Citation: Nanowire technology could make LCDs brighter, thinner, and cheaper (2008, October 3) retrieved 18 August 2019 from https://phys.org/news/2008-10-nanowire-technology-lcds-brighter-thinner.html (PhysOrg.com) — As nanoimprinting technology advances, scientists have shown that using nano-sized polarizers could significantly enhance the contrast ratio in liquid crystal displays (LCDs). For consumers, that means that TVs, computer monitors, and especially mobile displays could become brighter, lighter, and thinner in the future. Scientists Zhibing Ge and Shin-Tson Wu from the University of Central Florida in Orlando have presented their improved LCD design in a recent issue of Applied Physics Letters. They used a nanowire grid polarizer (NWGP) for backlight recycling, which enhances the LCD’s optical efficiency and thereby reduces its power consumption. “The method for fabricating large area wire-grid polarizers is advancing rapidly, benefiting from the huge research momentum of nano-imprinting technology,” Wu told PhysOrg.com. “Nowadays, it is possible to fabricate NWGPs with a pitch of 100 nanometers or smaller. Different from the reflective polarizers made from multilayer films, WGP is a grating structure which can exhibit a very high transmission contrast ratio. As a result, it holds potential for replacing the bottom sheet LP which is close to the backlight side in a LCD.”In conventional LCDs, the devices are sandwiched between a top and bottom layer of linear polarizers. While linear polarizers can provide a high contrast ratio (the difference between bright and dark luminance), they also tend to absorb more than 60% of the device’s backlight, resulting in a maximum light transmittance of just 40%. Ge and Wu show how replacing the bottom linear polarizer with a light-recycling NWGP, and keeping the top linear polarizer as it is, can improve the device’s optical efficiency. The scientists explain how the recycling process works: when unpolarized light from a source (such as a cold cathode fluorescent lamp or light-emitting diode) reaches the NWGP layer, only waves traveling perpendicular to the wire grids (p-waves) can penetrate the NWGP, and are transmitted. Waves traveling parallel to the wire grids (s-waves) are first reflected back to a light guide plate for recycling, but then they bounce back to the NWGP again. By reflecting back and forth, the s-wave has more chances to be converted to a p-wave and transmitted through the NWGP. This recycling process repeats several times before the light is absorbed or scattered away. As a result, the overall light efficiency can be improved by about 60%, as compared to using two linear sheet polarizers. Besides the increased efficiency, NWGPs could offer some other advantages compared with conventional LCDs. The NWGP that the scientists used here was only 200 nanometers thick (the linear polarizer is 210 micrometers thick), which would not only decrease unwanted light absorption, but also minimize light leakage and enable ultra-thin displays. In addition, the linear polarizer-NWGP configuration can provide a wide viewing angle: the scientists achieved a 100:1 contrast ratio across a 75° viewing cone using a conventional multi-domain vertical alignment LCD. “We plan to work with our contract sponsor Chi-Mei Optoelectronics Corporation to make test devices for this new device configuration,” said Ge. “In addition, we will apply this nano-wire grid polarizer technology to sunlight readable transflective LCDs for mobile devices and 3D displays. If the performance is good and cost is acceptable, then we expect this technology will have widespread applications in the consumer market in the near future.”More information: Ge, Zhibing and Wu, Shin-Tson. “Nanowire grid polarizer for energy efficient and wide-view liquid crystal displays.” Applied Physics Letters 93, 121104 (2008).Copyright 2008 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. The structure of the LCD, showing the linear polarizer (red stripes) as the top sheet and nanowire grid polarizer (green) as the bottom sheet for light recycling. Image credit: Zhibing Ge and Shin-Tson Wu. 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: Scientists Investigate How Fireflies Emit Different Colors of Light (2010, January 7) retrieved 18 August 2019 from https://phys.org/news/2010-01-scientists-fireflies-emit.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. More information: Isabelle Navizet, Ya-Jun Liu, Nicolas Ferre, Hong-Yan Xiao, Wei-Hai Fang, and Roland Lindh. “Color-Tuning Mechanism of Firefly Investigated by Multi-Configurational Perturbation Method.” J. Am. Chem. Soc. Doi:10.1021/ja908051h Scientists have discovered that the light-emitting luciferin molecule in fireflies can produce different colors of light depending on different polarities inside the molecule. Image credit: Wikimedia Commons. Iowa State University researcher developed forerunner of Nobel research in 1986 Copyright 2010 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. In a recent study, a team of scientists has proposed a new explanation for firefly color modulation in the Japanese Genji-botaru firefly that contrasts with previous explanations. Using recent X-ray data and theoretical simulations, the researchers suggest that the wavelength of the emitted light depends on the polarity of the microenvironment in the firefly’s light-emitting molecules. Lead author Isabelle Navizet from Beijing Normal University and University Paris-Est, along