World IPv6 Day test runs 24 hours starting June 8

first_img Citation: World IPv6 Day test runs 24 hours starting June 8 (2011, January 20) retrieved 18 August 2019 from https://phys.org/news/2011-01-ipv6-internet-protocol-billion-space.html IPv6 guide provides path to secure deployment of next-generation Internet protocol On June 8, 2011 major web companies such as Facebook, and Yahoo!, will allow IPv6 to run on their main websites for 24 hours. These websites along with Google have more than one billion combined visits each day. They are joining major content delivery networks Akamai and Limelight Networks along with the Internet Society, for the first global-scale 24 hour trial run of the new Internet Protocol, IPv6.Internet users will not have to do anything to prepare for this 24 hour global event. According to the Internet Society, the vast majority of users, about 99.5%, will be unaffected. There will be some cases where users may experience connectivity problems due to the fact that their home network device is not configured correctly.The major goal of World IPv6 Day is to identify the potential problems under controlled testing and address them in a timely manner. Organizations involved in this global event will be working alongside operating system manufacturers, networking vendors and ISPs to minimize the number of users affected.World IPv6 Day marks a critical day in Internet history that will pave the way for future growth and enabling more computers, networks and handheld devices to come online. Explore further IPv6 is a new version of the Internet Protocol that is designed to succeed the existing Internet Protocol version 4. More information: World IPv6 Day, IPv6 © 2010 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. (PhysOrg.com) — Today’s Internet protocol, IPv4, is expected to run out of space this year. On World IPv6 Day the first steps will be taken to test a long-term solution that will address the 30 year old 32 bit addresses.last_img read more

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Microsoft Security Essentials misses AVTest Certified status

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. Citation: Microsoft Security Essentials misses AV-Test Certified status (2013, January 18) retrieved 18 August 2019 from https://phys.org/news/2013-01-microsoft-essentials-av-test-certified-status.html Explore further © 2013 Phys.org More information: blogs.technet.com/b/mmpc/archi … st-test-results.aspxcenter_img AV-Test is an independent testing lab based in Germany. As a service provider in IT security and anti-virus research, they aim at detecting and analyzing malware, and informing customers of results. Their work is done at laboratories in Magdeburg and Leipzig.Microsoft’s site presents Microsoft Security Essentials as “built for individuals and small businesses, but “based on the same technology that Microsoft uses to protect giant businesses.”Microsoft missed certification by one point on the current test. In the previous failure the company missed certification by half a point. “During November and December 2012 we continuously evaluated 25 home user security products using their default settings,” said the AV-Test account of its recent testing. “We always used the most current publicly-available version of all products for the testing. They were allowed to update themselves at any time and query their in-the-cloud services. We focused on realistic test scenarios and challenged the products against real-world threats. Products had to demonstrate their capabilities using all components and protection layers.”Microsoft, meanwhile, issued a statement regarding the test results. “We continually evaluate and look at ways to improve our processes. We know from feedback from customers that industry testing is valuable, and their tests do help us improve,” said Joe Blackbird, program manager, Microsoft Malware Protection Center, in a response. “We’re committed to reducing our 0.0033 percent margin to zero.”On Microsoft’s side, he said, “We conduct a rigorous review of the results whenever test results warrant it. We take the protection of our customers very seriously, and the investments we make to do these reviews is an example of that commitment.”At the same time, he said, it was difficult for independent anti-malware testing organizations to devise “tests that are consistent with the real-world conditions that customers live in.” Blackbird reviewed a number of points, using figures to support his views. He offered “some key upfront data points to keep in mind.” Among the points listed in his response: “AV-Test’s test results indicate that our products detected 72 percent of all ‘0-day malware’ using a sample size of 100 pieces of malware. We know from telemetry from hundreds of millions of systems around the world that 99.997 percent of our customers hit with any 0-day did not encounter the malware samples tested in this test.” Microsoft anti-virus program evicts Chrome browser (Phys.org)—Microsoft Security Essentials failed another certification test by independent testing lab, AV-Test Institute. The group publishes test results every two months. Microsoft Security Essentials 4.1 was among three failures, in the testing that was done for the months of November and December 2012. The testing looked at over two dozen consumer antivirus security programs. The other two that failed certification were PC Tools Internet Security 2012 and AhnLab Internet Security 8.0.last_img read more

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Intel developer event to discuss 16 Tbits MXC interconnect breakthrough

