Citation: High reliability of flexible organic transistor memory looks promising for future electronics (2010, July 8) retrieved 18 August 2019 from https://phys.org/news/2010-07-high-reliability-flexible-transistor-memory.html More information: Soo-Jin Kim and Jang-Sik Lee. “Flexible Organic Transistor Memory Devices.” Nano Letters. DOI: 10.102/nl1009662 . Contact information: jangsik[at]kookmin.ac.kr (Left) A photograph of the 3 x 3 cm2 flexible organic memory devices. (Right) A diagram of the memory device architecture. Image credit: Soo-Jin Kim and Jang-Sik Lee. Explore further Engineers Jang-Sik Lee and Soo-Jin Kim from Kookmin University in Seoul, Korea, have published the details of the flexible organic transistor memory in a recent issue of Nano Letters. “The advancement in this memory device is the improved reliability and stability,” Lee told PhysOrg.com. “Actually, organic electronic devices suffer from the severe degradation in terms of device performance according to the operation time. Here, we demonstrated the improved data retention and endurance capability by optimizing the memory device structures. In addition, the flexible memory devices are found to be very stable in repeated bending cycles, confirming the good mechanical stability.”As the researchers demonstrated in their study, the memory device can offer controllable threshold voltage for writing and erasing information, storage times of more than a year, and reliability after hundreds of repeated programming/erasing cycles, as well as good flexibility that could endure more than 1,000 repeated bending cycles. Plus, all the fabrication processes could be carried out at low temperatures, enabling lower manufacturing costs.To design the memory, the researchers took advantage of existing organic transistor devices, which already offer excellent performance. By embedding gold nanoparticles (as charge-trapping elements) and dielectric layers (as charge tunneling and blocking elements) into organic thin-film transistors, the researchers created organic memory devices with similar electrical and mechanical properties as the transistors. The resulting organic transistor-based memory was synthesized on a flexible substrate of about 3 x 3 cm2.As the researchers explained in more detail, the programming and erasing operations were performed by applying a positive or negative 90-volt pulse for one second to the bottom-gate electrode. For writing information, a negative voltage was applied, which caused charge carriers to tunnel through a 10-nm-thick tunneling layer to reach the gold nanoparticles in the gate dielectric layer. In the charge-trapping layer, each nanoparticle trapped 4-5 holes, which the researchers defined as written states. The written states could be erased by applying a positive voltage that caused the gold nanoparticles to eject the holes. A reading voltage of -8 volts could be applied to measure and read the drain current. The engineers showed that these programming, reading, and erasing operations could be carried out repeatedly with less degradation compared to other memory devices. “The flexible memory devices that have previously been reported are based on resistive switching memory devices,” Lee said. “In that case, we need additional active components (for example, a diode or transistor) to operate the resistive switching memory elements. The memory devices developed in this study are based on the field-effect transistors, and memory elements are embedded in the gate dielectric layers of organic transistors. So the program/erase operations can be controlled by the transistor operations. This is a great advantage in terms of device scaling and circuit design since the structure is similar to the conventional flash memory devices. So we can use the state-of-the-art flash memory technology to design and fabricate the integrated flexible memory devices.” Currently, the researchers are working on further enhancing the memory properties of these organic transistor-based memory devices, such as by decreasing the operating voltage. In addition, since most of the device is transparent except for the electrodes, the researchers hope to incorporate transparent electrodes to create a fully transparent, flexible memory device. “The flexible organic memory devices can be applied to wearable/stretchable/foldable electronic devices,” Lee said. “In addition, there is almost no limit in substrate materials and geometry, so the integration of memory devices onto unconventional substrates is possible. Finally, we think the memory devices can be adopted in see-through displays and head-up displays in the near future.”• Learn about becoming PhysOrg.com sponsor 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. (PhysOrg.com) — With the constant demand for high-performance nonvolatile memory devices, researchers continue to develop better memories – ones with low power consumption, good reliability, and low manufacturing costs. In a recent study, engineers from Korea have demonstrated a flexible memory based on an organic transistor, which they say could be easily and cheaply integrated, along with transistors and logic circuits, into flexible electronic devices. Organic flash memory developed 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.
