for food, and this could explain why adult krill form less densely packed swarms, since they are more negatively buoyant than juveniles, and have to expend more energy in swimming. They need more food than the juveniles, and benefit from less competition.Another finding of the research that was opposite to the expectation was that superswarms are more likely to occur at night. It was previously believed this would be less likely, since krill feed at night.The habit of forming superswarms containing trillions of juveniles means that most of the young krill in the Antarctic Ocean are likely to be in just a few superswarms. This means krill may be much more susceptible to overfishing than thought previously since fishing fleets can locate and catch entire swarms. In doing so, they may be wiping out most of the krill in the Southern Oceans, and hence endangering everything else in the food chain that depends on them.More information: Variability and predictability of Antarctic krill swarm structure, Geraint A. Tarling et al., Volume 56, Issue 11, November 2009, Pages 1994-2012, doi:10.1016/j.dsr.2009.07.004© 2009 PhysOrg.comlast_img read more

Quantum guessing game reveals insight into strongerthanquantum correlations

first_img(PhysOrg.com) — In information processing, physicists are often in search of ways to turn classical strategies into quantum ones, with the implication that the quantum version is somehow stronger, faster, or more secure than its classical counterpart. However, quantum strategies do not always perform better than classical ones. As a case in point, a new study has compared the strength of classical and quantum correlations in a simple number guessing game and found no difference in performance. Further, the physicists found that a third form of correlations – post-quantum correlations – could outperform both quantum and classical forms. Post-Quantum Correlations: Exploring the Limits of Quantum Nonlocality More information: Mafalda L. Almeida, et al. “Guess Your Neighbor’s Input: A Multipartite Nonlocal Game with No Quantum Advantage.” Physical Review Letters 104, 230404 (2010). DOI: 10.1103/PhysRevLett.104.230404 Copyright 2010 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. 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 In their study, Mafalda Almeida from the ICFO-Institut de Ciencies Fotoniques in Barcelona and coauthors found that classical and quantum correlations performed equally in a game called “Guess Your Neighbor’s Input.” The game involves a group of players in a ring who each receive an input number of either 0 or 1. The point of the game is that each player tries to guess the number of the person to their right. Of course, players are not allowed to know any information about their neighbor’s numbers before guessing, nor to communicate after having received their numbers. In order to win the game, players are allowed to share physical resources, such as classical or quantum correlations. Importantly, all these resources must be “no-signaling”; that is, they cannot enable instantaneous communication.The no-signaling principle is fundamental for physicists dealing with the concept of nonlocality. In nonlocality, one object can influence another object at a distance, such as through entanglement. However, this phenomenon cannot be used to send information faster than light, which prevents a direct conflict with Einstein’s theory of relativity. Nonlocal correlations, which physicists define as those violating a Bell inequality, are important because they serve as a key resource for quantum information processing.However, in the game in this study, the researchers found that players gained no advantage at guessing the correct numbers by using quantum resources compared to classical ones. This makes sense, since it seems that players should require signaling in order to improve their guessing accuracy, and neither quantum nor classical correlations involve signaling.Yet when the physicists looked at what happened when the players use no-signaling correlations (that is, correlations that satisfy the no-signaling principle) that are even stronger than those allowed in quantum mechanics (i.e. they had a higher degree of violation of a Bell inequality), they did find a surprise. No-signaling correlations could actually outperform the quantum and classical correlations, suggesting that quantum correlations obey a stronger version of the no-signaling principle.“Our study highlights a fundamental difference between quantum correlations and certain post-quantum correlations (that is, correlations stronger than those allowed in quantum mechanics, but which nevertheless obey the no-signaling principle),” Nicolas Brunner, coauthor and a physicist at the University of Bristol, told PhysOrg.com. “This is significant because it strongly indicates that quantum correlations could obey a stronger version of the no-signaling principle.”This game is the first that involves entanglement among more than two bits (called “multipartite entanglement”) to identify some of the boundary (or gap) between quantum correlations and the stronger no-signaling correlations. However, the results also raise further questions, such as what kind of physical principle might limit quantum non-local correlations? Why do (theoretical) post-quantum correlations seem to not exist in nature? And if they did exist, could these correlations be used for other information tasks? Right now, these questions are likely a long way from being answered. Citation: Quantum guessing game reveals insight into stronger-than-quantum correlations (2010, June 22) retrieved 18 August 2019 from https://phys.org/news/2010-06-quantum-game-reveals-insight-stronger-than-quantum.html Explore furtherlast_img read more

