The value of vegetation Researchers have constructed a network of the relatedness between products, providing insight into the economic question of why some countries can quickly climb the manufacturing ladder, while others fail to develop more sophisticated products. While the model may sound intuitive, this research is the first time that countries’ different economic growth patterns have been explained by a product network. Past economic theories have relied on a country’s productive factors (labor, land, infrastructure, etc.) or technological capabilities, but have disregarded product similarities when explaining a country’s growth. In a sense, the product network incorporates these other factors under one model.As part of a test of their model, the researchers asked if, given enough time, all countries could reach most of product space, particularly the richest parts. They found that the answer depends on the overall proximity of product space, as well as a country’s original positioning. For example, Chile and Korea have similar levels of production and export sophistication, but because Korea produces some core products, it can extend its sophisticated product line faster than Chile. The researchers even found that with countries that were developmentally similar, some were on a path to structural transformation while others seemed headed toward a dead end.“What surprised me along the year and a half that this work took was the broad set of implications and questions that were opened,” Hidalgo said. “There are many hard science studies on complex systems where the application of the findings is not well defined. Here we have a well defined area of application (industrial policy), yet the study lends itself for research in similar data sets. We are working on other areas of applications, such as research and health policy.”The researchers suggest that, for economic policy, estimating a country’s position in product space could have important consequences. For instance, countries in close proximity to other products could benefit the most from a relevant structural transformation, whereas countries at the periphery would need to make much longer jumps and would likely present a greater challenge to reform projects.“The proximity between products in the space increases as more countries export them in tandem,” Hidalgo explained. “Thus the movement of countries deforms the space. The technique does not provide a general solution for policymaking, but a new method to analyze and tailor policies for individual countries.” Product space networks of many nations can be seen at www.nd.edu/~networks/productspace/country.htm . Citation: Hidalgo, César, Klinger, Bailey, Barabási, Laszlo, and Hausmann, Ricardo. “The Product Space Conditions the Development of Nations.” Science, 27 July 2007, Vol. 317, 482-487.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. Explore further Citation: Nation’s position in ‘product space’ determines economic growth (2007, August 29) retrieved 18 August 2019 from https://phys.org/news/2007-08-nation-position-product-space-economic.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. In a recent issue of Science, physicists César Hidalgo and Laszlo Barabási from Notre Dame, along with economists Bailey Klinger and Ricardo Hausmann from Harvard University, have presented a network of what they coined as the “product space.” In the network, connections show the probabilities that a country exports a pair of products. Their results show how the types of products a nation produces and exports determines the probability of that nation developing more competitive products, thus influencing its overall economic wealth and growth.“As a joke, I can say that this is what happens when a Venezuelan (Ricardo Hausmann) a Canadian (Bailey Klinger) a Hungarian/Rumanian (Laszlo Barabasi) and a Chilean (me) meet in Cambridge, Massachusetts,” Hidalgo told PhysOrg.com of the work’s motivating factors. “They redefine the way in which economic growth is understood.” “In fact, this work was a multi-step process,” he continued. “Ricardo and Bailey had come up with the idea of a distance between products but were not clear of how to make sense of it at the global scale. That’s were I came in and built the network, making the interpretation of a sophisticated concept more intuitive and visual.”The researchers used trade data where all exports are coded within 775 product classes obtained from a National Bureau of Economic Research project. The structure of the product space is such that more sophisticated products (such as metal, machinery, and chemicals) formed the core, and had connections to many other products. A variety of other products (such as fishing, agriculture, textiles, electronics, and mining) comprised different clusters in the periphery of the product space. The product space can be used to visualize the patterns defined by the exports of a particular country. As a rule of thumb, poor countries tend to occupy the periphery of the space while rich countries are preferentially located at the core of it. Since countries can move through the product space by developing goods similar to those they already produce, poorer countries have a more difficult time extending their product variety. But, in simplified terms, it’s easy for the rich to get richer. Product space: Different product groups with links color-coded with their proximity value, and node size proportional to world trade. Credit: Hidalgo, et al. (Click here for a larger version)