Scientists have known for almost twenty years that some species of sponge are carnivorous; instead of absorbing organic material in ocean water like other sponges, they actually catch their prey and then use chemicals to break them down. It wasn’t known if Chondrocladia lyra, discovered by geologists exploring deep water off the coast of California, was a meat eater or not, due to the depths at which it lives – almost two miles down. In this new research, the harp sponge, as it’s been nicknamed due to its physical similarity to the musical instrument, has been found to be not only carnivorous but able to mate via sperm package delivery. Citation: Researchers document new species of carnivorous sponge (w/ Video) (2012, November 12) retrieved 18 August 2019 from https://phys.org/news/2012-11-document-species-carnivorous-sponge-video.html Sea sponges busted by researchers © 2012 Phys.org The researchers studied the sponge using deep sea vehicles and in so doing found that they look like multi-vaned harps, each with balls on the top ends of its “strings.” The strings have Velcro-like hooks for catching invertebrate prey. Captured prey is channeled to an enclosure where it is covered in chemicals that break it down for absorption. But the balls also serve another purpose; each contains packets of spermatophores that are released into the surrounding water where they are carried to other sponges by currents. Other sponges are fertilized when they capture them.The researchers also found that the harp sponge are anchored to the sea floor by what are known as rhizoids, which resemble a root system and that the number of vanes individual specimens can have, vary from sponge to sponge, ranging from 1 to 6. They noted too that once a sponge is fertilized, eggs that sit at the midpoint of the strings between the base and balls swell up as new sponges develop.The researchers theorize that the harp sponge developed its elaborate structure as a means of maximizing surface area to allow for catching the most possible prey. Journal information: Invertebrate Biology Credit: MBARI More information: Lee, W. L., Reiswig, H. M., Austin, W. C. and Lundsten, L. (2012), An extraordinary new carnivorous sponge, Chondrocladia lyra, in the new subgenus Symmetrocladia (Demospongiae, Cladorhizidae), from off of northern California, USA. Invertebrate Biology. doi: 10.1111/ivb.12001AbstractChondrocladia (Symmetrocladia) lyra subgen. nov., sp. nov., is described from northeast Pacific sites at Escanaba Ridge and Monterey Canyon at depths of 3316–3399 m. Two retrieved specimens are described in detail, while variations are described in ten photographed or videotaped specimens. The basic structure, termed a vane, is harp- or lyre-shaped. From 1 to 6 vanes extend by radial growth from the organism’s center. The orientation among the vanes is approximately equiangular, such that together they display pentaradiate, tetraradiate, triradiate, or biradiate symmetries. Each vane is formed by a horizontal stolon supporting a series of upright, equidistantly spaced branches each of which terminates at its apex in a swollen ball in all observed specimens except the paratype. Swellings occur midway along the branches in the holotype, but not in the paratype. A linear row of filaments project from the sides, front, and back of each branch, and also from the tops of each stolon. The terminal balls are the sites of spermatophore production and release; mid-branch swellings are sites of oocyte maturation. The two megasclere spicule types have specific distributions; styles support rhizoids, stolons, and branches, while subtylostyles support filaments and terminal balls. Anchorate isochelae cover all surfaces. Enclosed crustacean prey on branches and stolons provide direct evidence of carnivory. The structure of the vanes maximizes surface area for passive suspension feeding. Increased surface area could also maximize spermatophore capture, with the sigmas projecting from the spermatophore surface being caught by projecting isochelae on filaments. Swellings on filaments are snared spermatophores, firmly fused to recipient tissues and undergoing destruction. Spermatophores on filaments are present in branch swellings containing early and mature oocytes. Oogenesis and maturation occur only in proximity to branch swellings, suggesting that development is induced by spermatophore reception. Symmetrical development of uniserial branched stolons (the vanes) characterized members of the new subgenus Symmetrocladia. 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)—Researchers working with a team from the Monterey Bay Aquarium Research Institute have confirmed that a species of sponge first spotted off the coast of California in 2000 by a team of geologists, is indeed new. They describe their work in studying the sponge – Chondrocladia lyra – in their paper published in the journal Invertebrate Biology. Explore further
