Orienting Flow in Carbon Nanotubes

first_img(PhysOrg.com) — Carbon nanotubes provide some of the most interesting possibilities for future technology. One of the more intriguing possibilities – with a variety of practical applications – is using carbon nanotubes for water transport. In the past, experiments have suggested that extremely fast water transport can be attained through carbon nanotubes as small as two nanometers in diameter by applying a pressure gradient. Citation: Orienting Flow in Carbon Nanotubes (2008, September 2) retrieved 18 August 2019 from https://phys.org/news/2008-09-carbon-nanotubes.html Professor N.R. Aluru at the Beckman Institute for Advanced Science and Technology at the University of Illinois at Urbana-Champaign, and Sony Joseph, who defended his Ph.D. thesis recently, have used computer simulations to explore a method by which water transport through smaller carbon nanotubes could be further enhanced. Some of the results of their work appears in Physical Review Letters: “Pumping of Confined Water in Carbon Nanotubes by Rotation-Translation Coupling.”“Until now,” Sony Joseph tells PhysOrg.com, “previous simulations had shown that single file water movement in short carbon nanotubes have net transport in both directions. But if you could get the water to orient in one direction, in a long tube, you could have net transport along that direction. This would further increase the flow rate when a pressure gradient is applied and be useful in many ways, including to allow us to mimic biological protein channels.”Joseph and Aluru used molecular dynamics simulation in long carbon nanotubes (around 10 nanometers long) to show the relationship between the flow direction of the water and the dipole orientation. “In order to maintain the direction,” professor Aluru explains, “we need either local electrical fields or chemical functional groups at the ends of the nanotubes. These orient the water and keep it flowing in one direction.” The two scientists point out that in order to change the direction of the water flowing through the carbon nanotube, one has only to reverse the direction of the electrical field.Focusing on using an external electrical field, Joseph and Aluru modeled how the field interacts with the water molecules. The molecules have a net zero charge, and interact with the field through torques. These torques are applied to the rotational degrees of freedom of the molecules. Changes to translational degrees of freedom in this water transport system, the scientists point out, are mostly due to how rotational and translational motions couple with each other. Some of the applications considered for carbon nanotube membranes include such items as drug delivery, desalination, and selective ion transport. Joseph and Aluru, however, are especially interested in using this technology for water purification and nanofiltration. “We are trying to show how this would aid the process of reverse osmosis,” Aluru says.Joseph and Aluru emphasize that, right now, this work is largely based on computer simulations with theoretical models. Joseph explains that right now water transport through nanotube membranes of two nanometers have been achieved, but that scientists are working toward pumping water through membranes that are less than one nanometer.“We’ve shown that it is theoretically possible to get this sort of water transport,” Joseph points out. “The next step is getting to the point where this could be tested.”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. Antigravity water transport system inspired by treescenter_img 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

Google Gets Ready For The Next Version of Android

first_img Google G1 Phone: Security Flaw Exposed Software developers will have the option to target different Android platform versions from within a single SDK installation. Developers will also find improvements to install Android SDK add-ons to access extended functionality that might be provided by OEMs, carriers, or other providers.In order to help developers prepare their applications for the release of Android 1.5 on phones, Google will be publishing a series of articles on their Android Developers Blog to highlight new APIs and other changes. In addition to the new APIs, other topics that will be covered include OpenGL, asynchronous tasks, system settings, and new Activity callbacks.From a user perspective, some improvement performances include faster camera start-up and image capture, faster acquisition of GPS location (powered by SUPL AGPS), smoother page scrolling in Browser, and speedier GMail conversation list scrolling. At present there are only two phones based on the open-source operating system. The HTC Dream (T-Mobile G1) and Vodafone’s HTC Magic. Samsung will be launching three Android phones this year; however release dates from Android supporters LG, Motorola and Sony Ericsson are not clear.© 2009 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. Citation: Google Gets Ready For The Next Version of Android (2009, April 14) retrieved 18 August 2019 from https://phys.org/news/2009-04-google-ready-version-android.htmlcenter_img (PhysOrg.com) — Android 1.5 is right around the corner and this version promises better camera and GPS performance, support for video recording and Bluetooth stereo. Also included in this new version is support for soft keyboards, live folders and speech recognition. Explore furtherlast_img read more