first_img Citation: Intel developer event to discuss 1.6 Tbit/s MXC interconnect breakthrough (2013, August 16) retrieved 18 August 2019 from https://phys.org/news/2013-08-intel-event-discuss-tbits-mxc.html MXC is the result of a two-year collaboration between Intel and Corning Cable Systems. Intel’s strength in the work has been its expertise in silicon photonics and Corning worked on the new fiber technology called Corning ClearCurve LW. In 1970, three Corning scientists came up with a low-loss optical fiber, described as a hair-thin strand of highly transparent glass able to transmit information by reflecting light through the length of its core. Corning takes pride in its work ever since in fiber optic manufacturing. On the Intel side, the company has been working on its silicon photonics technology, an area of focus for almost ten years, which involves “moving data with silicon and light,” in the words of Intel. This is an approach to using photons to move big amounts of data at very high speeds with extremely low power over a thin optical fiber.According to an Intel website page, the new connector can carry 1.6 terabits of information per second, has fewer moving parts, is less susceptible to dust and costs less than other photonics connectors. With those features, the interconnect can be a real advancement for data centers. Intel’s comments on the IDF website had this to say:. “Current optical connectors used in data centers are based on a design from the mid 1980s. Two years ago, Intel started working with Corning Cable Systems to design a brand new optical connector called MXC, using silicon photonics and a new fiber technology. MXC can carry up to 1.6 Terabits per second and is smaller than the connectors used today.” The IDF item also said the Corning fiber contribution to the MXC is called Corning ClearCurve LW.Participating in next month’s MXC lecture are David Hessong, MXC Product Line Manager and Scott Bickham senior development associate, both of Corning Cable Systems and, from Intel, Victor Krutul, director, of intel’s Silicon Photonics Operation.The topics in this session range from existing optical connector issues, MXC’s design goals, its edge over other optical connectors, and the MXC schedule. The Intel Developer Forum runs from September 10 to 12. © 2013 Phys.org Explore further New photonic architecture promises to dramatically change next decade of disaggregated, rack-scale server designscenter_img (Phys.org) —The word is out that Intel will present an entirely new optical interconnect technology for servers at the Intel Developer Forum in San Francisco next month. The MXC interconnect is capable of a peak transfer rate of 1.6 terabits per second. In advancing notes of what’s on the agenda at the upcoming developer forum, Intel posted a brief description of its MXC presentation scheduled for September 12. Once the posting went up, it did not take long for tech sites to see it and catch the significance. This is something big. More information: www.intel.com/content/www/us/e … tonics-research.htmlwww.corning.com/opticalfiber/f … berbasics/index.aspxintel.activeevents.com/sf13/co … search.ww#loadSearch 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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The ties that bind Recreating Darwinian ligand evolution in vitro