Star crust 10 billion times stronger than steel, physicists find Explore further Citation: Studying the ‘mountains’ and ‘starquakes’ that develop on neutron stars (2009, May 26) retrieved 18 August 2019 from https://phys.org/news/2009-05-mountains-starquakes-neutron-stars.html (PhysOrg.com) — Neutron stars have the potential to play an important role in understanding some of the mysteries of the universe. One of factors that could help lead to an understanding of gravitational waves and the mechanisms involved in giant flares in magnetars is the strength of the crust that forms on the outside of a neutron star. In an effort to better understand the neutron star crusts, Charles Horowitz, at Indiana University in Bloomington, and his colleague Kai Kadau, at Los Alamos National Laboratory in New Mexico, have used molecular dynamics to model neutron stars and come up with improved estimates of the breaking strain. “In 2004, a giant flare was detected coming from a magnetar. It had a huge amount of energy.” Horowitz tells PhysOrg.com. (A magnetar is a neutron star with a very powerful magnetic field.) “We think that this mechanism only makes sense if the crust is really, really strong. Such a large flare should only be possible if, by the time the crust broke, there was tremendous energy stored in the crust and magnetic field.” Horowitz hopes that the simulations run with Kadau will help shed more light on the workings of neutron stars, and even perhaps answer other questions about the universe. Their work is presented in Physical Review Letters: “Breaking Strain of Neutron Star Crust and Gravitational Waves.” Horowitz says that for many years, scientists have been studying neutron stars and the “mountains” that develop on them. The bulges that create gravitational waves are the results of temperature-dependent nuclear reactions near hot spots. “People have wondered how big they can get, how massive they could become before the crust breaks because of forces from the strong magnetic field,” he explains. It is this collapse that releases the flares that are sometimes detected. There are two main aims for studying the possibilities for the crust of a neutron star: Learning more about these stars – what the crust is made of and how they might function – and using neutron stars as a way to possibly detect gravitational waves. Horowitz and Kadau’s model might be able to help in both of these areas, since it offers a more detailed look at what goes on when a mountain is formed – and when it collapses, causing a “starquake.” In the first case, the simulation Horowitz and Kadau is working with shows that the crust is likely made up of ions. “It’s more or less composed of normal atoms,” Horowitz explains, “but they’ve been ionized. The huge pressure of the star squeezes the electrons in such a way as to create ions. We think that the material is slightly heavier than iron, possibly selenium.” Understanding neutron star mechanisms, however, may also help scientists find gravitational waves. “The mountains that form on these rapidly rotating neutron stars generate gravitational waves quite efficiently. If we understand how this works, we might be able to make better predictions of which neutron stars would be most likely to produce the strongest gravitational waves. It would give scientists a better place to look.” Horowitz explains that gravitational waves are curves in space-time, predicted by Einstein’s theory of general relativity. “To actually find these waves would be a major discovery and a confirmation of general relativity. And I think our model can help in that aim.” More information: C.J. Horowitz, Kai Kadau. “Breaking Strain of Neutron Star Crust and Gravitational Waves,” Physical Review Letters (2009). Available online: http://link.aps.org/doi/10.1103/PhysRevLett.102.191102 . 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. 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.
Gamma Ray Delay May Be Sign of ‘New Physics’ 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. (PhysOrg.com) — Robert Nemiroff and his colleagues at Michigan Technological University will be discussing new constraints on the so-called lumpiness of space-time at this year’s meeting of the American Astronomical Society. Image credit: NASA/Sonoma State University/Aurore Simonnet Nemiroff, also known for his Astronomy Pick of the Day site, has been studying photons that have been traveling through space for several billion years following a γ-ray burst that was recorded back in 1989. Called GRB 090510A, the burst let loose high energy photons that have been traveling through space at the speed of light; two of them are of special interest to physicists because they are believed to have left the same place at exactly the same time, which would seem to make them arrive here at exactly the same time as well. But, they won’t, due to the lumpiness of space-time and the long distance they have