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New StringTheory Notion Redefines the Big Bang

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. Along these lines, a group of theoretical physicists has recently published an interesting string-theory scenario that describes a new way to approach the development of the Big Bang. They propose that the universe began as a type of theoretical space-filling object called a “brane.”This work was published in the January 27, 2006, online edition of Physical Review Letters.“Perhaps the most ambitious problem in cosmology is the question of the initial conditions of the universe — what it looked like before expanding into the stars and planets we see today,” said a physicist involved in the study, Robert Leigh of the University of Illinois, to “We propose that the universe, before expansion, was an unstable brane that decayed into innumerable string-loops to form the universe as we now know it.”The conventional model for the expansion of the universe assumes that the universe once existed as a very small, point-like volume called a “singularity.” Then the Big Bang occurred, and the universe rapidly expanded. An extension of this, and one main competitor of the brane model, is the Big Crunch/Big Bang theory, which assumes that the universe was once vast, then “crunched” down to a singularity before expanding. The Big Bang/Big Crunch model implies that time existed before the Big Bang.The problem with the Big Crunch/Big Bang model is that the mathematical laws of classical general relativity do not work at a singularity. And if scientists cannot mathematically understand the singularity, they cannot, in theory, fully understand the geometry of spacetime, either before the Big Crunch or after the Big Bang.“Our brane model allows us to mathematically address what might have happened at the Big Bang, and also gives a novel interpretation of time in string theory,” said Leigh.He and his group propose that time began when, via a Big Bang-like event, the brane decayed into closed strings (loops) that propagated off to create the ordinary matter that makes up the universe. This scenario, while avoiding the mathematical problems of a singularity, also helps explain some other issues. For example, to us, the universe looks the same in every direction. Within this brane model, the homogeneity of the universe could be explained as the result of an early universe with homogenous initial conditions, such as a brane that evenly filled space. Leigh and his colleagues may further explore this in additional studies.Citation: “Brane Decay and an Initial Spacelike Singularity,” Phys. Rev. Lett. 96, 031301 (2006)By Laura Mgrdichian, Copyright 2006 Explore further Citation: New String-Theory Notion Redefines the Big Bang (2006, March 31) retrieved 18 August 2019 from Physicists say universe evolution favored three and seven dimensions String theory — the concept that all particles can be represented as strings or string-loops of incredibly minute length, oscillating at various frequencies — was initially developed to help explain why quarks, the tiny fundamental particles that make up protons and neutrons, are always confined within larger composite particles. However, string theory has evolved to allow scientists to deal with some wider issues. For example, they can use string theory to devise explanations for some grand problems in cosmology, such as the state of the universe — its shape, size, etc. — just after the Big Bang, when quarks roamed freely.last_img read more

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Researchers stumped by drug addiction paradox

first_img Explore further From chocolate and caffeine to nicotine and cocaine, many of our most addictive foods and drugs come from plant toxins. Considering that plants originally developed these toxins to deter herbivorous predators, it’s ironic that humans and other mammals don’t merely tolerate the toxins, but can crave them and even develop dependencies on them. As the researchers investigated further, they compiled other studies showing evidence that humans inherited these detox genes from their mammalian ancestors. Interestingly, although many modern animal species can tolerate plant toxins, different species possess different detox function levels. Even among humans from different geographic locations, these functions differ. Often, human populations with greater numbers of toxin-metabolizing genes originate from parts of the world that contain an abundance of those plants. For example, human populations in and near Turkey have a very high frequency of enzymes that can metabolize opiates, and the opiate poppy is native to the Turkish region.To conclude their argument against the evolutionary interpretation, the researchers explain that (pre-human) animals and plants did appear to have evolved the relevant genes simultaneously. If that’s the case, then the brain shouldn’t treat drugs as if they contained a fitness benefit, giving strong support to the paradox.“We have been surprised by how robust the paradox is – that is, in presenting the arguments at scientific meetings for several years now, no one has been able to refute the basic argument that plant ecological models and neurobiological models of drug use are in direct conflict,” Sullivan said. Many more questions also remain unanswered, but they may contain clues to an explanation. For example, there is contradictory evidence for whether commonly used drugs have become more or less potent as they’ve been domesticated. Also, as the researchers point out, current models explaining drug reward mechanisms don’t differentiate between different drugs – even though the pathways taken by opiates, cannabis, or any other drug are vastly different. Models of multiple-drug pathways might better explain drug appeal, the scientists suggest.Based on evidence from previous studies, Sullivan, Hagen, and Hammerstein note that plant toxins may actually have some kind of benefit for animals. For instance, because plant toxins are more harmful to some species than to others, the less affected species might actually consume levels of toxin that are tolerable to themselves but much worse for the parasites or pathogens that feed on them in order to protect themselves. For example, earlier humans that consumed nicotine (in much smaller amounts than today) could have received the benefit of fewer parasitic infections. Of course, the benefits also come with trade-offs.“The main implications for future research are that neurobiological theorists must consider facts emerging from plant ecology,” Sullivan said. “We are also planning field studies looking for relationships between human drug use and protection from helminth parasites.”More information: Sullivan, Roger J.; Hagen, Edward H.; and Hammerstein, Peter. “Revealing the paradox of drug reward in human evolution.” Proc. R. Soc. B. doi:10.1098/rspb.2007.1673. ( … nt/ql240r18116x5870/)Copyright 2008 All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of This paradox, presented by researchers in a new paper in Proceedings of the Royal Society B, works both ways: supposedly, the plants should never have developed toxins that reward animals for eating them, and humans should never have developed a reward mechanism for toxic plants. In their study, Roger Sullivan from California State University and the UC Davis School of Medicine, Edward Hagen from Washington State University, and Peter Hammerstein from Humboldt University in Berlin suggest that the most widely accepted evolutionary explanation of human drug reward might not be on the right track, and that the origins of drug addiction may be even more complicated than previously thought.“The greatest significance of the paper is in defining the paradox, and laying out the arguments in a manner that shows that it is a real conundrum and not a straw man argument,” Sullivan told “The paradox has deep implications for current drug reward theory because it implicitly suggests that many of the key assumptions in current drug reward theory are flawed.”Throughout history, plants have created their toxins by mimicking their own molecules that regulate metabolism, growth and reproduction. When ingested by herbivores, some of these molecules can interfere with nearly every step in the animal’s neural signaling process. In current evolutionary interpretations of drug addiction, these toxic substances trigger the brain’s reward center by rewiring the brain’s natural reward circuits, and falsely indicating a fitness benefit and blocking painful feelings. But, as Sullivan, Hagen, and Hammerstein show, this explanation makes several assumptions that contradict evidence from previous studies. Most significantly, it assumes that humans evolved in environments without exposure to drugs, and that the brain never evolved to protect itself from plant toxins. However, the researchers point to several other studies which show that the detoxification enzymes developed by animals (and which originally evolved in bacteria about 3.5 billion years ago) expanded in animals about 400 million years ago – about the same time that plants were evolving their own toxins. In other words, animals and plants seemed to have coevolved competitive genes in response to each other, which contradicts the evolutionary interpretation. Citation: Researchers stumped by drug addiction paradox (2008, April 16) retrieved 18 August 2019 from Data from the US National Survey on Drug Use and Health 2004: drug use in the last year. Credit: Sullivan, et al. ©2008 The Royal Society. No cure for Alzheimer’s disease in my lifetime 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