Is dark energy static or dynamic

first_img(Phys.org)—While hypothesized dark energy can explain observations of the universe expanding at an accelerating rate, the specific properties of dark energy are still an enigma. Scientists think that dark energy could take one of two forms: a static cosmological constant that is homogenous over time and space, or a dynamical entity whose energy density changes in time and space. By examining data from a variety of experiments, scientists in a new study have developed a model that provides tantalizing hints that dark energy may be dynamic. Copyright 2012 Phys.org 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. The scientists, Gong-Bo Zhao of the University of Portsmouth in the UK and the Chinese Academy of Science in Beijing; Robert G. Crittenden of the University of Portsmouth; Levon Pogosian of Simon Fraser University in Burnaby, British Columbia, and the University of Portsmouth; and Xinmin Zhang of the Chinese Academy of Science, have published their paper on the evidence for dynamical dark energy in a recent issue of Physical Review Letters.In their paper, the scientists focused on constraining dark energy’s equation of state, which has historically been a very difficult task. The equation of state characterizes the way that the universe is expanding, and scientists use observational data to constrain this parameter in an attempt to find its precise value in the real world. Knowing the true value of the equation of state would not only lead to a better understanding of dark energy, but gravity as well. The key question is whether the value of the equation of state ever equals -1, since that might point to the breakdown of Einstein’s theory of general relativity on cosmological scales. Some models have estimated an equation of state very near -1, which has prompted the search for a quantum theory of gravity.In the new study, the scientists’ main finding is that the latest observations give a slight preference to a dynamical dark energy model whose equation of state evolves from less than -1 at low redshifts to greater than -1 at higher redshifts – at some point equaling -1. “If this result were confirmed, it would imply an additional intrinsic degree of freedom of dark energy and could be a smoking gun of the breakdown of Einstein’s theory of general relativity on cosmological scales,” Zhao told Phys.org. 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. Citation: Is dark energy static or dynamic? (2012, November 12) retrieved 18 August 2019 from https://phys.org/news/2012-11-dark-energy-static-dynamic.htmlcenter_img More information: Gong-Bo Zhao, et al. “Examining the Evidence for Dynamical Dark Energy.” PRL 109, 171301 (2012). DOI: 10.1103/PhysRevLett.109.171301 Journal information: Physical Review Letters To attain this result, the scientists combined cosmological data from the latest supernova, cosmic microwave background, redshift space distortion, and baryonic acoustic oscillation measurements. Then they applied a new reconstruction method to the data, which has the advantage of minimizing the biases that occur in some other reconstruction methods. “Perhaps the greatest significance of the work is the demonstration of the method as a means of determining whether dark energy is dynamical without relying on an arbitrary model for how dark energy could evolve,” Zhao said. “It is quite interesting that when it’s applied to the present data, these dynamical models do well, even when accounting for their larger flexibility.”The scientists’ model allowed them to compare a range of dark energy models and determine which models best fit the combined data. Although the dynamical dark energy model was slightly preferred, the researchers noted that models with the cosmological constant still fit the data, though not quite as closely as the dynamical model. The results are still far from conclusive, but the scientists hope that future data might narrow down the models with greater accuracy. They hope that observations by the Planck spacecraft (launched in 2009; first data available in April 2013) and the Euclid spacecraft (launch date is 2019) could help pinpoint the dark energy models that most closely describe our expanding universe. The researchers explained that there are two general reasons why reconstructing the evolution of dark energy’s equation of state is so challenging.”There are two issues here; the first relates to the difficulty of observing changes to the rate of the Universe’s expansion,” Crittenden said. “It took us 70 or 80 years to realize that the expansion rate was even accelerating, and this is largely because it’s hard to find the reliable standard rulers and standard candles which we use to measure it. We are now attempting to distinguish between models which predict very small differences, and to do this convincingly we need future data such as will come from the Euclid satellite. “The second issue relates to our lack of clear alternatives to explain the acceleration; without knowing what it should look like, it’s harder to recognize it. Previous work has tended to assume particular forms for the dynamics, but if these assumptions were wrong, they give us biased information and could miss out on seeing the dynamics entirely. We have tried to make fewer assumptions, which allows us to reconstruct a much larger class of possible models and capture the dynamics if it is there. By improving the quality and quantity of the data, we should be able to verify or falsify a very broad class of dynamical models, which will be crucial to understand the nature of dark energy.” Statistical modeling could help us understand cosmic accelerationlast_img read more