New 4G network could cause widespread GPS dead zones

first_img(PhysOrg.com) — If a plan to build new 4G mobile phone base stations in the US goes ahead, engineers say GPS satellite navigation systems will be seriously jammed and huge areas of the country will become GPS dead zones. Explore further © 2010 PhysOrg.com Virginia company LightSquared communicates with satellites using low-power signals in the frequency range 1525 to 1559 MHz, which is close to the frequency range GPS uses (1559 to 1610 MHz). So far this has not caused interference problems but if the planned 40,000 new high-power 4G base stations are built they would use stronger signals in the same frequency range.LightSquared hopes to complete the 4G broadband network by 2015 at a cost of up to $8 billion. The network is expected to deliver mobile phone users download speeds of up to 10 megabits per second.Engineers Scott Burgett and Bronson Hokuf with Garmin International, a satellite navigation systems manufacturing company in Olathe, Kansas, say the stronger signals will be disastrous, seriously limiting GPS reception, causing widespread GPS jamming and depriving vast areas of the US of GPS coverage.The engineers carried out laboratory testing on a portable GPS device and a general Federal Aviation Administration (FAA)-certified aviation receiver. A Spirent GSS 6560 simulator representing the current configuration of 31 GPS satellites was used to simulate the GPS signals. The LightSquared transmission signal was simulated by a Rhode and Schwartz signal generator and amplified to produce the required signal strength.The results were that the GPS began to experience interference when 5.8 km or closer to the simulated LightSquared transmitter and lost the fix altogether when 1.1 km away. Interference started at 22.1 km for the aviation receiver, and total loss of fix occurred at 9.0 km from the transmitter.The US air force is also concerned about the interference. General William Shelton, head of the US Air Force Space Command, said at a recent Air Warfare Symposium in Orlando that if LightSquared’s network goes ahead and GPS systems are jammed we should “think about the impact.” He said he was hopeful a solution could be found but LightSquared had to prove they could operate without interfering with GPS.LightSquared spokesman Jeff Carlisle said the base stations are not at fault, but the problem could arise because some GPS receivers may be able to “see into” the neighboring frequency at which LightSquared operates. He said the company has already spent $9 million on a series of filters to prevent its current signals from interfering with the weak GPS signals, and if a problem will exist with the new network only some highly sensitive GPS receivers will be affected.LightSquared was given a provisional permit late last year by the US Federal Communications Commission (FCC), but the permit stipulated that the network should not cause interference with other signals.Burgett and Hokuf forwarded their report to the FCC on January 19. LightSquared is now required to submit an initial plan for working with federal agencies and GPS companies to determine how to deal with interference. The plan is due at the FCC by February 25, and a final report is due on June 15. LightSquared cleared to offer wireless broadband Citation: New 4G network could cause widespread GPS dead zones (2011, February 23) retrieved 18 August 2019 from https://phys.org/news/2011-02-4g-network-widespread-gps-dead.html 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