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Closing recreational fishing areas for shorter times could benefit fish and fishermen

first_imgThe researchers found that the level of fishing pressure significantly affects the outcomes of the strategies. For a low pressure scenario, the two-month closure strategy results in increased fish stock, comparable fish extraction, and negligible economic reduction compared to the no-closure strategy. However, the six-month closure strategy does not provide the same benefits, mainly because fishing increases at the two open sites for a longer time than for the two-month closure case, so the fish stock does not recover as quickly at the open sites.For a high pressure scenario, the six-month closure strategy had advantages over both the two-month closure strategy and the no-closure strategy. The higher fishing demand quickly leads to an overall decline in fish stocks at all three sites, and the six-month closure time gives the fish stock at the closed site more time to recover than the two-month closure time. However, the fish stock is lower than for the low pressure scenario, and the overall catch level is still much lower than for the low pressure scenario.Overall, the results show that the effects of management strategies can be very different from what one might expect without the benefit of integrated modeling. The researchers attribute the unexpected results to the fact that the model can account for the delicate balance and feedback effects involved in this multi-faceted system, which are difficult to account for without the model. They hope that, in the future, resource managers use integrated models like this one to develop and defend management strategies, which are often subjects of controversy.“From a technical point of view, the work is a very good practice to deliver better management options for addressing complex issues through integrated modeling of socio-economic and biophysical processes,” Gao said. “It brings forth several new ideas, such as using econometrically estimated models to drive agent behavior.”Hailu added that they are working on expanding the number of sites, and the model could be adjusted to analyze a wider variety of situations.“The framework is set, and it is possible to develop similar models for other natural resource management problems to take into account the complexity of the interaction between economic and biophysical features,” Hailu said. ( — A new model that analyzes the complex factors involved in recreational fishing has shown that modeling can lead to some unforeseen results. Among the model’s surprising conclusions is that, under low fishing pressure in a coral reef ecosystem, closing fishing areas for two months instead of six months can result in larger fish stocks and better fishing opportunities. The model, which simulates the impact of recreational fishing on fish stocks, the economic welfare of recreational anglers, and the surrounding coral reef environment, by incorporating a variety of factors and feedback effects, could be useful for formulating the best strategy for managing recreational fishing areas. “I think the main message is that resource managers and policy makers need to ensure that decisions are supported by modeling and analysis that is grounded on empirical facts,” coauthor Atakelty Hailu from the University of Western Australia told and coauthor Lei Gao, also from the University of Western Australia, will publish their study in an upcoming issue of Ecological Economics. As the researchers note in their study, recreational fishing continues to increase, and in some areas accounts for greater fish extraction than commercial fishing activities. For example, in 2008 in the Gascoyne Bioregion in Western Australia, recreational anglers caught 56 tonnes of spangled emperor while commercial fishers caught just 7 tonnes. In their study, the researchers developed a model that integrates six individual models: these models estimate the location, frequency, duration, and seasonality of an angler’s fishing trip; the angler’s expected catch; and the interactions among the fish and their coral reef environment. The researchers then applied this integrated model to evaluate different fishing site closure strategies for three recreational fishing sites at the Ningaloo Marine Park in Western Australia. The goal was to strike a careful balance between providing opportunities to enrich the experience and increase the economic value of recreational anglers while minimizing the impact on the fish stock and the natural environment.The researchers used their model to simulate three different site closure strategies: no closure, a two-month closure for one of three fishing sites at Ningaloo, and a six-month closure for one of three fishing sites at Ningaloo. They ran the simulations for low and high levels of fishing pressure, where high pressure was defined as twice the number of anglers per square kilometer at all fishing sites. They performed 50 replications for each experiment for a 25-year period (from 2010 to 2035), and averaged the results for each experiment. More information: Lei Gao and Atakelty Hailu. “Evaluating the effects of area closure for recreational fishing in a coral reef ecosystem: The benefits of an integrated economic and biophysical modeling.” Ecological Economics. To be published. A new model that accounts for the many impacts of recreational fishing could help policy makers determine the best management strategy. Image credit: US Fish and Wildlife Service Citation: Closing recreational fishing areas for shorter times could benefit fish and fishermen (2011, May 26) retrieved 18 August 2019 from Seafloor recovery from fishing gear impacts in Stellwagen Bank Marine Sanctuary slow, unstable © 2010 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.last_img read more