first_img Prof. Steven A. Benner discussed the paper that he, Dr. Kwame Sefah and their co-authors published in Proceedings of the National Academy of Sciences – starting with the main challenges they faced. One such challenge was overcoming the limitation of chemical theory by directly designing binders through in vitro recreation of the Darwinian processes that nature uses to molecular binders. “Current chemical theory is quite able to do broad brush design,” Benner tells Phys.org. Indeed, Benner notes, the scientists used current chemical theory to design the additional nucleotides in their AEGIS technology. “However,” he continues, “both at the highest level of quantum mechanics as well as the more practical level of molecular dynamics, the assumptions in models of reality are not good enough to allow energy output to be accurate to better than, say, 5 kcal per mole – the difference between success and failure in, as an example, a pharmaceutical.”Conversely, Benner adds, while Darwinism is incapable of doing what he calls big design, it is capable of fine tuning. The whole idea behind this strategy, he explains, is to construct by coarse design a system that is better able to support Darwinism and the laboratory environment. “This publication,” he points out, “represents the first case in which this combination has been fully successful.” (Benner notes that development of this technology was funded by the Defense Threat Reduction Agency, which consolidates a variety of US Defense Department functions to deal more effectively with the threats posed by nuclear, chemical, or biological weapons.)A second challenge, says Benner, was demonstrating the first example of SELEX using AEGIS to produce a molecule that binds to cancer cells. “Molecular biological and genetic engineering tools, which have advanced so far over the past half-century, and which have led to several Nobel Prizes, have been advanced for use with natural genetic systems, not our artificially expanded systems. Therefore, we needed to develop analogous molecular biological tools for AEGIS. These included tools to manufacturer the AEGIS components, chemistry to synthesize AEGIS oligonucleotides, enzymes to do AEGIS PCR amplification, procedures to sequence AEGIS DNA, and so on.” Incremental research and improvements in technology have allowed AEGIS DNA to be manipulated almost the same level as natural DNA is by classical molecular biology. Explore further © 2014 Phys.org. All rights reserved. Citation: The ties that bind: Recreating Darwinian ligand evolution in vitro (2014, January 24) retrieved 18 August 2019 from https://phys.org/news/2014-01-ties-recreating-darwinian-ligand-evolution.html Schematic of the AEGIS cell–SELEX used here. A GACTZP DNA library, consisting of randomized sequences and primer sites, was first incubated with the target cells. Unbound sequences were then removed by washing. Bound sequences having affinity to the target cells were collected. “Survivors” in the enriched collection were amplified using a FITC-labeled 5´-primer and a biotinylated 3´-primer by GACTZP six-nucleotide PCR (22). Enriched FITC-conjugated single-stranded DNA obtained from PCR products was used for the next round of selection. The binding affinity of survivors from 9th round up to 12th round of selection was monitored by flow cytometer. The survivors from 12th round selection were subjected to deep sequencing. Credit: Copyright © PNAS, doi:10.1073/pnas.1311778111 More information: In vitro selection with artificial expanded genetic information systems, PNAS Published online before print December 30, 2013, doi:10.1073/pnas.1311778111Related: 1Toward the Combinatorial Selection of Chemically Modified DNAzyme RNase A Mimics Active Against all-RNA Substrates, ACS Combinatorial Science 2013 15 (4), 174-182, doi:10.1021/co3001378 A tighter fit with artificial DNA Journal information: Proceedings of the National Academy of Sciences To address these challenges, the scientists had to develop chemical pipelines to synthesize AEGIS components on multi-gram scales; develop DNA and RNA polymerase to make DNA and RNA that contain AEGIS components; and create tools to restrict decomposition of DNA containing AEGIS components.Benner points out that because SELEX, as originally proposed by Larry Gold two decades ago, follows a simple recipe, their findings could possibly generate receptors, ligands, and catalysts having sequence diversities nearer to that displayed by proteins. Specifically, that recipe entails: 1. Synthesizing a library of xNA (xeno-nucleic acid, or synthetic DNA) molecules, typically containing 1011-1014 members. 2. Placing the library in contact with the target in order to separate molecules in the library that bind to the target from molecules that do not. (To select catalysts, xNA libraries are put in an environment where an ability to catalyze a reaction separates them from xNA molecules that cannot.) 3. Survivors are enriched in a pool of xNA molecules that bind to the target (or catalyze a reaction), and then amplified in a polymerase chain reaction (PCR). 4. After a sufficient number of rounds of selection, individual aptamers (oligonucleic acid or peptide molecules that bind to a specific target molecule) are recovered, sequenced, re-synthesized and characterized as molecular species having defined molecular structures.”As with many new technologies,” Benner explains, “SELEX was initially regarded as having high potential, and aptamers were hoped to eventually rival antibodies as binders. This potential has been fulfilled in part. xNA aptamers are known for many targets, including carbohydrates, small molecules, and peptides.” In fact, he adds, some aptamers have already entered the clinic – although only after extensive modification of the aptamers originally selected.”However, as SELEX evolved as a field,” Benner continues, “it became clear that the binding diversity and catalytic power of xNA aptamers built from standard nucleotides (G, A, C, and T/U) were not able to match the diversity and power of proteins, including antibodies. At the same time, targets for the best aptamers had a natural propensity to bind to xNA, yielding aptamers with nanomolar dissociation constants.” Dissociation constants are a specific type of equilibrium constant that measure the propensity of a larger object to reversibly separate, or dissociate, into smaller components. Ligands having nanomolar (nM) dissociation constants bind more tightly to a particular protein than those with micromolar (μM) dissociation constants. (A molar is a measure of amount-of-substance concentration.)”For example, Benner illustrates, “aptamers selected to bind to nucleocapsid proteins, reverse transcriptase and HIV integrase had affinities of 2 nM, 0.3-20 nM, and 10-800 nM, respectively. In contrast, aptamers against small molecules were generally selected to have poorer affinities in the micromolar range. For example, dissociation constant values reported for aptamers selected to bind citrulline and arginine ranged from 0.3 to 65 μM, while the values for specific aptamers that bind ATP and xanthine were only 3.3 and 6 μM, respectively.”Benner point out that similar disappointment was also the rule for xNAzymes (xNA molecules that catalyze a preselected reaction). “While many xNAzymes have been reported, the best again performed well only for reactions of nucleic acids themselves, including phosphate hydrolysis, transesterification (the process of exchanging the organic group R″ of an ester with the organic group R′ of an alcohol), xNA ligation, and xNA polymerization. Even here, however, the rates of reactions were not impressive, and certainly not impressive when compared to natural enzymes that have evolved over millions of years to catalyze a specific reaction.” He adds that they also did not perform orders of magnitude better than designed protein catalysts or antibody-based catalysts.”In retrospect,” Benner points out, “we might have expected xNA aptamers to not perform as well as proteins, since the latter are built from 20 different units and carry a wide range of chemical functionalities.” These include positively-charged nitrogens (on lysine and arginine), anionic groups (aspartate and glutamate), hydrophobic groups (valine, leucine and others), polarizable groups (such as the tryptophan indole and the methionine thioether), catalytic units (including histidine), and metal coordinating groups (cysteine and histidine). In contrast, he adds, standard xNA nucleotides carry little of this functionality. “Accordingly,” Benner continues, “the Benner group and others added functionality to the four standard nucleotides in an attempt to get better performing xNA molecules – and this too has had some success.” Examples include:Prof. David Perrin and his coworkers1 made DNA where each of the four standard xNA building blocks (GACT) carried a different functional group; applying these to select for DNA catalysts, they saw an improvement in the catalytic power of the emerging DNAzymes (DNA molecules that have the ability to perform a chemical reaction, such as catalytic action)SomaLogic modifies the 5-position of pyrimidines with benzyl, naphthyl, tryptamino, and isobutyl groups, inter alia, generating SOMAmers (Slow Off-rate Modified Aptamers); the company reports a set of these that detect ∼800 different human proteins in blood volumes as small as 15 microliters (μL), with affinities in the 0.1 picomolars (pM) – 1 μM rangeBenner also tells Phys.org that AEGIS–SELEX would be improved by the following investigations being developed in their laboratories:Strains of E. coli cells that can propagate plasmids containing GACTZP DNA (a form of xNA), which he notes is the core of their current activitiesA technology for directly sequencing single molecule Z:P pairsPolymerases with still higher levels of fidelity and efficiencyMoving forward, Benner tells Phys.org, the scientists are developing E. coli strains that can propagate plasmids containing GACTZP DNA, and are improving sequencing. “We also hope to also develop the chemistry and enzymology of the xNA S:B pair, as well as the xNA K:X and V:J pairs, in this order.”Benner notes that there are other areas of research that might benefit from their study. “Nearly everything in medicine involves the binding of molecules to other molecules,” he tells Phys.org. “This is true in the research laboratory, in clinical diagnostics, and even within patients. Medicine needs drugs that bind to therapeutic targets to cure diseases; diagnostics needs molecules that bind to markers to indicate the presence of the diseased state; and researchers need molecules that bind to functional molecules to track their movement within cells.” For this reason, he says, binding to and between targets is key to essentially all work done under the auspices of the National Institutes of Health (NIH), even when that binding is not the explicit focus of that work.”Accordingly,” Benner concludes, “biomedical researchers, diagnosticians and clinicians have long sought a technology that delivers binding molecules and catalysts on demand. In this vision, the technology would deliver binders quickly, reliably and inexpensively, to any researcher who has in hand some of the target. AEGIS-SELEX will be, we hope, this technology.” (Phys.org) —A key feature of certain chemicals is their ability to bind to other molecules – a property that emerged through evolution – but current chemical theory lacks the ability to design binders from first principles. To resolve this dilemma, scientists at the University of Florida and the Foundation for Applied Molecular Evolution have recreated these Darwinian processes in vitro (that is, in the laboratory). Their approach extracts nucleic acids as binders from DNA/RNA libraries to evolve through a process called Systematic Evolution of Ligands by Exponential Enrichment, or SELEX. (A ligand is a substance, usually a small molecule, that forms a complex with a biomolecule to serve a biological purpose,) However, natural DNA/RNA has only four nucleotides as building blocks, and so often yields poor binding molecules. By integrating synthetic biology, sequencing tools, and polymerase chain reaction (PCR) amplification, and additional DNA/RNA building blocks from an Artificially Expanded Genetic Information Systems (AEGIS), the scientists successfully demonstrated the first example of SELEX using AEGIS, producing a molecule that binds to cancer cells. 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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New solar desalination device improves efficiency by suppressing heat loss

