Krishak League vice president joins BNP

first_imgFarroque Alam Sarker, central vice president of Krishak League joined BNP on Wednesday. Photo: CollectedKrishak League central committee vice president Farroque Alam Sarker on Wednesday joined BNP ahead of the 11th Parliamentary elections, reports UNB.Hailing from Gaibandha-5 constituency, Farroque formally joined BNP by presenting a bouquet to party secretary general Mirza Fakhrul Islam Alamgir around 7:00pm at BNP chairperson’s Gulshan office, said a press release.Farroque also bought party’s nomination paper from Gaibandha-5 constituency.More than one hundred leaders-activists of ruling party student wing Bangladesh Chhatra League and Juba League also joined BNP with Farroque, said Gaibandha district unit BNP president Syed Moinul Hasan Sadik.BNP’s Rangpur divisional organising secretary Asadu Habib Dulu, and general secretary Mahmud Nabi Tutul were, among others, present on the occasion.last_img read more

Police Close 2 Violent Crime Cases in 2 Days

first_imgOver a span of two days D.C. police made arrests in a February shooting and a September stabbing that helped close two violent crime cases.On March 17, authorities said they arrested Delonte Mack, 29, Southwest, for suspected involvement in a Southwest shooting that happened on Feb. 25.Last month, a officer was patrolling in the Unit Block of N Street, SW when the officer heard the sound of gunshots nearby, police reported.Officials said the officer found a man lying out front of a restaurant on N Street, SW suffering from several gunshot injuries.The victim had been struck by gunfire in his buttocks, groin, foot and shoulder. The victim was taken to a local hospital and treated for his injuries.Mack was arrested and charged with assault with intent to kill while armed. Mack is scheduled to appear in court for a preliminary hearing on March 31, D.C. Courts said.On March 15, police made an arrest in a September stabbing that happened in the 5000 block of Bass Place, SE, police said.Authorities arrested Jeffrey Saunders, 31, and charged him with assault with intent to kill in the stabbing of a man on Sept. 27.Police said they found a man suffering from multiple stab wounds in the hallway of a Southeast apartment building around 2:55 a.m.A witness said he heard a woman screaming and came out into the hallway to see the victim on the floor face down bleeding from his injuries, police reported. The victim was taken to a local hospital and was treated for life threatening injuries.On Jan. 13, Chiquita Harris, 30, a resident of Southeast D.C., was arrested and charged with intent to kill in connection with the stabbing.A spokesperson for the department Alaina Gertz told the AFRO March 20 that the motives for both cases are unknown.last_img read more

Hybrid nanostructure with extreme light absorption looks promising for photovoltaics

first_img © 2013 Phys.org. All rights reserved. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. More information: Sander A. Mann and Erik C. Garnett. “Extreme Light Absorption in Thin Semiconductor Films Wrapped around Metal Nanowires.” Nano Letters. DOI: 10.1021/nl401179h The core-shell hybrid nanowire consists of a metal core wrapped with semiconductor thin films. Three different resonances excited at different wavelengths are shown. (b) The fraction of absorbed above-band gap photons in the silicon shell for a wide variety of configurations. Credit: Mann and Garnett. ©2013 American Chemical Society Now, somewhat counterintuitively, scientists have theoretically found that thin semiconductor films wrapped around metal nanowires have substantially better light absorption properties than solid semiconducting nanowires, despite the fact that they use less semiconducting material. At the same time, the metal core acts as a contact to efficiently extract charge carriers. By confronting the semiconductor thickness trade-off and offering exceptional performance, the nanostructures might become ideal building blocks for inexpensive photovoltaic and solar fuel applications.A paper on the new devices by Sander A. Mann and Erik C. Garnett at the Center for Nanophotonics at FOM Institute AMOLF in Amsterdam, The Netherlands, will be published in a future issue of Nano Letters.”The greatest significance to our work is that we provide a design for nanowire building blocks that incorporates both excellent light trapping properties and a local metal electrode contact (for current extraction),” Garnett told Phys.org. “Silver nanowire networks have already been used as high performance transparent electrodes and we expect that by coating them with thin semiconducting shells we will be able to make high-efficiency solar cells using cheap materials. It has now been observed in a number of papers that nanostructuring a material can increase light absorption even while using less semiconductor material. However, this paper takes the next step and starts thinking about how to design such structures with integrated electrical contacts.” One of the biggest advantages of the design is that it uses very thin semiconducting films while at the same time providing very good light absorption. As mentioned, thick semiconductor layers are needed for good light absorption, but high-quality semiconductor is very costly. This new core-shell geometry opens up a pathway to using cheap, abundant, and environmentally friendly semiconductors that previously were of too low quality for good charge extraction.In semiconductor objects smaller than the wavelength of light, as is the case with most nanowires for photovoltaic purposes, the optical properties are determined primarily by resonances. These resonances enhance absorption the most when they are critically coupled: the loss rates due to absorption in the semiconductor and due to radiative leakage (light escaping the nanowire before being absorbed) are equal. This is often the case near the band gap of the material, where absorption is weak, which leads to the highly counterintuitive result that absorption in the nanowire actually increases when the absorption coefficient decreases.As the scientists explain, in the core-shell geometry, extreme light absorption arises from increasing the number and strength of these resonances. Whereas in horizontal nanowires resonances are always spectrally separated (at different wavelengths), in the core-shell geometry they can overlap. Furthermore, horizontal solid seminconductor nanowires are very polarization-sensitive, but this is undesirable as light from the sun is unpolarized. The core-shell geometry gets rid of this polarization dependence by aligning resonances in both polarizations simultaneously.Overall, by demonstrating that excellent light absorption can be achieved in very thin semiconductor layers, this hybrid nanostructure offers an exciting new path toward realizing inexpensive solar technologies based on abundant and environmentally friendly semiconductors. The researchers plan to fabricate prototypes of the devices soon.”Our immediate plans are to make both single-nanowire and array solar cells based on these core-shell building blocks to verify our calculations experimentally,” Garnett said. Explore furthercenter_img Nanowire solar cells raise efficiency limit (Phys.org) —In photovoltaics, there is generally a trade-off in terms of semiconductor thickness, with thicker semiconductors offering better photon absorption and thinner ones offering higher charge carrier extraction efficiency. In recent years, scientists have begun investigating semiconductor nanowire solar cells, which tackle this tradeoff through morphology-dependent resonances that significantly enhance the absorption compared to a planar film. Journal information: Nano Letters Citation: Hybrid nanostructure with extreme light absorption looks promising for photovoltaics (2013, July 1) retrieved 18 August 2019 from https://phys.org/news/2013-07-hybrid-nanostructure-extreme-absorption-photovoltaics.htmllast_img read more