New offshore turbine design to create and store energy

first_img Citation: New offshore turbine design to create and store energy (2011, September 28) retrieved 18 August 2019 from https://phys.org/news/2011-09-offshore-turbine-energy.html Explore further SeaTwirl, according to the company website, is a “new principle to store and harvest offshore wind energy. SeaTwirl uses the ocean sea water as a bearing and can therefore use cheaper and heavier materials and function as a large low speed flywheel.” This new design will allow wind power generating plants to be built without the need for a gearbox, transmission line or roller-bearings. (PhysOrg.com) — While many are taking to the oceans and trying to find the best ways to harness offshore wind and provide clean energy from renewable sources, the basic design of any wind turbine is that of a windmill. That is until now. The new design in the works is by Ehrnberg Solutions AB, which is owned and operated by Daniel Ehrnberg. Ehrnberg is also the inventor behind this newly designed turbine called SeaTwirl. © 2011 PhysOrg.com More information: seatwirl.com/technology/the-principlevia IEEE Spectrum The new turbine, according to their video, is designed to be better suited for the ocean environment and use the benefits of both the air and the water. While the biggest prototype to date is 1:50 to scale, Ehrnberg hopes to have a fully functional turbine in the next four to six years and believes the SeaTwirl technology will be much more cost-effective. He plans to use undersea cables that are currently in place to bring the energy back to shore. Vertiwind: Floating wind turbine project launched 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

HTML5 spec editor slams Google gangs DRM bid

first_img More information: lists.w3.org/Archives/Public/p … ml/2012Feb/0274.htmldvcs.w3.org/hg/html-media/raw- … encrypted-media.html YouTube expands support for HTML5 (PhysOrg.com) — A draft proposal by Google, Microsoft and Netflix to introduce mechanisms for copy protection on web videos has generated strong opposition and a response that the proposal is “unethical.” Reaction has been strong against the powerful trio’s bid to see HTML5 carry digital rights management (DRM) tools. Explore further Citation: HTML5 spec editor slams Google & gang’s DRM bid (2012, February 25) retrieved 18 August 2019 from https://phys.org/news/2012-02-html5-spec-editor-slams-google.htmlcenter_img On the opposing side, developers and supporters of open systems argue that the very idea of adding DRM protection to video goes against the spirit of HTML5. “Any technology whose exclusive goal is to stop users from being able to make use of the content they have purchased is, in my opinion, unethical,” said Ian Hickson, HTML specification editor, in an interview with CNET. For Hickson, the Google-Microsoft-Netflix proposal is “just a plug-in platform in disguise.”The plan calls for proprietary plug-ins, called CDMs, or content decryption modules, which is not amenable to the open nature of HTML5, according to opposing arguments.The whole point of HTML5 is to move away from plug-ins; the introduction of such extensions, Hickson argued, would be tantamount to keeping plug-ins around.Specifically, Google, Microsoft and Netflix this week proposed a new web standard, in the form of the Encrypted Media Extensions proposal, and announced it on a W3C mailing list.The draft spells out a framework for bringing forth a system that manages protected content on the web browser. The proposed Encrypted Media Extensions standard would add a new set of API extensions for the HTMLMediaElement. The latter defines specialized properties and JavaScript methods available on HTML audio and video elements. These extensions would introduce DRM capabilities to HTML5-provided video.Whether some form of content protection is even necessary, leave alone ethical, is part of the present debate.Digital rights management permits only authorized video and audio. A solution to unauthorized copying has been seen in browser plug-ins for DRM protection. Hickson said he would rather see copyright law, not proprietary mechanisms, governing the use of video. He said there was no need for technology to protect content; the presence of copyright law was adequate.What next? Since the spec being proposed by the threesome is a draft, tech watchers see no guarantees that what the three propose will become an accepted standard, but at the same time there can be no guarantees that the debate will go south.Pressure to add some kind of DRM to HTML5 video is likely to continue, writes Scott Gilbertson in Webmonkey. “With Hickson very adamantly against it and Mozilla unlikely to support it in its current form, it’s not likely to move beyond the draft stage without some serious revisions.” © 2011 PhysOrg.com 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