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. © 2016 Phys.org Explore further (A) Schematics of conventional solar steam generation with direct water contact. (B) Schematics of solar desalination devices with suppressed heat loss and 2D water supply. Credit: (c) Proceedings of the National Academy of Sciences (2016). DOI: 10.1073/pnas.1613031113 (Phys.org)—A team of researchers at Nanjing University in China has developed a new kind of solar desalinating device that does not require a traditional solar concentrator or thermal insulation. Instead, as the group explains in their paper published in Proceedings of the National Academy of Sciences, they introduce a 2-D channel for water circulation that works through capillary action, thereby greatly reducing heat dissipation. More information: Xiuqiang Li et al. Graphene oxide-based efficient and scalable solar desalination under one sun with a confined 2D water path, Proceedings of the National Academy of Sciences (2016). DOI: 10.1073/pnas.1613031113AbstractBecause it is able to produce desalinated water directly using solar energy with minimum carbon footprint, solar steam generation and desalination is considered one of the most important technologies to address the increasingly pressing global water scarcity. Despite tremendous progress in the past few years, efficient solar steam generation and desalination can only be achieved for rather limited water quantity with the assistance of concentrators and thermal insulation, not feasible for large-scale applications. The fundamental paradox is that the conventional design of direct absorber−bulk water contact ensures efficient energy transfer and water supply but also has intrinsic thermal loss through bulk water. Here, enabled by a confined 2D water path, we report an efficient (80% under one-sun illumination) and effective (four orders salinity decrement) solar desalination device. More strikingly, because of minimized heat loss, high efficiency of solar desalination is independent of the water quantity and can be maintained without thermal insulation of the container. A foldable graphene oxide film, fabricated by a scalable process, serves as efficient solar absorbers (>94%), vapor channels, and thermal insulators. With unique structure designs fabricated by scalable processes and high and stable efficiency achieved under normal solar illumination independent of water quantity without any supporting systems, our device represents a concrete step for solar desalination to emerge as a complementary portable and personalized clean water solution.center_img Citation: New solar desalination device improves efficiency by suppressing heat loss (2016, November 22) retrieved 18 August 2019 from https://phys.org/news/2016-11-solar-desalination-device-efficiency-suppressing.html Sponge creates steam using ambient sunlight Journal information: Proceedings of the National Academy of Sciences As the demand for water continues to increase around the globe, even as supplies diminish, scientists have been hard at work trying to improve water desalination devices—if a cheaper, more efficient means could be found to turn seawater into drinking water, the problem would be solved. Unfortunately, conventional desalination plants are still expensive to operate, running at approximately 80 megawatt-hours per megaliter of water produced, making them practical only in arid regions that have a lot of money to invest—such as the Middle East. For that reason, many researchers have turned to solar power as a possible option—unfortunately to date, such systems are difficult to ramp up in a way that allows them to produce enough drinking water to be useful—mainly because of the need for optical concentrators and thermal insulation. In this new effort, the researchers describe a new type of solar desalination device that works without either of them.The reason most solar systems require thermal insulation is because of the need to separate water being heated from unheated water—failure to do so would lose heat to the input water supply. To get around this problem, the researchers used simple polystyrene foam to separate the heated water from the input stream and introduced a 2-D channel that relies on capillary action to circulate the water as it is heated by the absorber. Because of its 2-D nature, heat cannot pass backwards through the channel; thus, very little is lost. The team also created an absorber using graphene oxide, because, as they note, it has excellent solar absorbing properties and low thermal conductivity. Another benefit, they note, is that it can be folded, making the device transportable.The result is a relatively inexpensive, highly efficient solar powered water desalination device. There is one problem still to overcome, however, before the device can be put to use in the real world—because of the materials used it is not clear how long such a device would stand up to real world environmental conditions.last_img read more