traveled. In the abstract for the presentation, the authors suggest that because a high-energy time scale for the photons detected from the gamma-ray burst have been found, a new upper limit is in place on the dependence of energy on speed and light as it’s dispersed across the universe.Studies of high energy photons traveling through space have already shown there are differences in actual speeds recorded, though they are very, very small; seven parts in a billion trillion, according to a previous study done by researchers at Yale. Because of this and other studied phenomenon, various researchers have theorized that space-time isn’t actually continues as it appears, but is instead made up of very, very tiny elements that are almost unbelievably small, on the order of a 10-35 (the Planck length). In such theories, photons that have the highest amount of energy also have wavelengths that are near to the Planck length. This makes them more apt to intermingle with so-called “lumps” which slows them down. The amount of slowdown is obviously very tiny, but as the photons travel so far for so long, the effect is amplified.In their study, Nemiroff et al, find due to measured differences in the arrival time of the two photons, that new constraints are in effect that impact the lump size of space-time. Because of this, the lumpiness of space-time only becomes meaningful when things are roughly 1/500 the Planck length, which could, obviously, put some limits on quantum gravity theories. More information: Nemiroff, R. J., Connolly, R., & Holmes, J. A New Limit on Lorentz Invariance and Chromatic Dispersion Across the Universe from GRB 090510A (American Astronomical Society, 2011)AbstractA high-energy, fast-variability time scale for Fermi-detected gamma-ray burst GRB 090510A is found that creates a new strictest upper limit on the energy dependence of the speed and dispersion of light across the universe. In particular, evidence is presented for variability at or below Δ t = 0.00136 for super-GeV photons, a factor of 10 more limiting than any time scale previously claimed for a GRB at GeV energies, including a previous limit reported by Abdo et al (2008). This variability derives from the duration of three separate closely-arriving photon groups prominent only in photon data above 1 GeV. One pulse pair has an energy difference of Δ E >/~ 23.5 GeV. Coupled with a redshift of z >/~ 0.897, the resulting limits on the differential speed of light and Lorentz invariance were found for a concordance cosmology. It was found that Δ c / c < 6.09 x 10-21, a limit consistent with, but slightly stronger than, a previous limit found for a GRB by Schaefer in 1999. Given a generic dispersion relation across the universe where the time delay is proportional to the photon energy to the first power, the variability translates into a dispersion strength of k1 < 1.38 x 10-5 sec Gpc-1 GeV-1. This limit results in an upper bound on dispersive effects created, for example, by dark energy, dark matter, or the spacetime foam of quantum gravity. This dispersion constraint also results in the most stringent lower limit yet claimed for the onset energy scale of quantum gravity: MQG c2 > 7.43 x 1021 GeV.via Nature Explore further Citation: Physics team finds new constraints on how lumpy space-time can be (2012, January 11) retrieved 18 August 2019 from https://phys.org/news/2012-01-physics-team-constraints-lumpy-space-time.html © 2011 PhysOrg.com
Explore further (PhysOrg.com) — Researchers studying the planet Venus have found that despite a lack of a magnetic field, the planet has magnetotails, which on Earth are part of the process known as the Northern and Southern Lights. This, as the team describes in their paper published in Science, is due to the solar wind interacting with the planet’s ionosphere. 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. On Earth and other planets that do have a magnetic field, solar wind is deflected by the magnetism that surrounds the planet into the magnetosphere causing magnetic lines of force to break and reconnect, resulting in the show of lights in the night sky called an aurora. This process known as magnetic reconnection also causes the creation of magnetotails, or elongated stretches of the magnetosphere on the lee side of planets. This new research shows that Venus too has such magnetogtails, though the process of their creation is different.In analyzing data obtained from Venus Express, the probe sent by the European Space Agency, the researchers found that on Venus, the solar wind reacts with the ions in its ionosphere and in one instance resulted in what they describe as a magnetic plasma bubble stretching for some 2100 miles and lasting for just over a minute and a half. This they say is also an example of magnetic reconnection, albeit, one of a different kind.For years, researches have puzzled over mysterious flashes of light coming from Venus, and some have even speculated that they might be caused by magnetic reconnection, but until now lacked evidence. This new research adds strong credence to that theory and may also explain how some comet tails manage to disengage from their heads.As for whether the light generated by such instances of magnetic