with coauthors from the Chinese Academy of Sciences, Université d’Aix-Marseille, and Lund University, have published their results in a recent issue of the Journal of the American Chemical Society.Fireflies emit light from chemical reactions that occur in their lower abdomens. The emitted light arises from the oxidation of the organic substrate luciferin, catalyzed by an enzyme called luciferase. This series of complicated reactions also involve the participation of ATP (adenosine triphosphate) molecules and magnesium ions.Previously, researchers proposed that the key to understanding the bioluminescence color variation was the size of the luciferase protein cavity. The idea is that a larger cavity allows more energy loss than a smaller cavity, so a larger cavity leads to the emission of lower-energy red light, while a smaller one emits higher-energy yellow and green light.However, using new experimental data and simulations, Navizet and coauthors found that this theory doesn’t adequately explain the color modulation. Instead, their results suggest that the polarity of the luciferase protein cavity could be responsible for different colors. The cavity’s polarity can be adjusted by changing the number of water molecules and protein residues inside the cavity. The mutations of the residues involved in this H-bond network can lead to different polarizations acting on the luciferin and can change the color of the emitted light accordingly.“We’ve shown that the light wavelength does not depend on the rigid or loose structure of luciferase but on the water H-bond network inside the cavity,” coauthor Ya-Jun Liu of Beijing Normal University told PhysOrg.com. “Mutations of luciferase on residues involved in this network should modulate the color.”As Liu explained, understanding the relationships between the luciferase structure and the bioluminescence may have several applications.“Due to its high sensitivity and extreme specificity for ATP, luciferases are used as markers for the investigation of various biochemical processes in vitro and in vivo,” Liu said. “Knowing the modulation mechanism in fireflies can suggest which mutation to perform in order to produce mutants with specific light wavelengths. For example, in mammalian cells which absorb shorter wavelengths, red-light emitting luciferin-luciferase systems are useful. Knowing the mechanism of the modulation of the emission light and the sensibility to external factors such as pH, solvation, etc., is also important for luciferases as biosensors.” (PhysOrg.com) — There are more than 2,000 species of fireflies around the world, many of which are best known for their bioluminescence. Fireflies, which are not flies but beetles, produce flashes of light in order to communicate with each other and to attract mates. The color of light emitted by the luceferin molecule in fireflies can range from red to yellow to green. However, the chemical and physical origin of firefly color variation is not well understood. Explore further
More information: via: symmetry magazine This idea of the holographic universe is not new, but physicists at Fermilab are now designing an experiment to test the idea. Fermilab particle astrophysicist Craig Hogan and others are building a holographic interferometer, or “holometer,” in an attempt to detect the noise inherent in spacetime, which would reveal the ultimate maximum frequency limit imposed by nature. As Hogan explains in a recent issue of Fermilab’s symmetry magazine, the holometer will be “the most sensitive measurement ever made of spacetime itself.” Hogan and others have already built a one-meter-long prototype of the instrument. They have just begun building the entire 40-meter-long holometer and plan to start collecting data next year.The holometer consists of two completely separate interferometers positioned on top of one other. In each interferometer, a light beam is split into two different parts that travel in different directions. After bouncing off a mirror, the light beams are brought back together where the difference in their phases is measured. Even the smallest vibration will interfere with the light’s frequency during its travels and cause the two light beams to be out of sync. While interferometers have been used for more than 100 years, the key to the holometer is achieving extreme precision at high frequencies. The scientists say that the holometer will be seven orders of magnitude more precise than any atomic clock in existence over very short time intervals. By having two interferometers, the researchers can compare them to confirm measurements. In addition, the scientists are making sure that any vibration that is detected isn’t coming from the holometer itself. They will arrange sensors outside the holometer to detect normal vibrations, and then cancel these vibrations by shaking the mirrors at the same frequency.After taking these precautions, any detected high-frequency noise could be the jitter of spacetime itself, or “holographic noise.” The noise is expected to have a frequency of a million cycles per second, which is a thousand times higher than what the human ear can hear, noted Fermilab experimental physicist Aaron Chou. If the experiment does find this holographic noise, it would be the first glimpse beyond our three-dimensional illusion and into the universe’s true two-dimensional nature at the Planck scale. 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: Holometer experiment to test if the universe is a hologram (2010, October 28) retrieved 18 August 2019 from https://phys.org/news/2010-10-holometer-universe-hologram.html Researchers could herald a new era in fundamental physics Explore further (PhysOrg.com) — Many ideas in theoretical physics involve extra dimensions, but the possibility that the universe has only two dimensions could also have surprising implications. The idea is that space on the ultra-small Planck scale is two-dimensional, and the third dimension is inextricably linked with time. If this is the case, then our three-dimensional universe is nothing more than a hologram of a two-dimensional universe. © 2010 PhysOrg.com A conceptual design of Fermilab’s holometer. Image credit: symmetry magazine