Corning VP says Gorilla Glass headed for automobiles

first_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. Gorilla Glass is currently estimated to be in use by over a billion and a half devices the world over, and has become a household name. Its strength and resistance to scratching in addition to its very low weight has made it an ideal candidate for touch-screen devices. Corning makes the glass using a propriety chemical process that causes more than the normal number of ions to be introduced into the glass, adding to its strength and reducing the likelihood of cracking. Also, like the glass currently used in automobiles, it’s more likely to crack than shatter when subjected to extreme stress or impact.Evenson told those in attendance at the Summit that using Gorilla Glass in a car would cut down on the weight of the vehicle. Also, engineers could distribute the weight reduction in a way that would slightly alter the car’s center of gravity. Together, he explained, that would help cars with the new window glass gain a few extra miles out of each gallon of fuel. He also noted that because of the unique nature of Gorilla Glass, cars that used it as a replacement for current glass would be much quieter inside the cabin.Evenson also suggested that he expects at least one high-end car maker to begin using Gorilla Glass in at least some of its vehicles as early as next year, though he wouldn’t say which it was. He also briefly spoke about progress being made on a project he called microbiological glass, which he said, would kill bacteria on contact. He followed that by discussing another new product the company is working on called Willow Glass—a bendable type of glass that he said is currently about as thick as a dollar bill. He said its introduction will likely lead to the creation of hundreds of new devices. (Phys.org) —Corning Senior Vice President, Jeffrey Evenson told audience members at this year’s MIT Technology Review’s Mobile Summit, that its Gorilla Glass will very soon be used in automobiles. Currently, Gorilla Glass is used as part of a touch-screen for hand-held devices—from phones to tablet computers. Using the glass in automobiles Evenson said, would allow for better gas mileage and noise suppression. ‘Gorilla Glass’ maker looks beyond smartphones Citation: Corning VP says Gorilla Glass headed for automobiles (2013, June 12) retrieved 18 August 2019 from https://phys.org/news/2013-06-corning-vp-gorilla-glass-automobiles.htmlcenter_img © 2013 Phys.org Explore further More information: via MIT Tech Reviewlast_img read more

Researchers unlock genetic twist in differences in horn size with sheep

first_img Journal information: Nature In this new effort the researchers analyzed data collected from 1,750 sheep and found that there is a third category of sheep, those that have one type of each allele—they get the benefits of both—the live longer than the sheep with the biggest horns and mate more often than the sheep with tiny horns. This, the researchers suggest, explains why big horns haven’t become predominant—though they may lead to producing more offspring in the short time, those with smaller horns win out in the end by breeding over more seasons. Thus, natural selection results in splitting the difference to ensure the best chance of survival for the species as a whole.The researchers note that the same allele exists in both humans and mice, and has been found to be involved in bone density and sexual development. They suggest more research will need to be conducted to discern if the gene is a factor in either longevity or successful procreating in either species Soay is a small breed of bighorn sheep—they live in mountainous terrain on an island called Hirta and have what would appear to be a genetic anomaly. Some of the males have extremely large horns, while the horns of others are much smaller. Because research has shown that the males that have the larger horns are much more successful at mating, there is the question of why all the males don’t have large horns.To find out, a team working in a prior effort studied the genes of the sheep and discovered a particular allele (alternative forms of the same gene) responsible for horn size, called Ho. The sheep all have two of them—those sheep that have two of the large-size variant have large horns, while those with two of the small size variant had small or even no horns at all. But there was a catch. Sheep with smaller horns, for reasons that aren’t yet known, tend live longer. Three rams on the island of Hirta, St Kilda with different horn morphologies. The male on the left displays the scurred (vestigial) phenotype, meaning that it cannot compete with the normal-horned males for access to mates during the rut. Credit: Peter Korsten Citation: Researchers unlock genetic twist in differences in horn size with sheep (2013, August 22) retrieved 18 August 2019 from https://phys.org/news/2013-08-genetic-differences-horn-size-sheep.html Explore further More information: Life history trade-offs at a single locus maintain sexually selected genetic variation, Nature (2013) DOI: 10.1038/nature12489AbstractSexual selection, through intra-male competition or female choice, is assumed to be a source of strong and sustained directional selection in the wild. In the presence of such strong directional selection, alleles enhancing a particular trait are predicted to become fixed within a population, leading to a decrease in the underlying genetic variation. However, there is often considerable genetic variation underlying sexually selected traits in wild populations, and consequently, this phenomenon has become a long-discussed issue in the field of evolutionary biology. In wild Soay sheep, large horns confer an advantage in strong intra-sexual competition, yet males show an inherited polymorphism for horn type and have substantial genetic variation in their horn size6. Here we show that most genetic variation in this trait is maintained by a trade-off between natural and sexual selection at a single gene, relaxin-like receptor 2 (RXFP2). We found that an allele conferring larger horns, Ho+, is associated with higher reproductive success, whereas a smaller horn allele, HoP, confers increased survival, resulting in a net effect of overdominance (that is, heterozygote advantage) for fitness at RXFP2. The nature of this trade-off is simple relative to commonly proposed explanations for the maintenance of sexually selected traits, such as genic capture (‘good genes’) and sexually antagonistic selection. Our results demonstrate that by identifying the genetic architecture of trait variation, we can determine the principal mechanisms maintaining genetic variation in traits under strong selection and explain apparently counter-evolutionary observations.center_img Soay ram on the island of Hirta, St Kilda. Credit: Arpat Ozgul Dome-headed dinosaurs did more than just butt heads © 2013 Phys.org (Phys.org) —A team of researchers from the U.K. and Australia, working with sheep data obtained from a small island off the coast of Scotland has learned why it is that some sheep have large horns, while others do not. In their paper published in the journal Nature, the team describes how they studied data obtained over a 20 year period to discover the seeming contradiction with the sheep. 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

