Despite the abundant natural resources in Guyana and even with the expected production of oil, Guyana’s most important natural resource is its children.This is the view of former Attorney General Anil Nandlall as he distributed school bags and other essentials on behalf of East Berbice Sugar Workers Relief Committee as they prepare former sugar worker’s children for the new school year.“The responsibility of all of us is to ensure that the welfare of our children is always paramount and that whatever we do, we must ensure the advancement of our children’s welfare,” he said.Children of workers who were severed from the Skeldon estate when the factorySome of the children who received school bags and other essential school suppliesclosed its doors in December 2017 were given bags and other essential for the new school year complements of the East Berbice Sugar Workers Relief Committee (EBSWRC).The EBSWRC provided new school bags and other essentials for school to 150 students from the Corriverton, Skeldon and Messiah Primary Schools.Over 2000 workers at the Skeldon Estate were sent home when Government closed that estate.Speaking to the children and their parents at the Corriverton Primary School building, where the presentations were made last Saturday, Nandlall said we are living in a society where we are facing great challenges. Those challenges produce initiatives and organisations like the EBSEWRC.He noted that when the sugar estates were closed and thousands of workers lost their jobs and the future of their families became uncertain.“There children’s lives and future became dismal and out of that came this organisation and many of its kind right across the sugar belt. These organisations came up through the People’s Progressive Party working with other social partners to try to bring some relief to the sugar workers, their families and most importantly the children of the sugar workers,” Nandlall said.Member of Parliament Adrian Anamayah who is also a part of the organisation organised the presentation. He noted that most of the funding came from several Berbicians who nor reside overseas.Anamayah also related that the EBSEWRC has been providing hot meals to children of the severed workers since the start of the year.
Leaders and activists of the Jatiya Oikya Front join the rally in Sylhet on Wednesday. Photo: Anis MahmudJatiya Oikya Front began its maiden rally at the Registry Field in Sylhet to mobilise public support in favour of the alliance’s seven-point demand, including holding the 11th parliamentary polls under a non-party administration, reports UNB.The rally activities started around 2pm on Wednesday with recitation from the holy Quran and holy Gita. Sylhet city mayor Ariful Haque Chowdhury is presiding over the rally.Kamal Hossain will address the rally as the chief guest while BNP secretary general Mirza Fakhrul Islam Alamgir as the main speaker.Sylhet district unit general secretary Abu Kaher Chowdhury Shamim was the first speaker of the rally.It is the first political programme of the new alliance of four parties–BNP, Gano Forum, Jatiya Samajtantrik Dal (JSD-Rob) and Nagorik Oaky– since its formation on 13 October.Before the start of the rally, the senior leaders of the Oikya Front visited the Shrines of Hazrat Shahjalal (R), Shah Paran (R) and the grave of General MAG Osmani, and offered fateha there on Tuesday night and Wednesday morning.Several hundred leaders and activists of the party holding placards, banners and portraits of BNP founder Ziaur Rahman, chairperson Khaleda Zia and acting chairman Tarique Rahman started thronging the rally venue since noon. They chanted various slogans demanding Khaleda’s release from jail.Huge law enforcers have been deployed in the city and around the rally venue to maintain law and order.The Oikya Front’s seven-point demand includes installation of a neutral interim government, dissolution of parliament, reconstitution the election commission, release of all political prisoners, deployment of army and cancellation of the move to use electronic voting machine (EVM) for holding the next polls in fair and acceptable manner.After the Sylhet Rally, Oikya Front is scheduled to hold another such programme at Laldighi Maidan in Chattogram city on 27 October. However, they alliance did not yet get permission for the rally.
