These scarab beetles have structural defects that cause their bright colors. Credit: Brink, et al. 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 Decades later, scientists discovered the reason for this asymmetrical preference. The beetle’s shell consists of many layers of microfibrils aligned parallel with each other, which causes a preference for light polarized along the direction of the fibers. Each layer is rotated slightly relative to the layer above, forming a heliciodal stack twisting in the left direction. This alignment of the layers reflects left circularly polarized light, which is defined by the wave’s spiral shape rotating in the left direction.“Why nature may have given the scarab beetles the characteristic of reflecting only left-handed light is a difficult question,” scientist Johan Brink, who was part of a recent group investigating the phenomenon, told PhysOrg.com. “Coloration in insects is usually some kind of trade-off between camouflage and an attempt to find a mate. In some cases (usually with yellow, black and red), it is a warning to predators that they are poisonous. My feeling is that these scarabs are trying to make themselves more visible by broadening the reflection band. At this point, however, it is only an idea which has not been proven in depth.”Along with Brink, scientists Nick van der Berg and Linda Prinsloo from the University of Pretoria in South Africa and Ian Hodgkinson of the University of Otago in New Zealand have explained why this exceptionally bright-colored scarab species exhibits a reflectance spectrum of peaks that differs from other scarabs’ smooth and less-bright spectra. “From the mismatch between calculations of the measured spectra and calculations based on a perfect chiral structure, we suspected something had to be ‘wrong’ in the structure,” Brink said. “By trial and error, we discovered that one could simulate the actual spectra quite closely by assuming some defects in the organization of the layers. Only when we had some idea what to look for, we discovered exactly how the beetles did the trick.” In studying the bright green and red colors on a species of scarab beetle, scientists have found that the unusual reflection spectra is caused by defects in the structure of the exocuticle, or hard shell. Understanding how this structure causes the bright colors may help scientists design nano chiral reflectors for use in display and laser technologies in the future. By shining a light on the exocuticle and analyzing the reflected light, the scientists observed deep modulations in the spectra resulting in well-defined peaks, indicating the existence of perturbations in the heliciodal layers of the exocuticle. With a scanning electron microscope, the group found an interesting defect: while the layers of microfibrils appear at first glance to be evenly spaced, the scientists identified a point where the layer spacing suddenly changes by about 10% on the micrometer level. According to the scientists’ model, this period jump broadens the reflectance band by up to four times the width obtained from a perfect heliciodal stack. The scientists also investigated why some scarabs are red and some green. Assuming both varieties consist of the same material, the only difference lies in different thicknesses in the exocuticle layers. Alternatively, different colors on individual beetles—such as the green edges on a red beetle, or blue edges on a green beetle—occur when the angle of incidence increases.“We suspect that the green specimens grow a bit more slowly, possibly due to more arid conditions,” said Brink. ”The red specimens are found predominantly in wetter (and greener) areas, where they grow faster and produce thicker layers. This is then in line with the idea of making themselves more visible.”The scientists also suggest that understanding how nature’s “imperfect” engineering enhances the optical properties of the scarabs could lead to applications for display and laser technology.“Possible applications of this kind of ‘defect engineering’ could be broadband laser reflectors for semiconductor lasers, and narrow-band spike filters that are sometimes used in spectroscopy to identify and classify materials and minerals,” Brink explained.Citation: Brink, D. J., van der Berg, N. G., Prinsloo, L. C., and Hodgkinson, I. J. “Unusual coloration in scarabaeid beetles.” J. Phys D: Appl. Phys. 40 (2007) 2189-2196.Copyright 2007 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. Citation: Beetles’ bright colors may influence new light technology (2007, April 11) retrieved 18 August 2019 from https://phys.org/news/2007-04-beetles-bright-technology.html While more than 30,000 species of scarab beetles exist throughout the world, the species studied by the scientists was Gymnopleurus virens, which is found mainly in southern Africa. In the early 1900s, scientists found that this scarab beetle reflected almost entirely left-handed (left circularly polarized) light, and almost no right-handed light—the only known example of this phenomenon in nature. Best-candidate supernova erupting every year and on the brink of catastrophe This electron micrograph image shows a cross-section of part of an exocuticle of the green scarab beetle. The white line at right marks the point where the separation between layers increases by 10%. Credit: Brink, et al.