To address this problem, a team of researchers from Harvard University, the National Autonomous University of Mexico, and Haverford College in Haverford, Pennsylvania, has developed an extremely large-scale automated computational screening method to study potential molecular structures for organic photovoltaic devices (OPVs). They introduced the initiative, called the Harvard Clean Energy Project (CEP), http://cleanenergy.harvard.edu/ in a recent issue of the Journal of Physical Chemistry Letters where they present some early results, with more studies to follow.CEP’s overall goal is to identify an organic material that can increase the efficiency of OPVs from the current record of 9.2% to 10-15%, as well as expand the currently limited lifetimes to more than 10 years. A solar cell with these two features could push the power generation costs of organic solar cells below that of other currently available energy sources.To achieve this goal, the project has taken a highly collaborative approach. It relies on input and feedback from experimentalists from Zhenan Bao’s group at Stanford and other research groups. To analyze the large number of molecules, the project combines conventional modeling strategies with strategies from modern drug discovery, along with ideas from machine learning, pattern recognition, and cheminformatics. Also, the project utilizes volunteer computing by IBM’s World Community Grid (WCG) to supply part of the large-scale computational power. Volunteers who would like to donate computer time can download a free and virus-free program from the IBM website that uses their computers for screening the materials while their computer is idle. “Roughly, every 12 hours of donated free CPU time will result in a new molecule added to our database of candidate organic materials for solar cells,” Alán Aspuru-Guzik of Havard, who is one of the project’s leaders, told PhysOrg.com. “The database will aid scientists in accelerating the discovery of novel solar materials.” “The great variety in properties found in our candidate library is quite remarkable, as is the small parameter space that makes for promising OPVs and that has to be hit,” said Johannes Hachmann of Harvard, another of the project’s leaders. “The latter underlines the value of our high-throughput approach.”Using a calculation hierarchy, the method rates each candidate motif at each step with respect to the desired properties, and expedites further characterization for the most promising candidates. The hierarchy technique is already proving valuable: a preliminary analysis has revealed that only about 0.3% (3,000–5,000) of the screened structures have the necessary energetic levels to realize organic solar cells with 10% or higher efficiency. While an unaided search would have a very small chance of identifying these molecules, CEP can move all of the promising candidates forward for additional analysis.“So far, we have made a proof-of-principle study in collaboration with Zhenan Bao’s group at Stanford,” said Aspuru-Guzik. “We screened eight different variants of a parent compound for organic semiconductors, and this resulted in a compound with an astonishing large hole mobility. This gives us confidence that the type of approach followed in the WCG will yield useful information to the community.”In addition to searching for molecules with specific structures, the project also gives researchers a better understanding of structure-property relationships of molecules in general. Knowing these design principles will allow scientists to not only improve screening, but also to actively engineer novel organic electronics at a future stage.“On the one hand, the collection provides on-demand access to specific compounds with a wide range of desired properties and electronic structures for all sorts of applications, not only for OPVs,” Hachmann said. “On the other hand it forms a solid foundation to learn about structure-property relationships. Lastly, it will be a useful resource for theoreticians to assess the performance of different computational methods and can serve as a parameter repository in this chemical space.”As more technical results arrive, the researchers are building a reference database that will be available to the public by 2012. The data should accelerate the search for optimal OPV materials, and provide valuable data for the development of organic electronics in general. The researchers hope that one day the search will lead to a clean source of electricity that can compete with conventional energy sources, although it’s difficult to predict exactly when that will be.