X On Thursday’s Houston Matters: Leaders of Houston’s largest school district are weighing whether to freeze teacher salaries. The vote is expected to happen at tonight’s board meeting. We look at the fight for pay at HISD with News 88.7’s Laura Isensee.The buildup of sediment in the San Jacinto River contributed to much of Kingwood’s flooding during Harvey, and work recently begun to dredge about two miles of the river to reduce its potential to flood. It’s the first major flood mitigation project tied directly to Harvey. But is it enough to protect Kingwood?Also this hour: We learn what feminism looks like in a “post-feminist” society. It’s a question University of Houston-Downtown psychology professor Dr. Kristin Anderson explores in her book Modern Misogyny: Anti-Feminism in a Post-Feminist Era.And we learn about a new children’s book written by retired astronaut Clayton Anderson, called A is for Astronaut: Blasting Through the Alphabet.WATCH: Today’s Houston Matters 360-Degree Facebook Live Video.We offer a free podcast here, on iTunes, Stitcher and other podcasting apps. This article is part of the Houston Matters podcast Share 00:00 /50:37 To embed this piece of audio in your site, please use this code: Listen
, Advanced Materials 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. The work demonstrated the atomic geometry of metallic quantum contacts that could be modulated with light and the ability to reverse switch (on/off, vice versa) their conductance using plasmonic heating. While the atom-by-atom separation of electrodes were clearly observed, they could also adjust the gap size, between the electrodes at sub-angstrom resolution by controlling the intensity of light. Zhang et al. showed that the plasmon can potentially breakthrough the diffraction limit of light to realize nanofocusing, to transfer the plasmon-controlled atomic switch to realize highly integrated nanodevices; opening a new path to engineer nanoelectronic devices. Explore further While generating a nanogap was crucial to fabricate single molecule-based devices, engineering an adjustable atomic-scale gap has remained a significant challenge. Although fixed gap sizes could not be adjusted post-fabrication, the gap-size could be readily and continuously adjusted through plasmonic heating at sub-angstrom resolution, as shown by Zhang and the research team. For this, they used a commercial light-emitting diode (LED) lamp as a light source in the experiments with an AC adaptor to continuously control the intensity of light. The experimental setup did not require special optical hardware or high power laser sources. They used a commercially available gold wire with a constriction in the middle on a spring steel substrate to construct the nano contacts. Then using a ‘mechanically controllable break junction’ (MCBJ), the scientists stretched the constriction by bending the substrate, and observed it with scanning electron microscopy (SEM) images. Thereafter, the scientists reduced the cross-section of the constriction to form two separate electrodes. When they turned the light on, the conductance increased and decreased when the light was turned off; the large conductance resulting from light illumination strongly reconnected the two separated electrodes.The scientists analyzed the phenomenon at the level of atomic arrangement, upon light illumination. They showed that the nanogaps had strong absorption of light in the visible and near infrared regions due to localized surface plasmon resonances (LSPR). When the frequency of the LED light matched the oscillation frequency of the free electrons and the electromagnetic field at the tip of the electrodes, the LSPR around the gap was excited. The absorbed light then converted to thermal energy causing nanoelectrode expansion and their reconnection. The conductance reached its maximum value when the system was at thermal equilibrium. When the light was shut off, the electrons separated once more. Characterization of MCBJ devices and simulation of expansion distribution of the electrodes upon light illumination. a) System for the measurement of optical spectroscopy. b) Measured dark field scattering spectra from the gap area that employs three different samples. The gap size is ~2 nm in sample A and ~0.2 nm in sample B. The electrodes were strongly reconnected, and no nanogap is observed in sample C. Plasmonic resonances are indicated by the arrows. c) Model used in the simulation. Parts of the large metal wire close to the nanotips were considered. The gap size between two nanotips is initially set to 2 nm. The polarization of the incident light is parallel to the x-axis. d) Expansion distribution (in X component) when equilibrium temperature was established. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0144-z. , Light: Science & Applications Zhang et al. also observed how the nanogap size could be precisely modulated by light by showing that the conductance could be modified in the tunneling region, between the gap of the two electrodes, by controlling the LED light. When the light intensity was fixed, they could keep the tunneling current constant for longer. The scientists estimated the distance between the two electrodes using the Simmons equation; used to describe the relationship between the tunneling current and the tunneling gap size. They could thereby precisely control the distance between the two separated electrodes at sub-angstrom accuracy using the light intensity.To confirm that the origin of switching behavior was plasmon-induced heating in the nanoscale plasmonic systems, the scientists investigated the scattering spectrum of the MCBJ samples to reveal the frequency of plasmonic resonance. The results indicated that the conductance change related to the expansion of the electrodes due to plasmonic heating. Zhang et al. also performed finite element method simulations to estimate the expansion of the electrodes and solved the electric field distribution, temperature distribution and thermal expansion on light illumination, using the COMSOL Multiphysics program package. The simulation calculated the maximum displacement of the electrodes as approximating 0.4 nm. Zhang et al. were able to further optimize the switching frequency by optimizing the characteristic dimensions for heat transfer. In this way, the scientists experimentally proved that atomic switches could be rapidly operated via plasmonic heating. Illumination system with different frequencies. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0144-z Dependence of conductance on the incident light. a) Real-time measurement of the conductance upon the LED light illuminations in the tunneling regime. Vbias = 1 mV. b) Schematic of the gap size variation upon light illumination. The dashed lines indicate the new position of the nanoelectrodes upon LED illumination. c) The conductance of the tunneling gap dependent on the laser polarization. When a p-polarized laser (pink) is employed, the conductance is approximately two times larger than the conductance when an s-polarized laser (orange) is employed. The laser central wavelength is 640 nm with a bandwidth of 5.7 nm, and the maximum laser power density is 0.5 mW/mm2. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0144-z. , Nature Nanotechnology © 2019 Science X Network Current modulated by the light illumination. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0144-z. LEFT: a) A metal wire with a notch in the middle is fixed on the substrate. The notch can be stretched until it finally breaks due to the bending of the substrate, which produces two separated electrodes. b SEM images of the notched microwire during the stretching process. Scale bar: 50 μm. c Real-time measurement of the current with the light switched on/off every 50 s–60 s. Zoomed image: conductance decreases in quantum steps at multiples of G0 (=2e2/h) as the light intensity decreases. d Schematic of the atomic arrangement, which corresponds to four conductance states upon light illumination. State 1: the two electrodes are separated by a few angstroms (G ≪ 1 G0). State 2: the two electrodes are reconnected upon light illumination (G ~ 80 G0). State 3: the two electrodes are stretched, and a gold atom chain is formed before the nanocontact breaks when the light intensity is reduced (G ~ 1 G0). State 4: the two electrodes are separated again due to the heat dissipation as the light is completely turned off (G ≪ 1 G0). RIGHT: Fabricating a nanocontact. a) Setup to roundly cut the metal wire. The metal wire was sandwiched between a knife blade and a supporting platform. The platform can move in the vertical (Z) and parallel (X) directions with a resolution of ~5 μm. b) SEM image of the nanogap after breakage of nanocontact. Scale bar: 5 μm. c) Optical micrograph of the metal wire with a notch in the middle. Scale bar: 50 μm (d) SEM image of the metal wire. Scale bar: 20 μm. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0144-z. In the method developed by Zhang et al. light can be used to control electrical conductance at the junction between gold nano-electrodes by heating electrons at the electrode surface, in a technique known as ‘plasmonic heating.’ They validated the experimental mechanisms using simulations. The research team expanded electrodes via plasmonic heating to close the gap and turn the switch on, paving the way to build single-molecule transistors and nanopore-based biosensors at the nanoscale. Molecular junctions were previously investigated as an approach to build nanoswitches by employing photochromic (light sensitive) molecules that switched between two distinct isoforms. The present work by Zhang et al. contrastingly demonstrated conductance switch behavior only with a bare metallic contact, under light illumination, without any molecules. They demonstrated the conductance of bare metallic quantum contacts as reversible switches across eight orders of magnitude to substantially exceed the performance of the previous molecular switches. The scientists were able to adjust the gap size between the two electrodes after the switch process with sub-angstrom accuracy, by controlling the light intensity or polarization. Illumination system with different frequencies. Credit: Light: Science & Applications, doi: 10.1038/s41377-019-0144-z More information: Weiqiang Zhang et al. Atomic switches of metallic point contacts by plasmonic heating, Light: Science & Applications (2019). DOI: 10.1038/s41377-019-0144-z K. Terabe et al. Quantized conductance atomic switch, Nature (2005). DOI: 10.1038/nature03190 Kasper Moth-Poulsen et al. Molecular electronics with single molecules in solid-state devices, Nature Nanotechnology (2009). DOI: 10.1038/nnano.2009.176 Tsuyoshi Hasegawa et al. Atomic Switch: Atom/Ion Movement Controlled Devices for Beyond Von-Neumann Computers, Advanced Materials (2011). DOI: 10.1002/adma.201102597 Scientists have recently developed a light controlled nano-switch to lay groundwork for atomic device development in nanotechnology. They engineered the switches at the nanoscale in a first step toward fully integrated electronic device miniaturization. The multidisciplinary research was conducted by Weiqiang Zhang and co-workers, and an international team of collaborators. Results of the study are now published in Light: Science & Applications. Journal information: Nature To understand how conductance depended on the light intensity, the scientists performed experiments where the maximum light intensity within each illuminated circle gradually increased. Zhang et al. showed that the maximum conductance in each circle increased approximately linearly with the intensity of light. They obtained repeatable data of the current as a function of the light intensity and showed how the conductance of quantum contact, could be regulated by the intensity of light. In the present study, Zhang et al. used this principle to show how a metallic, atomic scale contact could be operated reliably as a conductance switch through controlled illumination of light. To engineer the metallic atomic-scale contact they precisely stretched a metal nanowire using the mechanically controllable break junction. When they reduced the cross-section of the metal wire to a few nanometers or a few atoms, the diameter became comparable to the Fermi wavelength of the electrons, allowing quantum-mechanical effects to strongly influence the properties of electron transport. Using these principles, Zhang et al. showed how the conductance of an atomic gold contact could be switched from a few quanta of conductance to hundreds of quanta, and vice versa with light illumination. The scientists were able to reversibly switch the metallic quantum contacts between the open and closed state by controlling the light intensity. They created a nanogap between the quantum contacts within which coherent tunneling governed electron transport. In-plane coherent control of plasmon resonances for plasmonic switching and encoding Citation: Atomic switches by plasmonic heating of metallic contact points (2019, April 3) retrieved 18 August 2019 from https://phys.org/news/2019-04-atomic-plasmonic-metallic-contact.html Engineering electronic devices using functional building blocks at the atomic scale is a major driving force in nanotechnology to form key elements in electronic circuits, which were previously miniaturized using mechanical tunneling, bias voltage/current operation and electrochemistry. Previous studies did not, however, address the concept of atomic switches controlled by plasmonic heating. Surface plasmons are coherent delocalized electron oscillations at the interface between two materials that form metallic nanostructures, which can be concentrated into the subwavelength gaps between the materials. In principle, when the resonance frequency of surface plasmons match the frequency of the incident light, the plasmon resonance is excited to produce strong light absorption and substantial plasmonic heating.