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Two new tidal disruption events discovered

first_imgArtist’s impression of a tidal disruption event. Image credit: ESA/C. Carreau In two recently published scientific papers, an international team of astronomers has presented the detection of two new tidal disruption events (TDEs). Using the Palomar Observatory located near San Diego, California, the researchers discovered flares of radiation which turned out to be TDEs. Their findings were described in papers published online March 2 and 3 on the arXiv pre-print server. TDEs are astronomical phenomena which occur when a star passes close enough to a supermassive black hole and is pulled apart by the black hole’s tidal forces, causing the process of disruption. Such tidally disrupted stellar debris starts raining down on the black hole and radiation emerges from the innermost region of accreting debris, which is an indicator of the presence of a TDE.For astronomers and astrophysicists, TDEs are potentially important probes of strong gravity and accretion physics, providing answers about the formation and evolution of supermassive black holes.The first TDE identified in the 1990s took the form of luminous soft X-ray outbursts in quiescent galaxies from the ROSAT survey. More recent TDE discoveries were made by surveys like the intermediate Palomar Transient Factory (iPTF), which utilizes the 1.2-meter Samuel Oschin Telescope at Palomar Observatory. Now, a team of astronomers reports another detection of TDEs from the iPTF survey.The newly found TDEs were spotted on May 29 and Aug. 29, 2016 and designated iPTF16axa and iPTF16fnl respectively. A series of follow-up observations using NASA’s Swift space observatory and ground-based telescopes was also conducted to gain insights into the evolution of these two events.The researchers found that iPTF16axa was detected 49 rest-frame days after disruption. They discovered that its light curve shows no color evolution with time and has a constant temperature of about 30,000 K. They also found that this TDE is hosted by a Sloan Digital Sky Survey (SDSS) galaxy with an estimated black hole mass of approximately 40 million solar masses – one of the highest black hole masses among TDE hosts known to date. The data provided by Swift allowed the team to exclude the possibility that the detected flare of radiation could be caused by a variable active galactic nucleus (AGN) and confirmed that it originated from a TDE.”Both Swift UVOT observations and the follow up spectra of iPTF16axa are consistent with the object being a TDE rather than a supernova or a variable AGN,” the paper reads.Moreover, the research indicates that the massive black hole and the short rise time suggest that general relativity effects might play an important role in this event. In contrary to iPTF16axa, iPTF16fnl is hosted by a galaxy (designated Markarian 950) with a much less massive black hole – about two million solar masses. It is the lowest black hole mass in TDE hosts among the optical sample of TDEs. The team also noted that iPTF16fnl shows very strong emission in ultraviolet wavelengths, with a temperature of about 19,000 K. They added that this TDE is very unusual when compared to other such events.”iPTF16fnl is remarkable in three ways: it is the nearest well studied TDE (66.6 Mpc), and it has one of the shortest exponential decay timescales (about 15 days) and one of the lowest peak luminosities,” the researchers wrote. 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. © 2017 Phys.org More information: arxiv.org/pdf/1703.00965.pdfarxiv.org/pdf/1703.01299.pdf Researchers discover a black hole feeding frenzy that breaks records Citation: Two new tidal disruption events discovered (2017, March 9) retrieved 18 August 2019 from https://phys.org/news/2017-03-tidal-disruption-events.html Explore furtherlast_img read more

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Seeing smaller through cells A natural singlecell biomagnifier for subwavelength imaging