“In principle, we want the search to last as little as possible,” Aspuru-Guzik said. “Obviously, things are more complicated: It takes human time to catalog and understand the results, as well as to select molecules for further screening. We are in the process of selecting the top candidates of our initial screening and releasing them in a publication. We want to further screen the most promising candidates with more calculations to ascertain and verify their potential as organic solar cell materials.”To participate and download the client software developed by IBM and Harvard, go to http://cleanenergy.harvard.edu and click “Download.” The website contains video tutorials for the installation. By screening millions of molecules, researchers hope that the Clean Energy Project will identify a material that can be used to fabricate organic solar cells that have an efficiency of 10-15% and a lifetime of more than 10 years – properties that would make organic solar cells cost-competitive with other energy sources. Image credit: Hachmann, et al. ©2011 American Chemical Society Copyright 2011 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. With traditional approaches to analyzing and characterizing materials, researchers typically rely on their past experiences with certain materials and their own empirical intuition. Due to the long time required for synthesis and characterization, only a few examples can be experimentally studied per year. In contrast, CEP can characterize thousands of molecules per day, and the CEP library already contains about 10 million molecular motifs of potential interest. Citation: Millions of molecules screened in search for the ideal organic solar cell material (2011, September 12) retrieved 18 August 2019 from https://phys.org/news/2011-09-millions-molecules-screened-ideal-solar.html (PhysOrg.com) — Currently, the cost of electricity from commercial silicon solar cells is about 10 times higher than the cost of utility-scale electricity. In order to make solar cells cost-competitive with currently available energy sources, some researchers are looking to organic materials. Not only are organic materials less expensive than inorganic materials like silicon, but they’re also non-hazardous, lightweight, easily processed, and can be made semi-transparent and molded into almost any shape. The problem is there are literally millions of organic materials to choose from, and identifying those few that have the best optical and electronic properties is extremely challenging. 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. Electrical conductor sparks interest More information: Johannes Hachmann, et al. “The Harvard Clean Energy Project: Large-Scale Computational Screening and Design of Organic Photovoltaics on the World Community Grid.” The Journal of Physical Chemistry Letters, 2011, DOI:10.1021/jz200866s
When earthquakes occur due to tectonic plates rubbing against one another, cracks open up in the ground leaving behind what look like wounds. Researchers have been studying these wounds to see if they might offer any new information that would help scientists better understand earthquakes in general. To that end, the researchers in this new effort embarked on a program called the Wenchuan earthquake Fault Scientific Drilling project. Five boreholes were drilled down into various parts of the fault and then sensors were sent down to collect heat and permeability measurements. The boreholes were drilled 178 days after the deadly earthquake in the region struck (which killed over 70,000 people.) At the time of initial drilling, the team found approximately 1 centimeter of new fault gouge, a type of rock that has been pulverized.Subsequent measurement over a period of 18 months showed that the rock in the fault was slowly becoming less permeable—as the fault healed, water was less able to make its way through the rock. This was expected, of course. What surprised the research team, however, was how quickly the fault was being repaired by mineral deposits left behind by water flow. They described it as “significantly faster” than lab experiments had shown.Another surprise was a periodic tendency of the faults to lose ground in their healing process. The rock would suddenly become more permeable, the sensors showed, and then once again become less so as the healing process resumed. The team traced this to other seismic activity such as earthquakes that occurred in Sumatra in 2010 and in Japan in 2011.The researchers acknowledge their data relates to just one fault zone in the aftermath of one earthquake, but their findings suggest that similar studies should be done following future earthquakes to help determine if what they observed is the normal case for healing fault zones. Journal information: Science More information: Science 28 June 2013: Vol. 340 no. 6140 pp. 1555-1559 DOI: 10.1126/science.1237237 © 2013 Phys.org 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 (Phys.org) —A team of Chinese researchers along with representatives from the US and Japan have found that ground fractures along fault lines due to earthquakes appear to heal faster than previously thought. In their paper published in the journal Science, the team reports on data found by boring holes along the fault line responsible for the 2008 Sichuan earthquake in China. Citation: Drilling study finds faults after earthquakes heal faster than previously thought (2013, June 28) retrieved 18 August 2019 from https://phys.org/news/2013-06-drilling-faults-earthquakes-faster-previously.html Helping to forecast earthquakes in Salt Lake Valley