Modernday metabolism could have originated in 4billionyearold oceans

first_img Metabolism may have started in our early oceans before the origin of life In a new study, researchers have found that some of the metabolic processes (glycolysis and the pentose phosphate pathway) that convert sugars into energy and molecular building blocks share many similarities with the chemical reactions that could have occurred in non-living four-billion-year-old Archean oceanic sediments. The results suggest that the metabolic reactions in our modern-day cells could, in principle, have originated from chemical reactions in an environment that preceded life.The researchers, Markus A. Keller and Markus Ralser from the University of Cambridge and coauthors, have published their paper on the ancient metabolism-like reactions in a recent issue of Science Advances.The work builds on a paper published by some of the same authors in 2014, in which they recreated environments similar to Earth’s ancient oceans in the lab and observed chemical reactions that formed glucose, pyruvate (a product of glycolysis), and precursors of modern-day nucleic acids and amino acids, in a similar way that living organisms do today. One of the most striking things about the results from that paper was that the ancient sediments enabled the reactions without containing enzymes, since enzymes came into existence during the evolution of modern organisms. Enzymes are proteins that speed up metabolic reactions, and living things greatly depend on them to catalyze their metabolism. Without enzymes, metabolic reactions would occur too slowly for life as we know it to exist.Although these ancient sediments lacked enzymes, they did contain large amounts of iron, and the researchers showed in the 2014 study that iron can act as a catalyst in place of enzymes. It’s widely thought that iron existed in much higher concentrations in the ancient oceans than in modern oceans because the ancient oceans did not contain any oxygen, and this condition enabled large quantities of iron to dissolve. In the new paper, the researchers have shown that these 4-billion-year-old iron-catalyzed reactions can not only produce some of the essential chemicals of metabolism, but like metabolism, they also have the ability to switch biochemical pathways on and off. This ability enables modern cells to react to changes in the environment. By performing more than 4000 highly sensitive mass spectrometry and nuclear magnetic resonance experiments, the researchers found, for example, that neutral-pH conditions favor glycolysis, while alkaline-pH conditions favor the pentose phosphate pathway. This finding suggests that relatively moderate changes in the environment could have led to changes in metabolism. In addition, the researchers observed that the presence of iron accelerates the reaction rates over most of the pH range, with some reactions exhibiting a 100-fold rate increase. These examples of conditional reactivity provide a method of regulating the reactions, which is an essential feature of metabolism.Overall, the similarities demonstrate that modern-day metabolism could have originated from pre-enzymatic iron-catalyzed chemistry—but whether it actually did or not remains an open question. Explore further (Phys.org)—A gigantic number of chemical reactions take place inside our bodies every second, all synchronizing with each other to produce the energy and chemical compounds that we need to survive. Together these reactions make up our metabolism, which is one of the defining features of life. However, scientists continue to debate the origins of metabolism: Did this complex arrangement of reactions evolve over time in living things due to survival advantages, or was it acquired, in a basic form, from the non-living environment? Scientists constructed this metabolism-like chemical network from non-enzymatic reactions that could have occurred in Earth’s 4-billion-year-old oceans. The network shows that the reaction types depend on pH and the reaction rates depend on iron concentration (arrow thickness and red color intensity indicate the relative acceleration). Credit: Keller, et al. Science Advances More information: Markus A. Keller, et al. “Conditional iron and pH-dependent activity of a non-enzymatic glycolysis and pentose phosphate pathway.” Science Advances. DOI: 10.1126/sciadv.1501235last_img read more