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Chemists figure out a way to force apart click chemistry bonds

first_img Triazole is a ring shaped chemical compound that is formed during the reaction that occurs between azide and alkyne when mixed with copper. Its formation is considered to be a type of “click” or snap-together chemistry reaction due to the fact that the components click together in a very tight formation; sort of like wooden floor panels that click together to keep from sliding apart under constant abuse from foot traffic. Such bonds once formed have traditionally been very difficult to force apart, even under intense heat. Now however, Bielawski and his team have figured out a way to do it using brute force.To pull the components of triazole apart, the team attached polymer chains to either side of the individual molecules, then immersed them in a solution and applied ultrasound. Doing so caused tiny bubbles to form of a certain size that soon collapsed, leaving a vacuum behind. The vacuum force then pulled the components of the molecule apart by yanking on the polymer chains. The end result is azide and alkyne, the original components in their original forms.The experiment is the first of its kind, showing that such compounds can be torn apart by force, opening the door to all kinds of other possibilities where researchers wish to be able to take compounds apart piece by piece without impacting anything else in the surrounding environment.In their paper the team points out that such types of forced reactions might already be taking place in nature leading to failures of materials in previously unexplainable ways; or worse in pharmaceuticals that break down in the body leading to perhaps dangerous consequences.Looking towards the future, this new method of tearing apart chemical bonds might lead to new types of sensors that can detect stress or be used as a type of “bodyguard” for other compounds that can be taken apart and removed when its usefulness has run its course. © 2011 ( — Normally when chemists think of methods to urge chemical reactions, brute force is not really very high on the list; while such techniques might be useful for breaking apart materials, i.e. bashing cement to get smaller pieces of cement; it’s generally not been a useful way to tear apart the molecules that actually comprise the compound itself. At least till now. Christopher Bielawski and colleagues at the University of Texas, as described in their paper in Science, have figured out a way to unbind triazole to get back its original components azide and alkyne, using nothing but force. Scripps Research Institute awarded patent for remarkable chemical technology Chemical structure of en:1,2,3-triazole created with ChemDraw. Image: Wikipedia. More information: Unclicking the Click: Mechanically Facilitated 1,3-Dipolar Cycloreversions, Science 16 September 2011: Vol. 333 no. 6049 pp. 1606-1609. DOI: 10.1126/science.1207934ABSTRACTThe specific targeting of covalent bonds in a local, anisotropic fashion using mechanical methods offers useful opportunities to direct chemical reactivity down otherwise prohibitive pathways. Here, we report that embedding the highly inert 1,2,3-triazole moiety (which is often prepared using the canonical “click” coupling of azides and alkynes) within a poly(methyl acrylate) chain renders it susceptible to ultrasound-induced cycloreversion, as confirmed by comprehensive spectroscopic and chemical analyses. Such reactivity offers the opportunity to develop triazoles as mechanically labile protecting groups or for use in readily accessible materials that respond to mechanical force. Explore further Citation: Chemists figure out a way to force apart click chemistry bonds (2011, September 16) retrieved 18 August 2019 from 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

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Ambrosia beetles have highly socialized systems