Researchers characterize mysterious ultraluminous Xray sources

first_imgArtist’s impression of SS 433. Credit: NASA The only known supercritical accretor in the Milky Way galaxy is SS 433, a highly exotic eclipsing binary star system. Its primary object is likely a black hole. Its secondary companion is believed to be a late A-type star based on its light spectrum. The secondary in SS 433 is losing mass into an accretion disk as it spirals in toward the primary, which is slowly consuming it. In turn, as the accretion disc spirals in toward the primary, it becomes super-heated and emits intense X-rays. Physicists are fascinated by the exotic nature of SS 433, but also by its strong resemblance to ultraluminous X-ray sources (ULXs), which are astronomical sources of X-rays that are less luminous than the nuclei of active galaxies, but are more luminous than any known stellar process. These are sources of X-rays that exceed the Eddington luminosities of neutron stars and stellar black holes. Recently, a group of researchers from Russia and Japan have compared the optical spectra of ULXs to SS 433 and have determined that ULXs with X-ray luminosities of ~1040 erg S-1 must constitute a homogenous class of objects that most likely have SCADs. They have published their results in Nature Physics. The most popular models for ULXs have either intermediate mass black holes with standard accretion disks or stellar-mass black holes with accretion disk luminosity exceeding the Eddington limit. Based on X-ray data alone, it is not possible to distinguish these models, so the researchers have turned to optical spectroscopy to find unique information about ULXs. Using the 8.2 meter Subaru Telescope of the National Astronomical Observatory of Japan, located at the Mauna Kea Observatory on Hawaii, they obtained high-quality spectroscopic data from a number of ULX sources.They have determined that ULX spectra are quite similar to late nitrogen Wolf-Rayet stars (WNLs), which exhibit broad emissions of ionized nitrogen and helium or carbon. They have very high surface temperatures and produce intense stellar winds. The spectra from ULXs also resemble those of luminous blue variable stars (LBVs) in the compact stages of stellar development. Because the physical conditions of its disk wind may be similar to WNL stars, SS 433 also bears a strong resemblance to ULXs. The authors write, “Such spectra of high luminosities with prominent He II emission lines have never been observed from any stellar-mass black hole X-ray binaries, except for SS 433 and those having WNL donors [secondaries losing mass to the accretion disks of primaries in binary systems].” They exclude a number of stellar cases, including ULXs with WNL donors that exhibit stellar winds with the observed spectra. Wind terminal velocity is determined by surface gravity, making it difficult to explain the rapid variability of the He II line width in the recorded spectra. The authors conclude that SS 433 is intrinsically the same as ULXs, but is an extreme case with a particularly high mass accretion rate from its secondary, which accounts for the presence of its persistent jet outflows. © 2015 Phys.org Journal information: Nature Physics Explore further More information: “Supercritical accretion disks in ultraluminous X-ray sources and SS 433.” Nature Physics (2015) DOI: 10.1038/nphys3348AbstractThe black hole mass and accretion rate in ultraluminous X-ray sources (ULXs) in external galaxies, whose X-ray luminosities exceed those of the brightest black holes in our Galaxy by hundreds and thousands of times1, 2, is an unsolved problem. Here we report that all ULXs ever spectroscopically observed have almost the same optical spectra, apparently of WNL type (late nitrogen Wolf–Rayet stars) or LBV (luminous blue variables) in their hot state, which are very scarce stellar objects. We show that the spectra do not originate from WNL/LBV-type donors but from very hot winds from the accretion disks with nearly normal hydrogen content, which have similar physical conditions to the stellar winds from these stars. The optical spectra are similar to that of SS 433, the only known supercritical accretor in our Galaxy3, although the ULX spectra indicate a higher wind temperature. Our results suggest that ULXs with X-ray luminosities of ~1040 erg s−1 must constitute a homogeneous class of objects, which most likely have supercritical accretion disks.center_img Ultra-luminous X-ray sources in starburst galaxies (Phys.org)—Many black holes are believed to have surrounding accretion disks of matter trapped by gravity and spiraling toward the event horizon. Supercritical accretion disks (SCADs) are those with mass accretion rates exceeding the Eddington limit—this describes the maximum possible luminosity of an energetic body when the outward force of radiation is in equilibrium with gravitation. Masses that exceed the Eddington luminosity to produce SCADs emit extremely intense stellar winds from their outer layers. Citation: Researchers characterize mysterious ultraluminous X-ray sources (2015, June 9) retrieved 18 August 2019 from https://phys.org/news/2015-06-characterize-mysterious-ultraluminous-x-ray-sources.html 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 hints on why some bird hosts reject parasitic eggs while