Explore further A team of researchers from institutions in Germany, India, and Japan discovered this surprising result while observing the ant species Leptogenys processionalis travel down linear trails. Like many other ant species, these ants form trails with their pheromones that remain stable for hours or even days, making the trails analogous to vehicular highways. “Our study clearly demonstrates that ant traffic is very different from vehicular traffic, in spite of superficial similarities,” Andreas Schadschneider, of the University of Köln and the University of Bonn in Germany, told PhysOrg.com. “It also raises a fundamental question: how do the ants achieve practically ‘free-flow’ up to such high densities; our experiment demonstrates what happens and we also make a theoretical model of what might be responsible for this behavior.”To observe the ants in their natural setting, the researchers set up video cameras at sections of 10 different one-way trails that had no intersections or routes that branched off. Surprisingly, the scientists never observed individual ants speeding up to overtake another ant in front; the ants followed each other in single file. This behavior, of course, contrasts with vehicular highway traffic, as well as most other known traffic forms. Most significantly, the scientists found that, unlike vehicular traffic, the average velocity of ant traffic remains the same in spite of increasing density. Consequently, the greater the density, the greater the flux, so that more ants travel down the trail segment in a given amount of time. In contrast, vehicles on a highway tend to slow down when the traffic density increases, eventually resulting in a traffic jam. Along the same lines, the researchers noted that most types of high-density traffic exhibit mutual blocking, in which a vehicle is prevented from moving by neighboring vehicles and also contributes to the blocking of those vehicles. However, the researchers did not observe mutual blocking in the ant trails.As the researchers suggested, perhaps evolution has optimized ant traffic flow, since ants are known to have highly developed social behaviors. In their study, the scientists observed that ants tend to form platoons in which they move at almost identical velocities, allowing them to travel “bumper-to-bumper” while maintaining their velocity. At higher densities, platoons merge to form longer platoons. But because their head-distance remains the same, traffic still maintains its same velocity even as density increases. This behavior is very different from highway traffic, in which vehicles close together tend to slow down. Citation: Optimized by Evolution, Ants Don’t Have Traffic Jams (2009, March 30) retrieved 18 August 2019 from https://phys.org/news/2009-03-optimized-evolution-ants-dont-traffic.html (PhysOrg.com) — As highway traffic increases, you’d probably expect a traffic jam, where vehicles slow down due to the high density. While traffic jams are a common occurrence on our highways, high density traffic has completely different effects for ants traveling on trails. As a new study has found, ants don’t have traffic jams. Rather, as ant traffic density increases, the traffic maintains the same average velocity as at low densities. While observing ants traveling on a trail, scientists observed that, unlike in vehicular traffic, the average velocity of ant traffic remains the same in spite of increasing density. Image credit: Alexander John, et al. “For the ants, an efficient transport system is essential for the survival of a colony,” Schadschneider said. “Food sources are usually not in the immediate neighborhood of the nest and so the transport has to be well organized. Therefore it is not surprising that evolution has optimized the behavior of the ants (or all social insects). On the other hand, human transportation systems still reflect a certain desire for freedom and individuality. In contrast to ant traffic, what dominates in human traffic are two things: selfish (non-cooperative) behavior, and large body weight of vehicles where any contact between the vehicles would be costly (for the cars as well as for the riders’ lives). Ants, on the other hand, do not mind body contacts which become unavoidable at high densities.”As he explained, understanding ant behavior will require further study: “Now entomologists have to connect this behavior of ants to their ‘thinking and sensing’ process. Our work opens up the possibility of collaborations between entomologists, physicists, mathematical modelers and traffic scientists.”While this study shows that the collective marching of ant traffic seems to be very different from vehicular traffic, the scientists suggest that ant traffic might be more analogous to human pedestrian traffic. They plan to explore this analogy in the future, and they predict that their results could have applications in swarm intelligence, ant-based computer algorithms, and traffic engineering. “To our knowledge, so far applications in swarm intelligence mainly draw from the analogy with the formation of ant trail networks,” Schadschneider said. “Our study was focused on a different aspect, namely the usage of an already existing trail. Combining both approaches could open promising perspectives for future applications, e.g. in optimization problems.“From a traffic engineering point of view, the results give some indication on how to improve the situation on our highways,” he added. “As the example of the ant trail shows, non-egoistic behavior could improve the situation for almost everybody. However, this will be difficult to achieve since, very much in contrast to the ants, drivers and their cars are very different. Another interesting point is the relevance of communication between the vehicles. On ant trails this is achieved mostly on a chemical basis. In the future, our cars might be connected electronically and transmit e.g. information about velocity changes immediately. This would allow the driver to react much quicker to a new situation.”More information: John, Alexander; Schadschneider, Andreas; Chowdhury, Debashish; and Nishinari, Katsuhiro. “Trafficlike collective movement of ants on trails: absence of jammed phase.” Physical Review Letters, 102, 108001 (2009).Join PhysOrg.com on FacebookCopyright 2009 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. Ants show us how to make super-highways 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.