first_img Play Shuffling behavior by an adult female in the entrance tunnel of a gallery. This sequence shows the typical shuffling behavior by an adult female, which serves to shift balls and pieces of waste material (sawdust and frass) out of the entrance tunnel for final disposal. Note that during this video sequence a third-instar larva (first scene: 0-12 s) and a teneral female (last scene: 55-59 s) are providing the shuffling female with new material for disposal. Video: PNAS. However, researchers led by Peter Biedermann from the University of Bern have developed an alternative glass observation tube similar to the ambrosia beetles natural environment that they can use to observe natural behavior and their results have been published in this month’s Proceedings of the National Academy of Sciences.In observing these beetles in their natural environment, the researchers discovered that the ambrosia beetles live in a highly socialized system. The adult females work to protect the colony and make sure the fungus gardens they rely on for food are tended to. The adult males spend most of their time grooming and mating with females.The young beetles are put to work too. The Ambrosia beetle larvae are put to work cleaning and digging to expand the nest area. Beetle suspect in deaths of red bay trees Morphology of a brood chamber in artificial medium, with different larval instars and a teneral female. Image (c) PNAS, doi:10.1073/pnas.1107758108 Explore further © 2011 PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen Citation: Ambrosia beetles have highly socialized systems (2011, October 4) retrieved 18 August 2019 from Play Balling behavior by a larval worker within the brood chamber. This sequence shows an example of balling by a third-instar larva that is surrounded by other larvae and a pupa. With this behavior larvae collect waste material (sawdust and frass) to form balls that can be shifted in the gallery or dumped out of its entrance. Video: PNAS. The researchers compare these beetles to the other highly socialized insects such as wasps and ants. However, there research left them with an unanswered question that Beidermann hopes to answer with continued study. From what they determined, the beetle larvae seem to hinder the growth of mold. Beidermann plans to study whether they use a type of bacteria to produce antibiotics similar to that of the leaf-cutter ants or if they produce some sort of secretion that accomplishes it on its own. PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen ( — Ambrosia beetles have long eluded scientists when it comes to being able to study their natural social structure. These beetles live deep within the solid wood of trees and when you disturb their natural nest, the beetles disappear. More information: Larval helpers and age polyethism in ambrosia beetles, PNAS, Published online before print October 3, 2011, doi:10.1073/pnas.1107758108AbstractDivision of labor among the workers of insect societies is a conspicuous feature of their biology. Social tasks are commonly shared among age groups but not between larvae and adults with completely different morphologies, as in bees, wasps, ants, and beetles (i.e., Holometabola). A unique yet hardly studied holometabolous group of insects is the ambrosia beetles. Along with one tribe of ants and one subfamily of termites, wood-dwelling ambrosia beetles are the only insect lineage culturing fungi, a trait predicted to favor cooperation and division of labor. Their sociality has not been fully demonstrated, because behavioral observations have been missing. Here we present behavioral data and experiments from within nests of an ambrosia beetle, Xyleborinus saxesenii. Larval and adult offspring of a single foundress cooperate in brood care, gallery maintenance, and fungus gardening, showing a clear division of labor between larval and adult colony members. Larvae enlarge the gallery and participate in brood care and gallery hygiene. The cooperative effort of adult females in the colony and the timing of their dispersal depend on the number of sibling recipients (larvae and pupae), on the presence of the mother, and on the number of adult workers. This suggests that altruistic help is triggered by demands of brood dependent on care. Thus, ambrosia beetles are not only highly social but also show a special form of division of labor that is unique among holometabolous insects. 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

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Security experts warn of risky attacks on techloaded cars

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 © 2012 Experts point out that the numerous computers known as electronic control units, or ECUs, require tens of millions of lines of computer code to manage interconnected systems. These range from engines, brakes and navigation to lighting, ventilation and entertainment. The same wireless technologies that power cell phones and Bluetooth headsets are in cars and in turn are vulnerable to remote attacks.Unlike PCs, though, the attacker’s goal with cars may not be to rob the victim of information but to steal the car, or spy on in-car conversation, or cause the vehicle to crash. McAfee, a subsidiary of Intel and known for its security work to remedy PC viruses, are conducting research on car security at a Beaverton, Oregon garage. Bruce Snell, a McAfee executive, confirmed that automakers are not blind to risks of cyber attacks and are aware of auto system-hacking repercussions far different from seeing laptop data swiped and wiped. McAfee, a subsidiary of Intel, issued a report on automotive systems security with a title that reveals what it sees as the coming risks: “Caution: Malware Ahead.”Researchers of the University of California, San Diego, and the University of Washington have already figured out how to hack into a modern car using a laptop. The same research team extended the scenario to remotely mount attacks via Bluetooth. According to the McAfee paper, another attack scenario was presented by researchers of the University of South Carolina and Rutgers. They demonstrated it was possible to mount an attack on a vehicle and compromise passengers’ privacy by tracking Radio Frequency Identification (RFID )tags using long-distance readers at around 40 meters; the RFID tags are used in tires for sensor data over wireless short-distance communication to the vehicle.Reports do not single out vendors because the issues are relevant to the entire industry; automakers use common suppliers and processes. Nonetheless, a Reuters check of vendor initiatives shows concern in responses.Major U.S. automakers did not say if they knew of any instances in which their vehicles had been attacked with malicious software or if they had recalled cars to fix security vulnerabilities. At the same time, nothing is impossible and they are working to keep their systems as safe as possible.Ford has its security engineers working on SYNC in-vehicle communications and entertainment system to ensure it is as resistant as possible to attack, according to the Reuters report. Toyota Motor Corp, the world’s biggest automaker, said it was not aware of any hacking incidents and that hacking was at least close to impossible. A Toyota source said the vehicles are designed to change their coding constantly. Chrysler is joining industry groups and outside organizations to tackle car security.As noted in Car and Driver, as more people start to access car networks, the auto industry will beef up relevant security. That may also mean something all too familiar to the PC industry, a relentless skirmish between hackers and automakers. ( — Now that tiny computers and electronic communications systems are being designed into cars, hackers can look toward the car, like the PC, as potential roadkill. If cars are to become computers on wheels, a number of security experts are expanding their focus on car security systems and sources of security threats. U.S. computer scientists from California and Washington state have already identified ways in which computer worms and Trojans are carried over to automobiles. Conduits include onboard diagnostics systems, wireless connections and even tainted CDs played on radios systems. Citation: Security experts warn of risky attacks on tech-loaded cars (2012, August 20) retrieved 18 August 2019 from McAfee warns of hacker threat to autoslast_img read more