reconnection on Venus can truly be called an aurora, that remains up for debate. On Earth the Northern and Southern lights, also known as aurora borealis and aurora australis are named after the Roman goddess of dawn and thus are not tied to any specific scientific phenomenon, so it wouldn’t seem to be a stretch to use the same term for a similar effect discovered on another planet. Journal information: Science © 2012 PhysOrg.com Cluster opens a new window on ‘magnetic reconnection’ in the near-Earth space More information: Magnetic Reconnection in the Near Venusian Magnetotail, Science DOI: 10.1126/science.1217013ABSTRACTObservations with the Venus Express magnetometer and low-energy particle detector revealed magnetic field and plasma behavior in the near-Venus wake symptomatic of magnetic reconnection, a process that occurs in the Earth’s magnetotail but is not expected in the magnetotail of a non-magnetized planet like Venus. On 15 May 2006, the plasma flow in this region was toward the planet and the magnetic field component transverse to the flow was reversed. Magnetic reconnection is a plasma process that changes the topology of the magnetic field and results in energy exchange between the magnetic field and the plasma. Thus, the energetics of the Venus magnetotail resembles that of the terrestrial tail where energy is stored and later released from the magnetic field to the plasma. Citation: Venus found to have aurora type magnetotails (2012, April 6) retrieved 18 August 2019 from https://phys.org/news/2012-04-venus-aurora-magnetotails.html Venus. Photo courtesy of NASA
A bird-like robot perches on a human hand. As shown in the video, the researchers performed flight tests starting with launching the robot by hand from a height of about 2.5 meters. During the 1.5-second-long flight, the robot’s speed decreases from 4.7 m/s to just under 2.5 m/s at the time of landing. As the robot glides to within a short distance of the hand target, it pitches up to a high angle of attack and then lands.As the engineers explain, the ability to hand perch represents a significant step toward designing flying robots capable of close interaction with humans. In the future, they plan to work on a go-around capability to accommodate failures during perching attempts.via: IEEE Spectrum Montage of snapshots taken from the video of a flight test showingperching on a hand. Image credit: A. Paranjape, et al. “We believe we have the first demonstration of autonomous/robotic flight of a bird-like micro aerial vehicle (MAV) perching on a human hand,” said project leader Soon-Jo Chung of the University of Illinois at Urbana-Champaign. A paper on the demonstration is under review for the IEEE Transactions on Robotics.Hand perching involves two phases. First, the robot has to maneuver while gliding in order to reach the desired position, which it achieves by reorienting its articulated wings. Second, it has to “pitch up” right before landing to briefly climb and quickly reduce its touchdown speed. (Phys.org) — Among the many challenges of designing flying robots is getting them to land gracefully. By taking a cue from birds, a team of engineers has developed a flapping-wing flying robot that can land by perching on a human hand. It’s a bird, it’s a plane, it’s a robot bird (w/ video) © 2012 Phys.Org Explore further More information: A. Paranjape, J. Kim, and S.-J. Chung. “Closed-Loop Perching of Aerial Robots with Articulated Flapping Wings,” IEEE Transactions on Robotics, under review, 2012. Pre-release paper here. 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: Bird-like robot perches on a human hand (w/ Video) (2012, May 3) retrieved 18 August 2019 from https://phys.org/news/2012-05-bird-like-robot-perches-human-video.html
(Phys.org) —Researchers from Princeton University in the U.S. together with colleagues from Zhejiang University of Science and Technology in China have developed a new kind of atomic magnetometer that is just as sensitive as others of its kind but doesn’t need to be shielded from the Earth’s magnetic field. The team reports on their new device in the journal Physical Review Letters. 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 Journal information: Physical Review Letters Devices that can measure magnetic fields—magnetometers—are very useful in a wide variety of scientific applications. In recent years, such devices have been made more sensitive by using superconducting materials but they have the drawback of needing to be cryogenically cooled. Another approach has been to use atomic magnetometers—they don’t have to be super-cooled, but they do need to have shielding put in place to prevent Earth’s magnetic field from interfering with their readings. They work by using a pump laser to polarize the spin states of atoms inside the device. A probe laser is then used to read the spin precession once the device is ready to read a specific magnetic field—it’s all based on the Zeeman Effect that is induced by an external magnetic field.The new atomic magnetometer the group developed works essentially the same way as others of its kind, with two notable exceptions. The first is that the team uses a multi-pass cell—the probe laser makes many passes while