first_img Some birds lay eggs in the nests of other birds so that they will not have to raise them, this practice is known as parasitic egg laying, and works well enough for parasitic species to survive. But not all hosts welcome the parasitic eggs, some ignore them, or push them out of the nest. Also, some of the hatchlings are better guests than others, cuckoos for example, are known to push the other hatchlings out of the nest. In this new effort, the researchers sought to learn why it is some hosts are more tolerant than others.To find out, they looked at prior studies of parasitic bird practices—in all they found data on 198 different species, and took note of factors such as the environment in which the birds lived, the location, etc. and then drew up a phylogenetic tree. In studying their tree they were able to spot commonalities, such as that birds in northern latitudes were more likely to reject parasitic eggs. They also found that hosts tended to tolerate chicks that required a different diet than their own—such chicks would likely die anyway. Also, they found that eggs of parasitic chicks, such as cuckoos, that would hatch into birds larger than their own were often rejected—they same fate often befell eggs from birds that were a close relative. The researchers also noted that when some species such as cuckoos experienced high rejection rates from one species, they tended to move to another.In answer to the original question of why some birds tolerate parasitic eggs, the researchers suggest it is because sometimes it is almost impossible for host birds to tell the difference between eggs, and sometimes it is because the danger of harming their own young accidently is too great. They note that many species have constantly evolving egg coloring or design patterns to help prevent deception. Egg colours make cuckoos masters of disguise Explore further © 2015 Phys.org More information: The costs of avian brood parasitism explain variation in egg rejection behaviour in hosts , Biology Letters, DOI: 10.1098/rsbl.2015.0296 AbstractMany bird species can reject foreign eggs from their nests. This behaviour is thought to have evolved in response to brood parasites, birds that lay their eggs in the nest of other species. However, not all hosts of brood parasites evict parasitic eggs. In this study, we collate data from egg rejection experiments on 198 species, and perform comparative analyses to understand the conditions under which egg rejection evolves. We found evidence, we believe for the first time in a large-scale comparative analysis, that (i) non-current host species have rejection rates as high as current hosts, (ii) egg rejection is more likely to evolve when the parasite is relatively large compared with its host and (iii) egg rejection is more likely to evolve when the parasite chick evicts all the host eggs from the nest, such as in cuckoos. Our results suggest that the interactions between brood parasites and their hosts have driven the evolution of egg rejection and that variation in the costs inflicted by parasites is fundamental to explaining why only some host species evolve egg rejection. Common cuckoo. Image: Wikipedia.center_img Journal information: Biology Letters (Phys.org)—A pair of researchers with Australia National University has conducted a study of parasitic egg laying with birds and as a result has found some hints on why it is that some hosts reject parasitic eggs while others do not. In their paper published in The Royal Society – Biology Letters, Iliana Medina and Naomi Langmore describe the study they conducted and what they learned as a result. Citation: Study offers hints on why some bird hosts reject parasitic eggs while others do not (2015, July 9) retrieved 18 August 2019 from https://phys.org/news/2015-07-hints-bird-hosts-parasitic-eggs.html 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