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Closer look at ancient giant sea scorpion suggests poor vision limited its

first_img Explore further Sam Ciurca, a curatorial affiliate with the Department of Invertebrate Paleontology at Yale, holds a model of a pterygotid. 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: What big eyes you have: the ecological role of giant pterygotid eurypterids, Published 9 July 2014 DOI: 10.1098/rsbl.2014.0412AbstractEurypterids are a group of extinct chelicerates that ranged for over 200 Myr from the Ordovician to the Permian. Gigantism is common in the group; about 50% of families include taxa over 0.8 m in length. Among these were the pterygotids (Pterygotidae), which reached lengths of over 2 m and were the largest arthropods that ever lived. They have been interpreted as highly mobile visual predators on the basis of their large size, enlarged, robust chelicerae and forward-facing compound eyes. Here, we test this interpretation by reconstructing the visual capability of Acutiramus cummingsi (Pterygotidae) and comparing it with that of the smaller Eurypterus sp. (Eurypteridae), which lacked enlarged chelicerae, and other arthropods of similar geologic age. In A. cummingsi, there is no area of lenses differentiated to provide increased visual acuity, and the interommatidial angles (IOA) do not fall within the range of high-level modern arthropod predators. Our results show that the visual acuity of A. cummingsi is poor compared with that of co-occurring Eurypterus sp. The ecological role of pterygotids may have been as predators on thin-shelled and soft-bodied prey, perhaps in low-light conditions or at night.Press release Acutiramus cummingsi. Credit: Biology Letters, Published 9 July 2014 doi: 10.1098/rsbl.2014.0412 A specimen from Yale’s collections. © 2014 Fossil discovery in Alps challenges theory that all deep sea animals evolved from shallow water ancestors ( —A team of researchers from Yale University and University College Cork in Ireland has concluded that the ancient giant sea scorpion (Acutiramus cummingsi) wasn’t quite as terrifying as initial reports had suggested. In their paper published in the journal Biology Letters, the team describes how they conducted an analysis of the ancient sea creature’s vision abilities and found them to be lacking—they suggest A. cummingsi’s eyesight was so poor that the arthropod most likely survived by eating plants or slow moving soft-shelled prey. When scientists first learned of A. cummingsi, (which existed over 400 million years ago) via fossil finds, they imagined a creature capable of chasing down cephalopods of all sizes and crushing their hard-shells. More recently, another team found that the giant pincers (with teeth on them no less) sported by the creature didn’t have enough muscle behind them to tear apart hard shells to get inside. Now, in this new study, it appears the largest known arthropod ever to have lived on this planet, had vision so poor it wouldn’t have been able to chase and catch such prey anyway.To gain a better understanding of just how well the creatures were able to see, the researchers studied several fossil specimens, some with eye lenses that were big enough to study unaided by microscopes—smaller specimens were examined using an electron microscope. The researchers then made estimates of lens angle and eye size and compared what they’d found with the eye parts of modern creatures. In so doing, they came to the conclusion that A. cummingsi, wasn’t able to see very well at all—so poor was their vision that they wouldn’t have been able to catch anything moving very fast, which would have relegated the giant to the bottom of sea, feeding on plants and soft-bodied (or already dead) creatures, in the dark. The researchers note that their work isn’t the definitive last word on the hunting abilities of the giant sea scorpion, however, because a lot of what happens with vision, happens in the brain, which of course can’t be studied, because there are no associated brain fossils to examine. Citation: Closer look at ancient giant sea scorpion suggests poor vision limited its hunting abilities (2014, July 9) retrieved 18 August 2019 from Journal information: Biology Letterslast_img read more

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Of catalysts and chirality Highlyselective growth of structurespecific singlewalled carbon nanotubes