reading the spin of the atoms in the device—typically rubidium vapor—this enhances the signal. The second difference is the team uses a technique to allow the polarizing to take place very quickly (within 1ms of laser pumping)—before relaxation of the spin states occurs. Doing so has the added benefit of helping to eliminate noise in the system allowing for more precise readings. The end result is an atomic magnetometer that is able to measure magnetism that is one hundred billion times smaller than the Earth’s field, without the need for shielding.Such a magnetometer is expected to be useful for such applications as measuring biological fields, geological instrumentation, experimental physics and even in land mine detection. The team that developed the new device isn’t resting on its laurels, however, they are currently looking at ways to make the device smaller and more portable. Record measurement of extremely small magnetic fields More information: Subfemtotesla Scalar Atomic Magnetometry Using Multipass Cells, Phys. Rev. Lett. 110, 160802 (2013) DOI: 10.1103/PhysRevLett.110.160802AbstractScalar atomic magnetometers have many attractive features but their sensitivity has been relatively poor. We describe a Rb scalar gradiometer using two multipass optical cells. We use a pump-probe measurement scheme to suppress spin-exchange relaxation and two probe pulses to find the spin precession zero crossing times with a resolution of 1 psec. We realize a magnetic field sensitivity of 0.54 fT/Hz1/2, which improves by an order of magnitude the best scalar magnetometer sensitivity and exceeds, for example, the quantum limit set by the spin-exchange collisions for a scalar magnetometer with the same measurement volume operating in a continuous regime. Citation: New atomic magnetometer doesn’t need to be shielded from Earth’s magnetic field (2013, April 26) retrieved 18 August 2019 from https://phys.org/news/2013-04-atomic-magnetometer-doesnt-shielded-earth.html © 2013 Phys.org Credit: J. Shi/Princeton University/PRL
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 Planetary influences on young stellar disks (Phys.org)—An international team of astronomers, led by Markus Janson of Stockholm University in Sweden, has discovered mysterious sharp symmetric features around young double star, named AK Sco. The discovery is baffling scientists as they are still unsure about the nature of these features, pondering the possibilities that they are highly eccentric rings or two separate spiral arms in the disk around the star. Moreover, these features may have been caused by circumbinary planets interacting with the disk. The results were published on Dec. 14 in the arXiv journal. AK Sco, located about 460 light years from Earth, is a spectroscopic binary star in the Upper Centaurus–Lupus (UCL) stellar association. It is a relatively young system, at least in astronomical terms, as scientists estimate it to be from 10 to 20 million years old. Spectroscopic binaries are systems in which the stars are so close together that they appear as a single star even in a telescope. The only evidence of a binary star comes from the Doppler effect on its emitted light. Periodic Doppler shifts of the wavelengths of lines are seen in the spectrum, as the stars move through their orbits.Janson and his colleagues made the discovery using the European Southern Observatory’s (ESO) Very Large Telescope (VLT), located in Chile. The observations were conducted in April 2015 as a part of the Search for Planets Orbiting Two Stars (SPOTS) program. The scientists made use of the Spectro-Polarimetric High-contrast Exoplanet Research (SPHERE) instrument recently installed on VLT. SPHERE is a powerful planet finder and its objective is to detect and study new giant exoplanets orbiting nearby stars using a method known as direct imaging.Detecting the sharp features in near-infrared imaging of AK Sco’s disk was a surprise for the scientists as they expected to find rather exoplanets in the neighborhood. However, what they found, might not be planets at all.”We report the discovery of resolved scattered light emission from the circumbinary disk around the well-studied young double star AK Sco. The sharp morphology of the imaged feature is surprising, given the smooth appearance of the disk in its spectral energy distribution,” the astronomers wrote in the paper.They researchers have noticed that the central binary star has a semi-major axis of approximately 0.16 astronomical units or AU and that the disk appears to have a gap with an inner rim at 0.58 AU. The images of AK Sco obtained by the SPHERE instrument reveal that the system has ‘arms’ extending from each side of the central star almost symmetrically. The scientists also found out that these features constitute scattered radiation from off-axis material in the circumbinary disk.The mysterious sharp features could represent an eccentric ring of material surrounding a gap. The scientists note that such structures are often found in disks that contain rings of material with gaps inside them. However, other observations conducted by ESO’s Atacama Large Millimeter Array (ALMA) don’t support this theory.Another explanation taken into account by Janson and his