Multifunction mirror. This metamaterial mirror reflects light with the resonant frequency at an angle determined by the placement of antenna-like omega inclusions of various designs. The blue beam strikes the mirror at a right angle but is reflected at 45 degrees. For the red beam, which has a different frequency, the metamirror is transparent. Credit: V. Asadchy/Aalto Univ/ Physics Magnetic mirrors enable new technologies by reflecting light in uncanny ways Normal mirrors reflect light back at an equal but opposite angle, which works well for some purposes. Over the past several years, scientists have discovered that applying metamaterials to the surface of a regular mirror allows for manipulating the reflective angle. In this new effort, the researchers have found that metamaterials could be used both for manipulating certain frequencies and for reflecting purposes while at the same time allowing other frequencies of light to pass through unchanged. With such a mirror it would be possible, for example, to make a mirror/window that allows normal and infrared light through, but not ultraviolet.In their work, the researchers found that embedding tiny copper wires (which they call inclusions) inside of a clear material that normally allowed microwaves to pass through allowed them to create a mirror that could be used to reflect microwaves in ways they chose while also allowing light and other radiation to pass through unchanged. By manipulating the size and shape of the inclusion, the researchers could choose the frequency they wanted to impact and the reflection angle. The technique works, they explain because the microwaves cause the tiny wires to oscillate at the same frequency as the original microwaves, but only for a very short time—they are very soon released at the same frequency, but travel in a different direction. The team also created a metamirror that was capable of focusing all of the microwaves to a single point, as is normally done with a parabolic receiver.The team reports that computer simulations showed that the technique could be used to reflect incoming radiation back in virtually any direction and note that such mirrors could find a variety of uses, such as single panels that perform multiple duties, e.g. serving as both a solar collector and radio wave receiver, or a single panel that could route different radio waves from space to different receivers, saving on costs. (Phys.org)—A small team of researchers working at Aalto University in Finland has discovered a way to create “metamirrors” capable of acting on a single radiating frequency while allowing others to pass through. In their paper published in the journal Physical Review Letters, the researchers describe how they embedded metamaterials in certain other materials allowing for the creation of metamirrors with interesting properties. Journal information: Physical Review Letters This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Explore further Citation: Metamaterials used to make metamirrors capable of reflecting one frequency and ignoring all others (2015, March 11) retrieved 18 August 2019 from https://phys.org/news/2015-03-metamaterials-metamirrors-capable-frequency.html © 2015 Phys.org More information: Functional Metamirrors Using Bianisotropic Elements, Phys. Rev. Lett. 114, 095503 – Published 6 March 2015, dx.doi.org/10.1103/PhysRevLett.114.095503 ABSTRACTConventional mirrors obey the simple reflection law that a plane wave is reflected as a plane wave, at the same angle. To engineer spatial distributions of fields reflected from a mirror, one can either shape the reflector or position some phase-correcting elements on top of a mirror surface. Here we show, both theoretically and experimentally, that full-power reflection with general control over the reflected wave phase is possible with a single-layer array of deeply subwavelength inclusions. These proposed artificial surfaces, metamirrors, provide various functions of shaped or nonuniform reflectors without utilizing any mirror. This can be achieved only if the forward and backward scattering of the inclusions in the array can be engineered independently, and we prove that it is possible using electrically and magnetically polarizable inclusions. The proposed subwavelength inclusions possess desired reflecting properties at the operational frequency band, while at other frequencies the array is practically transparent. The metamirror concept leads to a variety of applications over the entire electromagnetic spectrum, such as optically transparent focusing antennas for satellites, multifrequency reflector antennas for radio astronomy, low-profile conformal antennas for telecommunications, and nanoreflectarray antennas for integrated optics.