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. (Phys.org) —Japanese research center RIKEN has opened an investigation, Nature is reporting, related to reports of anomalies with images published in the same journal as part of a paper on a revolutionary approach to generating stem cells. New simple way to reset cells could be transplant “game changer” Explore further Journal information: Nature © 2014 Phys.org The paper, titled “Stimulus-triggered fate conversion of somatic cells into pluripotency” described an acid-bath approach the team used to generate the type of stem cells that can grow into any body part. The approach was so much simpler than current methods that it created quite a stir in biology labs across the world. Soon after publication of the paper last month, however, comments began appearing on science blogs noting what appeared to be anomalies or inconsistencies with some of the images that were published along with the paper. Some suggested that one image had been spliced, others that parts of a placenta shown in one image may have been reused in another. As questions about the images used in the paper have grown, it appears that RIKEN, the institute where lead author and researcher Haruko Obokata works, has decided to look a little deeper to find out what is going on.Complicating the issue is that several research organizations have reported that they have thus far been unable to reproduce the results claimed by Obokata et al, though all have acknowledged publicly that they have not used the same types of cells in their experiments and that while the procedure sounds relatively straight forward, it’s actually very difficult to carry out.Problems with images in a research paper don’t necessarily mean there are problems with the research, as other posters have noted. It could be simple communication problems between writers and/or the publisher. One of the authors listed on the paper, Charles Vacanti, told Nature that he believes the image problems are due to a mix-up of some sort during the publication process—he’s requested a correction.For its part, Nature, in posting an announcement about the move by RIKEN, appears to be taking the wait and see approach—they note that the image inconsistencies appear to cast doubt on the paper as a whole, but refrain from commenting on its own vetting process as it applied to the paper it published. Obokata has not responded to queries from Nature or anyone else, though she and her team are reportedly working to uncover the source of the problem with the images and will be publishing a reply in Nature at some point. Citation: Image anomalies cast shadow on acid-bath stem-cell study (2014, February 18) retrieved 18 August 2019 from https://phys.org/news/2014-02-image-anomalies-shadow-acid-bath-stem-cell.html Stress-treated lymphocytes expressed pluripotency marker Oct4. Right: STAP cells. Credit: Haruko Obokata
Nuclear Pore Complex. Credit: studyblue.com Journal information: PLoS Biology (Phys.org)—If asked to describe the differences between humans and frogs, a child might say that one hops and rib-its while the other walks and talks. If we ask that same child how to build a frog, they will probably need a few minutes with Google. Assuming they are good, they might find that for humans you start with a diameter of 5.2nm for their nuclear pore complexes (NPCs), while for frogs the parameter you use is 10.7nm. That one detail determines a lot about what is possible in the cell, and therefore the entire organism. © 2016 Phys.org 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. New findings help explain how molecules are speedily transported into and out of the cell’s nucleus The reason for going into all this detail here is that to understand where Eukaryotes came from we need to understand the partitioning of the cell. The origins of NPCs (and therefore the nucleus) is only half the equation. The other half is mitochondria. The link between the two is established when we realize that in unloading almost all their DNA to the nucleus, the mitochondria had to solve much the same re-localization problem that the NPC translocators have to solve. To get their own protein products, now encoded and made by the host cell, mitochondria developed an analogous (but different) double membrane system of import/export translocators known as the Tim-Tom and Sam families of proteins. In chloroplasts, these are known as the Tic-Toc translocators. The kicker is, if we take Nick Lane’s word for it, the NPC first evolved because of the pressures applied by the acquisition of the mitochondria:Namely, the NPCs served to fence out the ribosomes from the nucleus so that the relatively slow operating spliceosomal machinery had time to work on the many rogue introns and newly acquired endosymbiont genes which managed to get mitochondrial localization sequences appended to themselves.The remarkable thing that the Rockefeller group found in their studies from the dawn of eukaryotes is that despite retaining a similar composition of important protein motifs and domains, there were gaping architectural dissimilarities between opisthokonts (yeast and vertebrates), and a group of creatures known as trypanosomes. The trypanosomes are known for many things, not least of which is being the parasites responsible for Chagas disease and African sleeping sickness. A key feature is that as a class, they have highly evolved (and degenerate as the case may be) mitochondria. The other peculiar thing about trypanosome mitochondria is their extensive use of RNA editing, typically of uracil. Some