colleagues is that these structures are spiral arms that could be induced through gravitational instability or through the influence of a planet or binary companion. These two spiral arms are wound in opposite directions—one unwinding clockwise and the other counter-clockwise. But the fact that the features are so apparently symmetric, speaks against this hypothesis.What is worth noticing, either of these scenarios mentioned earlier, may point to circumbinary exoplanets in the disk. The features could be created by one or several planets interacting with the disk.Whichever proposed theory is true, the authors of the paper highlight the importance of the new generation adaptive optics systems – like this installed on the SPHERE instrument – in the search of disks around stars. They hope that these features will detected more often in near future as a result of implementing new technology of observations. SPHERE high-contrast images of AK Sco. All images show the two arms of the disk discussed in the paper. Credit: Markus Janson et al. 2015 © 2015 Phys.org More information: Detection of Sharp Symmetric Features in the Circumbinary Disk Around AK Sco, arXiv:1512.04552 [astro-ph.SR] arxiv.org/abs/1512.04552AbstractThe Search for Planets Orbiting Two Stars (SPOTS) survey aims to study the formation and distribution of planets in binary systems by detecting and characterizing circumbinary planets and their formation environments through direct imaging. With the SPHERE Extreme Adaptive Optics instrument, a good contrast can be achieved even at small (<300 mas) separations from bright stars, which enables studies of planets and disks in a separation range that was previously inaccessible. Here, we report the discovery of resolved scattered light emission from the circumbinary disk around the well-studied young double star AK Sco, at projected separations in the ~13—40 AU range. The sharp morphology of the imaged feature is surprising, given the smooth appearance of the disk in its spectral energy distribution. We show that the observed morphology can be represented either as a highly eccentric ring around AK Sco, or as two separate spiral arms in the disk, wound in opposite directions. The relative merits of these interpretations are discussed, as well as whether these features may have been caused by one or several circumbinary planets interacting with the disk. Citation: Mysterious sharp symmetric features detected around young double star (2015, December 17) retrieved 18 August 2019 from https://phys.org/news/2015-12-mysterious-sharp-symmetric-features-young.html
© 2016 Phys.org Explore further Citation: Fossils of early tetrapods unearthed in Scotland (2016, December 7) retrieved 18 August 2019 from https://phys.org/news/2016-12-fossils-early-tetrapods-unearthed-scotland.html More information: Jennifer A. Clack et al. Phylogenetic and environmental context of a Tournaisian tetrapod fauna, Nature Ecology & Evolution (2016). DOI: 10.1038/s41559-016-0002AbstractThe end-Devonian to mid-Mississippian time interval has long been known for its depauperate palaeontological record, especially for tetrapods. This interval encapsulates the time of increasing terrestriality among tetrapods, but only two Tournaisian localities previously produced tetrapod fossils. Here we describe five new Tournaisian tetrapods (Perittodus apsconditus, Koilops herma, Ossirarus kierani, Diploradus austiumensis and Aytonerpeton microps) from two localities in their environmental context. A phylogenetic analysis retrieved three taxa as stem tetrapods, interspersed among Devonian and Carboniferous forms, and two as stem amphibians, suggesting a deep split among crown tetrapods. We also illustrate new tetrapod specimens from these and additional localities in the Scottish Borders region. The new taxa and specimens suggest that tetrapod diversification was well established by the Tournaisian. Sedimentary evidence indicates that the tetrapod fossils are usually associated with sandy siltstones overlying wetland palaeosols. Tetrapods were probably living on vegetated surfaces that were subsequently flooded. We show that atmospheric oxygen levels were stable across the Devonian/Carboniferous boundary, and did not inhibit the evolution of terrestriality. This wealth of tetrapods from Tournaisian localities highlights the potential for discoveries elsewhere. 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. Planet Earth has experienced several mass extinctions, five of which are considered to be the greatest because of the huge loss of plant and animal life. Over the course of one such extinction event, called the Late Devonian mass extinction, approximately 75 percent of all animal species on the planet were believed to have gone extinct. In the years that followed, some of those species that did survive, such as groups of early tetrapods. eventually evolved into what would become the ancestors of amphibians, birds, mammals and reptiles. Unfortunately, the fossil record for creatures of this period is very thin—few specimens have been found, and those that have are fragments rather than complete skeletons. This time period is particularly important in the timeline of evolutionary history because it