first_img Explore further Citation: Of catalysts and chirality: Highly-selective growth of structure-specific single-walled carbon nanotubes (2014, July 16) retrieved 18 August 2019 from Journal information: Nature While researchers have been vigorously investigating the use of catalysts to template SWNTs structure – as evidenced by the many papers published in this area – success has proven elusive. “We succeeded,” Li adds, “because we have two significantly different ideas – namely, we recognized that catalysts with high melting points are necessary for using the catalyst as structural template; we found the right recipe to obtain catalysts with high melting points; we realized that the unique structure of the catalyst is essential to achieving high selectivity and specificity. Moreover, as inorganic chemists we’ve long known about molecular clusters, their characteristics and how to prepare them – so the idea using molecular clusters as the precursor for W-Co alloy nanoparticles came naturally to us, resulting in our designing the new pathway for preparing W-Co alloy nanoparticles.”In their paper, the scientists say that since using high-melting-point alloy nanocrystals with optimized structures as catalysts has demonstrably allowed production of single-chirality nanotubes at an abundance of >92%, they expect that their results will pave the way for total chirality control in SWNT growth, thereby promoting the development of SWNT applications. “Based-on our understanding about the SWNT growth mechanism and the experimental data we already have,” Li says, “we’re confident that our strategy of growing SWNTs with desired structure and chirality using catalysts with designed structure and high stability can become a standard approach.” Moreover, tungsten, cobalt, iron, and nickel are abundant, inexpensive metals, and their carbon source is ethanol, so production costs can be low – an obvious advantage for future commercialization. © 2014 Scheme showing identical (12,6) nanotubes grown from W-Co alloy nanocatalysts. Credit: Yan Li Prof. Yan Li discussed the paper she and her co-authors published in Nature with “The properties of SWNTs are totally determined by their structure, or chirality – and in many applications, it’s required that materials present uniform properties,” Li tells As an example, she says that when using SWNTs to build field effect transistors (FETs), it’s always hoped that all SWNTs have the identical structure, thereby exhibiting the same performance. “However,” Li adds, “chirality-controlled growth has been a great challenge in the field for twenty years – but we’ve developed a new strategy to realize the goal.” Li notes that there are two factors important for reducing the alloying temperature: tungsten and cobalt atoms being already well-mixed in the precursor, and the particles being of nanoscale dimensions. Accordingly, their strategy is based on a new family of catalysts – tungsten-based alloy nanocatalysts – for carbon nanotube growth. “These catalysts maintain their crystallized structure under the very high temperatures needed for carbon nanotube growth, and also exhibit a very unique structure that serves as a carbon nanotube template.” The tungsten-based alloy forms at extremely high temperature – normally well above 2000°C –necessitating special facilities, since it is extremely difficult to perform this procedure using standard laboratory equipment – and in addition, Li points out, it is difficult to control the size, structure and morphology of the resultant alloy under such conditions. “We used a precursor molecular cluster† to obtain tungsten-cobalt (W–Co) alloy nanoparticle nanocatalysts at the moderate temperature of ~1000°C,” Li says, “which made SWNT production much easier.”The key to solving this two decade-old chirality-controlled SWNT growth challenge was, stated simply, a new idea. “Though extensive effort has been made exploring chirality-selective SWNT growth, no efficient approach had been developed. This is partially due to our not having sufficient insight into the SWNT growth mechanism,” she explains. “Indeed, it’s quite difficult to collect enough information in situ during the nanotube growth process – but it’s this very information that can help us to understand the mechanism. Fueled by my more than ten years’ experience in SWNT growth, I had a novel idea about using catalysts to guide the structure of SWNTs.” Beyond their own field, Li tells, there are other areas of research that might benefit from their study. “In alloy metallurgy, our idea of using some special precursor to dramatically reduce the alloying temperature may be adopted because it may remarkably reduce energy consumption – and the lower-process temperature can greatly ease materials and control systems requirements for production apparatus. In addition, using alloy catalysts of unique structure to produce molecules with a predesigned structure can be widely used in chemical synthesis. Finally,” Li concludes, “our methods for characterizing SWNT chirality composition can be used in basic carbon nanotube research.” ( —Carbon – the chemical basis of all known life and an element known as far back as the 8th century BC – exists in a range of forms, or allotropes, with remarkably diverse properties. (Diamond, for example, is transparent and extremely hard tetrahedral lattice that conducts electricity poorly but is an excellent thermal conductor. Graphite, on the other hand – a moderate electrical conductor – is a soft, black, flaky solid formed from sheets of flat hexagonal lattices known as graphene.) Among carbon’s allotropes, carbon nanotubes are cylindrical graphene-based nanostructures with properties central to many fields of materials science and technology. In particular, single-walled carbon nanotubes (SWNTs) are carbon nanotubes whose properties change with their chirality – that is, the arrangements of the carbon atoms, which is based on tube diameter and wrapping angle as specified by what is known as their (n,m) value. These variants behave either as electrical conductors or semiconductors with different bandgaps (the energy range in a solid where no electron states can exist), making them extremely desirable for nanoelectronics applications. While this characteristic depends on the SWVTs all being in chiral form or the other, it has historically been very difficult to selectively grow one form alone, with the highest selectivity of 55% being achieved using carefully-chosen particles as catalysts in the chemical vapor deposition synthesis growth process. Recently, however, scientists at Peking University, Beijing have used tungsten-based bimetallic alloy nanocrystals as catalysts to directly produce single-chirality (that is, either left- or right-handed) SWNTs at a greater than 92% purity. By so doing, the researchers say, their results set the stage for complete control over SWNT chirality growth, and thereby further SWNT application development.center_img Depiction of eight carbon allotropes. (a) diamond; (b) graphite; (c) lonsdaleite; (d-f) fullerenes: C60 (Buckminsterfullerene), C540, C70; (g) amorphous carbon; (h) single-walled carbon nanotube (SWNT). Credit: Wikimedia. Created by Michael Ströck (mstroeck). CC BY-SA 3.0 More information: Chirality-specific growth of single-walled carbon nanotubes on solid alloy catalysts, Nature 510, 522–524 (26 June 2014), doi:10.1038/nature13434Related:† Na15[Na3,{Co(H2O)4}6{WO(H2O)}3(P2W12O48)3]nH2O, denoted as {W39Co6Ox}1Helicity-dependent single-walled carbon nanotube alignment on graphite for helical angle and handedness recognition, Nature Communications 4:2205 (29 July 2013), doi:10.1038/ncomms3205 Chirality-controlled growth of single-walled carbon nanotubes 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. Content of (12,6) SWNTs in sample measured with Raman spectroscopy. Credit: Yan Li One of the most exciting potential applications is in electronics. Li points out that the 2009 International Technology Roadmap for Semiconductors (ITRS) selected carbon-based nanoelectronics – Including carbon nanotubes and graphene – as promising technologies targeting commercial demonstration in the next 10-15 year horizon, and so to receive additional resources and detailed road mapping. “For the large-scale application of SWNTs in nanoelectronics,” Li points out, “SWNTs with identical structure are desired. Our method of growing SWNTs with identical structure is therefore a very important part of the development of carbon nanotube-based electronics.”Citing another example, Li notes that Prof. Lianmao Peng and his team have shown1 that SWNTs can be used to achieve efficient photovoltage multiplication in SWNT-based solar cells. She notes that structure-identical SWNTs can also be used in such devices, so if the nanotubes are used, solar cells with accurately adjusted photovoltage can be obtained. “There are definitely much more potential applications,” Li adds. Now we have SWNT samples with identical structure, we can explore more interesting properties and possible applications that we could never before imagine.”Li also mentions their use of Vienna Ab-initio Simulation Package for self-consistent density functional theory simulations. “Simulation provides insights not readily available through experimental data alone. It can also help theorists understand the mechanism of various processes.”Moving forward, Li says, the scientists are focused on three key steps:• Designing more catalysts to produce SWNTs with a wider range of chiralities• Further optimizing the process to improve chirality selectivity, and therefore purity• Exploring bulk synthesis , Nature Communicationslast_img read more