of their degenerate mitochondria have lost all their tRNA genes and must import them to translate protein. Other trypanosome mitochondria have lost their entire coding capacity altogether, and serve mainly as organelles to synthesize iron sulfur clusters or other eclectic products. At the other extreme, many trypanosomes have a huge specialized mitochondria known as a kinetoplast, which services their primary flagellum using a unique system of mini- and maxi- DNA circles. These circle parse and replicate the mtDNA in a highly evolved way not seen in any othr known organism. Incidentally, the name of opisthoconts, (of which we are one) comes from “opistho-” or “behind”, and “-kont” meaning flagellum. Most primitive creatures like trypanosomes (“trypano” means “to bore”), actually swim backwards, pulling themselves along by the corkscrew action of their flagellum. Only when things get too crowded, like in thickened blood, do they reverse gears and back out.Among the critical conserved components that the researchers in all eukaryote NUPs were the major protein folds on the core scaffold Nups lining the main pore. The Nups form the two inner rings which are in turn sandwiched between two outer rings. They contain folds known as α-solenoids and β-barrels or propellers. The importance of these folds is increasingly appreciated as they continue be found at the heart of many newly determined protein crystal structures. The mitochondrial Tom and Sam translocases have them, as do various vesicle coat proteins, including clathrin/adaptin, COPI, and COPII proteins. The authors note that these proteins share architectural characteristics with outer ring Nups, and hint at a common ancestry between the endomembrane trafficking system and the NPC. This so-called ‘proto-coatomer hypothesis’ further suggests that key components of the cell’s secretory system took origin by virtue of their ability to bend membranes, a key first step in the assembly of the pore.The further one goes out from the core, the less one finds NPC features conserved in the various clades across the millennia. Many peripheral proteins which interact with the core, like the importins and exportins which bind the localization signals and adapters, similarly tend to diverge. This general trend seems to closely parallel the predictable complexification of other major assemblies in the cell. For example, we recently detailed how comparative phylogenetics has unmasked the conserved cores of the ribosome, common enzyme complexes, ion channels, and the GTP coupling so essential to everything from the NPC cycle to olfactory reception. One specific feature seemingly unique to NPCs the authors found is a loss of an initial symmetry over time: in the ancestral condition it seems that the phenylalanine-glycine (FG) repeats responsible for the selective permeability barrier were fairly uniformly distributed. Over time, creatures from yeasts to man developed a critical asymmetric distribution, favoring FG repeats on either the nuclear or cytoplasmic side. The significance and ubiquity of a tiny feature like this has yet to be seen, however in the protein business, today’s anecdote is frequently tomorrow’s canonical motif. In a recent paper published in Plos Biology, researchers from Rockefeller university went fishing for various NPC ‘interactomes’ in order to trace of the origins and 1.5 billion year evolutionary history of Eukaryotes. The interactome is exactly what it sounds like: any exhaustive set of molecules that can be connected with thin black lines in a figure in a research paper. Practically speaking, this meant starting with a few fluorescently-tagged versions of known core nuclear pore component proteins (called nucleoporins or Nups), and ‘walking out’ from there using affinity capture and mass spectrometry to identify other proteins that stick.While there are plenty of contenders for the title of world’s greatest protein complex—the ribosome, proteosome, ATPase, and centromere for example—the NPC may be the mightiest of all. At an undisputed 50 MEGADaltons (124 for the mammalian), the NPC contains about 500 subunits comprised of some 30 different Nups. Rather than splashed together like a respiratory complex, the NPC is carefully assembled into an 8-fold symmetric structure that rivets the double nuclear membrane together. To give some idea of the budget that cells are on, the nucleus might have 2000 NPCs (more if mitosis is coming), each ferrying consumables at a rate of 1000 translocations per second.What exactly is a translocation you might ask, and who gets to go in or out? That depends on a lot of things, like that minimum pore size we mentioned above. Although there is no hard and fast size limit to what can pass through by unaided diffusion, things slow down considerably for proteins at around 60kDa. Above that, translocation doesn’t become energy dependent per say, but ultimately the ferryman needs to get paid with the hydrolysis of two GTP each time the turnstyle turns. The way it works is neatly described by something known as the Ran-GTP cycle. Many folks are familiar with the idea of gradients across membranes (usually electrical, proton, sodium or other ion), which are harnessed to power auxiliary movements. The Ran cycle is said to run on a Ran protein gradient where the concentration of the GTP bound form is high inside. and GDP bound form is low outside the nucleus. The tricky part is biasing the pore to get things moving in the right direction. Ribosomes