A new way to make biaxial nematic phase liquid crystals

first_imgA team of researchers from the University of Colorado in the U.S. and Université Paris-Saclay, in France has developed a new way to make biaxial nematic phase liquid crystals. In their paper published in the journal Science, the group describes the technique they developed and possible uses for the results. Philippe Poulin, with CNRS, University of Bordeaux offers a Perspective piece on the work done by the team in the same journal issue. Liquid crystals have become hugely important over the past half-century due to their use in phones, television sets and other screened devices. The type of crystals used in such devices are known as nematic phase liquid crystals, because their molecules line up in a certain way. They are also generally uniaxial, which means they line up in the same direction, but not necessarily in the same plane. But in recent years, scientists have begun to see that biaxial nematic phase crystals could offer additional benefits. Prior research has shown that because they would have fast switching speeds, they could serve an important role in the development of new electro-optical applications. Unfortunately, the development of such crystals has not met with much success. Some researchers have tried using board-like molecules while others have tried mixing rod-like molecules with disk-shaped molecules. Neither approach has produced the desired results. In this new effort, the researchers tried a new tactic—one that overcomes problems seen with the other methods.The new technique involves combining and mixing two types and sizes of nanorods—one organic the other inorganic. The inorganic nanorods were 1000 nanometers, while the organic nanorods were just two nanometers long on average. But there was more—the researchers had to tinker with the mixture to get the smaller rods to rest perpendicular to the larger rods, thus creating two planes. The researchers also found that the resultant biaxial nematic is not simply a superposition of the two nematics—the anisotropic properties between the two kinds of rods caused the smaller rods to be distributed in a way that resulted in biaxiality without the need for additional ingredients. This, the team notes, suggests the properties of the new liquid crystals are even richer than expected. More information: Haridas Mundoor et al. Hybrid molecular-colloidal liquid crystals, Science (2018). DOI: 10.1126/science.aap9359AbstractOrder and fluidity often coexist, with examples ranging from biological membranes to liquid crystals, but the symmetry of these soft-matter systems is typically higher than that of the constituent building blocks. We dispersed micrometer-long inorganic colloidal rods in a nematic liquid crystalline fluid of molecular rods. Both types of uniaxial building blocks, while freely diffusing, interact to form an orthorhombic nematic fluid, in which like-sized rods are roughly parallel to each other and the molecular ordering direction is orthogonal to that of colloidal rods. A coarse-grained model explains the experimental temperature-concentration phase diagram with one biaxial and two uniaxial nematic phases, as well as the orientational distributions of rods. Displaying properties of biaxial optical crystals, these hybrid molecular-colloidal fluids can be switched by electric and magnetic fields. How to make a biaxial nematic. Previous efforts to make biaxial nematics with either boardlike molecules or component mixtures have had limited success. Mundoor et al. used a different strategy to create a biaxial nematic by tuning the interactions between long inorganic nanorods and short organic molecules. Credit: V. ALTOUNIAN/SCIENCE Explore further © 2018 Phys.orgcenter_img Journal information: Science Citation: A new way to make biaxial nematic phase liquid crystals (2018, May 18) retrieved 18 August 2019 from https://phys.org/news/2018-05-biaxial-nematic-phase-liquid-crystals.html New type of liquid crystal identified; Holds promise of faster, lower priced liquid crystal displays 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