first_img LEFT: Optical manipulation of a single fluorescent nanoparticle. (a) Schematic diagram showing a fluorescent nanoparticle suspended on the surface of a mirror and trapped by the biomagnifier. (b) SEM image showing the PS fluorescent nanoparticles with an average radius of 50 nm. (c) Emission spectrum showing the central emission wavelength of the fluorescent nanoparticles located at 600 nm. (d–f) Optical images show the trapping process of a single PS nanoparticle with the biomagnifier. The process consisted of three successive steps: before trapping (d), during trapping (e), and after release (f). g–i Fluorescence images showing the fluorescence spot of the PS nanoparticle before being trapped (g), during trapping (h), and after release (i). j–l Three-dimensional color mapping of the fluorescence spots of the nanoparticle as shown in g–i. m Real-time trace of the position of the trapped nanoparticle in the x and y directions. (n) Trapping potential of the trapped nanoparticle in the x and y directions with parabola fittings. (o) Composite fluorescence images show the movement trace of the trapped nanoparticle in the x–y plane by controlled movement of the biomagnifier. RIGHT: Numerical simulation and calculation. (a–c) Optical intensity distributions of light focusing by a 4-μm biomagnifier fully immersed in water (a), semi-immersed in water (b), and suspended on the surface of a mirror (c). The illumination light source was set as a Gaussian beam with a wavelength of 560 nm. (d–f) Optical intensity distributions of the light spots from the biomagnifier corresponding to (a–c) in the x–z plane. (g) Optical intensity profiles at the focal planes of the output light from the biomagnifiers in the x direction. (h) FEM simulation results for the normalized waist of the light spot w/λ (w is the waist radius of the light spot and λ is the wavelength of the input light) and the ratio D/d (the width of the linear region where light enters the biomagnifier at its front surface is referred to as D, and the width of the output light beam at the rear surface is (d) as a function of the biomagnifier diameter. (i) Simulated intensity distribution of near-infrared trapping light showing that a nanoparticle (radius: 50 nm) is trapped in the gap between the biomagnifier and mirror. The input optical power of the trapping light was set to 10 mW. (j) Simulated optical forces of the nanoparticle trapped in the light spot as a function of the nanoparticle position along the x direction. (k) Calculated trapping potential of the trapped nanoparticle as a function of the position along the x direction. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0168-4 More information: Yuchao Li et al. Single-cell biomagnifier for optical nanoscopes and nanotweezers, Light: Science & Applications (2019). DOI: 10.1038/s41377-019-0168-4 Hamid Pahlevaninezhad et al. Nano-optic endoscope for high-resolution optical coherence tomography in vivo, Nature Photonics (2018). DOI: 10.1038/s41566-018-0224-2 Bo Huang et al. Breaking the Diffraction Barrier: Super-Resolution Imaging of Cells, Cell (2010). DOI: 10.1016/j.cell.2010.12.002 , Cell Scientists therefore investigated simpler optical imaging schemes based on dielectric microspheres to overcome the diffraction limit common to conventional microscopes. While the technique is label-free and feasible, such microspheres are based on artificial inorganic materials such as silicon dioxide (SiO2), titanium dioxide (TiO2) and barium titanate (BaTiO3). Researchers are therefore interested in developing a natural biomaterial to construct a biocompatible device for bioimaging, manipulation and biomagnification at nanoscale spatial resolution. 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 Experimental imaging performance of different biomagnifiers. (a) Schematic diagram showing that the biomagnifier collects the near-field nanostructures from an object and forms a virtually magnified image that can be captured by a conventional optical microscope. (b–e) Optical images of different biomagnifiers constructed from bacterial (b), yeast (c), red blood (d), and stem cells (e) that are partially submerged in cell suspension. f SEM image of a two-dimensional hexagonal close-packed silica nanosphere array assembled by a photopheresis technique. (g–j) Optical images of the silica nanosphere array magnified through biomagnifiers based on bacterial (g), yeast (h), red blood (i), and stem cells (j). (k) SEM image of the surface of a Blu-ray disk grating with a line width of 200 nm and spacing of 100 nm. l–o Optical images of the Blu-ray grating structure magnified through biomagnifiers based on bacterial (l), yeast (m), red blood (n), and stem cells (o). p Intensity profile along the dotted line across the Blu-ray grating structure indicated in o. q Blue dots showing the magnification factor M of the images obtained by the biomagnifiers as a function of the biomagnifier diameter. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0168-4 Optical microscopes and tweezers can image and manipulate objects at the microscale for applications in cellular and molecular biology. The optical resolution is, however, hampered by the diffraction limit and therefore both microscopes and tweezers are unable to image and manipulate nano-objects directly. Emerging techniques in plasmonic/photonic nanoscopes and nanotweezers aim to achieve nanometer-scale resolution, although high-index material structures can easily cause mechanical and photothermal damage to the nanoscale biospecimens. Citation: Seeing smaller through cells: A natural single-cell biomagnifier for subwavelength imaging (2019, July 22) retrieved 18 August 2019 from https://phys.org/news/2019-07-smaller-cells-natural-single-cell-biomagnifier.html Schematic illustration and material characterization. (a) Schematic illustration of the experimental setup. A conventional reflection-mode microscope equipped with a CCD camera and ×100 objective lens was used to observe samples and record images. The inset shown in a PC screen schematically depicting how the biomagnifier is used to magnify and image the subcellular structures inside a bio sample. (b) SEM image of the fiber tip with a diameter of 1.0 μm at its tapered end. (c) SEM image showing yeast cell-based biomagnifiers with smooth surfaces and spherical shapes. d-f Dark-field images showing 644-nm red light (d), 532-nm green light (e), and 473-nm blue light (f) transmitting through the biomagnifier and being focused into subwavelength light spots with waist radii of 370, 300, and 270 nm, respectively. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0168-4 MEMS-in-the-lens architecture for laser scanning microscopy To investigate the applications of biomagnifiers, Li et al. imaged human epithelial cells as imaging targets by growing epithelial cells on a mirror substrate for enhanced light-matter interactions via the interference of the illumination light and reflection light. While it was difficult to distinguish the fibrous cytoskeleton and bilayer structures under a conventional optical microscope, after positioning a biomagnifier on top of the epithelial cells the scientists were able to resolve both structures. To improve the imaging field of view (FOV), they trapped the biomagnifier on a fiber tip and moved it to scan the samples. For example, Li et al. used the setup to scan nanopatterned letters that stood for an acronym of Jinan University—JNU, which they first created on silicon using electron-beam lithography. In a recent study now published on Light: Science & Applications, Yuchao Li and colleagues at the Institute of Nanophotonics in China, developed an optical microscope system using living cells as tiny lenses to image and manipulate objects smaller