and mRNAs made in the nucleus need to get out, while nuclear proteins translated in the cytoplasm need to get in. These affairs are all neatly enforced by an expansive array of adapters which recognize and bind canonical nucleic acid cytoplasmic localization sequences on the former, and amino acid nuclear localization sequences on the later. Citation: Mapping the nuclear pore complex: 1.5 billion years of innovation (2016, February 24) retrieved 18 August 2019 from https://phys.org/news/2016-02-nuclear-pore-complex-billion-years.html Explore further More information: Richard Robinson. The Trypanosome Nuclear Pore Reveals 1.5 Billion Years of Similarities and Differences, PLOS Biology (2016). DOI: 10.1371/journal.pbio.1002366Samson O. Obado et al. Interactome Mapping Reveals the Evolutionary History of the Nuclear Pore Complex, PLOS Biology (2016). DOI: 10.1371/journal.pbio.1002365
More information: Romana Baltic et al. “Superlattice of Single Atom Magnets on Graphene.” Nano Letters. DOI: 10.1021/acs.nanolett.6b03543 Citation: Superlattice of single-atom magnets aims for ultimate limit of high-density data storage (2016, November 17) retrieved 18 August 2019 from https://phys.org/news/2016-11-superlattice-single-atom-magnets-aims-ultimate.html © 2016 Phys.org (Phys.org)—Scientists have fabricated a superlattice of single-atom magnets on graphene with a density of 115 terabits per square inch, suggesting that the configuration could lead to next-generation storage media. Single-atom magnet breaks new ground for future data storage (Left) A superlattice of single dysprosium atoms on a graphene-iridium substrate. (Right) The superlattice has a very large magnetic hysteresis, indicating high magnetic stability. Credit: Baltic et al. “Single-atom magnets represent the ultimate limit for ultrahigh-density magnetic storage devices,” Stefano Rusponi, a physicist at the Ecole Polytechnique Fédérale de Lausanne (EPFL) and coauthor of the new research, told Phys.org. “So far, researchers have mainly focused on the magnetic properties of single atoms and small clusters randomly distributed on the supporting surfaces.” [See previous papers here and here.] “In our new paper, we demonstrate the ability to realize a superlattice of single atoms having stable magnetization. This represents the first prototype of a storage media based on a single atom per bit.”As the researchers explained, a key challenge in using an array of atomic magnets as a data storage device is to ensure that the magnets are stable and do not interact with each other, since this could result in data loss.To address this challenge, the research team, led by Professor Harald Brune at EPFL, took advantage of the good magnetic properties of dysprosium atoms, along with the properties of the graphene-iridium substrate.Part of the reason for the highly stable magnetization is because of the lattice mismatch between graphene and iridium, which creates a periodic moiré pattern. This periodic pattern leads to an equidistant arrangement of the most favorable dysprosium adsorption sites.When the dysprosium atoms are deposited onto the substrate at about 40 K, their surface diffusion is activated, which causes them to jump around on the surface. This motion allows them to reach the most favorable adsorption sites determined by the moiré pattern, so that they form a highly ordered array, with an average distance between atoms of just 2.5 nanometers. Once assembled, the atoms’ magnetic stability can be affected in a few ways, including by scattering with electrons and phonons on the surface, as well as by quantum tunneling of the magnetic states.Fortunately, two of the beneficial properties of graphene are its very low electron and phonon densities, which protects the dysprosium atoms against scattering. In addition, the dysprosium atoms have a favorable magnetic ground state that protects against quantum tunneling of the magnetization. Both properties contribute to the high magnetic stability of the superlattice.Measurements showed that the superlattice has a very large magnetic hysteresis—which is a measure of the irreversibility of a magnet—that outperforms the best dysprosium-based single-ion molecular magnets. The researchers explain that the high magnetic stability depends on all of the combined properties of the atoms and the graphene-iridium substrate, and that missing just one of these properties greatly reduces the stability.One of the current drawbacks of the design is that the magnetic stability decreases at higher temperatures. In the future, the researchers plan to improve the superlattice’s thermal stability, possibly by growing graphene on an insulating substrate. “The magnetic stability of the dysprosium atoms is limited to temperatures below 10 K and is sensitive to contamination, thus requiring ultra-high vacuum conditions for our experiments,” Rusponi said. “In the future, we plan to improve the performances of the single-atom magnet superlattice. First, we intend to increase the maximum temperature at which the magnetic stability survives by finding the optimum combination of single atom species and supporting substrate. Second, we intend to protect the superlattice with a capping layer preserving the properties of the magnetic atoms.” Journal information: Nano 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