Carbon features in the COS spectrum of Y453. Image credit: Dixon et al., 2017. Researchers investigate chemical composition of globular cluster NGC 6362 More information: arxiv.org/pdf/1708.01315.pdf Explore further Citation: Astronomers reveal insights into the nature of a distant ultraviolet-bright star (2017, August 14) retrieved 18 August 2019 from https://phys.org/news/2017-08-astronomers-reveal-insights-nature-distant.html © 2017 Phys.org A team of astronomers led by William Dixon of the Space Telescope Science Institute in Baltimore, Maryland, has presented new spectral analysis of the ultraviolet-bright star Y453. The study, presented Aug. 3 in a paper published on arXiv.org, reveals insights about the star’s physical parameters, chemical composition and its evolution. Y453 is part of the globular cluster Messier 4, or M4 (also known as NGC 6121) located about 7,200 light years away from the Earth. The enigmatic ultraviolet-bright stars like Y453 are evolving objects, either from the asymptotic giant branch (AGB) or directly from the extreme horizontal branch (EHB), onto the white-dwarf cooling curve. Therefore, stellar parameters and photospheric abundances of such stars could improve our knowledge about low-mass stellar evolution and white-dwarf formation.In order to better understand Y453 and ultraviolet-bright stars in general, Dixon’s team has observed this star with the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST). The observations, carried out on February 9, 2015, allowed the researchers to obtain important information about Y453.”We have performed a spectral analysis of the UV-bright star Y453 in M4,” the authors wrote in the paper. The team acquired crucial information about Y453’s mass, radius, luminosity, effective temperature and photospheric abundances. They compared these parameters with new evolutionary models, and the star’s abundances with the cluster values.According to the study, Y453 has an effective temperature of 71,675 K, which proves that the star is much hotter than previously thought. Initial optical observations showed that it has an effective temperature of about 56,000 K. The spectral analysis reveals that Y453 has a mass of approximately 0.53 solar masses, a radius of just 0.17 solar radii, and a luminosity (log luminosity of Y453/solar luminosity) of 2.84. These values are consistent with the values expected of an evolved star in a globular cluster.”We scale the model to match the star’s optical and near-infrared magnitudes and derive a stellar mass and luminosity that are consistent with the values expected of an evolved star in M4,” the paper reads.The values derived by researchers indicate that Y453 most likely evolved from the blue horizontal branch, departing the asymptotic giant branch before third dredge-up. The researchers also measured the star’s photospheric abundances of helium (He), carbon (C), nitrogen (N), oxygen (O), silicon (Si), sulfur (S), titanium (Ti), chromium (Cr), iron (Fe), and nickel (Ni). They found that the abundances of carbon, nitrogen and oxygen are 0.25 dex greater than those of the second-generation red-giant branch (RGB) stars, while the silicon and sulfur abundances match those of the cluster. Moreover, abundances of the iron-peak elements (except for iron itself) are enhanced by 1.0 to 3.0 dex.”It is likely that the observed abundances of Y453 represent the combined effects of multiple diffusion and mechanical processes within the stellar photosphere,” the astronomers concluded. 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 Cataclysmic variables (CVs) are binary star systems comprising of a white dwarf and a normal star companion. They irregularly increase in brightness by a large factor, then drop back down to a quiescent state. Polars are a subclass of cataclysmic variables, distinguished from other CVs by the presence of a very strong magnetic field in their white dwarfs.IGR J19552+0044 was detected in 2006 by the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) space telescope. Subsequent observations of this highly variable X-ray source have shown that it is a magnetic cataclysmic variable. Now, Tovmassian’s team has revealed the results of a new follow-up optical observational campaign, which helped the researchers to obtain further information about this variable object.For their observations, the astronomers employed three telescopes at the National Astronomical Observatory (OAN) in Sierra San Pedro Mártir, Mexico, two Panchromatic Robotic Optical Monitoring and Polarimetry Telescopes (PROMPT) at Cerro Tololo Inter-American Observatory (CTIO) in Chile, and one telescope of South African Astronomical Observatory (SAAO) in South Africa. In the study, the authors also included data obtained by the MDM Observatory on Kitt Peak, Arizona as well as the results provided by the Center for Backyard Astrophysics (CBA), a global network of telescopes observing CVs.This comprehensive observational campaign spanning three years (from June 2011 to July 2014) allowed the team to classify the studied X-ray source correctly.”We conducted follow-up optical observations to identify the sources and periods of variability precisely and to classify this X-ray source correctly,” the paper reads.According to the study, photometric and spectroscopic observations reveal that the white dwarf of IGR J19552+0044 has spin period and binary orbital period of 83.6 and 81.3 minutes, respectively. These