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Cosmic radiation causes fluctuations in global temperatures but doesnt cause climate change

first_img © 2015 Citation: Cosmic radiation causes fluctuations in global temperatures, but doesn’t cause climate change (2015, March 9) retrieved 18 August 2019 from More information: “Dynamical evidence for causality between galactic cosmic rays and interannual variation in global temperature.” PNAS 2015 ; published ahead of print March 2, 2015, DOI: 10.1073/pnas.1420291112AbstractAs early as 1959, it was hypothesized that an indirect link between solar activity and climate could be mediated by mechanisms controlling the flux of galactic cosmic rays (CR) [Ney ER (1959) Nature 183:451–452]. Although the connection between CR and climate remains controversial, a significant body of laboratory evidence has emerged at the European Organization for Nuclear Research [Duplissy J, et al. (2010) Atmos Chem Phys 10:1635–1647; Kirkby J, et al. (2011) Nature 476(7361):429–433] and elsewhere [Svensmark H, Pedersen JOP, Marsh ND, Enghoff MB, Uggerhøj UI (2007) Proc R Soc A 463:385–396; Enghoff MB, Pedersen JOP, Uggerhoj UI, Paling SM, Svensmark H (2011) Geophys Res Lett 38:L09805], demonstrating the theoretical mechanism of this link. In this article, we present an analysis based on convergent cross mapping, which uses observational time series data to directly examine the causal link between CR and year-to-year changes in global temperature. Despite a gross correlation, we find no measurable evidence of a causal effect linking CR to the overall 20th-century warming trend. However, on short interannual timescales, we find a significant, although modest, causal effect between CR and short-term, year-to-year variability in global temperature that is consistent with the presence of nonlinearities internal to the system. Thus, although CR do not contribute measurably to the 20th-century global warming trend, they do appear as a nontraditional forcing in the climate system on short interannual timescales. Next solar maximum may be safest time for manned missions to Mars The Crab Nebula from VLT . Credit: FORS Team, 8.2-meter VLT, ESO A research collaborative has published a paper in the Proceedings of the National Academy of Sciences that mathematically establishes such a causal link between CR and year-to-year changes in global temperature, but has found no causal relationship between the CR and the warming trend of the 20th century. Understanding cosmic radiation and global climateIn 1911, Charles Thomas Rees Wilson determined that ionizing radiation leads to atmospheric cloud nucleation. Increased cloudiness in the upper troposphere reduces long-wave radiation and results in warmer temperatures. Increased cloudiness in the lower troposphere leads to reduced incoming radiation, thereby decreasing global temperatures.But the flux of cosmic rays interacting with the atmosphere is affected by the solar wind and Earth’s own magnetic field. The solar wind, particularly at the region between the sun’s termination shock and the heliopause, acts as a barrier to cosmic rays and decreases the flux of low-energy cosmic radiation. Earth’s magnetic field deflects cosmic rays toward the poles, which produces the aurorae observed at certain latitudes. Therefore, researchers have theorized that the extent to which cosmic rays affect the Earth’s climate depends on this combination of factors.Going to the dataTo study the effects of cosmic radiation on global temperature, the researchers compared two sets of data and devised a method to examine their causal connection. Past statistical analyses, while suggesting correlation of the effects of CR and temperature flux, were unable to actually establish causation. The authors applied a recently developed analytical method called convergent cross mapping (CCM) that was specifically designed to measure causality in nonlinear dynamical systems.The data sets they analyzed included a CR proxy called the aa index that characterizes magnetic activity resulting from the interaction of the solar wind and Earth’s magnetic field. In the set, a stronger solar wind and stronger magnetic disturbances yield a higher aa index. They compared it with the United Kingdom’s Met Office HadCRUT3 data set of global temperature in the post-1900 period. Journal information: Naturecenter_img CCM helps to distinguish causality from spurious correlations in the time systems of dynamical systems, detecting whether two variables belong to the same dynamical system. If variable X is influencing variable Y, causality is established—but only if states of X can be recovered from the time series of Y. “Simply put,” the authors write, “CCM measures the extent to which the historical record of the affected variable Y (or its proxies), reliably estimates states of causal variable X (or its proxies).”Modestly cosmic resultsThe CCM method can identify both bidirectional causality (in which X and Y are mutually coupled) and unidirectional causality (in which X influences Y, but Y has no influence on X). The analysis produced the expected unidirectional causality between global temperature change and cosmic radiation—information about global temperature is not present in the cosmic radiation time series, but mapping from global temperature change to cosmic radiation succeeded, indicating that CR information was actually recoverable from analysis of GT fluctuations.”Our results suggest weak to moderate coupling between CR and year-to-year changes of GT,” they write. “However, we find that the realized effect is modest at best, and only recoverable when the secular trend in GT is removed.” This “secular trend” is the warming widely believed to be caused by excess carbon in the atmosphere, an effect the researchers accounted for by first-differencing. “We show specifically that CR cannot explain secular warming, a trend that the consensus attributes to anthropogenic forcing. Nonetheless, the results verify the presence of a nontraditional forcing in the climate system, an effect that represents another interesting piece of the puzzle in our understanding of factors influencing climate variability,” they write. (—Unlike electromagnetic radiation, which consists of massless and accelerated charged particles, galactic cosmic rays (CR) are composed mostly of atomic nuclei and solitary electrons, objects that have mass. Cosmic rays originate via a wide range of processes and sources including supernovae, galactic nuclei, and gamma ray bursts. Researchers have speculated for decades on the possible effects of galactic cosmic rays on the immediate environs of Earth’s atmosphere, but until recently, a causal relationship between climate and cosmic rays has been difficult to establish. , Proceedings of the National Academy of Sciences 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.last_img read more