With molecules, though, things become tricky. The emission of a photon typically sets a molecule to rotating or vibrating. “They don’t return to the same state they started in,” DeMille explains. “The frequency of the laser is no longer correct for its photons to be absorbed by the molecules.” In order to get around this problem, the team at Yale built on a couple of different ideas. He says that Michael di Rosa of Los Alamos National Laboratory pointed out several years ago that certain molecules were not likely to begin vibrating, so that they could be used. However, di Rosa’s scheme would take at least six different lasers working at the same time such that the rotating (and occasionally vibrating) molecules would all absorb photons. A recent idea came from Jun Ye’s group at JILA, who pointed out that some classes of molecules could avoid vibration and rotation, but in these molecules the time needed to complete an absorption-emission cycle would be so long that slowing and cooling would be inefficient. (PhysOrg.com) — “For years, we have been using laser cooling to trap and manipulate atoms,” David DeMille tells PhysOrg.com. “This has been very useful for both basic science and many applications. Recently there has been great interest in cooling and trapping molecules as well. Their rich internal structure makes molecules useful for a wide range of new experiments and possible applications.” Explore further Schematic depiction of the experimental result. Credit: J. Barry Buffer gas cooling could open up the field of ultracold physics Photo of the experimental apparatus, including E. Shuman. Credit: Mellissa DeMille 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. “We took elements of these two ideas,” DeMille says, “and combined them. We looked at situations where you could have the best of both schemes and picked what should be the easiest case.” Using strontium monofluoride, the team at Yale was able to experimentally demonstrate a scheme for optical cycling in this diatomic molecule using two diode lasers, which are common and inexpensive. “We deflected a beam of molecules using a large number of photon kicks from the laser, which is an important step toward laser cooling.”Based on these results, lasercooling of strontium monofluoride should be within reach. “We suggest that by adding one more of these simple diode lasers, we should be able to take it the next level and actually cool the molecules. Our calculations show it should work, and we are in the process of experimenting with it now.”More information: Shuman, Barry, Glenn and DeMille, “Radiative Force from Optical Cycling on a Diatomic Molecule,” Physical Review Letters (2009). Available online: http://link.aps.org/doi/10.1103/PhysRevLett.103.223001. Copyright 2009 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. Citation: Using lasers to cool and manipulate molecules (2009, December 7) retrieved 18 August 2019 from https://phys.org/news/2009-12-lasers-cool-molecules.html Of course, the complexity that makes molecules interesting also makes them more difficult to manipulate than atoms. Using lasers to cool molecules, therefore, comes with its own set of problems. DeMille, a scientist at Yale University, believes that a solution may have been found. He has been working with Yale colleagues Edward Shuman, John Barry and David Glenn to come up with a viable method of laser cooling for molecules. Their ideas and preliminary experimental results on the subject can be found in Physical Review Letters: “Radiative Force from Optical Cycling on a Diatomic Molecule.”“Arguably the most difficult part of cooling molecules is trying to apply a force that opposes the molecule’s velocity. For atoms, this is accomplished using the Doppler effect. A moving atom sees incident light at a Doppler-shifted frequency. By the appropriate choice of laser frequency, you can ensure that the atom preferentially absorbs photons opposing its motion.” DeMille says. “The atom receives a small kick along the laser beam from each photon it absorbs, then emits its own photon in a random direction. This cycle returns the atom to its original state, but on average it has been slowed down a little. Do this some tens of thousands of times, and you can slow an atom enough for it to be trapped and manipulated.”