discording results indicate that the studied CV is an asynchronous polar. “The system is not an ordinary polar. The photometric period that we identify with the spin period of the magnetic white dwarf is 2.8 percent shorter than the spectroscopic period; we think the latter reflects the orbital period of the system. This is one of the extreme cases of asynchronism,” the researchers wrote in the paper.The study underlines that such rate of asynchronism is among the largest observed in a few similar objects. The scientists are also uncertain about the source of this deviation, however the growing number of found asynchronous polars suggests that such anomaly is not as rare as originally thought. Besides detecting the asynchronism, the authors estimated the magnetic field strength of the white dwarf in this system. They reveal that this value is more likely about 16 MG and not higher than 20 MG. New magnetic cataclysmic variable star discovered Explore further (Phys.org)—An international team of astronomers led by Gagik H. Tovmassian of the National Autonomous University of Mexico (UNAM) has uncovered new details into the nature of a cataclysmic variable known as IGR J19552+0044. New observations reveal that this object is an asynchronous short period polar. The finding was presented October 5 in a paper published online on the arXiv pre-print server. More information: IGR J19552+0044: A new asynchronous short period polar: “Filling the gap between intermediate and ordinary polars”, arXiv:1710.02126 [astro-ph.SR] arxiv.org/abs/1710.02126AbstractBased on XMM—Newton X-ray observations IGR J19552+0044 appears to be either a pre-polar or an asynchronous polar. We conducted follow-up optical observations to identify the sources and periods of variability precisely and to classify this X-ray source correctly. Extensive multicolor photometric and medium- to high-resolution spectroscopy observations were performed and period search codes were applied to sort out the complex variability of the object. We found firm evidence of discording spectroscopic (81.29+/-0.01m) and photometric (83.599+/-0.002m) periods that we ascribe to the white dwarf (WD) spin period and binary orbital period, respectively. This confirms that IGR J19552+0044 is an asynchronous polar. Wavelength-dependent variability and its continuously changing shape point at a cyclotron emission from a magnetic WD with a relatively low magnetic field below 20 MG. The difference between the WD spin period and the binary orbital period proves that IGR J19552+0044 is a polar with the largest known degree of asynchronism (0.97 or 3%). Power spectra multiband photometry of IGR 1955+0044. The solid lines are powers after clean procedure is applied to powers presented as dotted lines. The bluish curves are for the V band, the red are for the I band, and the green are for the WL light curves. Credit: Tovmassian et al., 2017. Citation: Astronomers identify new asynchronous short period polar (2017, October 16) retrieved 18 August 2019 from https://phys.org/news/2017-10-astronomers-asynchronous-short-period-polar.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.
Malda (WB): The passengers of DN Bhramhaputra Mail today protested against non-functioning of AC units in some coaches in Malda town station disrupting train services for hours, a GRP official said. The passengers of the Delhi-bound train from Guwahati, which arrived at the Malda town station at about 4 am, pulled the chain when it was leaving the platform. They alleged that no action had been taken even after their complaints at Siliguri and Malda railway stations, GRP Inspector-in-charge of Malda town station Partha Chanda said. After partial repair of AC units, the passengers boarded the train which resumed journey at about 8 am, he said. Train services were disrupted in the section for hours following the incident, he said.
Kolkata: Abhay Singh, the head of the Anti-Corruption Branch in Kolkata of the Central Bureau of Investigation (CBI), has been transferred to Ranchi. He was looking into the probe of the Narada sting operation.Sources said an officer from Delhi will be posted in his position in Kolkata. Singh, who had been looking into the probe of the Narada sting operation, will be taking charge of the CBI’s Ranchi office.It may be mentioned that the Special Director of CBI, Rakesh Asthana, visited Kolkata on Wednesday and he held a meeting with all senior officers of the agency, including the investigating officers of all the ongoing cases.He held the meeting at Nizam Palace.He had directed the officers to take necessary steps to expedite the process of all the ongoing cases and to file the final chargesheets by the end of 2018.Asthana had also taken stock of the ongoing cases that include the Saradha Group scam, Narada sting operation and Rose Valley Group’s case.
Online food ordering platform Foodpanda on Tuesday said it has partnered with Indian Railway Catering and Tourism Corporation (IRCTC) to allow passengers order food from restaurants during their train journeys. IRCTC is a subsidiary of the Indian Railways that handles catering, tourism and online ticketing operations. A pilot of the proposed association will be launched at the New Delhi Railway station, Foodpanda said in a statement, without disclosing the timeline. After Delhi, the service will be extended to more cities like Mumbai, Bengaluru, Pune and Chennai in due course of time, it added.