12,461 research outputs found
Exchange bias effect in the phase separated Nd_{1-x}Sr_{x}CoO_3 at the spontaneous ferromagnetic/ferrimagnetic interface
We report the new results of exchange bias effect in Nd_{1-x}Sr_{x}CoO_3 for
x = 0.20 and 0.40, where the exchange bias phenomenon is involved with the
ferrimagnetic (FI) state in a spontaneously phase separated system. The
zero-field cooled magnetization exhibits the FI (T_{FI}) and ferromagnetic
(T_C) transitions at ~ 23 and \sim 70 K, respectively for x = 0.20. The
negative horizontal and positive vertical shifts of the magnetic hysteresis
loops are observed when the system is cooled through T_{FI} in presence of a
positive static magnetic field. Training effect is observed for x = 0.20, which
could be interpreted by a spin configurational relaxation model. The
unidirectional shifts of the hysteresis loops as a function of temperature
exhibit the absence of exchange bias above T_{FI} for x = 0.20. The analysis of
the cooling field dependence of exchange bias field and magnetization indicates
that the ferromagnetic (FM) clusters consist of single magnetic domain with
average size around \sim 20 and ~ 40 \AA ~ for x = 0.20 and 0.40, respectively.
The sizes of the FM clusters are close to the percolation threshold for x =
0.20, which grow and coalesce to form the bigger size for x = 0.40 resulting in
a weak exchange bias effect.Comment: 9 pages, 9 figure
TERMITE FAUNA OF KRAKATAU AND ASSOCIATED ISLANDS, SUNDA STRAITS, INDONESIA
Frequent volcanic eruptions, submergence and emergence of some of theIndonesian islands has made them ail object of intense biogeographical significance. These geological catastrophies resulted in complete sterilization of the area biologically, wiping out all forms of life. Subsequent reuegetation and establishment of new fauna attracted many scientists, some of them having made very significant contributions.The present contribution deals with termite fauna of Krakatau and associated islands. In all, twenty five species and 13 genera, the highest number so far reported, from Carita (9 species), Panaitan Islands (6 species), Rahota Besar (2 species), Anak Krakatau and Sertung (1 species each) have been recorded in this publication. Of these, while, Prorhinotermes panaitanensis is new to science, two species (Glyptotermes besarensis and G. panaitanensis) have been described recently by the senior author (MLT). Similarly Glyptotermes minutus, Nasutitermes culasiensis and Hospitalitermes buzpnensis have been recorded for the first time from the Indonesia. Several other species are new distributional records. Nasutitermes matagensis matagensiformisand Schedorhinotermes javanicus are the most successfully colonizedspecies, recorded almost in all the islands under reference.Besides the taxonomic treatment of the fauna, the paper also gives key to genera based on soldier caste
A multi-wavelength access network featuring WiMAX transmission over GPON links
âThis material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder." âCopyright IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.âAn IEEE802.16e compliant PON architecture with wavelength band overlay has been demonstrated. Transparent transmission of mobile-WiMAX RF channels over multi-wavelength GPON links, based on FDM, has demonstrated at remote receivers standard WiMAX EVM figures with 1E-11 GPON bit-error-rates
Optical frequency tripling with improved suppression and sideband selection
Journal Article, Impact factor:3.749A novel optical dispersion tolerant millimetre-wave radio-over-fibre system using optical frequency tripling technique with enhanced and selectable sideband suppression is demonstrated. The implementation utilises cascaded optical modulators to achieve either an optical single sideband (OSSB) or double sideband-suppressed carrier (DSB-SC) signal with high sideband suppression. Our analysis and simulation results indicate that the achievable suppression ratio of this configuration is only limited by other system factors such as optical noise and drifting of the operational conditions. The OSSB transmission system performance is assessed experimentally by the transport of 4 WiMax channels modulating a 10 GHz optical upconverted RF carrier as well as for optical frequency doubling and tripling. The 10 GHz and tripled carrier at 30 GHz are dispersion tolerant resulting both in an average relative constellation error (RCE) of -28.7 dB after 40 km of fibre. (C)2011 Optical Society of AmericaFundação para a CiĂȘncia e Tecnologi
Cannabinoid signalling in TNF-alpha induced IL-8 release
Original article can be found at: http://www.sciencedirect.com/science/journal/00142999 Copyright Elsevier B.V. DOI : 10.1016/j.ejphar.2006.04.015Peer reviewe
A Search for Blues Brothers: X-ray Crystallographic/Spectroscopic Characterization of the Tetraarylbenzidine Cation Radical as a Product of Aging of Solid Magic Blue
Magic blue (MB+Ë SbCl6â salt), i.e. tris-4-bromophenylamminium cation radical, is a routinely employed one-electron oxidant that slowly decomposes in the solid state upon storage to form so called âblues brothersâ, which often complicate the quantitative analyses of the oxidation processes. Herein, we disclose the identity of the main âblues brotherâ as the cation radical and dication of tetrakis-(4-bromophenyl)benzidine (TAB) by a combined DFT and experimental approach, including isolation of TAB+Ë SbCl6â and its X-ray crystallography characterization. The formation of TAB in aged magic blue samples occurs by a Scholl-type coupling of a pair of MB followed by a loss of molecular bromine. The recognition of this fact led us to the rational design and synthesis of tris(2-bromo-4-tert-butylphenyl)amine, referred to as âblues cousinâ (BC: Eox1 = 0.78 V vs. Fc/Fc+, λmax(BC+Ë) = 805 nm, Δmax = 9930 cmâ1 Mâ1), whose oxidative dimerization is significantly hampered by positioning the sterically demanding tert-butyl groups at the para-positions of the aryl rings. A ready two-step synthesis of BC from triphenylamine and the high stability of its cation radical (BC+Ë) promise that BC will serve as a ready replacement for MB and an oxidant of choice for mechanistic investigations of one-electron transfer processes in organic, inorganic, and organometallic transformations
Driven Intrinsic Localized Modes in a Coupled Pendulum Array
Intrinsic localized modes (ILMs), also called discrete breathers, are
directly generated via modulational instability in an array of coupled
pendulums. These ILMs can be stabilized over a range of driver frequencies and
amplitudes. They are characterized by a pi-phase difference between their
center and wings. At higher driver frequencies, these ILMs are observed to
disintegrate via a pulsating instability, and the mechanism of this breather
instability is investigated.Comment: 5 pages, 6 figure
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