More information: Volkswagen press release: www.haveit-eu.org/displayITM1. … sp?ITMID=117&LANG=EN (PhysOrg.com) — Volkswagen, as part of the European wide research project HAVEit, has announced the Temporary Auto Pilot (TAP), a set of features added to a car that aids in speed control, lane-assist and crash avoidance. Explore further Much like the highly touted driverless vehicles in the news of late, the new vehicle system from VW works by means of sensors and cameras mounted on various parts of the exterior of a vehicle. Assistance comes via cruise control, automated braking when curves are noted (or to avoid a collision), steering assist to keep the vehicle in the proper lane, passing assistance and assistance in stop and go traffic. Unlike other vehicles in the news however, the TAP is not meant to serve as a driverless vehicle; it’s more of a guardian angel, watching over a driver and instantly correcting mistakes.The company is quick to point out that the driver is still in control the entire time the TAP system is in use, and thus must continue to actually drive the vehicle; TAP should be thought of as more like driver extensions, they say, not as an autonomous system that can take over the driving when asked.Critics have already suggested that the new additions might actually make a car less safe to drive, citing the fact that humans as a rule tend to focus less sharply when they don’t have complete control of things. Since its not clear yet just how much control the human will have when the TAP is engaged, these criticisms seem premature. If after all, the person continues to drive the car the entire time the TAP is engaged, and the TAP only makes itself known if and when it performs corrective actions when errors are made by the human driver, it would seem this would require the driver to continue to maintain as much control as has been the case up to now.In any case, the test vehicle, a modified Passat, marks another giant leapt towards fully automated cars; this because it’s clear that Volkswagen fully intends to put such an equipped vehicle on the market in just the next few years. This stands in stark contrast to other concept cars demonstrated by others such as BMW, and Google, which still have many hurdles to overcome. The difference here is that VW’s system is comprised of off-the-shelf components and the fact that the driver continues to maintain control at all times.In any case, it seems clear that it won’t be too long before human beings will no longer be trusted to drive themselves around. Citation: Volkswagen announces ‘Temporary Auto Pilot’ with advanced features (2011, June 27) retrieved 18 August 2019 from https://phys.org/news/2011-06-volkswagen-temporary-auto-advanced-features.html ‘Smart cars’ that are actually, well, smart 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 HAVE-IT (Highly Automated Vehicles for Intelligent Transport)
© 2011 PhysOrg.com More information: Press release The National Science Foundation is investing $27.5 million to start the project and plans to invest some $50 million throughout the next four years. Stampede will be an Intel and Dell powered system. It will be made of up several thousand Dell Zeus servers containing 8-core processors and each server will contain 32GB of memory. The cluster will be using Intel’s new Many Integrated Core (MIC) co-processors codenamed “Knights Corner.” This will provide the entire system with a total of 10 petaflops of performance. Citation: Texas Stampede supercomputer to join the eXtreme Digital (XD) program (2011, September 23) retrieved 18 August 2019 from https://phys.org/news/2011-09-texas-stampede-extreme-digital-xd.html Also included in Stampede will be 16 Dell servers with a terabyte of shared memory and 2 GPUs each that will be used for large data analysis. There will be 128 NVIDIA graphics processing units to provide remote visualization and a high performance Lustre file system for data intensive computing. The entire Stampede system will provide a peak performance of 10 petaflops, 272,000 gigabytes of memory and 14 million gigabytes of disk storage.Stampede will be used to support computational and data driven science and engineering projects throughout the U.S. and allow researchers to create advanced methods for petascale computing. The goal will also be to use Stampede to train the next generation of scientists and researchers in advanced computational science and technology.The University of Texas at Austin is set to break ground in November 2011 for a new data center which will house Stampede. Explore further (PhysOrg.com) — As part of a