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Researchers find the genome of the cultivated sweet potato has bacterial DNA

first_img EU to simplify GMO import approval: sources Explore further Citation: Researchers find the genome of the cultivated sweet potato has bacterial DNA (2015, April 21) retrieved 18 August 2019 from The researchers suggest their findings could have an impact on the perception of GMOs by some who oppose their creation on the grounds that it is not safe. They claim that humans eating food that was genetically modified naturally, over thousands of years, proves that such foods are not harmful. Journal information: Proceedings of the National Academy of Sciences (—A team of researchers with members from Belgium, China, Peru and the U.S. has found evidence of bacterial DNA in the genome of the cultivated sweet potato. In their paper published in Proceedings of the National Academy of Sciences, the team describes their findings as an example of a naturally occurring transgenic food crop. Sweet potatoescenter_img More information: The genome of cultivated sweet potato contains Agrobacterium T-DNAs with expressed genes: An example of a naturally transgenic food crop, Tina Kyndt, PNAS, DOI: 10.1073/pnas.1419685112AbstractAgrobacterium rhizogenes and Agrobacterium tumefaciens are plant pathogenic bacteria capable of transferring DNA fragments [transfer DNA (T-DNA)] bearing functional genes into the host plant genome. This naturally occurring mechanism has been adapted by plant biotechnologists to develop genetically modified crops that today are grown on more than 10% of the world’s arable land, although their use can result in considerable controversy. While assembling small interfering RNAs, or siRNAs, of sweet potato plants for metagenomic analysis, sequences homologous to T-DNA sequences from Agrobacterium spp. were discovered. Simple and quantitative PCR, Southern blotting, genome walking, and bacterial artificial chromosome library screening and sequencing unambiguously demonstrated that two different T-DNA regions (IbT-DNA1 and IbT-DNA2) are present in the cultivated sweet potato (Ipomoea batatas [L.] Lam.) genome and that these foreign genes are expressed at detectable levels in different tissues of the sweet potato plant. IbT-DNA1 was found to contain four open reading frames (ORFs) homologous to the tryptophan-2-monooxygenase (iaaM), indole-3-acetamide hydrolase (iaaH), C-protein (C-prot), and agrocinopine synthase (Acs) genes of Agrobacterium spp. IbT-DNA1 was detected in all 291 cultigens examined, but not in close wild relatives. IbT-DNA2 contained at least five ORFs with significant homology to the ORF14, ORF17n, rooting locus (Rol)B/RolC, ORF13, and ORF18/ORF17n genes of A. rhizogenes. IbT-DNA2 was detected in 45 of 217 genotypes that included both cultivated and wild species. Our finding, that sweet potato is naturally transgenic while being a widely and traditionally consumed food crop, could affect the current consumer distrust of the safety of transgenic food crops.Press release In modern times, scientists have created what are known as genetically modified organisms (GMOs), where plants or animals are modified to suit the particular needs of people in a certain region—to allow corn to grow in a dry climate for example. One common method of creating GMOs is to use bacteria that have been found able to modify the genes of a host as a carrier agent. GMOs have been met with suspicion in many parts of the world with some places banning them outright. Now, in this new effort, the researchers have found an example of a natural GMO that people have been eating for thousands of years: the sweet potato.Sweet potatoes have been growing wild in South America for thousands of years—over time, they were cultivated by people, and have since become a popular food in many parts of the world. But now it appears that a type of bacteria similar to the kind used by modern scientists to create many GMOs found its way naturally to cultivated sweet potatoes many generations ago and modified its DNA. To make this discovery, the researchers collected 291 sweet potato samples from cultivated sources across the globe along with nine wild sources and subjected them all to DNA analysis—they found that all of the cultivated potatoes carried at least two stretches of Agrobacterium DNA, while the wild species carried one. Their findings suggest the transfer of DNA to the potatoes occurred a long time ago, before they were carried to and grown in other parts of the world. © 2015 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. Ipomoea batatas, Convolvulaceae, Sweet Potato, storage roots; Karlsruhe, Germany. Credit: Wikipedialast_img read more