is when creatures first began climbing out of the sea to move about on land.The fossils found by the research team include two specimens that appear to represent amphibian ancestors while another three are believed to be from bird, mammal and reptile ancestors. Among the finds are other fossil bits that have yet to be identified. All of the fossils came from relatively small creatures—the largest skull was approximately 80 millimeters in length. The team describes the creatures as lizard-like and report that they lived approximately 355 million years ago. They suggest the fossils represent a critical step in the evolution of animal life from a period when creatures were evolving new features that made it possible to live on land—such as limbs and lungs.Prior to this find, researchers have uncovered just two fossil finds from the gap—one from a site in Canada and another in the U.S. In the past, researchers have theorized that there was a dearth of creatures that had bones to leave behind, possibly due to low atmospheric oxygen levels.The new finding strengthens theories suggesting that the lack of fossils from the gap years is due to researchers simply not finding them. The left hand image shows the late Stan Wood pointing to the place where he found most of the tetrapod fossils from Willlie’s Hole near Chirnside, taken in 2010, and the right hand image shows the National Museums Scotland-organised excavation of that site in 2015. Co-authors Walsh and Millward left and centre, with lead author and PI Clack on the right. Credit: Left hand image: Jennifer A. Clack Right hand image: Robert N. G. Clack. (Phys.org)—A team of researchers working at a dig site in Scotland has found tetrapod fossils dated to approximately 15 million years after the Devonian mass extinction—a time period experts in the field have referred to as “the gap,” because so few fossils of creatures from that time period have been found. In their paper published in the journal Nature Ecology & Evolution, the team describes the fossils they uncovered and outline their place in the evolution of animal life on our planet. Biggest map of dinosaur tree yet suggests they emerged 20 million years earlier than thought
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. Part of the renormalised SALT HRS spectrum of J1845−4138 (black) compared with the median spectrum of V652 Her near maximum radius obtained by Jeffery et al. (2015, red). Credit: Jeffery, 2017. © 2017 Phys.org Citation: Rare extreme helium star identified by astronomers (2017, June 20) retrieved 18 August 2019 from https://phys.org/news/2017-06-rare-extreme-helium-star-astronomers.html Feuding helium dwarfs exposed by eclipse Extreme helium stars (EHes) are supergiants much larger and hotter than the sun, but less massive. They are almost devoid of hydrogen, which is unusual, as hydrogen is the most abundant chemical element in the universe. EHes are characterized by relatively sharp and strong lines of neutral helium, which indicates low surface gravities and atmospheres dominated by helium. Besides helium, these stars also have significant amounts of carbon, nitrogen and oxygen. EHe was first detected in 1942.The discovery of GALEX J184559.8−413827 was announced in 2011 and was based on the data provided by NASA’s Galaxy Evolution Explorer (GALEX) satellite. Given that the star was classified as a helium-rich “hot subdwarf,” it was put on a target list for observations of chemically peculiar objects with the high-resolution spectrograph (HRS) on the Southern Africa Large Telescope (SALT), located near Sutherland, South Africa.Now, Simon Jeffery of the Armagh Observatory and Planetarium in College Hill, Northern Ireland, presents the results of new observations of GALEX J184559.8−413827 conducted with HRS in March 2017. According to Jeffery, the high-resolution spectrum obtained with the use of HRS indicates that the observed object is a nitrogen-rich EHe star.”A spectroscopic survey of stars classified as helium-rich subdwarfs, especially He-sdB or sdOD using 8m-class telescopes has been undertaken. This paper reports an observation of one such star obtained with the high-resolution spectrograph on the Southern Africa Large Telescope. (…) SALT HRS observations of a faint-blue star previously classified He-sdB (Vennes et al. 2011) demonstrate it to be a nitrogen-rich EHe star similar to the pulsating EHe star V652 Her,” the paper reads.Jeffrey acknowledged that GALEX J184559.8−413827 is four magnitudes fainter than V652 Her. Spectroscopic similarities with V652 Her suggest the new EHe star has similar evolutionary status, which suggests that it formed as a result of a double helium white dwarf merger. Moreover, it also means that GALEX J184559.8−413827 could evolve to become a helium and nitrogen-rich hot subdwarf within about 100,000 years.Notably, GALEX J184559.8−413827 is the first EHe star to be discovered for nearly 40 years. This highlights the extreme rarity of such stars.The question that remains unanswered is whether GALEX J184559.8−413827 also pulsates like V652 Her. So far, no evidence of any periodic variability of the new EHe star was found. Jeffery concluded that his study is promising when it comes to future detections of