In technology news, phone users were alarmed when it was announced that an Israeli firm can steal phone data in seconds—Cellebrite’s demonstration showed just how vulnerable phones still are. More optimistically, researchers with Ulsan National Institute of Science and Technology demonstrated thermoelectric paint that enables walls to convert heat into electricity. Also, a team working in Australia reported that a frontline attack against HIV infection is closer to reality—suggesting that significant progress has been made in developing a vaccine for those infected. And a team at the University of Bristol announced the ‘Diamond-age’ of power generation as nuclear batteries were developed using nuclear waste to create an artificial diamond.In planetary news, mathematician Harry Stern with the University of Washington found evidence that showed Captain Cook’s detailed 1778 records confirm global warming today in the Arctic—comparing earlier notes with modern satellite imagery showed how much the ice edge has moved. Also a team at the Danish Meteorological Institute noted that the overheated Arctic was a sign of a climate change ‘vicious circle’—air over the ice cap was nine to 12 degrees Celsius above average during the prior four weeks, a truly unusual phenomenon that they attribute to a variety of events related to global warming. Less ominous, a pair of researchers, Tom Edinburgh with the University of Reading and Jonathan Day with the University of Cambridge found that Antarctic explorers helped make a discovery—100 years after their epic adventures—logs from ship captains hundreds of years ago showed that sea ice around Antarctica has hardly changed.And finally, for those people who are holding out hope that scientists will figure out how to stop aging before it is too late for them, a team of researchers from UCLA and Caltech reported that they were meeting with some success in turning back the aging clock—by removing mutated DNA from mitochondria. Theory that challenges Einstein’s physics could soon be put to the test Explore further Albert Einstein (ScienceX)—It was another good week for physics as a pair of researchers, João Magueijo with Imperial College London and Niayesh Afshordi with the Perimeter Institute suggested that a theory that challenges Einstein’s physics could soon be put to the test—first proposed in the early 90’s, the theory has matured to the point that the pair believe it has finally become testable. Also a team at Caltech found new clues emerging in a 30-year-old superconductor mystery regarding how they actually work by confirming that the pseudogap represents a distinct state of matter. Citation: Best of Last Week – Challenging Einstein, the Arctic overheating and a breakthrough in slowing down aging (2016, November 28) retrieved 18 August 2019 from https://phys.org/news/2016-11-week-einstein-arctic-overheating-breakthrough.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. © 2016 ScienceX
Darjeeling: Inclusion of Gorkha sub-communities in the Scheduled Tribe list issue, at present occupies the centre stage of Hill politics. While Binay Tamang, chairman of the Board of Administrators, Gorkhaland Territorial Administration, on Thursday shot a letter to Union ministers to this effect, the Gorkha National Liberation Front is sending a delegation to Delhi to pursue the issue.”We have sent letters to the Union Home minister and Tribal Affairs minister to take up the issue and expedite the process. We have also sent a request letter to Sikkim Chief Minister Pawan Chamling, to pursue the matter,” stated Tamang. Also Read – Heavy rain hits traffic, flightsThe GTA chairman stated that during his talks with Chief Minister Chamling on March 27 in Gangtok, the CM had assured that he would write to Delhi to this effect and even pursue the matter personally.”West Bengal Chief Minister Mamata Banerjee has already sent recommendations to Delhi for the inclusion of 11 Gorkha communities in the ST list, after the matter was passed in the Bengal Assembly in February 2014. During her last visit to Darjeeling, we had raised the issue. She stated that she had already taken up the issue and that a committee had visited the hills to study the ground situation. We then apprised her that no physical verification has taken place yet. Following this, the state government had sent a fresh recommendation again on February 16, 2018,” stated Tamang. Also Read – Speeding Jaguar crashes into Merc, 2 B’deshi bystanders killedHe stated that he will also be visiting Delhi soon to pursue the issue. The GNLF, while addressing the Press in Darjeeling on Thursday, stated that they will be sending a team to Delhi to pursue the issue. “We demand that all left out Gorkha sub-communities have to be included in the ST list. Even the sub-communities included in the Scheduled Caste list have to be delisted and included in the ST list, as it was in 1931,” stated Neeraj Zimba, GNLF spokesperson. In 1931, there was a gazette notification declaring the entire Gorkha population as Hill Tribes. In 1954, they were delisted.Based on the 1931 notification, late Subash Ghising, the erstwhile president of GNLF, had raised the demand of inclusion of all the left out Gorkha sub-communities in the ST list and inclusion of the Darjeeling hills in the 6th Schedule of the Indian Constitution.”We are merely demanding a relisting. Even Prime Minister Modi has given his assurance to this effect. The West Bengal government has done the needful and already sent two recommendations. The ball is now in the Centre’s court. Time has come to see how committed BJP and Prime Minister Modi is to the Gorkha cause,” added Zimba.