than the wavelength of light. They showed sub-diffraction-limit imaging and manipulation of nano-objects with a non-invasive device, which they constructed by trapping a cell on a fiber tip. The trapped cell formed a biomagnifier that could magnify nanostructures with a resolution of 100 nm, under white light microscopy. Using the biomagnifier, Li et al. formed a nano-optical trap to precisely manipulate an individual nanoparticle with a 50 nm radius. The technique provides a high-precision tool for optical imaging, sensing and assembly of bio-nanomaterials without mechanical or photothermal damage. Optical imaging to manipulate small objects is crucial for medical diagnosis, biological sensing, cellular exploration, molecular training and materials assembly. Tweezers and microscopes are standard devices for noncontact imaging and manipulation of minute samples ranging from a few nanometers to several microns. Nevertheless, it is challenging to use the technology to image at the nanoscale, since optical resolution is restricted to approximately half the illumination wavelength. Scientists have achieved dramatic progress of near-field nanoscopes and nanotweezers in the past few decades to achieve optical imaging at nanometer resolution. These imaging techniques were withheld by high-index inorganic materials such as noble metals and semiconductors used for their fabrication—that can mechanically damage samples of biological cells or tissue during near-field imaging and manipulation. During experimental imaging, the scientists positioned a semi-submerged biomagnifier on top of a test sample and collected the underlying near-field information from the sample, to form a virtual image as detected by an optical microscope. Li et al. prepared a variety of biomagnifiers using diverse cells including bacteria, yeast, red blood cells and stem cells. For the first imaging sample, they used a two-dimensional hexagonal silica nanosphere array with a 200 nm diameter on a glass substrate using a photophoretic technique. Only nanospheres with biomagnifiers on top of them could be resolved during imaging, whereas nanospheres without biomagnifiers could not be resolved using a conventional microscope. The magnification factor M of the stem-cell based biomagnifiers was determined to be 3.3 times larger (x3.3), and the scientists showed the experimental M depended on the biomagnifier’s diameter. Subsequently, Li et al. performed all experiments using biomagnifiers of this diameter. Li et al. selected biological cells to replace microspheres since cells are both abundant and biocompatible in contact with biological systems. For instance, scientists can use living cells to manipulate light in biological environments and act as optofluidic microlenses, optical probes and even incorporate E.coli as biophotonic waveguides. In the present work, Li et al. enhanced the index contrast of living cells by using a spherical shape semi-immersed in a medium to achieve focusing at the sub-wavelength. The scientists captured biological images using the subdiffraction light spot to illuminate targeted samples along with white-light microscopy. The nano-sized light spot exerted a strong optical gradient force to trap and manipulate a single nanoparticle enabling the biomagnifier to also function as an optical nanotweezer.The scientists conducted all experiments under a reflection-mode optical microscope coupled to a charge-coupled device (CCD) camera and objective lens. They used light sources at 390 nm, 560 nm and 808 nm for excitation, illumination and trapping respectively. Using an optical fiber with a tapered tip, Li et al. trapped the biomagnifier at the end of the fiber, which they controlled by moving the tip using a micromanipulator. Li et al. selected smooth and spherical cells to minimize image aberration and noted the cells to exhibit better focusing performance when semi-immersed in solution to maintain cell viability. Thereafter, when they simultaneously irradiated near infrared (IR) and UV laser beams on the biomagnifier through an objective lens, they could trap and excite the nanoparticles. For these experiments, the scientists used fluorescent nanoparticles with a 50 nm average radius. When they trapped a single nanoparticle in the focus of a biomagnifier, they observed both optical and fluorescent images of the sample of interest. Li et al. then calculated the trapping stiffness of the particle in real-time using standard optical tweezers. The ability to manipulate a single nanoparticle without contact and precisely via optics will be useful to assemble well-regulated nanostructures. When Li et al. numerically investigated the imaging mechanism and trapping stiffness of biomagnifiers using 3-D simulation and COMSOL software. They observed the subdiffraction-limit light focusing ability resulted from a combined “photonic nanojet” effect and coherent interference enhancement by the mirror.Limitations of the method included imaging aberration and distortion due to the inhomogeneous intracellular structures of the natural biomagnifier, compared to dielectric microspheres with uniform refractive indices. Fortunately, intracellular materials were optically transparent to visible and near-infrared light and the optical interactions were relatively weak inside a single cell. Intracellular activities could also change the partial refractive index distribution in a cell to cause light distortion during trapping and imaging, but most intracellular activities were ultrafast and did not influence the imaging scheme.In this way, Yuchao Li and colleagues developed a new experimental imaging technique and verified the experimental capabilities with FEM simulations. Li et al. integrated optical nanoscopes and nanotweezers in a single device to image and manipulate nanostructures simultaneously for the first time in the present work. They promoted the resolution of the technique to 100 nm and proposed a label-free imaging procedure. The scientists envision the living biomagnifier to open new opportunities in super-resolution imaging, real-time sensing and precise nano-assembly of bionanomaterials to form nanoarchitectures of interest. (a) Schematic illustration of the experimental setup. A conventional reflection-mode microscope equipped with a CCD camera and ×100 objective lens was used to observe samples and record images. The inset shown in a PC screen schematically depicting how the biomagnifier is used to magnify and image the subcellular structures inside a bio sample. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0168-4 , Nature Photonics © 2019 Science X Network Journal information: Light: Science & Applications Nano-optical imaging of subcellular structures and nanopatterned letters. (a, b) Optical images of the subcellular structures of a human epithelial cell using a conventional optical microscope (a) and biomagnifiers (b). The positions of four biomagnifiers are marked as A–D. For comparison, the biomagnifiers can resolve the fibrous cytoskeleton (indicated as A–C) inside the cell and two-layer structures (indicated as D) on the cell membrane, which are indistinguishable by the conventional microscope. c–e SEM (c), dark-field (d), and optical images (e) of nanopatterned letters JNU representing the acronym of Jinan University. The line width of the nanopatterned letters is 100 nm, which is smaller than the diffraction-limit resolution of the conventional optical microscope. f–h Optical images showing that the biomagnifier trapped on the fiber tip can scan and image the nanopatterned letters J (f), N (g), and U (h) by moving the fiber. The line width of the nanopatterned letters was magnified from 100 to 400 nm. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0168-4last_img read more