Measurement of the finestructure constant casts doubt on dark photon theories

first_img Journal information: Science Explore further Citation: Measurement of the fine-structure constant casts doubt on dark photon theories (2018, April 13) retrieved 18 August 2019 from https://phys.org/news/2018-04-fine-structure-constant-dark-photon-theories.html NA64 hunts the mysterious dark photon Precision measurements of the fine-structure constant. A comparison of measurements. “0” on the plot is the CODATA 2014 recommended value. The green points are from photon recoil experiments; the red ones are from electron ge − 2 measurements. The inset is a close-up view of the bottom three measurements. Error bars indicate 1s uncertainty. StanfU, Stanford University; UWash, University of Washington; LKB, Laboratoire Kastler Brossel; HarvU, Harvard University. Credit: Science (2018). DOI: 10.1126/science.aap7706 This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.center_img A team of researchers from the University of California and Lawrence Berkeley National Laboratory has conducted an ultra-precise measurement of the fine-structure constant, and in so doing, have found evidence that casts doubts on dark photon theory. In their paper published in the journal Science, the group describes their measurement process and what they found by using it. © 2018 Phys.org More information: Richard H. Parker et al. Measurement of the fine-structure constant as a test of the Standard Model, Science (2018). DOI: 10.1126/science.aap7706AbstractMeasurements of the fine-structure constant α require methods from across subfields and are thus powerful tests of the consistency of theory and experiment in physics. Using the recoil frequency of cesium-133 atoms in a matter-wave interferometer, we recorded the most accurate measurement of the fine-structure constant to date: α = 1/137.035999046(27) at 2.0 × 10−10 accuracy. Using multiphoton interactions (Bragg diffraction and Bloch oscillations), we demonstrate the largest phase (12 million radians) of any Ramsey-Bordé interferometer and control systematic effects at a level of 0.12 part per billion. Comparison with Penning trap measurements of the electron gyromagnetic anomaly ge − 2 via the Standard Model of particle physics is now limited by the uncertainty in ge − 2; a 2.5σ tension rejects dark photons as the reason for the unexplained part of the muon’s magnetic moment at a 99% confidence level. Implications for dark-sector candidates and electron substructure may be a sign of physics beyond the Standard Model that warrants further investigation. The fine-structure constant is a number that characterizes the strength of the force of electromagnetic interactions between charged particles, such as those that are involved in keeping electrons from traveling outside of their atoms. Up until now, it has been derived using the magnetic properties of electrons and calculations that are still considered to be theoretical. As the researchers note, more precise measurements allow for testing the Standard Model of particle physics. To that end, they sought to measure the constant through more direct means. To accomplish this feat, they aimed a laser at cesium-133 atoms (matter-wave interferometry) to force them into quantum superposition and then took a close look at what happened between them as they relaxed back to their natural state. The interference that occurred, the team reports, revealed the speed at which the atoms traveled when they were struck by the laser—they used that number to determine the fine-structure constant. They claim their work has allowed for calculating the fine-structure constant to better than one part per billion.The researchers report that the number they determined has closely matched the theory, which offers some confirmation of theories that suggest electrons are not made up of smaller, unknown particles. But it also casts doubt on theories surrounding the existence of dark photons.Dark photons, theory has suggested, are particles nearly identical to photons, but have mass. They may also interact with other particles. If proof could be found of their existence, it would bolster theories regarding dark matter in general, because dark matter theory suggests they would be the force carrier. On the bright side, because the number they extracted was close to that theorized, but not exact, there is still room for other particle theories to explain the discrepancy.last_img read more