National Science Foundation grant, the Texas Advanced Computing Center, or TACC, from the University of Texas at Austin announced its plans to develop and support a new supercomputer they are naming Stampede. It is set to be operational in January of 2013 and will be a part of the eXtreme Digital (XD) program with the National Science Foundation and enable scientists to share computing resources, data and expertise interactively. Sun and The University of Texas Power Up One-of-a-Kind Supercomputer 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: Researchers find social lifestyle also helps mole rats live a long time (2015, January 28) retrieved 18 August 2019 from https://phys.org/news/2015-01-social-lifestyle-mole-rats.html (Phys.org)—A pair of researchers based at New York University has found a second explanation for the long lifespan of naked mole rats—their social networks. In their paper published in The Royal Society Proceedings B, Scott Williams and Milena Shattuck describe the statistical analysis they undertook in comparing the lifespan of various species of animals and comparing them against other factors such as size, environment and degree of social behavior and what they found in doing so. 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. Factor in naked mole rat’s cells enhances protein integrity © 2015 Phys.org More information: Ecology, longevity and naked mole-rats: confounding effects of sociality? Published 28 January 2015. DOI: 10.1098/rspb.2014.1664 Explore further Naked mole rats live a ridiculously long time for their size—they average just three or four inches in length, but live for up to thirty years (underground in parts of Africa). Prior research has found that as a general rule, life spans are longer for animals that are bigger—mice, for example, tend to live just three years. So what gives? After much study, scientists have found that the rodents have a large amount of a certain type of protein in their tissue that appears to ward off aging and things like cancer. The protein appears to do its magic by causing genes to be more careful in how they make new proteins. But how did this protein magic get started in mole rats, and why does it persist? Prior research has shown that their fossorial (living in a burrow) existence is a factor—animals that live underground tend to live longer, partly because it helps them avoid predators. But other underground animals do not live nearly as long, so there has to be another reason—that is what Williams and Shattuck sought to better understand by taking a closer look at their communal lifestyle.Naked mole rats live a lot like bees or ants, with workers doing different jobs and a queen that does the reproducing—an unusual trait for a rodent. Suspecting that it might have something to do with their longevity, the research duo began doing some research, creating a database of different animals (440 mammals) that allowed for comparing longevity with their environment and social habits. Analysis revealed that mammals that both live underground and do so socially, tend to live longer than those that do just one or the other, or neither. Thus it appears that the mole rats remarkable lifespan is at least partly due to both its underground environment and their social lifestyle. naked mole-rat. Credit: Joshua Clark
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. One of the biggest applications for steel is, of course in making cars, though its dominance has been slipping in recent years as engineers seek to find lighter substitutes. At issue is weight, steel is heavy because it is made mostly out of iron. Adding other lighter metals tends to make it less flexible or weaker. In this new effort, the researchers report that they have found a mix that allows for creating a low-density steel that is stronger and more flexible than much more expensive titanium alloys.The secret, the team explains, lies in causing new structure shapes to be formed during the heating process and by using the right mix of ingredients. They used the traditional mix of iron, carbon, aluminum and manganese and then added some nickel. The nickel, they found reacted with the aluminum, creating nanometer sized B2 crystals that formed within and between the steel grains during the annealing process. To make sure the crystals were spread evenly among the metal, the team studied samples under an electron microscope. Chemists know that B2 crystals are resistant to shearing, thus steel with such crystals should be extremely strong, and that is what the researchers found when they tested their new alloy. © 2015 