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For culture vultures

first_imgBefore the new year sets in, brush up on your knowledge of modern Indian art. Head to this exhibition of paintings by Gopal Ghose whose works have even been appreciated by Jawaharlal Nehru. His sketches of the infamous man-made famine of 1943 received a lot of appreciation. The exhibition has been brought to the Capital by Calcutta-based gallery Akar Prakar. DETAILAt: National Gallery of Modern Art, Jaipur House, India GateOn Till: 19 JanuaryDRAMA OF RELATIONSHIPS Also Read – ‘Playing Jojo was emotionally exhausting’Or take a look at the bold works of Puja Kshatriya. Her solo visual art exhibition Pause & Play is about an interplay of monochromatic figures, emphasising the dual nature and complexities of relationships. Headless figures, amputated or shifted limbs add an element of surrealism and the deconstruction.. DETAILAt: Artspeaks India, 5 Kehar Singh Estate, Lane No. 2, Westend Marg, Said-ul-ajabOn Till: 25 JanuaryTimings: 11am to 7 pmACTING IT UP The Capital is abuzz with plans and preparations for new year’s eve. In case your calendar is still not set, and if you happen to be a theatre enthusiast, get ser for some ‘emotional drama’. The play Ghera, directed by Swaroopa Ghosh, is presented by second year students of the SRC acting course. The story is an adaptation of Bertolt Brecht’s The Caucasian Chalk Circle. The play is a parable about a peasant girl who rescues a baby. DETAILAt: Shri Ram Centre, Mandi House On Till: 1 January Timings: 6.30 pmSOME MUSIC FOR YOUR EARSHowever, if you are more of a wild party person, drive towards the Qutab Minar area. Dance the night away with female DJ duo Electroverts.DETAILAt: Blue frog, The Kila, Seven Style Mile, Mehrauli Timings: 10.30 pm to 1.30 am Entry: Rs 6,000 per headlast_img read more

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Three city joints in Asias best restaurants list

first_imgThree of the capital’s tony eateries are among a list of 101 Best Restaurants in Asia 2013.Varq at The Taj Mahal Hotel that serves Indian cuisine was ranked at number six and ITC Maurya’s Bukhara, frequented for its delectable north Indian cuisine, was at number 24.The Taj Palace Hotel’s Orient Express, which specialises in French cuisine, was ranked at 55.The other Indian restaurants which made it to the list include Indigo in Mumbai and Karavalli in Bangalore. The former serves modern European cuisine and the latter serves Indian cuisine.The restaurants have been judged on the basis of cuisine, style, decor, service, value and don’t miss categories by the panelists of 101 Best Restaurants in Asia 2013, which was conducted by New York-based food website The Daily Meal.last_img read more

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Sebi bans 7 individuals from market in LGS Global case

first_imgSebi has barred seven individuals from the capital market for six years after finding them guilty of manipulating trading in the shares of LGS Global over a period of three years beginning 2008. After noticing irregularities, Sebi had initiated a probe into trading in certain scrips, including LGS, during the years 2008, 2009 and 2010.An analysis found that prima facie certain entities had indulged in creating artificial volume by trading in a synchronised manner carrying out off-market transfers among themselves for the purpose of meeting settlement obligations of another and in turn contributing to the price rise. Also Read – I-T issues 17-point checklist to trace unaccounted DeMO cashRelated to the case, Sebi had passed an interim order in February 2011, restraining 39 persons/entities from accessing the securities market. Sebi, in an order issued late yesterday, imposed a 6-year ban on seven individuals — Bhavesh Pabari, Bipin Jayant Thaker, Prem Mohanlal Parikh, Hemant Madhusudan Seth, Mala Hemant Seth, Ankit Sanchaniya and Bharat Shantilal Thakkar — from the securities market. The period of prohibition already undergone by them, pursuant to the interim order issued in February 2011, would be taken into account for computing the ban period.  Also Read – Lanka launches ambitious tourism programme to woo Indian tourists“It is clarified that the restraint/prohibition imposed on the noticees shall run concurrently with the restraint/ prohibition imposed by Sebi vide order dated May 13, 2015 in the matter of dealings in the shares of Goldstone Technologies Ltd,” the regulator said.The notices in the present proceedings have already been restrained by Sebi, through an order in May 2015 in the matter related shares of Goldstone Technologies, from accessing the securities market. In a separate order yesterday, the regulator banned 239 entities for making illegal gains of Rs 614 crore through manipulation of shares of four companies listed on the BSE’s SME trading platform. Sebi’s clamp down follows irregularities witnessed in the scrips of four companies — Eco Friendly Food Processing Park, Esteem Bio Organic Food Processing, Channel Nine Entertainment and HPC Biosciences. The four companies as well as 235 other entities, including many individuals, have been banned from the securities market.Clears Catholic Syrian Bank’s Rs400-cr IPO planNew Delhi: Catholic Syrian Bank has received capital market regulator Sebi’s approval to raise up to Rs 400 crore through an initial public offer (IPO). With this, the number of firms that have got Sebi nod for an IPO since the beginning of the year has gone up to 21. The company in March had filed its draft red herring prospectus (DRHP) with Sebi through its lead merchant banker, ICICI Securities. Sebi issued its final observations on the draft offer documents on June 23, which is necessary for any company to launch a public offer. “The bank will issue equity shares aggregating up to Rs 4,000 million,” the draft papers stated.last_img read more

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