new EHe stars.”This discovery suggests that there are more EHe stars waiting to be found, at least with relatively low luminosities. A higher signal-to-noise spectrum will allow abundances and other parameters to be refined further,” he wrote in the paper. More information: GALEX J184559.8-413827: a new extreme helium star identified using SALT, arXiv:1706.03377 [astro-ph.SR] arxiv.org/abs/1706.03377AbstractA high-resolution spectrum of the helium-rich ‘hot subdwarf’ GALEX J184559.8-413827 (J1845-4138) obtained with SALT HRS demonstrates it to be the first extreme helium (EHe) star to be discovered in nearly 40 years. A quantitative analysis demonstrates it to have an atmosphere described by Teff = 26 170 +/- 750 K, log g /(cm s^-2) = 4.22 +/- 0.10, and a surface chemistry characterised by CNO-processed helium, a 1% contamination of hydrogen (by number), and a metallicity 0.4 dex subsolar. Its distance and position are consistent with membership of the Galactic bulge. Its sharp absorption lines place strong constraints on both the rotation and microturbulent velocities. Spectroscopically, J1845-4138 closely resembles the pulsating EHe star V652 Her, generally considered to be the product of a double helium white dwarf merger evolving to become a helium-rich sdO star. (Phys.org)—Astronomers have identified another rare example of an extreme helium star. The star, designated GALEX J184559.8−413827 (or J1845−4138 for short), was initially classified as a faint helium-rich “hot subdwarf,” but new spectroscopic observations reveal that this star is more hydrogen-deficient than previously thought. The finding is available in a paper published June 11 on arXiv.org. Explore further
They were not able to determine the motives behind the rock boring by the shipworms, but note that it is not likely a means of obtaining any sort of nutritional value. They suspect the little mollusks meet their nutritional needs courtesy of bacteria that live in their gills—though they have not ruled out the possibility of food being pulled into its siphon. © 2019 Science X Network Shipworms are water-dwelling bivalve mollusks—they are well known because of their tendency to chew through wood and digest it. They came to prominence during the heyday of wooden ships—the small mollusks would bore holes in them, at times making them unfit to sail. More recently, they are known for making holes in piers and other wooden structures used in the water. In this new effort, the researchers have found a species of shipworm that does not eat wood at all, but instead bores through limestone.The researchers report that the new kind of shipworm was actually first spotted back in 2006, but it was not until recently that it was carefully studied. After capturing specimens by breaking open the rocks they occupied, the researchers put them in tanks in their lab. They report that the shipworms were small—on the order of 150 millimeters long. They were white and more closely resembled worms than other mollusks. They also differed physically in significant ways from wood-eating shipworms—for instance, they have larger, flatter teeth more suited to boring through rock. The rock borers also lacked the sac used by wood eaters to digest wood. The researchers suggest that such physical differences indicate that the rock-eating shipworm likely did not evolve from its wood-eating relatives, but more likely diverged from them a very long time ago. The shipworms were observed to gnaw their way into the limestone. A little while later, the researchers observed the shipworms excreting sand. Journal information: Proceedings of the Royal Society B Explore further A team of researchers affiliated with several institutions in the U.S. has found and identified a species of shipworm that eats rock instead of wood. In their paper published in Proceedings of the Royal Society B, the group describes their study of the bivalve and what they found. The river bedrock is shaped by large holes bored by the shipworm. Credit: Marvin Altamia and Reuben Shipway Citation: Shipworm that eats rock instead of wood found in river in the Philippines (2019, June 19) retrieved 18 August 2019 from https://phys.org/news/2019-06-shipworm-wood-river-philippines.html Morphology of Lithoredo abatanica: (a) juvenile specimen (PMS-4313H); (b) small adult specimen (PMS-4134 W); (c) large adult specimen (holotype PMS-4312Y); (d) pallet pair outer face; (e) pallet pair inner face; (f) shell valves; (g) scanning electron micrograph of shell valve; (h) magnified region from (g) showing valve denticulation; (i) magnified region from (h). In, intestine; MC, mantle collar; Pa, pallet; Si, siphon; SV, shell valve. Scale bar (a–c) = 5 mm, (d–f) = 1 mm, (g–i) = 200 µm, 100 µm and 5 µm respectively. Credit: Proceedings of the Royal Society B: Biological Sciences (2019). DOI: 10.1098/rspb.2019.0434 New species of wood-munching (and phallic-looking) clams found at the bottom of the ocean More information: J. Reuben Shipway et al. A rock-boring and rock-ingesting freshwater bivalve (shipworm) from the Philippines, Proceedings of the Royal Society B: Biological Sciences (2019). DOI: 10.1098/rspb.2019.0434Press release 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.