Phys.org Journal information: Nature Annealed microstructure of high-specific-strength steel (HSSS). Fine FeAl-type B2 precipitates form during annealing in between the B2 stringer bands in steel matrix. Note that grain boundaries of recrystallized austenite crystals are visible in the image. The specimen was annealed for 15 min at 900 C. Credit: Hansoo Kim Alcoa touts step toward stronger aluminum for cars Annealed microstructure of high-specific-strength steel (HSSS). Fine FeAl-type B2 precipitates form during annealing in between the B2 stringer bands in steel matrix. Note that grain boundaries of recrystallized austenite crystals are visible in the image. The specimen was annealed for 15 min at 900 C. Credit: Hansoo Kim Annealed microstructure of high-specific-strength steel (HSSS). Fine FeAl-type B2 precipitates form during annealing in between the B2 stringer bands in steel matrix. Note that grain boundaries of recrystallized austenite crystals are visible in the image. The specimen was annealed for 15 min at 900 C. Credit: Hansoo Kim Annealed microstructure of high-specific-strength steel (HSSS). Fine FeAl-type B2 precipitates form during annealing in between the B2 stringer bands in steel matrix. The specimen was annealed for 15 min at 900C. Credit: Hansoo Kim (Phys.org) —A trio of researchers with South Korea’s Graduate Institute of Ferrous Technology has found a way to create a new low-density steel that is stronger, lighter and more flexible than the conventional steel that is used in so many manufacturing applications. In their paper published in the journal Nature, the team describes the process they used and their hopes that it might replace conventional steel in some applications sometime in the near future. Annealed microstructure of high-specific-strength steel (HSSS). Fine FeAl-type B2 precipitates form during annealing in between the B2 stringer bands in steel matrix. The specimen was annealed for 15 min at 900 C. Credit: Hansoo Kim Annealed microstructure of high-specific-strength steel (HSSS). Fine FeAl-type B2 precipitates form during annealing in between the B2 stringer bands in steel matrix. Note that grain boundaries of recrystallized austenite crystals are visible in the image. The specimen was annealed for 15 min at 900 C. Credit: Hansoo Kim The researchers have already teamed with POSCO, one of the biggest steel makers in the world to see if the new kind of steel they have come up with might be usable in cars or even airplanes. The first step will be to see if the process is scalable, and if so, if it can be used to produce the new low-density steel at a cost that is competitive with conventional steel—the researchers are optimistic because all of the ingredients are low cost metals. Citation: New process allows for stronger, lighter, flexible steel (2015, February 5) retrieved 18 August 2019 from https://phys.org/news/2015-02-stronger-lighter-flexible-steel.html More information: Brittle intermetallic compound makes ultrastrong low-density steel with large ductility, Nature 518, 77–79 (05 February 2015) DOI: 10.1038/nature14144AbstractAlthough steel has been the workhorse of the automotive industry since the 1920s, the share by weight of steel and iron in an average light vehicle is now gradually decreasing, from 68.1 per cent in 1995 to 60.1 per cent in 2011 (refs 1, 2). This has been driven by the low strength-to-weight ratio (specific strength) of iron and steel, and the desire to improve such mechanical properties with other materials. Recently, high-aluminium low-density steels have been actively studied as a means of increasing the specific strength of an alloy by reducing its density3, 4, 5. But with increasing aluminium content a problem is encountered: brittle intermetallic compounds can form in the resulting alloys, leading to poor ductility. Here we show that an FeAl-type brittle but hard intermetallic compound (B2) can be effectively used as a strengthening second phase in high-aluminium low-density steel, while alleviating its harmful effect on ductility by controlling its morphology and dispersion. The specific tensile strength and ductility of the developed steel improve on those of the lightest and strongest metallic materials known, titanium alloys. We found that alloying of nickel catalyses the precipitation of nanometre-sized B2 particles in the face-centred cubic matrix of high-aluminium low-density steel during heat treatment of cold-rolled sheet steel. Our results demonstrate how intermetallic compounds can be harnessed in the alloy design of lightweight steels for structural applications and others.