Astronomers investigate a recently reactivated radio magnetar

first_imgA UK-German team of astronomers has conducted observations of a peculiar radio magnetar known as XTE J1810–197, which turned on in December 2018 after an almost decade-long period of quiescence. Results of these observations provide more information about the magnetar properties, and were presented in a paper published March 6 on arXiv.org. Explore further © 2019 Science X Network Artist’s conception of a powerful magnetar. Image credit: ESO/L. Calçada. Astronomers find unexpected ‘heartbeats’ in star This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Citation: Astronomers investigate a recently reactivated radio magnetar (2019, March 14) retrieved 18 August 2019 from https://phys.org/news/2019-03-astronomers-reactivated-radio-magnetar.html More information: L Levin et al. Spin frequency evolution and pulse profile variations of the recently re-activated radio magnetar XTE J1810-197. arXiv:1903.02660 [astro-ph.HE]. arxiv.org/abs/1903.02660 Magnetars are neutron stars with extremely strong magnetic fields, more than quadrillion times stronger than magnetic field of our planet. Decay of magnetic fields in magnetars powers the emission of high-energy electromagnetic radiation, for instance, in the form of X-rays or radio waves.To date, only 23 magnetars have been identified and XTE J1810–197, with a spin period of around 5.54 seconds and magnetic field strength at a level of 2 trillion G, was detected as the first of only four known such objects to emit radio pulsations. Radio emission from XTE J1810–197 was discovered in 2004, one year after an X-ray outburst from this source was observed. The star subsequently exhibited highly variable pulsed radio emission until late 2008, when it entered a radio-quiet state.Anticipating radio reactivation of XTE J1810–197, a group of astronomers led by Lina Levin of Jodrell Bank Centre for Astrophysics at the University of Manchester, UK, began observing this magnetar in 2009 with the Lovell telescope at Jodrell Bank Observatory (JBO). On December 8, 2018, the scientists detected a bright pulsed radio signal at 1.52 GHz from this source, which marked the end of a nearly decade of its radio-quietness.”After spending almost a decade in a radio-quiet state, the Anomalous X-ray Pulsar XTE J1810–197 turned back on in early December 2018. We have observed this radio magnetar at 1.5 GHz with ∼daily cadence since the first detection of radio reactivation on December 8, 2018,” the astronomers wrote in the paper.According to the study, the pulse profile of XTE J1810–197 has changed significantly since detection. However, the profile changes observed during the first two months since the reactivation were less extreme when compared to what was observed the last time when this source was active.”The pulse variations seen so far from the source have been significantly less dramatic, on timescales from hours to months, than seen in 2006,” the paper reads.The researchers report that the magnitude of the spin frequency derivative of XTE J1810–197 has increased by a factor of 2.6 over the 48-day data set, with the most rapid increase occurring during the first 15 days.Moreover, the astronomers identified 50-millisecond oscillations seen in the pulse profile of the magnetar for about 10 days after it was re-detected. These oscillations have a characteristic frequency of 20 Hz and are seen at different frequencies and different telescopes at the same time. The authors of the paper assume that such oscillations could be related to surface waves triggered in the neutron star crust with a wide spectrum of frequencies.In concluding remarks, the researchers propose further monitoring of XTE J1810–197 in order to find out whether or not the pulse profile of the magnetar will experience more variations over time.last_img read more

Knocking at the hearts of Delhi music lovers

first_imgIt was an eventful Saturday evening in the Capital, as the ambience at India Islamic Centre echoed with soulful renditions of ghazals. With Farrukh Baig sung each from his debut album Dastak, the audience present could not help but get mesmerised with the lyrics in sync with melodies.Farrukh fell in love with music at a very tender age of eight. However, he started his formal musical training at the age of fifteen. His first Guru was Ustad Qamar Mohd. Khan, a renowned All India Radio artist and a recipient of President of India Award. Also Read – ‘Playing Jojo was emotionally exhausting’Though he did not restrict himself to any one particular genre of music initially but developed a special liking for ghazals later on. During his college days, besides studies, it was just cricket and music. Soon he realized that to excel in either cricket or music, he had to give up one– and what he gave up is his victory today.Farrukh’s debut album, Dastak was launched by noted Indian film director and producer Mahesh Bhatt. Bhatt appreciated Baig’s singing as well as the lyrics and the music of the album. He expressed happiness to see a youngster who has taken ghazal as his passion and urged everyone to contribute for the revival of the music genre. Also Read – Leslie doing new comedy special with Netflix’Farrukh’s voice echoes in your hearts even after the song has ended,’ said Bhatt at the event.Despite being a management graduate and working in the corporate sector, it was music which remained an integral part of Baig’s life. His musical journey included doing shows all over, composing and singing a couple of title songs for serials, and some music shows on television.The album has six ghazals which have been written by Dr. M.S.Rahi and the music has been  arranged by Navneet Kedar. Dastak will be available in the market both on the online platform as well as offline from the date of its launch.After the grave loss of Ghazal king Jagjit Singh, here is a young lad who has taken a plunge to sincerely promote and revive the fading art.last_img read more