(Phys.org)—A new model developed by a team of researchers with member affiliations in Argentina, France and Mexico, depicts a possible scenario to explain why gas giants do not migrate into the star they are orbiting during their early stages. In their paper published in the journal Nature, the researchers note that prior efforts to build a model that could explain gas giant growth and behavior did not take tidal effects into account and thus could not show why they survived. Martin Duncan of Queen’s University offers a News & Views piece on the work done by the team in the same journal issue. 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: Model shows how gas giants could have survived and spun away from their star (2015, April 2) retrieved 18 August 2019 from https://phys.org/news/2015-04-gas-giants-survived-spun-star.html Gas giants, such as Jupiter and Saturn, exist today because of certain processes that went on during their early development—but until now, no one had come up with a reasonable model to explain those processes—most showed the gas giants migrating into their star during their early stages, rather than spinning away from it.In this new model, the researchers believe tidal effects are the key. It all starts, they note, with a material disk surrounding a nearly born star. Material in that disk crashes into other material and some of it sticks—as that happens over and over more accretion takes place until the evolving planet grows large enough to start capturing gas in its atmosphere. Once that happens, the researchers say something interesting happens—as new material falls through the gas into the solid core of the planet, heat is released. That heat is then transferred back to the surrounding gas, and because the planet is spinning, parts of the gas, ahead of and behind the planet, expand—more so on the trailing side. That results, the researchers claim, in what they call a heating torque that actually pushes the still evolving planet away from its star. The model also suggests that the distance the planet is pushed from its star depends on the material that was in the original disk which made its way to the core of the new planet. Heavier elements would naturally offer more torque, but a planet’s eventual resting place would also depend on the size of the planet that formed.The model is just a first step in a new direction in trying to explain how gas giants came to be and where—research will continue both by the team with this new idea and of course by many others in the field. This is Jupiter’s Great Red Spot in 2000 as seen by NASA’s Cassini orbiter. Credit: NASA/JPL/Space Science Institute © 2015 Phys.org Journal information: Nature More information: Planet heating prevents inward migration of planetary cores, Nature 520, 63–65 (02 April 2015) DOI: 10.1038/nature14277AbstractPlanetary systems are born in the disks of gas, dust and rocky fragments that surround newly formed stars. Solid content assembles into ever-larger rocky fragments that eventually become planetary embryos. These then continue their growth by accreting leftover material in the disk. Concurrently, tidal effects in the disk cause a radial drift in the embryo orbits, a process known as migration. Fast inward migration is predicted by theory for embryos smaller than three to five Earth masses. With only inward migration, these embryos can only rarely become giant planets located at Earth’s distance from the Sun and beyond, in contrast with observations. Here we report that asymmetries in the temperature rise associated with accreting infalling material produce a force (which gives rise to an effect that we call ‘heating torque’) that counteracts inward migration. This provides a channel for the formation of giant planets and also explains the strong planet–metallicity correlation found between the incidence of giant planets and the heavy-element abundance of the host stars. Explore further Rocky planets may orbit many double stars
Explore further Citation: Gravity sensors might offer earlier warning of earthquakes (2016, November 23) retrieved 18 August 2019 from https://phys.org/news/2016-11-gravity-sensors-earlier-earthquakes.html Homing in on a potential pre-quake signal 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. More information: Jean-Paul Montagner et al. Prompt gravity signal induced by the 2011 Tohoku-Oki earthquake, Nature Communications (2016). DOI: 10.1038/ncomms13349AbstractTransient gravity changes are expected to occur at all distances during an earthquake rupture, even before the arrival of seismic waves. Here we report on the search of such a prompt gravity signal in data recorded by a superconducting gravimeter and broadband seismometers during the 2011 Mw 9.0 Tohoku-Oki earthquake. During the earthquake rupture, a signal exceeding the background noise is observed with a statistical significance higher than 99% and an amplitude of a fraction of μGal, consistent in sign and order of magnitude with theoretical predictions from a first-order model. While prompt gravity signal detection with state-of-the-art gravimeters and seismometers is challenged by background seismic noise, its robust detection with gravity gradiometers under development could open new directions in earthquake seismology, and overcome fundamental limitations of current earthquake early-warning systems imposed by the propagation speed of seismic waves. (Phys.org)—A team of researchers from France, the U.S. and Italy has found evidence from the Tohoku-Oki earthquake that sensors that measure changes in gravity might offer a way to warn people of impending disaster faster than traditional methods. In their paper published in the journal Nature Communications, the group describes how they analyzed data from gravity sensors near the epicenter of the Tohoku-Oki quake back in 2011 and found that it was possible to isolate gravitational changes due to the earthquake from the noise of other events. © 2016 Phys.org Journal information: Nature Communications Ruins from the 1906 San Francisco earthquake, remembered as one of the worst natural disasters in United States history. Credit: Public Domain Current earthquake warning systems rely on a network of seismic sensors—they listen for P-waves below the ground which are generated by an earthquake and send a signal to an alarm if they are heard. Such a system offers those in the vicinity of a quake from a few seconds to perhaps a minute to take safety measures. In this new effort, the researches wondered if it might be possible to detect subtle changes in gravity measurements near the epicenter of a quake to offer those in harm’s way a little more time to prepare for it—because gravity waves travel at the speed of light.Prior research has shown that there are subtle changes in gravitational pull around the epicenter of a quake, due to changes in the density of the rock in the area. But until now, it was not clear if such changes could be picked out from all the other background noise. To find out, the researchers pulled data from gravimeter sensors located approximately 500 kilometers from the epicenter of the Tohoku-Oki quake and compared what they found in the record with data from five seismic stations in the same area. They noted also that it took 65 seconds for the P-waves to reach the seismic stations. To find out if the quake data would stand out amongst the noise of other natural events (such as the changing tides) the team looked at measurements taken over the 60 days prior to the quake and then at the data from the day before, the day of, and the day after the quake. In looking at the data, the researchers found that they were able to “see” a small blip—one that stood out enough to confirm a quake had occurred.More research will have to be done before it can be proven that a network of gravity sensors would truly offer people more time to prepare for a quake (depending on how close they are to the epicenter), but the results from this initial study seem promising.
A levitated nanosphere as an ultra-sensitive sensor An international team of researchers has developed a tiny, liquid-based engine powered by a demixing fluid. In their paper published in the journal Physical Review Letters, the group describes their little engine and possible uses for it. The engine is essentially a tiny sphere orbiting a laser beam in a liquid solution. The sphere in the experiments was extremely tiny (2.48 micrometers in diameter) and made of iron oxide and silica. The liquid solution was a mixture of water and lutidine. The two ingredients were important, because together, they formed a critical liquid mixture that would separate at a desired temperature. In this case, separation occurred when its temperature warmed to approximately 34 degrees C.Starting the tiny engine involved first placing the sphere into the liquid solution (held below its separating point) and then capturing it with optical tweezers—a laser beam. Initially, the sphere was held in place. The iron oxide allowed the sphere to absorb heat, which propelled the sphere away from the center of the optical tweezer beam. The power of the laser beam was then slowly raised, causing the temperature of the sphere to rise, which in turn caused a rise in temperature of the surrounding liquid. Eventually, as the temperature of the liquid reached its critical point, the two fluids became un-mixed, forcing the sphere to move slightly. But because it was still held in place by the tweezers, it moved in a partial arc. The sphere’s temperature heated the liquid, further pushing the sphere when it reached its de-mixing point. This happened repeatedly, pushing the sphere all the way around the tweezer. It continued orbiting the tweezers for as long as laser power was applied.The researchers note that the system had a small range of temperatures in which the sphere would smoothly orbit—applying to little laser power caused the sphere to stop, too much and the sphere’s orbit would become erratic and at some point, it would break free of the tweezers grasp. The researchers suggest their engine could be used as a tiny mixer. 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: Tiny engine powered by demixing fluid (2018, February 12) retrieved 18 August 2019 from https://phys.org/news/2018-02-tiny-powered-demixing-fluid.html Going in circles. A micrometer-sized silica sphere with irregular iron oxide inclusions is trapped by optical tweezers (red area indicates focused laser light). Heating of the sphere by the light causes a near-critical liquid mixture to develop local concentration variations (trailing bubbles) that push the sphere to revolve around the beam. Credit: F. Schmidt/Univ. of Gothenburg More information: Falko Schmidt et al. Microscopic Engine Powered by Critical Demixing, Physical Review Letters (2018). DOI: 10.1103/PhysRevLett.120.068004ABSTRACTWe experimentally demonstrate a microscopic engine powered by the local reversible demixing of a critical mixture. We show that, when an absorbing microsphere is optically trapped by a focused laser beam in a subcritical mixture, it is set into rotation around the optical axis of the beam because of the emergence of diffusiophoretic propulsion. This behavior can be controlled by adjusting the optical power, the temperature, and the criticality of the mixture. © 2018 Phys.org Explore further Journal information: Physical Review Letters